Renewable Energy for Rural Schools (Booklet) · · 2013-08-12Renewable Energy for Rural Schools Cover Photos: Upper Right: Children at a school powered by renewable energy sources

Renewable Energy for Rural Schools

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Cover Photos:Upper Right: Children at a school powered by renewable energy sources in Neuquén, Argentina.

Tom Lawand, Solargetics/PIX008261

Left: Two 1.0 kW wind turbines supply electricity to the dormatory of the Villa Tehuelche Rural School, a remoteboarding school located in southern Chile.

Arturo Kuntsmann, CERES/UMAG/PIX08262

Lower Right: Small boys play in the school yard of the newly electrified Ipolokeng School in South Africa.Bob McConnell, NREL/PIX02890

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Antonio C. JimenezNational Renewable Energy Laboratory

Tom LawandBrace Research Institute

November 2000

Published by theNational Renewable Energy Laboratory

1617 Cole BoulevardGolden, Colorado 80401-3393United States of America

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ii Renewable Energy for Rural Schools

FOREWORD

A few years ago, during my tenure as the United States ambassador to the small African nations of Rwandaand Lesotho, I was responsible for administering the Ambassador's Self-Help Funds Program. This discretionarygrants program, supported by the United States Agency for International Development (USAID) funds, allowedthe ambassador to selectively support small initiatives generated by local communities to make their schoolsmore efficient, increase economic productivity, and raise health standards. These funds were used to purchaseequipment and materials, and the communities provided the labor necessary for construction. During this time, I was reminded of my earlier training in a one-room school in rural Bellair, Florida, in the United States. Theschool, which was without heat and hot water and dependent solely on kerosene lamps for lighting, made mewonder how much more I might have learned had today’s advanced renewable energy technologies for ruralschools been available to my generation. Following this diplomatic tour, I was asked to serve as chair person forRenewable Energy for African Development (REFAD)—a nonprofit organization dedicated to the application ofrenewable energy technologies in the rural villages of Africa.

In South Africa, with support from the National Renewable Energy Laboratory (NREL) and the U.S. Depart-ment of Energy (DOE), more than one hundred college teachers and representatives from nongovernmentalorganizations (NGOs) have participated in renewable energy capacity building programs. As a result, severalinstitutions initiated research projects. In Port Elizabeth, the technikon now offers a bachelor's degree in renew-able energy studies. In South Africa, the government collaborated with industry and awarded concessionairefunds to implement a country-wide rural electrification program. In several South African countries, the UnitedNations Educational, Scientific, and Cultural Organization (UNESCO) provided 2-year funding to establish university chairs in renewable energy. In Botswana, REFAD conducted a careful evaluation of the government's40-home photovoltaic (PV) pilot project. The evaluation showed that the introduction of solar technology to thisrural village had a decided positive impact on microeconomic development, health improvements, and schoolperformance—each of which plays an important role in ensuring continued sustainability in rural villages.

Perhaps one of the most satisfying achievements of REFAD's work was the establishment of a "LivingRenewable Energy Demonstration Center" in the KwaZulu/Natal region near Durban, South Africa. The majoruniversities and technikons in Durban worked together to establish a KwaZulu/Natal/Renewable EnergyDevelopment Group (KZN/REDG) among the NGOs. This group pooled its limited resources to provide renew-able energy input to a single community. As a result of the group's action, three schools are being transformedinto solar schools. Myeka High School now operates a 1.4kWp hybrid PV/gas system, which powers 20 comput-ers, a television, a video cassette recorder (VCR), the lights in three classrooms and the headmaster’s personalcomputer and printer. Systems are also being installed at Chief Divine Elementary School and Kamangwa HighSchool.

When you talk with the beneficiaries of these solar projects, you cannot help but be impressed by how muchthese initiatives are needed by those of us who labor at the grass-roots level in developing countries. When onefamily returned from Gabarone to Botswana's Manyana Village following the installation of the 40-home PVpilot project, they were asked why they had returned. The father’s reply was quite a revelation: "BecauseManyana is now a modern city." The defining parameter for determining city status for his family was electrification.

"Renewable Energy in Rural Schools" is an inexpensive, yet comprehensive reference source for all localNGOs and schools that are seeking technical guidance for the integration of renewables as a part of the physicaland instructional aspects of their schools. This practical one-stop, hands-on Guide will be welcomed by in-country practitioners, Peace Corps volunteers, and by U.S. colleges and universities engaged in the preparationof students for services in developing countries. I commend the authors for preparing this much-needed document, and I hope that NREL will continue to provide the necessary support for these kinds of initiatives.

Leonard H.O. Spearman, Ph.D, Chair, Renewable Energy for African DevelopmentDistinguished Professor, Coppin State College

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PREFACE

Education of rural communities is an important national and international priority. In manycountries, however, the availability of electricity to support rural educational activities is less thanadequate. In recent years the development of reasonably priced and reliable renewable energy systems has made it possible to provide electricity and thermal energy for lighting, computers,telecommunications/distance learning, and on-site living accommodations in remote areas. A number of international, national, and local institutions, nongovernmental organizations, foundations, and private companies are supporting the deployment of renewable energy systems in rural communities in the developing world where rural education is a national priority.

Because renewable energy is regionally diverse, choosing the appropriate renewable energy system will be regionally and site dependent. Although photovoltaic (PV) lighting systems havepaved the way and are being deployed in many remote communities around the world, other smallrenewable sources of electricity should be considered. One of the objectives of this guidebook is toexpand the remote electricity opportunity beyond PV to areas of good wind or hydro resources.Also, in the near future we expect to see micro-biomass gasification and direct combustion, as wellas concentrated solar thermal-electric technologies, become commercial rural options.

The three important factors driving the selection of the appropriate technology are the local natural resource, the size and timing of the electrical loads, and the cost of the various components,including fossil fuel alternatives. This guidebook reviews the considerations and demonstrates thecomparisons in the selection of alternative renewable and hybrid systems for health clinics.

The National Renewable Energy Laboratory’s (NREL’s) Village Power Program has commis-sioned this guidebook to help communicate the appropriate role of renewables in providing ruraleducational electricity services. The two primary authors, Tony Jimenez and Tom Lawand, combinethe technical analysis and practical design, deployment, and training experience that have madethem such an effective team. This guidebook should prove useful to those stakeholders consideringrenewables as a serious option for electrifying rural educational facilities (and, in many cases, associ-ated rural clinics). It may be useful as well to those renewable energy practitioners seeking to definethe parameters for designing and deploying their products for the needs of rural schools.

This is the second in a series of rural applications guidebooks that NREL’s Village Power Program has commissioned to couple commercial renewable systems with rural applications, suchas water, health clinics, and microenterprise. The guidebooks are complemented by NREL’s VillagePower Program’s application development activities, international pilot projects, and visiting professionals program. For more information on this program, please contact our Web site,http://www.rsvp.nrel.gov/rsvp/.

Larry FlowersTeam Leader, Village PowerNational Renewable Energy Laboratory

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CONTENTS

How to UseThis Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Introduction: Definition of Need . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Chapter 1: School Energy Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Chapter 2: Solar Thermal Applications and Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Case Study: Solar Stills for Water Supply for Rural Schools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Case Study: Solar Hot-Water Heating in Nepal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

Chapter 3: Electrical System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Photovoltaics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Wind-Turbine Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Micro-hydro . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Diesel Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Inverters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Controllers/Meters/Balance of Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Chapter 4: System Selection and Economics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Chapter 5: Institutional Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Chapter 6: Case Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

#1A — School Electrification Program in Neuquén, Argentina . . . . . . . . . . . . . . . . . . . . . . . . . . .36

#1B — School Electrification in Neuquén . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

#2 — The Concessions Program in Salta, Argentina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

#3 — Wind Turbine Use at a Rural School in Chile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

#4 — School Lighting in Honduras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

#5 — Biogas Plant in a Rural School in Bangladesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

#6 — A Renewable Training Center in Lesotho . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

Chapter 7: Lessons Learned . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53

About the Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

iv Renewable Energy for Rural Schools

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HOW TO USE THISGUIDE

Who is this guide for?This guide is designed for decision-makers

in developing areas responsible for schools, par-ticularly those who are charged with selecting,installing, and maintaining energy systems.Schools are run by many different types of orga-nizations, including government agencies, religious institutions, and many private organi-zations. This guide is designed to help decision-makers in all these types of agencies to betterunderstand the available options in providingenergy to schools.

What is the purpose of this guide?

This publication addresses the need forenergy in schools, primarily those schools thatare not connected to the electric grid. This guidewill apply mostly to primary and secondaryschools located in non-electrified areas. In areaswhere grid power is expensive and unreliable,this guide can be used to examine other energyoptions to conventional power. The authors’ goal is to help the reader to accurately assess aschool’s energy needs, evaluate appropriate andcost effective technologies to meet those needs,and to implement an effective infrastructure toinstall and maintain the hardware.

What is in this guide?This Guide provides an overview of school

electrification with an emphasis on the use ofrenewable energy (RE). Although the emphasisis on electrification, the use of solar thermal technologies to meet various heating applica-tions is also presented. Chapter 1 discusses typical school electrical and heating applica-tions, such as lighting, communications, waterpurification, and water heating. Information ontypical power requirements and duty cycles forelectrical equipment is given. Chapter 2 is an

overview of solar thermal applications and hardware. Chapter 3 discusses the componentsof stand-alone electrical power systems. For each component, there is a description of how it works, its cost, lifetime, proper operation andmaintenance, and limitations. Chapter 4 includesan overview of life-cycle cost analysis, and a discussion of the various factors that influencethe design of stand-alone RE systems for a par-ticular location. Chapter 5 addresses the varioussocial and institutional issues that are required tohave a successful school electrification program.Although there is an emphasis on large-scaleprojects supported by governments or large, private agencies, much of the content relating to maintenance, user training, and project sustainability will be of interest to a wider audience. Chapter 6 describes six school casestudies. Chapter 7 summarizes general lessonslearned that can be applied to future projects.These are followed by a list of references, a bibliography, and a glossary of terms usedthroughout this guide

Renewable Energy for Rural Schools 1

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INTRODUCTION: DEFINITION OF NEED

Current State of Rural SchoolsA large proportion of schools in the develop-

ing world do not have access to basic services,including running water, toilets, lighting, and insome cases, even the pencils and books so neces-sary to the process of education. Schools in ruralcommunities are generally worse off than thoselocated in urban areas, and those schools locatedin remote rural areas are least favored of all.They sit at the far end of the table, are often thelast to be served from the education budget, andwhat they do get tends to cost more because theyare on the periphery. Communications withthese schools are difficult, and they rarely havethe infrastructure required to keep things run-ning smoothly. Despite their being last in line for resources, schools in remote areas often fill alarger local role than do schools in urban areas.The school may be the only institution in a givenrural area, and serves not only for education, butalso for other community activities.

-There is an increasing need for rural popula-tions to improve education so that they mayincrease productivity and improve theirstandard of living. It is important to bridge thisgap so that the rural areas can become moreeconomically sustainable and reverse the trendof migration from the rural to the urban areaswith all the latter's problems.

Renewable energies have a role to play inrural schools. Remote communities are oftenideal sites for many RETs (renewable energytechnologies) for two reasons: (1) the highercosts of providing conventional energy in theseareas, and (2) reduced dependence on fuel andgenerator maintenance. RETs offer lower operat-ing costs and reduced environmental pollution.This provides long-term benefits, which, if fullyevaluated by decision-makers, could impact thechoice of technology in favor of RE (renewableenergy) systems. However, since RE systems arerelative newcomers on the energy-supply side,they are not often given proper consideration forremote school applications. Part of the fault liesin the lack of widely available information aboutthe capabilities and applications of RETs. Part ofthe problem is due to the reluctance of plannersand policy makers to change from accepted practices. They are more comfortable withproven, well-accepted systems, notwithstandingthe existing problems and costs of conventionalenergy systems.

Problems Associated with Existing Energy Delivery Systems

Often, electricity for remote schools is sup-plied by standard-diesel or gasoline-poweredelectric generators. In many cases, the school and adjacent buildings form a mini-grid directlyconnected to the generator. The latter is operatedperiodically during the day and evening whenpower is required. In some instances, the gen-erator can be operated continuously, but this iscostly, and only happens in rare circumstances. A large problem with standard energy deliverysystems is that school personnel require trainingin the use, operation, and maintenance of the

2 Renewable Energy for Rural Schools

Figure I.1. Children of the Miaozu people in frontof their school on Hainan Island.

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system. Most of the people associated with education in rural schools—teachers and custo-dians—don't have the training, or the experi-ence, to operate equipment of this type. Thislesson should be retained when considering theimplementation of RE systems. The use of REsystems will not eliminate the training require-ment. While simple RE systems require lesstraining than conventional systems, the trainingrequirements increase with increasing systemcomplexity. Thus simple, rugged designs arevital for systems that are destined for use inremote areas.

Problems with conventional systems include:

• Fuel provision

• Fuel cost

• Fuel-delivery system reliability

• Generator spare parts: availability, cost, anddelivery

• Generator repair: the availability of a qualifiedmechanic or technician

• Maintenance and repair costs.

Conventional generators are a mature tech-nology, and when used under the proper condi-tions, with a proper service infrastructure inplace, they can provide years of satisfactory service. Unfortunately, in a significant number

of remote rural schools, the generators are oftenin a state of disrepair, leading to serious conse-quences that adversely impact the functioning ofthe school. The lack of electricity exacerbates thealready high teacher-turnover rate, which has anegative impact on the quality of education.

The Role of Energy and Water in the AppropriateFunctioning of Schools

The applications of energy in remote schoolsare discussed in Chapter 1. In order for schools to function properly, clean water is necessary for drinking, sanitary cooking, kitchen require-ments, and gardening. It is also essential that thestudents (frequently coming from poor back-grounds, living in houses often devoid of freshwater), learn the use and management of clean-water sources as part of their education. Waterand energy are vital components of life—theopportunity to learn about these fundamentalsin school should not be missed. For studentsattending rural schools, it may constitute theonly occasion when they can learn about theseessential components of modern society. This is a vital opportunity to train the students in basiclife skills before sending them back to the oftengrim reality of rural poverty and deprivation.


Figure I.2. PV system, including panels, batteries, and regulator box at a schoolin Collipilli Abajo, Argentina.

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CHAPTER 1: SCHOOL ENERGYAPPLICATIONS

Chapter OverviewThe overall needs of rural schools differ

from the needs of urban schools. In many remoterural schools, the teacher, often accompanied byhis/her family, lives in residence, either directlyin the school building or in an attached building.

This Chapter describes the most commonschool applications, which are listed below. The Tables in this Chapter give typical powerrequirements and duty cycles for rural schoolelectrical applications.

• Lighting, water pumping and treatment,refrigeration, television, VCR

• Space heating and cooling

• Cooking

• Water heating

• Water purification

• Radio communications equipment.

Lighting (Indoor/Outdoor and Emergency Lights)

Electricity offers a quality of light to whichgas or kerosene cannot compare. Kerosene lighting is most common in non-electrified com-munities. Kerosene is a known safety hazard andcontributes to poor indoor air quality. Electriclight greatly improves the teacher’s ability to


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equipmentPV modules

Ventilation fans

Flourescent lights

Computer

Radio-transmitter

Water purifier

Sand filter

Figure 1.2. PV powered lights in a rural school inNeuquén, Argentina.

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Figure 1.1. School showing potential applications.


present a variety of subjects in a more appealingway. It also permits the more efficient handlingof administrative tasks, and other non-teachingfunctions. Outdoor light makes the rural schoolmore accessible at night. In non-electrified com-munities, a school with light becomes a strongcommunity focus. The building can be used atnight for training purposes, adult education, cul-tural events, community meetings, and the like.

When using a RE system, energy efficiencyis key to affordability.Investments in efficientsystems generally result incapital and operating costsavings. Table 1.1 showsthe light produced by candles, kerosene lamps,and various types of elec-tric lights. The Table alsoshows the electrical con-sumption of the variouselectric lights. What is not shown in the Table isthe large qualitative supe-riority of electric lightingover kerosene and candles.

The Table makes clear great efficiency of compact- fluorescent (CF) lights compared toother electric lighting technologies. Compared to incandescent lights, CF lights give four toseven times the light per watt-hour consumed.With an expected service life of up to 10,000hours, CF lights last up to ten times longer thanincandescent bulbs.

Communications—Radio-Telephone, Email, Fax, and Short-Wave Radio

Radio and radio-telephone communicationsgreatly increase the efficiency of school opera-tions in remote locations. Communication isessential for routine operation and managementfunctions, including procurement of suppliesand visits by other teachers. Reliable communi-cations facilitate emergency medical treatmentand evacuation when a student or staff memberbecomes suddenly ill.

School communications require very littleelectrical energy. Stand-by power consumptionmay be as little as 2 watts (W). Power consump-tion for transmitting and receiving are higher, onthe order of 30-100 W, but this is generally forvery short periods of time. For example, many


Lamp Type Rated Light Efficiency Lifetime Power Output (lumens/watt) (hours) (watts) (lumens)

Candle 1-16

Kerosene lamp 10-100

Incandescent 15 135 9 850 bulb 25 225 9 850 100 900 9 850

Halogen 10 140 14 2,000 bulb 20 350 18 2,000

Fluorescent 8 400 40 5,000 tube 13 715 40 5,000 20 1,250 40 7,500

Compact 15 940 72 10,000 fluorescent 18 1,100 66 10,000 27 1,800 66 10,000

Table 1.1. Power Consumption for Lighting

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Figure 1.3. PV panels mounted on the ground and on a radio-transmittertower.

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rural schools and health clinics have reliable,two-way regional communication by means ofvery high frequency (VHF) radio with electricityprovided by a single 30-W PV module.

ComputersThe use of computers, which require small

amounts of reliable power, for information trans-mittal purposes is burgeoning around the world.There are photo-cell powered telephones thatuse satellites for telephone transmission, permit-ting access to email services. The availability of acomputer system can expose the students to thistype of technology. In most rural schools, it maybe impossible to envisage the use of this equip-ment. However, the world situation is changingrapidly and the use of RE-power generating sys-tems offers a wealth of opportunities that werenot imaginable some decades ago.

Teaching Aids—VCRs,Televisions, Radios, FilmProjectors, and Slide Projectors

Audio-visual equipment can make a signi-ficant contribution to the improvement of

education in rural areas and the use of theseteaching aids is increasing. The energy requiredto operate small television sets or video-cassetterecorders is not excessive (see Table 1.2). Theseloads can easily be provided by small RE systems.

Water Delivery and TreatmentWater is used for drinking, washing, cooking,

toilets, showers, and possibly, gardening. Watermay have to be pumped from a well or surfacesource or it may flow by gravity from a spring.Depending upon the local situation, it may benecessary to pump water to an overhead tank inorder to make water available to the school facili-ties. Rainwater might also be collected from theschool roof and stored in a rainwater cistern.Cooking and drinking water may have to betreated if the water is dirty or contaminated withfecal coliforms. In the latter case, solar water dis-infection can be used. The provision of someclean, potable water is essential for the operationof any school.

Food Preparation In many rural schools, snacks and a mid-day

meal are often provided. Cooking energy is


Figure 1.4. The interior of a classroom at the Ipolokeng School in South Africa, showing one ofthe computers powered by the PV unit on the roof.

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generally best met by biomass sources (wood,charcoal, biogas, etc.) or by conventional sources—kerosene, bottled gas, etc. In some cases, solarcookers can also be used. The selection of themost appropriate mix of cooking fuels willdepend upon the number of students and staff tobe fed, the available budgets, the reliability of

conventional energy sources, and the manage-ment capabilities of the school staff. Even if aschool has a generator or a PV or wind poweredbattery storage system, this energy should not beused for cooking purposes. Cooking requiresconsiderable energy and the use of electricity forthis purpose is very inefficient.

RefrigerationIn some schools, refrigeration is necessary for

preserving food and medical supplies. A refrig-erator must often be provided to ensure that thefamily of the teacher enjoys a certain level ofcomfort. Maintenance of this equipment must beaddressed.

There are two main classes of refrigerators,compression and absorption. Compressionrefrigeration offers great convenience and goodtemperature control. Vaccine refrigerators areavailable that use only a small amount of elec-tricity. These refrigerators are very small andvery expensive. Larger compression refrigera-tors tend to have large energy consumption.Planners should purchase energy efficient mod-els if compression refrigerators are envisioned.Manual defrost refrigerator/freezers use signifi-cantly less energy than do models with auto-matic defrost.

Absorption refrigerators use propane orkerosene to drive an absorption cycle that keepsthe compartment cold. Due to difficulties inmaintaining stable temperatures, particularlywith the kerosene models, absorption refrigera-tors have lost favor for use in storing vaccines.However, tight temperature control is lessimportant for food storage. Unless fuel supply isa problem, absorption refrigerators should beconsidered for use in off-grid schools. This willreduce the size of the electrical power systemand can result in significant capital-cost savings.

Space Heating and CoolingThere is no question that the renewable-

energy system might provide space heating, inparticular, if the school is located in an area witha cold winter. Generally, this load is handled by


Figure 1.5. This young girl in Cardeiros, Brazilcan fill her jug from the school water tank thanksto a PV powered pumping system installed 1992.Additional PV systems with batteries powerlights, a refrigerator, and a television set for theschool.

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Figure 1.6. A PV system at the Laguna MirandaSchool in Argentina powers lights, a water pumpand a radio.

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using heaters powered by petroleum productssuch as heating oil and kerosene, or wood orcoal. However in some instances, the space-heating furnace might require a small amount of electricity to power the burner or operate fans.In addition, some simple electric fans could beuseful, both in winter and in summer, to improvethe comfort level within the school. If the schoolis located in a very warm area, the renewable-energy system probably will not be designed tohandle an air-conditioner because the load canbe excessive. If some air-conditioning is pro-vided, it should be used sparingly. In addition,maintenance for this equipment must be pro-vided. In dry climates, evaporative cooling mayprovide a less energy-intensive option.

In most cases, load reduction should be theinitial strategy. Ensuring that the building is wellinsulated and sealed can reduce heating loads.

Shading and natural ventilation can reduce cool-ing loads.

Water Heating for Kitchen and Bathing Facilities

Like space heating, cooling, and cooking, theenergy use for water heating normally exceedsthe potential for power generated by small, electricity-producing RE systems. Hot water isneeded for the kitchen and bathroom facilities ofthe teachers and their families (especially incolder regions). Normally this load can be metwith simple solar water heaters or fossil fuel/biomass-combustion water heaters. The amountof hot water required for the teacher and kitchenis usually small, unless the school has facilitiesfor all students to take regular hot showers, inwhich case the load can be significant.

Washing MachineAs a labor and timesaving device a washing

machine contributes to the quality of life of theteacher and his/her family. If the washing ofadditional school articles is minimized, then theelectric load will not be excessive, especially ifenergy efficient models are selected. Front-load-ing washers tend to be more efficient than thetop-loading variety.

Kitchen AppliancesAppliances should be selected and used so as

to avoid overloading the RE generating system.Such appliances could include items such asmixers and juicers, but should not include elec-tric toasters, irons or electric kettles, as these con-sume too much electricity.

WorkshopGiven the remoteness of the school, and the

necessity to undertake minimal repairs, it maybe useful to provide electricity to run some sim-ple power tools, such as electric drills, sanders,and portable saws.


Table 1.2. Power and Energy Consumption for Various Appliances

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mAppliances Power On-time Energy/day (watts) (hours/day) (watt-hrs)

Lights (compact flourescent) 5–30 2–12 10–360

Lights (tube flourescent) 20–40 2–12 40–480

Communication VHF Radio Stand-by 2 12 24 Transmitting 30 1 30

Overhead Fan 40 4–12 160–480

Water Pump �(1500 liters/day 100 6 600 from 40 meters)

TV 12" B&W 15 1.0–4.0 15–60 19" Color 60 1.0–4.0 60–240 25" Color 15 130 1.0–4.0 130–520

VCR 30 1.0–4.0 30–120

AM/FM Stereo 15 1.0–12 15–180

Refrigerator/Freezer variable 1,100–3,000

Vaccine Refrigerator variable 500–1,100

Freezer variable 700–3,000

Washing Machine1 100–400 1.0–3.0 600–1,000/load (Energy Efficient Models)

Hand Power Tools 1.0–3.0 100–800

1 Energy usage figures do not reflect energy needed to heat the water used in the washer.


CHAPTER 2: SOLAR THERMALAPPLICATIONS ANDCOMPONENTS

Chapter IntroductionSolar thermal technologies are used for appli-

cations in which heat is more appropriate thanelectricity. This chapter gives an overview of sev-eral solar thermal applications and generaldescriptions of the hardware involved. Solarthermal energy is used to heat air or water usingsolar collectors. Collectors are shallow insulatedboxes covered by a rigid transparent cover madeof glass or certain types of plastic. Solar energy istrapped in the exposed space and converted intolow grade heat that is extracted by blowing air orcirculating water through the collector. A varietyof temperatures can be achieved depending

upon the construction of the solar collector andthe rate of flow of the water or air.

Solar Water Heating For most hot water applications, 45° to 50°C

is sufficient for showering and kitchen use.

A typical solar water heating system consistsof a solar collector connected to a hot waterreservoir. Active systems use pumps and con-trollers to circulate a fluid between the collectorand the storage tank. Due to their complexityand expense, active systems are generally notwell suited for use in remote developing areas.This chapter will focus on cheaper and simplerpassive systems. Passive systems are easiest todesign in use in warm climates where there areno hard freezes (i.e., temperatures don’t typicallygo below 10°C). These systems can be used incolder climates as well, but in these cases, provi-sion must be made for freeze protection.

Passive systems can be further subdividedinto thermosyphon systems and batch systems.

In solar thermosyphon systems, asolar collector (located at least two-thirds of a meter below the bottom ofthe hot-water reservoir) is connectedby means of plumbing to create aclosed loop with the hot-water tank.Typically, water is heated in pipes inthe collector, which consists of ametal absorber plate to which areattached water tubes spaced roughlyevery 15 cm in an insulated box fittedwith a transparent glazing. Water isheated in the collector and rises to thetop of the hot-water tank, replaced bycolder water from the bottom of thereservoir. During the day, this ther-mosyphon process continues. It ispossible to extract hot water from thetank as needed while the process con-tinues. The advantage of the ther-mosyphon system is that the heatedwater can be stored in an insulatedcontainer, possibly located indoors.This means the water loses less heatovernight compared to a batch system.


Figure 2.1. The simplest solar water heaters consist simply of ablack tank placed in the sun. Collector efficiency can beincreased by placing the tank inside inside an insulated glazedbox, as shown above.

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Tank

Glazing

Drain valves

Insulated plumbing lines

Insulated collection box

Pump flow


The hot water reservoir must be properly insu-lated to conserve the heat in the hot water.

A batch type of solar water heater is the sim-plest design and can be easily constructed. Thiscan consist of a metallic water tank placed hori-zontally on an insulated base and covered with atransparent cover. Reflectors can be used toincrease the radiation incident on the tank. Thesun heats the reservoir during the day, and hotwater can be extracted for evening showers andkitchen use at the end of the day. In areas wherethere are clear, cool nights with low, relativehumidity, these systems will lose quite a bit ofheat, and limited hot water may be available inthe early morning hours.

The costs of solar water heating systems varywidely, depending upon whether they are site-constructed with free labor/materials, or aremanufactured components /systems purchasedfrom a supplier. Prices might range from $0 (allused/donated materials constructed on site withdonated labor) to $200 (manufactured collec-tors/tanks/systems) per square meter.

To estimate the energy delivered per day,multiply the system collector area times the aver-age system efficiency times the average insola-tion (typically 3 kWh/m2 to 7 kWh/m2 per day,)incident on the collector. Use Table 2-1 to esti-mate system efficiency.

Solar Space HeatingBefore considering solar space heating, it is

essential that the building be properly insulatedand sealed. Otherwise, using solar air heaters

could be wasteful. After that, to the extent possi-ble, passive solar/daylighting strategies shouldbe used. (For pre-existing structures, the oppor-tunities for implementing passive strategies maybe limited.) Finally, after insulation, sealing andpassive strategies have been examined, simplesolar air heaters can further reduce the require-ment for fuel oil or wood, which are commonlyused for space heating purposes. Solar airheaters are best suited for use in schools thathave reasonably good solar radiation regimes inwinter. There are several types of solar airheaters, but the simplest and most effective con-sists of an external transparent glazing coveringa shallow collector insulated at the base, andgenerally containing a dark grill or mesh locatedin the air space.

For space heating applications, an exit-airtemperature from the solar air heater of 30º to50ºC is adequate to contribute to increasing theambient temperatures within the school build-ing. The size of the solar air heaters depends onthe indoor temperature that the school wouldlike to maintain. A small PV panel to operate asimple fan is very useful in increasing the effi-ciency of heat extraction from the collector. Thesolar collectors can be mounted on the walls ofthe building facing the Equator. In this way, theycan be used for either natural convection heatingand for summer ventilation. These relativelysimple systems have few maintenance problems,provided they are fitted with simple filters, espe-cially in dusty areas.

The estimated cost for a simple solar airheater system ranges up to $35.00 per squaremeter, depending as in the water case, howmuch donated labor/materials are used.

Solar PasteurizationSolar flat-plate collectors can be used to pas-

teurize water. These collectors consist of a blackabsorber plate in an insulated box covered by asheet of tempered glass. Water is circulatedthrough the collector for heating and thenpumped to a storage tank.


Table 2.1. Solar Water Heater Efficiencies

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mSystem Type System Efficiency

Active System1 50%

Thermosyphon System1 45%

Batch System1 30%

Batch System 50% (day/evening loads only)

1 Standard draw, equal weight to morning and evening draws.


Water or milk may be pasteurized by heatingit to 65°C for 30 minutes. Pasteurization disin-fects microbiologically contaminated water bykilling viruses, bacteria, and protozoa. However,it will not eliminate chemical pollutants or salts.

Solar pasteurization may also beachieved by placing water or milk contain-ers in a solar cooker—an insulated box cov-ered with glass. Reflectors increase theamount of sunlight directed into the box. Indirect sunlight, temperatures sufficient forpasteurization are easily achieved in thismanner.

Solar Water DisinfectionAs an alternative to pasteurization,

solar water disinfection can be used toeliminate bacteriological contaminationfrom drinking water supplies. (Note: Thistechnique only works against bacteriologi-cal contaminants, it will not eliminatechemical pollutants or salts.) Clear, butbacteriologically contaminated, water intransparent plastic bags is exposed todirect sunlight for four to six hours. Thewater can also be placed in thin, plastictransparent bottles, but care should betaken NOT to use bottles manufacturedfrom plastics made with the addition of an


Figure 2.2. Solar wall collector (SWC) operating modes.A solar wall collector may be used for both heating andventilation as illustrated above.

— Air evacuation opening closed— Exhaust port open— Air intake opening closed— Return port open

Heating

Air from the space to be heated, or from the HVAC system, is circulated through the SWC and back to the heated space.

— Air evacuation opening closed— Exhaust port open— Air intake open— Return port closed

Ventilation Air Preheating

Fresh air from outside is drawn through the SWC and into the heated space orto the HVAC system. No air from theheated space is recirculated backthrough the SWC.

— Air evacuation opening open— Exhaust port closed— Air intake partially open— Return port partially open

Thermosyphon Venting

The natural force of the thermosyphon,created by the flow of outside air through the SWC, will also draw air from thebuilding through the SWC to the outside.This air must be replaced by air enteringthe building elsewhere (preferably from the north side).

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Figure 2.3. Solar water disinfection in theCaribbean.

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ultra-violet (UV) wavelength inhibitor (used toensure a longer life for the bottle when exposedto solar radiation.) These bottles may not proveto be suitable for the solar water disinfectionprocess. The UV rays in sunlight inactivate path-ogenic bacteria such as fecal coliforms. There is asynergetic effect with water temperature. Betterresults are achieved when the plastic bags areplaced outside on smooth, dark surfaces thatpermit an increase in the temperature level of thewater. Decontamination takes longer in humid,cloudier regions than in dry and sunny climates.The required materials consist of suitable plasticbags and a thin, dark sheet, preferably of metalresting on a straw mat (to provide some insula-tion). This technique could be used in isolatedschools to produce potable drinking water forthe staff and students.

Simple solar thermal technologies, such aspasteurization and solar water disinfection, areeffective for treating small quantities of biologi-cally contaminated water. These are good alter-natives to boiling water for 15 to 20 minutes tokill bacteria. Often, boiling is not considered

because of the inconvenience and the require-ment for fuel.

Solar Water DistillationDistillation is the best single-method for

purifying water. It removes bacteria, salts, andpollutants of all types. Distillation is often usedto purify brackish water. The simplest stills con-sist of a sloping transparent cover (usually glass)over a shallow basin filled with 8 to 10 cm ofclean saline water. Solar radiation heats up thesaline water, causing evaporation. Water vaporcondenses on the underside of the transparentcover, where it is collected and stored in contain-ers. This condensed water vapor does not con-tain dissolved salts or bacterial and viralcontaminants, making it drinkable. Dependingupon sunlight and temperature, solar distillerscan produce 3-6 liters of potable water per dayper square meter of collector area. Sizes rangefrom family-sized units of two square meters tocommunity scale units of several thousandsquare meters. The costs of a solar distiller sys-tem vary from $30 to $300 per square meter. In a


CASE STUDY—Solar Stills for Water Supply for Rural SchoolsCountry: Argentina

Location: Chaco Salteño

Latitude: Tropic of Capricorn

Altitude (average): 350 m above sea level

Climatic conditions: Average insolation: 6 kWh/m2/day; Average yearly ambient temperature: 21°C

Period of operation during the year: Continuous

Schools provided with solar stills: Los Blancos and Capitan de Fragata Pagé

RE system: Site-assembled solar stills for the production of fresh drinking water

Installation: June 1995

Capacity: 6 greenhouse-type units, each 2.2 m2 in area producing approximately 50 liters distillate per day

Materials used: Fiberglass basins, glass covers, aluminum frames, Stainless-steel gutters, PVC piping

Feed water: Saline ground water up to 7 g/l salinity

Back-up systems: Rainfall catchment; delivery by tanker truck

Lessons Learned: The maintenance of the stills did not appear to be a major problem. Several of theconstruction materials selected for the stills could not withstand the high-levels of U.V. radiation andthe effects of hot saline brine


remotely located school, this technique could beused to produce water that can be used fordrinking, cooking and medicinal purposes.

Solar CookingSolar cookers can be used under favorable

solar radiation conditions to reduce the fossilfuel or biomass energy load normally used forpreparing meals. The majority of the energy isused for cooking the mid-day meal. Smalleramounts of energy are used for preparing break-fast and dinner for the staff and hot beverages

during the day. Some of the energy demandcould be met using simple box cookers. Theseconsist of insulated boxes with a sloping glazedcover and a rear hinged reflector. The cooker ismounted facing the Equator and is generallyturned 3 to 5 times a day to face the sun directly,thus, improving its performance. Other types ofcookers include concentrating cookers usingparabolic reflectors, or steam cookers using a flatplate collector to produce the steam connected to an insulated double boiler. Under reasonablesolar conditions, i.e., above 700 Watts/m2, it ispossible to cook a variety of meals. If the schoolhas a large population of students to feed, thensolar cooking is not the preferred option. Solarcooking should only be used to reduce theenergy demand from conventional sources.

Biomass CookersIn recent years, improved wood and charcoal

stoves have been developed with increased efficiency of biomass use. As wood and charcoalare generally the fuels most readily available inremote developing areas, it is possible to makeuse of more efficient community-sized stoves forthis purpose. It is easily possible to cook mealswith a mean-specific fuel consumption of 8 to10 kilograms of food cooked per kilogram of dry wood.


Figure 2.4. Solar Stills at a school in the Chaco,Argentina.

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Figure 2.5. Solar ovens—household model on right.



CASE STUDY—Solar Water Heating in Nepal

Details of School LocationBudhanilkantha SchoolP.O. Box 1018Bud HanilkanthaKathmandu, Nepal

This school uses solar water heaters to pro-vide hot water for bathrooms.

Specific Conditions of the School• The school consists of 24 buildings. The ori-entations of the buildings vary and in general,the roofs are pitched.

• The number of students at the school is 850,with 70 teachers and 150 custodians.

• The school operates for 9 months of the year.The normal occupancy time is from 08:30 to16:30 hours. It is a full boarding school with allstudents residing on the Campus. In addition,55 staff members reside at the school, and there are residents at the school throughout theyear, even in holiday periods. The school is notused in the evening for community educationpurposes.

Energy End Use in the School• Water Heating–This consistsmainly of solar water heating forthe student hostels and electricwater heaters for the staff quarters.

• Due to its urban location, theschool gets its electricity from thegrid. The electrical energy con-sumption (including lighting): Rs 80,000 ($U.S. 1,176) per month.The peak expenditure is Rs 150,000($U.S. 2,205) for a month duringwinter. Note the exchange rate forNepali rupees at the time of thiswriting (April 99) is $U.S. 1 = NRs 68.

Figure 2.6. Demonstration of improved woodcookstoves at the Renewable Energy TrainingCenter, Nuequen, Argentina.

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Figure 2.7. This solar water heater has provided hot water to this school in Nepal since 1978.

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• Space heating (winter only)—liquid propane gas (LPG)and electricity

• Cooking—communal and familial—electricity andLPG

• Educational aides—television sets 60VCRs 30Computers 30Printers 10

Type of Renewable Energy System in Operation

Solar Water Heaters:• Number of solar collectors—40 units.

• Collector types—Most of the installed water heatersuse an integrated design, where the collector and storageare in one piece. The more recent installations are ther-mosiphon types.

• Location—the collectors are fixed on the walls, or onthe terrace, and some are ground mounted.

• Equipment manufactured by the following compa-nies—Balaju Yantra Shala; Sun Works; Laxmi MechanicalSolar Works.

• All solar equipment manufactured in Nepal.

• Years of installation—major installation done from 1977to 1979 and some in the 1990s.

• Present condition of SWH systems—75% of the panelsare performing well, including the SWH systemsinstalled in 1977–1979.

• The school paid for the equipment and its installation.The school also handled the financial arrangements of capital investment and pays the operation and mainte-nance expenses. (Most O & M consists of changing bro-ken glass and repainting).

• Cost of equipment—a 300-liter SWH system costs $500to $600, including installation—there were extra chargesfor the plumbing for the supply of the hot water in thebuildings.

Micro-Hydro Turbine:• A demonstration 300-watt cross-flow, micro-hydro turbine provides electricity for lighting.

Operation and Maintenance of the Energy System• The School Maintenance Department handles the REsystems at the school. Technicians are trained in-house bythe Maintenance Department.

• Despite a slight drop in system efficiencies over theyears and some leakage, school authorities are satisfiedwith the performance of the units.

Education and Sociocultural Considerations• Students are familiarized with the RE systems suchsolar water heaters, PV cells, and the micro-hydro tur-bine. They study these systems as part of their courses.

• Due to the introduction of the solar water heating sys-tems, there are many SWH in the local community partic-ularly in the domestic sector. The principal barrier to thespread of this technology has been the affordability andthe development of an economic design. There is also alack of awareness of the technology.

• Although a complete survey has not been undertaken,there are a number of boarding schools in Nepal thathave installed SWH systems. A funding and familiariza-tion program would provide local impetus to the installa-tion of more systems in Nepal.

• On the regional and national scale, it should be notedthat many small companies manufacture SWH. Typically,the manufacturers do the system maintenance as well.

Acknowledgment:The information was provided by:

Gyani R. ShakyaChief Technology DivisionRoyal Nepal Academy of Science and TechnologyP.O. Box 3323Kathmandu, NEPAL


CHAPTER 3: ELECTRICAL SYSTEMCOMPONENTS

Chapter IntroductionThis chapter gives an overview of the main

components typically used in RE systems. Dieseland gasoline engine generators are also dis-cussed. For each item, the discussion includeshow the component works, proper use, cost, lifetime, and limitations.

System Overview

IntroductionA hybrid system comprises components that

produce, store, and deliver electricity to theapplication. Figure 3.1 shows a schematic of ahybrid system. The components of a hybrid sys-tem fall into one of four categories describedbelow.

Energy GenerationWind turbines and engines use generators to

convert mechanical motion into electricity. PVpanels convert sunlight directly into electricity.

Energy StorageThese devices store energy and release it

when it is needed. Energy storage oftenimproves both the performance and economicsof the system. The most common energy storagedevice used in hybrid systems is the battery.

Energy ConversionIn hybrid systems, energy conversion refers

to converting AC electricity to DC or vice versa.A variety of equipment can be used to do this.Inverters convert DC to AC. Rectifiers convertAC to DC. Bi-directional inverters combine thefunctions of both inverters and rectifiers.

Balance of System (BOS)BOS items include monitoring equipment, a

dump load (a device that sheds excess energyproduced by the system), and the wiring andhardware needed to complete the system. Notethat the term "BOS" is not strictly defined. Inother contexts, energy conversion equipmentand batteries may be considered BOS items.

Photovoltaics

Introduction PV modules convert sunlight directly into

DC electricity. The modules themselves, havingno moving parts, are highly reliable, long lived,and require little maintenance. In addition, PVpanels are modular. It is easy to assemble PV


Figure 3.1. Hybrid System Configuration:Generalized hybrid system configuration showingenergy generation components (photovoltaic, wind turbine, and generator), energy storagecomponents (batteries), energy conversioncomponents (inverter), and balance of systemcomponents (direct current source center andcharge controller). Courtesy of Bergey WindCompany

Batteries

DC loads AC loads

Inverter

Generator

PV array

Wind turbine02

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Wind/PV/Diesel Hybrid System

DC source center


panels into an array of arbitrary size. The maindisadvantage of PV is its high capital cost.Despite this, especially for small systems, PV is often a cost-effective option, with or withoutanother power source, as the savings of use pays back the initial cost.

PV Module ConstructionPV modules consist of individual cells that

are wired together in series and in parallel toproduce the desired voltage and current. Thecells are usually encapsulated in a transparentprotective material and typically housed in analuminum frame.

PV cells fall into three types, monocrys-talline, polycrystalline, and thin film (amor-phous). Amorphous cells are generally lessefficient, and may be less-long lasting, but areless expensive and easier to manufacture.

Performance Characterization PV modules are rated in terms of peak watts

(Wp). This rating is a function of both panel sizeand efficiency. This rating scheme also makes it

easy to compare modules from different sourcesbased upon cost per Wp. The rating is theamount of power that the module will produceunder standard reference conditions (1kW/m2;25°C [77°F] panel temperature.) This is roughlythe intensity of sunlight at noon on a clear sum-mer day. Thus, a module rated at 50 Wp will pro-duce 50 W when the insolation on the module is1 kW/m2. Because power output is roughly pro-portional to insolation, this same module couldbe expected to produce 25 W when the insolationis 500 W/m2 (when operating at 25°C).

PV array energy production can be estimatedby multiplying the array’s rated power by thesite’s insolation on the panel’s surface (typically1400–2500 kWh/m2 per year; 4–7 kWh/m2/day). The resulting product is then derated byapproximately 10%–20% to account for lossescaused by such things as temperature effects(panels produce less energy at higher tempera-tures) and wire losses.

Module OperationMost PV panels are designed to charge 12-V

battery banks. Larger, off-grid systems may haveDC bus bar voltages of 24, 48, 120 or 240 V. Con-necting the appropriate number of PV panels inseries enables them to charge batteries at thesevoltages. For non-battery charging applications,such as when the panel is directly connected to awater pump, a maximum-point power tracker(MPPT) may be necessary. A MPPT will matchthe electrical characteristics of the load to thoseof the module so that the array can efficientlypower the load.

Module Mounting and Tilt Angles In order to maximize energy production, PV

modules need to be mounted so as to be orientedtowards the sun. To do this, the modules aremounted on either fixed or tracking mounts.Because of their low cost and simplicity, fixedmounts are most commonly used. These type ofmounts can be made of wood or metal, and canbe purchased or fabricated almost anywhere.

Tracking mounts (either single or dual axis)increase the energy production of the modules,


Figure 3.2. Ground-mounted PV panels at a ruralschool in Neuquén province, Argentina.

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particularly at low latitudes, but at the price ofadditional cost and complexity. The relative costeffectiveness of tracking mounts versus addi-tional modules will vary from project to project.

Capital and Operating CostsPV modules are available in a variety of rat-

ings up to 300 Wp. Individual PV panels can beconnected to form arrays of any size. Modulesmay be connected in series to increase the arrayvoltage, and can be connected in parallel toincrease the array current. This modularitymakes it easy to start out with a small array andadd additional modules later.

The costs of a PV array are driven by the costof the modules. Despite declining prices in thelast two decades, PV modules remain expensive.Retail prices for modules bottom out at about$5.50 per Wp. For bulk purchases, prices can gobelow $4.00 per Wp. Warrantees typically are for10 to 25 years. Current modules can be expectedto last in excess of 20 years. The remaining PVarray costs consist of mounts, wiring, and instal-lation. These are typically $0.50–$1.50 per Wp.

PV panels (not necessarily the remainder ofthe system) are almost maintenance free. Mostly,they just need to be kept clean, and the electricalconnections need periodic inspection for looseconnections and corrosion.

Wind-Turbine Generators

IntroductionWind turbines convert the energy of moving

air into useful mechanical or electrical energy.Wind turbines need more maintenance than a PVarray, but with moderate winds, > 4.5 meters persecond (m/s), will often produce more energythan a similarly priced array of PV panels. LikePV panels, multiple wind turbines can be usedtogether to produce more energy. Because wind-turbine energy production tends to be highlyvariable, wind turbines are often best combinedwith PV panels or a generator to ensure energyproduction during times of low wind speeds.This section will focus on small wind turbineswith ratings of 10 kW or less.

Wind-Turbine Components The components common to most wind tur-

bines are shown in Figure 3.3 below. The bladescapture the energy from the wind, transferring itvia the shaft to the generator. In small wind tur-bines, the shaft usually drives the generatordirectly. Most small wind turbines use a perma-nent magnet alternator for a generator. Theseproduce variable frequency (wild) AC that thepower electronics convert into DC current. Theyaw bearing allows a wind turbine to rotate toaccommodate changing wind direction. Thetower supports the wind turbine and places itabove any obstructions.

Wind-Turbine PerformanceCharacteristics

A wind-turbine’s performance is character-ized by its power curve, which relates wind-tur-bine power output to the hub-height windspeed. Power curves for selected machines areshown in Figure 3.4. Turbines need a minimumwind speed, the "cut-in" speed, before they startproducing power. For small turbines, the cut-inspeed typically ranges from 3 to 4 m/s. After cut-in, wind-turbine power increases rapidlywith increasing wind speed until it starts level-ing off as it approaches peak power. The energy


Figure 3.3. Typical wind-turbine components

Blades

Generator

Tail

Tower

Yaw bearing

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density in moving air is proportional to the cubeof the velocity. Thus, wind turbines producemuch more power at higher wind speeds than atlower wind speeds, until the wind speed reachesthe "cut-out" speed. Most small turbines producepeak power at about 12–15 m/s. The turbine willproduce at peak power until the wind speedreaches the turbine’s "cut-out" speed. Cut-out,usually occurring at 14 to 18 m/s, protects theturbine from overspinning in high winds. Mostsmall turbines cut-out by passively tilting (furl-ing) the nacelle and rotor out of the wind. Aftercut-out, wind-turbine power output usuallydoes not decrease to zero, but remains at30%–70% of rated power.

Wind turbines are rated by their power out-put at a specified wind speed, e.g., 10 kW at12 m/s. The wind speed at which a turbine israted, though usually chosen somewhat arbitrar-ily by the manufacturer, is typically near thewind speed at which the turbine produces themost power.

The non-linear nature ofthe wind-turbine power curvemakes long-term energy per-formance prediction more dif-ficult than for a PV system.Long-term performance pre-diction, requires the windspeed distribution rather thanjust the average wind speed.Long-term performance canthen be found by integratingthe wind-turbine power curveover the wind speed distribu-tion. Wind-turbine perfor-mance may also depend uponthe application for which it isused.

Wind-Turbine CostsWind-turbine prices vary

more than PV module prices.Similar sized turbines can dif-fer significantly in price. This iscaused by wide pricing varia-tions among different turbinemanufacturers and by widely

varying tower costs based on design and height.Installed costs generally vary from $2,000 to$6,000 per rated kW. Unlike the case for PV, windturbines offer economies of scale, with largerwind turbines costing less per kW than smallerwind turbines.

Maintenance costs for wind turbines are variable. Most small wind turbines require somepreventive maintenance, mostly in the form ofperiodic inspections. Most maintenance costswill probably be due to unscheduled repairs(e.g., lightning strikes and corrosion). Gipe1

claims a consensus figure of 2% of the total sys-tem cost annually.

Micro-hydro

IntroductionMicro-hydro installations convert the kinetic

energy of moving or falling water into electricity.These installations may require more extensive


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Wind Turbine Power Curves

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Figure 3.4. Selected wind-turbine power curves


civil works than other technologies, but atappropriate sites, micro-hydro can be, on a lifecycle basis, a very low cost option. The waterresource of a micro-hydro installation may besubject to seasonal weather extremes such asdrought or freezing, but unlike PV or wind tur-bines, a micro-hydro installation can producepower continuously on a day-to-day basis.Because of this continuous power production,even a small installation will produce largeamounts of energy.

ComponentsThe components of a micro-hydro installa-

tion are shown in Figure 3.6. The civil works,consisting of a water channel, diverts water fromthe stream or river to the penstock. The penstockconveys the water under pressure to the turbine.The piping used in the penstock must be largeenough to avoid excessive friction losses. Differ-ent types of turbines are available, depending onthe head and flow rate available at the site.Impulse turbines, such as the Pelton or Turgoturbine have one or more jets of water impingingon the turbine, which spins in the air. Thesetypes of turbines are most used in medium andhigh head sites. Reaction turbines, such as theFrancis, Kaplan, and axial turbines are fullyimmersed in water. They are used more in lowhead sites. The turbine is connected to a genera-tor that produces electricity. Both AC and DCgenerators are available. Governors and controlequipment are used to ensure frequency controlon AC systems and dump excess electricity pro-duced by the wind turbine.

Performance and CostThe power output of a micro-hydro system is

a function of the product of the pressure (head)and flow rate of the water going through the tur-bine. Figure 3.7, shows the expected generatoroutput under various site conditions. The selec-tion of a site is usually a compromise betweenthe available head & flow rate and the cost of thewater channel & penstock. Because micro-hydrosystems produce continuous power, even a smallsystem will produce a large amount of energy.For example, a 125-watt system will produce


Figure 3.5. Small wind turbines, solar oven, andradio tower at the Las Cortaderas Primary School250 km west of Neuquén, Argentina.

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Figure 3.6. Components of a micro-hydroinstallation. Fraenkel, Peter (1991) Micro-hydroPower: A Guide for Development Workers. ITPublications in association with the StockholmEnvironment Institute, London.

Weir andintakeCanal

Forebay

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Tail race

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3 kWh a day. The water resource of a micro-hydroinstallation may be subject to seasonal variationsdue to winter freezing, spring runoff, and drought.In cases where peak power demand is greaterthan what the installation can supply, a batterybank can be used to store energy during lowdemand periods for use in high demand periods.

Due to varying requirements for water chan-nels and penstock, the cost of micro-hydro sys-tems will vary widely from location to location.In general, the cost for most systems is $1,000 to$4,000 per kW. Maintenance costs are looselyestimated to be around 3% of the capital cost peryear. Much of the maintenance consists of regu-lar inspections of the water channel and pen-stock to keep them free of debris. Micro-hydroinstallations can be very long lived, with main-tained systems lasting in excess of 50 years.

Unlike PV and wind systems, micro-hydroinstallations are not modular. The availablewater resource and size of the civil works andpenstock place an ultimate limit on the poweroutput of a given micro-hydro system. Increas-ing the capacity of the civil works is expensive.Thus, micro-hydro installations require thatlong-term load demand be carefully considered.

Diesel Generators

IntroductionGenerators consist of an engine driving an

electric generator. Generators run on a variety offuels, including diesel, gasoline, propane, andbiofuel. Generators have the advantage of pro-viding power on demand, without the need forbatteries. Compared to wind turbines and PVpanels, generators have low capital costs buthigh operating costs.

Cost and PerformanceDiesel generators are the most common type.

They are available in sizes ranging from under2.5 kW to over 1 megawatt (MW). Compared togasoline generators, diesel generators are moreexpensive, longer lived, cheaper to maintain,and consume less fuel. Typical costs for smalldiesel generators (up to 10 kW) are $800 to $1,000per kW. Larger diesels show economies of scale,costing roughly $7,000–$9,000 plus ~$150 perkW. Typical diesel lifetimes are on the order of25,000 operating hours2. Larger diesels are usu-ally overhauled rather than replaced. Overallmaintenance costs can be estimated to be 100% to 150% of the capital cost over this 25,000-hourlifetime. An operator must provide day to daymaintenance and the generator must be periodi-cally overhauled by a qualified mechanic. Dieselgenerator fuel efficiency is generally 2.5–3.0 kWh/liter when run at a high loading. Efficiency drops


Figure 3.7. Estimated hydropower generator outputas a function of head and flow rate.

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Figure 3.8. Typical generator at an isolatedmountain school. Teachers and custodiansgenerally have no training in the maintenance andoperation of these units.

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off sharply at low loads. This poor low-load effi-ciency is the bane of many generator-only sys-tems. The generator must be sized to cover thepeak load, but then often runs at low load muchof the time.

Less common than diesels, gasoline genera-tors cost less and are available in very small sizes(as low as a few hundred watts). Otherwise,gasoline generators are inferior in most respectsto their diesel counterparts. For sizes larger thanabout 1 kW, prices range from $400 to $600 perkW. The minimum price is roughly $400 regard-less of size. Lifetimes are short, typically only1,000 to 2,000 operating hours. Fuel efficiency ispoor, peaking at roughly 2.0 kWh/liter. Part-load fuel efficiency is worse than for diesel gen-erators. Gasoline generators are best used whenthe loads are very small or the anticipated runhours total no more than roughly 400–600 hoursper year.

Given the previous discussion, several pointsregarding the optimum use of generatorsemerge. For maximum fuel economy, the genera-tor should be run at a high load (> 60%). Con-versely, low-load operation should be avoided.Not only does this decrease the fuel efficiency,there is evidence that low-load operation resultsin greater maintenance costs.

Batteries

IntroductionBatteries are electrochemical devices that

store energy in chemical form. They store excessenergy for later use in order to improve systemavailability and efficiency. By far the most com-mon type of battery is the lead-acid type. A dis-tant second is the nickel-cadmium type. Theremainder of this section discusses the lead-acidbattery.

Battery Selection Considerations

Deep-Cycle versus Shallow-CycleAlthough batteries are sized according to

how much energy they can store, in most cases a lead-acid battery cannot be discharged all the

way to a zero state of charge without sufferingdamage in the process. For remote power appli-cations, deep-cycle batteries are generally recom-mended. Depending upon the specific model,they may be discharged down to a 20%–50%state of charge. Shallow-cycle batteries, such ascar batteries, are generally not recommended,though they are often used in small PV systemsbecause of the lack of any alternatives. They canbe prudently discharged only to an 80%–90%state of charge and will often be destroyed byonly a handful of deeper discharges.

Flooded versus Valve RegulatedFlooded batteries have their plates immersed

in a liquid electrolyte and need periodic rewater-ing. In contrast, in valve regulated batteries, theelectrolyte is in the form of a paste or containedwithin a glass mat. Valve regulated batteries donot need rewatering. Flooded batteries generallyhave lower capital costs than valve regulatedbatteries and with proper maintenance, tend tolast longer. On the other hand, where mainte-nance is difficult, valve regulated batteries maybe the better choice.

LifetimeBattery lifetime is measured both in terms of

cumulative energy flow through the battery (fullcycles) and by float life. A battery is dead when it


Figure 3.9. Batteries allow an RE system to provide24 hour power. Photovoltaic panels or a windgenerator can recharge the batteries.

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reaches either limit. For example, discharging abattery twice to 50% is one full cycle. For manybatteries, as long as the battery state of charge iskept within the manufacturer’s recommendedlimits, the lifetime cumulative energy flow isroughly independent of how deeply the batteryis cycled. Depending upon the brand and model,battery lifetimes vary widely, ranging from lessthan 100 full cycles to more than 1500 full cycles.Float life refers to how long a battery that is con-nected to a system will last, even if it is never oronly lightly used. Typical float lives for goodquality lead-acid batteries range between 3 and10 years at 20°C (68°F). Note that high ambienttemperatures will severely shorten a battery’sfloat life. A rule of thumb is that every 10°C(18°F) increase in average ambient temperaturewill halve the battery float life.

SizeThe storage capacity of a battery is com-

monly given in amp hours at a given rate of dis-charge. When multiplied by the battery’snominal voltage (usually 2, 6, or 12 V), this givesthe storage capacity of the battery in watt-hours.(Dividing this number by 1000 gives the batterystorage capacity in kWh) This storage capacity isnot a fixed quantity, but rather varies somewhatdepending on the rate at which the battery is dis-charged. A battery will provide more energy if itis discharged slowly than if it is dischargedrapidly. In order to facilitate uniform compari-son, most battery manufacturers give the storagefor a given discharge time, usually 20 or 100hours. Individual batteries used in RE andhybrid systems are available in capacities rang-ing from 50 amp hours at 12 V to thousands ofamp hours at 2 V (0.5 kWh to several kWh).

CostThe variations in cycle and float life,

described earlier, make comparison of the cost-effectiveness of different batteries somewhatproblematical. As a general starting point, costsare on the order of $70–$100 per kWh of storagefor batteries with lifetimes of 250 to 500 cyclesand float lives in the range of 5 to 8 years. Therewill be additional one-time costs for a shed,racks, and connection wiring.

Inverters

IntroductionInverters convert DC to AC electricity. This

capability is needed because PV modules andmost small wind turbines produce DC electricitywhich can be used by DC appliances or stored inbatteries for later use. Most common electricalapplications and devices require AC electricity,which cannot be easily stored.

Inverter Selection ConsiderationsOutput wave form: Inverter output wave

forms fall into one of three classes, square wave,modified sine wave, and sine wave. Square-wave inverters are the least expensive, but theiroutput, a square wave, is suitable only for resis-tive loads such as resistance heaters or incandes-cent lights. Modified sine-wave invertersproduce a staircase square wave that moreclosely approximates a sine wave. This type ofinverter is the most common. Most AC electronicdevices and motors will run on modified sinewave AC. Some sensitive electronics may notwork with modified sine wave AC and requiresine-wave inverters. Sine-wave inverters pro-duce utility grade power, but of course cost morethan the other types of inverters.

Conversion efficiency: Inverter efficiencyvaries with the load on the inverter. Efficienciesare poor at low power levels and generally verygood (>90%) at high power levels. Mid rangeefficiency varies widely between inverters andmay be an important selection criterion. Otheritems to consider are the inverter’s no-loadpower draw and the presence of a "sleep mode".Sleep mode reduces the inverter power draw to afew watts when there is no load on the inverter.

Switched versus parallel: A parallel invertercan supply power to a load simultaneously witha diesel generator. With a switched inverter,either the inverter or the generator, but not bothat the same time, supplies power to the load.

Stand-alone capability: A line-commutatedinverter uses the 50Hz/60Hz signal from thegrid to regulate the frequency of its output. Such



units are not for use in stand-alone systemsunless it is planned to keep a diesel on continu-ously. A self-commutated inverter doesn’t needthe grid for frequency regulation. Related con-siderations are how tightly the inverter can regu-late frequency and voltage and its ability tosupply reactive power.

One-phase or three-phase: Whether to get aone phase or three phase inverter depends uponthe loads to be served and the type of distribu-tion system to be used. Three phase inverters aremore costly than one-phase inverters becauseeach phase requires a separate inverter stage. Aconsideration when selecting a three-phaseinverter is its ability to serve unbalanced loads.

Sizing: Inverters are usually sized accordingto their maximum continuous power output.Most inverters, however, are capable of handlingsignificantly more power than their rated size for short periods of time. This surge capability isuseful for meeting the occasional oversized loadsuch as starting a motor.

Costs: Inverter costs are roughly $600–$1,000per kW for good quality modified sine- waveinverters. The technology for inverters largerthan 5 kW is not as mature as for smaller invert-ers and costs may be somewhat higher.

Controllers/Meters/Balance ofSystems

Introduction Controllers and meters act as the brains and

nervous system of a RE or hybrid system. Con-trollers route the energy through the systemcomponents to the load. Metering allows theuser to assess system health and performance. Inmany cases, the various controlling and meter-ing functions of a system will be spread out overseveral different components. The complexity ofthe controls depends upon the size and complex-ity of the system and the preferences of the user.Controllers have had problems with reliabilityand lightning strikes, making careful controllerdesign and lightning protection important con-siderations.

Purposes and Functions• Battery high/low voltage disconnect: A high-voltage disconnect protects the battery againstovercharging. A low-voltage disconnect protectsthe battery against over discharging. These arecritical functions that should be included in allsystems with batteries.

• System protection: A controller can includefuses or breakers to protect against short circuitsand current surges.

• Battery charging: A controller with a properbattery charge algorithm (with temperaturecompensation) will do much to increase batterylifetime.

• AC and DC bus current and voltage monitor-ing: Monitoring the current and voltage on theDC and AC buses lets the user check that thecomponents and system are properly operating.

• Turn components on or off: The controller canbe programmed to turn components on and offas needed without user intervention.

• Divert energy to a dump load: The purpose ofa dump load is to shed excess energy. Dumploads may be needed if the system contains windturbines, micro-hydro, or generators. A dumpload is essentially one or more big resistors thatdissipate electricity by converting it to heat.Available dump loads are either water- or air-cooled. Dump loads are sometimes used to con-trol the frequency of the AC output of a system.

• Balance of system (BOS): The BOS includesthe additional items such as wiring, conduit, andfuses that are needed to complete a system.

• DC source center use: Several manufacturersnow offer DC source centers. These combinemuch of the system wiring, fusing, and con-trollers into one tidy, easier to install package.The use of source centers will increase systemcosts somewhat, but offer easier system installa-tion, less complex wiring, and easier systemmonitoring and control. The use of a source cen-ter should be considered, especially for systemsin remote sites that lack easy access to technicalassistance.



CHAPTER 4: SYSTEM SELECTIONAND ECONOMICS

IntroductionThe first section of this chapter describes life-

cycle cost analysis and explains how and why itshould be used when analyzing the economics ofvarious options. The second part of this chapterdiscusses the various factors influencing systemdesign: load, available resource, componentcosts, and desired level of service. Included arecharts that show how typical system costs varyas a function of load and resource.

Life-Cycle Cost Analysis

Why Use Life Cycle Cost Analysis?A common error when performing simple

economic analysis is basing the analysis uponinitial cost and short time periods. Because thetotal cost of a project is the sum total of its initialcost and its future costs, life-cycle cost (LCC)analysis is more appropriate. Initial costs areincurred at the beginning of the project; thesetypically include expenditures for equipmentpurchase and installation. Future costs areincurred later in the life of the project, includingoperation and maintenance costs such as person-nel, fuel, and replacement equipment.

System options will have different combina-tions of initial and future costs, making consis-tent comparison between the options moredifficult. This issue is pertinent to school electri-fication because RE options tend to have highinitial costs and low operating costs whereasgenerators have low initial costs but high operat-ing costs. Choosing options based solely on ini-tial cost may lead to higher overall costs over thelife of the system.

LCC is the preferred method for evaluatingthe economics of different projects with differinginitial and future costs. LCC involves calculating

the total cost of an option by summing the dis-counted annual costs of that project over its life-time. Any economics textbook will provide moredetails on how to do an LCC analysis. The resultsof LCC and most other economic analyses aresensitive to the inputs; thus, parametric analysisshould be done over a plausible range of inputvalues.

LCC implicitly assumes that the optionsbeing compared provide comparable levels ofservice. If the options provide differing levels ofservice, this difference should be accounted forin the option selection process.

Operating CostsSome RE projects fail or incur higher than

expected operating costs caused by improperinstallation and lack of operator training. Suffi-cient project funds should be allocated to ensureproper training of installers and operators.

The cost of servicing single systems in dis-persed communities can also contribute to highoperating costs. The cost of servicing RE systemscan be greatly reduced if the systems can be ser-viced locally and the service costs are sharedwith other applications in or near the commu-nity.

Fuel SubsidiesIn many countries, fuel costs are artificially

low because of government subsidies. The prob-ability and effects of the removal of fuel subsi-dies some time during the lifetime of the projectshould be considered.

Income GenerationRE systems often produce excess energy,

which can be used to generate income in thecommunity. This income can be accounted for inthe LCC analysis.

Design Considerations and Economics

This section describes the factors that affectsystem configuration and costs. The main con-siderations driving system selection are load,



resource, costs (component, fuel, and operating),and quality of service.

LoadThe load is a major driver of RE system

design. A designer needs to know the peak load,the average load, the seasonal and diurnal loaddistribution, and the quality of service needed.

Determining in advance the energy load of aschool is a study in itself. Questionnaires andmethodologies have been developed that permitthe detailed assessment of the potential energydemand for the school. Unfortunately, given thegeneral lack of resources in most instances,detailed assessments are not made. Planners anddesigners of projects are located at considerabledistances from the schools and often providestandard designs.

A number of considerations affect theamount and type of energy needed at a particu-lar school. They include:

• The projected operating hours of the school(Both time of day and time of year). Early morn-ing, late afternoon or evening classes will lead toa larger lighting load than schools with a strictlydaytime schedule. In some areas, schools don’toperate in the winter due to excessive snowfall.These schools will have a reduced heating loadcompared to a similarly situated school thatoperates in the winter. The effect on energydemand of local conditions, such as the modifi-cation of of school hours during planting andharvesting seasons should also be taken intoconsideration.

• Except in circumstances where solar cookingproves practical, a school offering a hot meal willhave larger fossil fuel or biomass requirements.

• Energy requirements of teacher and family: Inmany remote schools in developing areas, theteachers generally come from urban, developedregions of the country. They are by no meansaccustomed to living without regular and reli-able sources of energy. In order to ensure stabil-ity, it is vital that they can be comfortable so thatthey can fulfill the conditions of their teachingcontracts.

• Whether the school is primarily used in thedaytime for education, and the degree to whichit is used as a community center during non-school hours, and whether there are student resi-dents on a regular basis.

• The design and construction or the school andrelated buildings. Proper building design canreduce energy requirements tremendously. Day-lighting reduces the need for lighting during theday. In cold climates, adding proper insulation,sealing the building and proper passive designwill reduce the heating load.

All of the above factors have a direct impacton the energy demand in the school for a varietyof services including electricity, thermal energyfor space and water heating, cooking energy forthe provision of meals, etc.

The system components, especially thewiring and power electronics, must be sized sothat the system can deliver the peak load. Theaverage load drives the size of the energy pro-ducing components and influences the compo-nents selected. PV systems are most competitiveat meeting loads of less than 1-2 kWh per day,and may be competitive at meeting larger loadsas well. Wind turbines and generators becomemore competitive with somewhat larger loads.Diurnal and seasonal load variations must beconsidered and may influence component selec-tion. Summer and daytime loads favor PV. Win-ter loads may be more suited for generators; ifwinter is the windy season, wind turbines maybe a good choice. If the wind and solar resourceare seasonally complementary (i.e., the windresource is good during the low-insolation sea-son), then a wind-PV hybrid system may bemore appropriate.

The last important load-related considerationis the quality of service desired. Quality of ser-vice refers to the system’s capability to meet theload given the variability in the solar and windresources. For a 100% RE system, the costs maybe excessive if very high quality of service isneeded. If system components, especially thebattery bank, are sized for the worst possible



case, the system will be oversized at all othertimes.

A school may have a mixture of critical andless critical loads. In this case, with proper loadmanagement, the system can be designed to besomewhat less robust than would be needed ifall the loads were critical. During times of lowresources, the less critical loads are turned off.

Even with the extra costs associated withhigh levels of service, 100% RE systems are oftenstill the most cost-effective solution for meetingthe small electrical load demands of ruralschools. A lower quality of service requirementwill improve the economics of RE in general andwind turbines in particular.

ResourcesThe available wind and solar resources

greatly influence both the configuration and thecost of a hybrid system. A good wind resourcewill favor the use of wind turbines, whereas a

good solar resource will favor the use of PV.Another consideration is the variability of theresource, both daily and seasonally. For a stand-alone RE system, the designer may be most inter-ested in the monthly average resource and sizethe PV array or wind turbines (or both) basedupon the lowest resource month. For a systemwith generator backup, basing the size of the REcomponents upon the average annual resourcemay be more appropriate.

Most locations experience seasonal varia-tions in solar insolation and wind speed distribu-tion. These variations make it difficult to getconsistent production from PV arrays and windturbines. Seasonal variations in insolation areusually driven by the changing length of the dayas the seasons progress. This type of variationcan be partially overcome by proper tilting of thePV panels. Insolation may also vary because ofthe existence of a rainy or cloudy season. Thewind resource is also often seasonally variable.

Even areas with relatively goodwinds often have a one or two monthperiod of low average wind speeds.In this case, a wind/PV, wind/dieselor wind/PV/diesel hybrid may beappropriate.

Although long-term averagesdrive the sizing of the wind turbineand PV capacity, the short-term (onthe order of days) fluctuations inwind and sun will influence theamount of storage required. Thelonger the expected length of lulls in the wind and sun, the larger theamount of storage needed. Theselulls drive up the cost of 100% RE systems. Systems with generatorback up do not need batteries sized to meet the largest anticipated lull in the resource.

Some of these points are illus-trated in Figure 4.1. This figureshows, for a particular location andset of cost assumptions, how the con-figuration of the lowest cost system


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Figure 4.1. This graph shows the least cost configuration for ahypothetical school as a function of average wind speed andaverage daily solar insolation. The results are meant to showgeneral trends only, and may not apply to a particular site. PV =photovoltaics, WTG = wind-turbine generator. Source: Author’sanalysis.


varies depending upon thelocal solar and wind resource.

Figure 4.2 shows the typi-cal range of costs for PV andwind-turbine generator(WTG) systems over a range ofloads. Each graph shows twobands that reflect costs giventwo levels of resource avail-ability. Because these are 100% RE systems, the resource levelis not the annual average, butrather the average for theworst month. A couple ofexamples will clarify the use of the graphs. Figure 4.2 (top)shows that a PV system capa-ble of handling an averagedaily load of 0.5 kWh, in alocale with the worst monthinsolation (3.0 sun hours/day),is expected to have a 25-yearnet present cost of between$2,500 and $5,000. Figure 4.2(bottom) shows a WTG systemthat meets an average dailyload of 1.0 kWh costs between$4,000 and $8,000 in a locationwith a worst month averagewind speed of 5.0 m/s.

GeneratorConsiderations

For larger loads (above~1–2 kWh/day), the big deci-sion is whether to use a gener-ator. Ultimately, this decisionwill depend upon an analysisof the site in question. The bigadvantage of generators istheir ability to provide poweron demand. The disadvan-tages of generators includehigh operating costs, becauseof fuel and maintenance, aswell as noise and pollution.


Figure 4.2. These graphs show the typical cost range of the listedtechnology (photovoltaic or wind turbines) for a system as a functionof average daily load. The resource availability listed (for both windand sun) is the month with the lowest resource availability. Source:Author’s analysis.

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Resource amounts below are for lowest resource month


Providing fuel and mainte-nance to remote sites is oftenproblematical. Figure 4.3shows the 25-year net presentcost (NPC) of a 2.5 kWhdiesel generator as a functionof average daily load andaverage daily run time. TheFigure plainly shows that it is the number of operatinghours that drives the cost ofusing a generator. If the num-ber of operating hours is low,generators can be competitivesources of energy. As theoperating hours increase,costs escalate. If the loadsconsist of things such aslights and water pumps thatare only on a few hours perday, then an all-diesel systemmay be cost competitive.

If the generator must berun more than a few hoursper day, another solution is needed. One possible solution is to use a generator-battery system. When the

generator runs, it charges a battery bank that willthen be used most of the time. The savings fromreduced generator run time vastly outweigh theconversion losses caused by cycling energythrough the battery.

Another solution is to combine the generatorwith PV panels and/or wind turbines, and bat-teries. The RE components minimize the genera-tor run time, keeping the generator operatingcosts to a minimum. The generator precludes theneed to oversize the RE components and thusreduces the capital costs.


Figure 4.3. This graph shows the 25-year netpresent cost of operating a diesel generator. Thetwo variables are average daily load (kWh/day) anddaily run hours. Note how the costs vary onlyslightly with load, but escalate rapidly withincreasing run hours.

Analysis assumptions:Generator Size: 2.5 kWGenerator Cost: $1,750Generator Lifetime: 25,000 operating hoursLevelized Maintenance Cost: $0.07/operating hourFuel Cost: $0.50 literNo Load Fuel Consumption: 0.125 liters/hourMarginal Fuel Consumption: 0.25 liters/kWhDiscount Rate: 5%

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CHAPTER 5:INSTITUTIONALCONSIDERATIONS

Chapter IntroductionAlthough this Chapter focuses mostly on

various institutional, organizational, and socialissues that should be addressed prior to initiat-ing a large-scale project, much of the informationin this Chapter is also applicable to smaller scaleprojects as well. The advantages and disadvan-tages of various institutional arrangements arediscussed. The need to provide adequateresources for post-installation service and sup-port is stressed throughout this Chapter.

IssuesReliability, convenience of use, and cost-

effective supply are major considerations forenergy delivery systems for virtually all applica-tions. For many remote community schools,there is often a lack of basic services, includingrunning water for washing and toilets as well asenergy for lighting, heating, and cooking. Allthese applications require energy.

Despite increased government and donorspending on RE systems for rural schools, theseprojects remain underfunded. In many countriesoperation and maintenance of existing servicesto schools often occupy most of the budget allo-cation, leaving little for upgrading rural schoolswith RE systems.

Policy and PlanningPolicy and planning concerns with respect to

energy supply to rural schools should include:

• Availability and quality of information: Typi-cally, little information about energy supplyoptions, particularly RE systems, is available indeveloping areas. Without good cost and relia-bility data, planners cannot make good decisionsabout which technologies to use.

• Resource assessment: Renewable energyresource data is usually unavailable. The datathat does exist often has not undergone any qual-ity control or analysis. The solar and windresource should be assessed to determinewhether they are adequate to operate RE sys-tems at the time of the year when the school is inuse. Similar considerations apply to projectsusing biomass.

• Availability of rural energy specialists: Publicagencies often lack energy specialists capable ofdetermining which technologies are most appro-priate for a particular application.

• Financial considerations: If the system is notexpected to be self financing, then options forsupplementary financing include subsidies, fis-cal incentives, and low interest loans.

• Technical options: This requires an assessmentof resource availability, energy demand profile,life-cycle costs, and environmental considera-tions. Electricity generation can make use ofwind, solar PV, micro-hydro, or biomass firedgenerators. The merits of mini-grids versusdirect application in a school may need consider-ation. Thermal energy needs can be supplied bysolar/wood-charcoal/biogas cook stoves, bio-mass/passive solar space heating, and solarwater heating.

• Combined applications: A facility can bedesigned to serve multiple uses. For example, aschool may also be used as a health clinic and acommunity center. Other applications that maybe served in addition to a school, include waterpumping and battery charging. Planning for suchcombined applications can make the systemmuch more valuable to the community for only a small additional cost. Combining applicationsmay allow the agency/organization paying forthe school RET to cost share with other agencies.

Barriers• Initial lack of institutional capacity (in imple-mentation, operation, and maintenance infra-structure).



• Lack of information about the various ruralenergy supply options.

• Perceived risk of introducing new technologi-cal systems based on RET’s by administratorsfamiliar with conventional energy systems.

• Import restrictions and other trade barriers;duties can distort costs and lead to inappropriatetechnology choices.

• Privatization of state-owned enterprises cansometimes lead to a decline in rural energy supply.

• Perceptions that RETs are too costly due to thecomparing options using initial cost rather thanlife cycle costing.

• Fuel and grid extension subsidies discouragethe use of RETs by reducing the cost of conven-tional energy technologies.

• Remote rural schools may have difficult access,thus hindering system installation and follow upmaintenance.

• In many countries, policies concerning the useof renewable energies for rural applications arenon-existent.

• Unclear institutional roles and responsibilities.

In many countries, schools are frequentlyunder national government control. In othercountries, they come under regional, state orprovincial purview. Additionally, religious andethnic schools are operated by a variety of non-governmental organizations (NGOs). This diver-sity can mean that there is no universal policyframework upon which to build a strategy forRE use in schools. Programs will have to bedeveloped at the national, provincial, regional orlocal level on a country by country basis. There-fore, considerable effort may be needed in manycountries to bring together the key parties at various levels to develop national-level commit-ments that will facilitate removal of barriers suchas import duties on RE equipment and subsidiesfor fossil fuels. Commitment on the nationallevel can lead to the creation of an adequate technical infrastructure for the operation andmaintenance of RET systems.

Delivery ApproachesSeveral channels exist for implementing

RETs in rural schools. Three commonly usedimplementation models include:

• Government agencies handling all activities

• Implementation using a combination of gov-ernment agencies and private companies

• Implementation by NGO’s (frequently involv-ing both Government and private sectors).

Regardless of the model used, the approachshould assist the country in establishing anindigenous supply and maintenance capabilityfor RET systems. The ultimate aim is the sustain-able and appropriate application of RE systemsin schools and other public and private buildings.

Management andImplementation byGovernment Agencies:

In this institutional approach, the govern-ment, e.g., Ministry of Education, does the plan-ning, system design, installation, maintenance,and repair of the RE systems. Often, it will relyon another government agency (e.g., the govern-ment owned utility or the Ministry of Energy) todesign, install, and implement and maintainenergy systems.

There are certain advantages to using thisapproach, one of which is that generally, theschools come under the purview of a Govern-ment Ministry. In any case, Governments mustorder the components for the different systemsfrom the private sector, where they are eithermanufactured or where the importation of theircomponents is handled.

In addition:

• National education programs have an estab-lished infrastructure for planning, management,technical, and logistical support to rural schools.This existing infrastructure may be used toimplement RE systems.



• Programs on a national scale may be largeenough to have sufficient critical mass todevelop and support a service infrastructure.

The disadvantage of the institutionalapproach to managing RE systems is that a lim-ited number of trained personnel in governmentservices familiar with RETs, both in numbers andtechnical experience, are available to accommo-date the needs of all regions of the country. Thesame will commonly apply to Ministry of Educa-tion technicians, who may be familiar with con-ventional energy systems, but will need trainingin the installation, maintenance, and repair ofenergy and RE systems. Proper training of tech-nicians will create a solid infrastructure, particu-larly in the early stages of planning, toadequately deal with RET systems.

Combined Government/PrivateSector Approach:

Another operational scenario uses manage-ment of the implementation programs by gov-ernment agencies with the actualimplementation using private contractors. In thisapproach, government officials plan the pro-gram to include RE solutions, and issue requestsfor bids to provide equipment and services. Pri-vate contractors provide equipment includinginstallation services. In addition, the contractormay provide maintenance and repair servicesunder a service agreement. Alternatively, theMinistry of Education may accept the serviceresponsibilities once the installation is complete.In Argentina, this is the model that has been usedsuccessfully to date in the provinces of Neuquénand Salta as part of a larger electrification con-cession. (See Case Studies One and Two in chap-ter Six). South Africa also used this model in itsschool electrification program. The utility,ESKOM, designed the systems and private con-tractors did the installations. The program wasdone this way to assist the development of SouthAfrica’s RET industry.

There are some advantages to this type ofprogram:

• Private contractors in the business of sellingand installing RE systems are usually equippedwith the knowledge, skills, and tools to providethe required services on a contractual basis.

• Ministries of Education may be betterequipped to establish and manage the programfor supply and implementation of RET than toactually perform the installation.

• Competitive procurements often result inlower costs.

With this type of institutional configuration,it is important for government agencies to pro-vide clear specifications for the procurement ofequipment and standards of acceptance for thequality of installations in the field. In addition,they will need to detail the needed user trainingand post installation maintenance support thatthe successful bidder will be expected to pro-vide. This will result in higher quality installa-tions that will have lower failure rates and thuslower maintenance and repair costs. With theproposals that fail to meet the standards screenedout, government purchasing agents can selectthe best offer from among the remaining propos-als, without having to be concerned with signifi-cant differences in the relative quality of thesubmitted proposals.

Training of RET system operators is essentialto ensure that systems will function with a mini-mum of down time. Any operator training andpost-installation maintenance support requiredof the contractor should be clearly specified.

Government agencies can also certify thatprivate contractors are competent to install systemsprofessionally in the field and establish lists ofqualified bidders for the installation of RE systems.

However, in many developing areas, compe-tent private sector contractors may not exist ormay be reluctant to undertake work in remoteareas because of excessive transportation andlabor costs that result in low or negative margins.



Management andImplementation by Non-GovernmentalOrganizations

Many NGOs run educational facilities inrural communities. In this approach, the NGOprocures, owns, operates, maintains, and repairsthe RE system.

Primary education throughout the world isunder the aegis of Government Ministries, whoprovide school-operating permits and set educa-tional standards. Hence, the NGO is directly intouch with public officials and can be broughtinto the loop when they are planning and imple-menting national or regional RE programs.There are other advantages:

• NGOs are often run by committed and moti-vated individuals who operate efficiently andeffectively on limited budgets. Decision-makingand project implementation is generally lessbureaucratic than a government process.

• NGOs generally have strong community rela-tionships. Consequently, they may be better ableto generate community support and participa-tion as well as collaborate with other service sec-tors such as health, agriculture, and enterprise.

In dealing with NGO’s, one must bear inmind the following:

• NGOs generally operate programs for a lim-ited number of establishments that they operateand maintain themselves. The scale of their pro-gram may not lend itself to significant support ofa commercial service infrastructure.

• NGOs may not have the specialized technicalknowledge or skills to implement RE technolo-gies without technical assistance.

• Small NGOs often have limited cash flow thatconstrains their ability to maintain the installedsystems.

It is important to incorporate a realisticunderstanding of the operating characteristics ofNGO’s into future Government planning vis àvis the introduction of RE techniques. For exam-ple, in the Bangladesh Biogas Case Study, CaseStudy #5, the school is an NGO whereas theplans and specifications for the biogas plant andthe technical expertise are vested in governmentor para-government agencies. In order to main-tain these plants in top working condition, itwould be essential to incorporate regular main-tenance and site visits of public sector techni-cians to ensure that the local staff are trainedproperly and that they are executing the opera-tion and maintenance activities correctly.

Service InfrastructureAn infrastructure includes a committed and

reliable institutional chain of command, ade-quate communication and transportation ser-vices, and the technology support structure(technical expertise, maintenance services, spareparts, etc.). Such an institutional infrastructure isessential so that operations concerning the pro-ject can be carried out with the least difficultyand expense, and within a reasonable timeframe. This structure might include, for instance,the schoolteacher or principal, the regional orprovincial school board, and the planning levelabove that. In addition, it may also include thelocal teacher, representatives of the local utility,and its chain of command.


Figure 5.1. Technician training course.

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Reporting on system operation and malfunc-tions, and the timely delivery of parts and ser-vices require satisfactory communication andtransportation services. Proper communicationsequipment (e.g., short-wave radio) can be veryuseful in ensuring timely delivery of messages,services, and supplies.

Although the RETs under consideration arecommercial, in remote areas of the developingworld, there is frequently a lack of well-devel-oped and reliable services to install, maintain,and repair systems in the field. This service infrastructure is not always easy to set up, but iscritical to the success of a project. If the RETinstallation is the first or one of the first in anarea, implementers need to consider carefully:

• Reporting system malfunctions: who reportsthem, how are they reported, and to whom dothey report?

• Maintaining the system: who maintains it andhow?

• Maintaining a local stock of critical supplies,spare parts, and test equipment: who orders theparts or supplies, who supplies replacementparts, and how are these parts delivered (espe-cially to remote areas)?

• Arranging regular training of field techni-cians, operators, and users: who arranges thetraining, and where will the training take place?

• Arranging training of new staff: how can newstaff at a particular school be re-trained?

• Replacing failed and worn out components:is there a budget for replacement parts and com-ponents, and what is unacceptable downtime?

User Interface/Training of Users

Training at all levels, from policy makers tosystem users, is a critical requirement for sus-tainability and replication. Training is requiredfor all aspects of the project, including analysis,


Figure 5.2. Individual photovoltaic (PV) power systems at this village school in Ceara, Brazil areproviding electricity for television, refrigeration, street lighting, and water pumping. International PVprojects such as this one (partially sponsored by DOE and Brazilian utilities), are often financedthrough utilities, banks, or other governmental organizations.

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design, implementation, operation, mainte-nance, and evaluation. At the planning and deci-sion-making level, training efforts should focuson information transfer and comparative analy-sis methodologies. In addition to initial training,there must be periodic refresher training. Due toturnover in the ranks of users and technicians,provision must be made to train individuals whobecome responsible for operating and maintain-ing RE systems in the months and years after theinitial installations. It may be desirable to offeran accreditation program to the technicians.

In order to assure continuity in the operationof the RE systems, regular servicing by compe-tent specialists is important. In addition, trainingthe end users (i.e., the local teacher(s) and theschool custodians) in operation and maintenanceprocedures will pay dividends since RE special-ists may only be able to make periodic visitsbecause of the remoteness of the school location.

In order to ensure adequate training in RETsat all levels, from system design to installationand maintenance, people with sufficient experi-ence and understanding of local conditionsshould provide this training. These personsmight not always be available and this couldconstitute a major barrier to the proper introduc-tion of RE systems into a region. One method for establishing regional capability is to set up

regional centers of excellence affiliated with localuniversities. An example of this is the Center forthe Study of Wind Resources (CERES) at the Universidad de Magallanes in Punta Arenas,Chile. These Centers can provide design, train-ing, and technical assistance to projects in thesurrounding area.

Financing Questions:In some instances, financing limitations con-

stitute a major barrier to the introduction of REsystems. Adequate financing by itself, however,will not ensure that systems are properly man-aged and operated. Financing will be needed forthe RE system program design, the purchase ofequipment as well as the operation and mainte-nance of the systems, training, and if it doesn’talready exist, the establishment and support of asupply and maintenance infrastructure. Thereexist unfortunate examples where nationalauthorities and international agencies have pro-vided funding for hardware and short term visiting specialists, only to have the systemseventually fail for lack of funds for completetraining, operation, and maintenance, infrastruc-tural support and communications. The lessonsof the past need careful examination to ensuregreater success with new RE programs.



CHAPTER 6: CASE STUDIES

Chapter IntroductionThis chapter provides six case studies. The

case studies highlight different aspects of RETimplementation in schools. Combined, the casestudies provide valuable lessons that can be usedto improve future projects.

CASE STUDY #1A — School Electrification Programin Neuquén, Argentina

IntroductionThis case study is divided into two parts.

This first part describes the overall program. Thesecond part describes a specific school in moredetail.

BackgroundThe province of Neuquén is located along

the Andean mountain chain in the northern section of Patagonia, stretching from latitude36°S to 41°S. The province covers approximately94,000 km2 and has a population of 250,000(1991). Warm, dry summers and cold, dry

winters characterize the area. Night time tem-peratures often drop below freezing even in thesummer. The annual average solar radiation isaround 4.0 sun-hours per day, with seasonalextremes of 1.2 sun-hours/day in the winter, and7.0 sun-hours/day in the summer. The Westernhalf of the province is largely rural and moun-tainous with difficult access by road.

The local authorities have recognized that itis important to provide education in theseremote communities. Hence, there are more than150 schools located in remote and rural areas ofthe province. Because of the difficult access andheavy winter snows, many of the more remoteschools operate on a spring/fall schedule andshut down during the winter. Teachers typicallylive on-site in adjoining or nearby housing.

Of the 112 schools for which information isavailable, 34 are grid connected, 43 have gas ordiesel-powered electrical generators, 27 use pho-tovoltaic systems as their only source of power,and eight have no electricity. Nearly all of theschools have gas-powered stoves with which tocook, and wood stoves to bake bread. Wood orbottled gas is burned for water and space heat-ing. In some of the schools, gas or diesel genera-tors, when functioning properly, provide powerfor lighting and for pumping, distributing, andsometimes, heating the water. Most of the remoteschools have battery-powered radio communi-cation systems. At some schools, two small PVpanels, mounted on an antenna tower, charge 12-V DC batteries for the radios. All of these systems require maintenance, which the school-teachers undertake.

The principal alternative to PV are motorgenerator sets. The relative inaccessibility of thesites hampers proper maintenance and conse-quently these units are frequently out of service.The low population density of the region makesgrid extension unlikely for most of the schools.For these schools, photovoltaic systems offer agood alternative. The PV systems must be prop-erly designed, installed, and maintained—atten-tion must be paid to training local operators.


Figure 6.1. Typical PV panel installation, NahuelMapi, Argentina.

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The Renewable Energy ProgramThe Renewable Energy Program envisages

the installation of photovoltaic systems (and to alesser degree, wind-electric generators) in ruralschools. During the period 1987 to 1989, theDirección Provincial de Telecomunicacionesinstalled PV panels at schools for radio transmit-ters. The first PV system for lighting and educa-tional aides in a school was installed in 1987.Since 1994, 26 additional PV systems and onewind-turbine system have been installed. Thereare no plans to extend this Program. The installa-tion of additional PV systems generally respondsto a request coming from the schools.

These photovoltaic systems are designed toprovide electricity for the basic needs at theschools; lighting classrooms and operating smallelectrical appliances, such as short-wave andAM/FM radios, VCRs, and televisions. In gen-eral, the systems do not provide enough energyto operate large appliances such as microwaveovens, washing machines, refrigerators, andpower tools.

The main organizations involved in the pro-gram are the Consejo Provincial de Educacióndel Neuquén (responsible for education in theprovince of Neuquén) and the local utility (EnteProvincial de Energía del Neuquén—EPEN).EPEN purchases and installs the equipment andprovides maintenance. The provincial govern-ment pays the capital, installation, and mainte-nance costs.

User TrainingEPEN provides system maintenance training

to the teachers. Each school receives a manual ofoperation and maintenance for the PV system.The teacher is responsible to verify that the bat-teries are properly functioning, the regulatorsare working, and the PV panels are clean. Theteacher reports system malfunctions directly toEPEN offices.

EPEN has an agreement with the ProvincialSecretary of Education to provide technical sup-port to the Educational Program on RenewableEnergy and Rational Use of Energy. EPEN staffgives courses for teachers and helps in the prepa-ration of educational material.

This Program makes use of the Demonstra-tion Center for Solar Energy Technologies estab-lished in Neuquén City, a co-operative programwith the Brace Research Institute of McGill Uni-versity, Canada. At this location, trainees areexposed to a variety of RE applications (includ-ing solar water heating, solar cooking, PV waterpumping and lighting, improved wood stoves,and solar drying).


Figure 6.2. RE Training and demonstrationcenter, Neuquén Argentina.

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Figure 6.3. PV powered lights at a high school in Butalon Norte, Neuquén Province, Argentina.

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Institutional Aspects:In Argentina today there are several com-

panies selling PV equipment, including manu-facturers and importers. These companies havedealers in many cities that offer services andspare parts. However in the rural areas, services are very limited and replacement parts must often be ordered from the companyheadquarters.

Despite the limited presence of RE compa-nies in the rural areas, the installation of a PVsystem in a school is often followed by the instal-lation of additional PV systems in the surround-ing community. These systems have proven to bethe best choice for providing energy to remoterural dispersed houses. The rural people haveadopted this technology without problems.

Program AssessmentIn general, the photovoltaic and battery sys-

tems work satisfactorily. Most problems occurwith system maintenance and the training of thelocal residents. To remedy these problems, amaintenance manual was written that providesstep-by-step instruction in system maintenanceprocedures. Educational aids have been devel-oped and demonstration workshops held toimprove understanding of the systems. The highturnover of teaching staff makes it is essentialthat the school caretakers be involved in the useand maintenance of the systems. Steps have beentaken by the utility to ensure that their localoffices verify system maintenance. A thoroughpreliminary analysis of the energy and logisticsproblems at the schools is essential to achieveoptimum technical and operational perfor-mance. Equipment should have minimum main-tenance requirements and be easy to operate. It is important for the program to go beyond justthe photovoltaic system components to includetraining manuals, training courses, systemsmanagement, and equipment.

CASE STUDY #1B — School Electrification in Nequén, Argentina

An example of the PV equipment and instal-lations for school #293, Villa Puente Picún Leufú,highlighted below, is typical of the technical set-up at the other PV electrified schools in Nequén.

Location of the SchoolSchool #293—Villa Puente Picun Leufu—

Departamento Catan Lil (39°10'S-70° W),province of Neuquén, Argentina.

The school is located in a mountainousregion approximately 250 km west of the city ofNeuquén.

Description of SchoolThe school is a stone and brick building,

270 m2, all on one floor. It has a pitched roof withthe long axis in an east-west direction.

The school operates from the period Septem-ber to May (summer cycle). The normal dailyoccupancy time is 08:00 to 14:00 hours.

Students and StaffThe school has 25 students, one teacher, and

one porter. The students leave at the end ofclasses every day. There are occasional commu-nity meetings held in the school on an irregularbasis. One of the staff members resides at theschool.

Electrical Energy End Use in the School:Electrical energy applications consist of

40 lights of 20 watts each for a total installedcapacity of 800 watts.

There is also the following electronic equip-ment:

TV: 80 watts

VCR: 27 watts

Radio and tape recorder: 25 watts

Telecommunications equipment:there is aradio telephone that uses 120 watts while trans-mitting and 6 watts while on standby power



It should also be noted that no electricity isused for water pumping or water treatmentundertaken at the school. Nor is electricity usedfor water heating, space heating, and cooking atthis particular school.

Photovoltaic System DescriptionThe array consists of nine ground-mounted,

48-Wp PV panels.

Battery storage consists of 4–12 volt, 220 Ahbatteries. They are located in an insulated batterycontainer under the panels. There is one 12-voltregulator, maximum current from the panels is48 A, with load disconnection. A 250-wattinverter converts the 12-volt D.C. power into220-volt AC.

Installation InformationArgentinean suppliers provided all the

equipment:

• Solartec S.A. (Argentina) — modules, regula-tors, structure

• Williard Solar (Argentina) — battery

• HT Inverter (Argentina) — inverter

The equipment was installed in August 1997and is currently operating with no difficulty.

Financial Considerations• Cost of the PV system (including installationand taxes): U.S. $ 8,205.

• Cost of the internal installation (including lightfixtures, wiring, labor and taxes): U.S. $5,185.

Total Cost: U.S. $ 13,390.

The system was paid for by the Governmentof the province of Neuquén. Financial arrange-ments were handled by EPEN. The local govern-ment of Neuquén handles operation andmaintenance expenses. To date, the cost of main-tenance has been very low because the system isrelatively new and no parts require replacement.Based on EPEN's experience with other PV sys-tems in schools, the batteries should have a life ofapproximately 4 years. Other costs have beenestimated as follows:

• Replacement of PV modules: 1% annual

• Replacement of regulators and inverters: 5 %annual

The annual cost for maintenance is approxi-mately U.S. $500.

Operation and Maintenance (O & M) of the Energy System

The teacher and porter monitor the PV sys-tem. Repairs and maintenance are handled byEPEN. The school authorities are pleased withthe O & M situation. They have not noticed achange in the performance of the RE systemsince its installation.

Lessons LearnedThe principal problems with the RES encoun-

tered under this Program are:

• Lack of 12- or 24-V lights for this application(The lights available in the marketplace areemergency lights.)

• Problems with the inverters.

It should be noted that there have been noproblems with the use of PV systems in spite ofthe frequent change of teachers.

The principal lesson learned under this Pro-gram has been to confirm the advantages of REsystems compared to other stand-alone electricalgenerating systems.

AcknowledgementsInformation for these Case Studies comes fromGraciela Pedro of EPEN.

CASE STUDY #2 — The Concessions Program in Salta, Argentina

Background on the Provincial ProgramThe introduction of solar photovoltaic sys-

tems into rural schools in Salta has been ongoingsince 1991, when a number of schools and clinicswere equipped with PV systems. In mid 1998,however, a larger, more extensive program was



initiated and a significant number of ruralschools have subsequently been equipped withphotovoltaic systems.

Argentina’s remaining unelectrified popula-tion, estimated to number 2.5 million, liveswidely dispersed in rural areas. Because of thisdispersion, provision of electricity to this popu-lation through grid extension is estimated to costU.S.$8,000 per household. As a result, the Argen-tineans launched an innovative concession pro-ject, Programa de Abastecimiento Eléctrico de laPoblacion Rural Dispersa (PAEPRA) to facilitatethe introduction of RE systems into these iso-lated regions.

In the province of Salta, in northernArgentina, a concessionaire, Empresa ServiciosEléctricos Dispersos (ESED) installs the photo-voltaic systems, and the program is regulated bya Government agency, the Ente Regulador de losServicios Publicos (ERSP).

There are some 700 rural schools in theprovince of Salta that are not connected to thegrid, nor are they expected to be connected in thenear future. Of these, by February 1999, roughly130 have received PV systems, and a significantnumber in addition are slated to receive similarsystems during the next year.

Two companies, Solartec S.A. and BP Solar,provide the bulk of the photovoltaic systems forthe rural schools. The systems come in threesizes and are designed to provide 11, 15 and22 kWh per month, respectively. For the 11-kWhper month systems, the companies provide two75-Wp panels, along with a supporting structure,a charge regulator, batteries, and ancillary equip-ment. For the 15- and 22-kWh per month sizes,the systems contain three and four 75-Wp PVpanels, respectively. All systems are providedwith a manual covering installation, mainte-nance, and use of the systems.

ESED’s Obligation’s with Respect to School Electrification

Empresa Servicio Electricos Disperses(ESED) is the company that installs the PV sys-tems in the rural schools in Salta. They alsoinstall the internal and external wiring. Under its contractual obligations, ESED installs the systems and maintains them for the guaranteeperiod. They may later be subcontracted to pro-vide a service contract for system maintenance.

ESED is responsible for ensuring that the sys-tems are well mounted and that the users at theschool are trained in the operation and mainte-nance of the units. As non-electrified residencessurround the schools, one aim of the program isto acquaint the local inhabitants with the benefitsof RE systems.

The Role of ERSPThe Ente Regulador de Los Servicios Publi-

cos (ERSP) acts as an intermediary among thosewishing to be supplied with PV electricity, thecompanies supplying the services and equip-ment, and the funding agency, which is theprovince of Salta. The ERSP visits the areas inquestion and assesses their electrical needs. Thegovernment then subsidizes the installation andoperation of the appropriate PV system. In therural non grid-connected areas, applicationsinclude schools, clinics or individual house-holds. One of the high priorities is to make thepublic aware of this subsidized electrical service,


Figure 6.4. A PV system provides electricity tothis rural school in Salta province, Argentina.

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which the government offers through their con-tract with ESED.

As part of its intermediary function, ERSPmonitors and regulates the services provided bythe installation companies. By contractual oblig-ation, the installation companies are required toservice the PV systems. However, several factorscan stand in the way of prompt service.

1) All of the installation companies are based inSalta, the capital city of the province, and arelocated hours away by road from the remoteareas. This can cause long reaction times whenresponding to service calls from the remoteareas.

2) Many PV system users in remote areas don'thave access to local telephones for use in case ofa problem. Finding telephone services, or usingthe postal system, can be a lengthy process, leav-ing the user without electrical power for severalweeks or months.

3) The ERSP needs to examine claims by somePV system users prior to servicing. The installa-tion company is responsible for technical prob-lems with the PV systems, as well as anydifficulties arising from these technical prob-lems. If, however, the user has mishandled orneglected the proper operating guidelines of thesystem, then the individual is liable for the dam-ages. In this event, the user must be prepared topay for any repairs necessary.

For example, there have been some problemswith appliances short-circuiting when operatedfrom a PV system. In these events, the ERSPmust examine the situation to determine liability.If, for example, a fault in the PV system causedan overload leading to the short circuit, then theinstallation company must replace the appliance.If, however, the PV system for example wasdamaged by water leaking from an unrepairedroof, the user is at fault and the installation com-pany is not liable for any damages.

FinancingIn most cases, the government subsidizes the

installation cost. Generally, schools, clinics, andindividual householders request the installation

of PV systems directly from the ERSP. For exam-ple, a school in the Department of Anta, SantaRita, site #118, purchased a 22-kWh system. Thecost of the system was 450 Pesos (1 Peso =U.S.$1) of which the user was required to pay 100Pesos—i.e., 78% subsidy. Initially, the school wasthe only entity in the community requesting asystem. There are 14 residences in the immediatearea of the school. The PV system was installedin August 1998.

Program EvaluationInspection by ERSP representatives identi-

fied the following problems.

• Improper installation of PV panels in someinstances

• Varying inclinations of the solar panels (Thereshould be greater standardization within theprovince.)

• Shading of the collectors at different times ofthe year from large trees

• Poorly mounted panels are subject to theft.

One of the greatest concerns of the Ente Reg-ulador is that the local populations are not beingsufficiently informed and made aware of thegovernment subsidy program. Consequently,greater efforts are being made to publicize theprogram. To best promote the technology, visitsshould be organized to those locations that arealready equipped with PV systems. In this way,the local population can see functioning systemsand their benefits first hand.

AcknowledgmentInformation for this Case Study was provided by :

Pierre RieszerEnte Regulador de los Servicios Publicos (ERSP)Alvarado 6774400 Salta, Argentina



CASE STUDY #3 — Wind-Turbine Installation for a School in Chile:

IntroductionWind turbines supply electricity to a lodge

used by boarding students at a school in Chile.

The School and LodgingThe school, G-35 "Diego Portales" is located

in the village of Villa Tehuelche located about100 km from Punta Arenas. School is in sessionMarch through December. The lodge currentlyhouses 35 students (ages 6–14), and 3 adults (2inspectors and 1 teacher) during the school year.During the summer, the lodge is closed exceptfor some occasional weekend activities.

Electrical LoadsThe electrical load consists of 50 Philips

Lamps rated between 11 and 18 watts each. Onaverage, 10 lamps are on an average of sevenhours per day. In addition, there is a VCR and a20-inch TV set.

SystemInstallation took place from November 1994

through March 1995 under the direction of the

Center for the Study of Wind Resources (CERE)at the Universidad de Magellanes (UMAG) inPunta Arenas, Chile. Capital and installationcosts totaled $14,000 and were paid for usingregional funds.

The system consists of two Whisper 1000wind turbines, battery bank, controller, andinverter. The battery bank consists of eight Delco105 Ahr, 12-volt batteries. The controller wasdesigned and constructed by engineers from(UMAG). The inverter, rated at 1.5 kW, is fromTrace.

Operation and MaintenanceFour staff members have been trained to

operate the system. Backup maintenance is pro-vided by CERE/UMAG. Yearly maintenancecosts have proven to be variable but average$500 per year. ($300 for materials and manpowerand $200 for travel costs.) The batteries werereplaced in 1997 at a cost of $900.

AcknowledgmentInformation was provided by:

Arturo KuntsmannCenter for the Study of Wind Resources (CERE)Universidad de Magellanes (UMAG)Casilla 113-DPunta Arenas, Chile


Figure 6.6. Richard Hansen with students andstaff of the school at Santa Cruz Minas.

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Figure 6.5. Two 1.0 kW wind turbines provideelectricity to the dormatory of this remote schoolat Villa Tehuelche.

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CASE STUDY #4 — School Lighting in Hondurus

Introduction: In the aftermath of HurricaneMitch (October 1998) Soluz Honduras hasinstalled a PV lighting system at the elementaryschool in Santa Cruz. The lighting system is used to provide night literacy classes to the local population.

The School: Santa Cruz Minas is located inthe department of Santa Barbara in NorthwestHonduras. The three-classroom facility is cin-derblock construction with a corrugated cementfiber roof. There are five teachers, one of whomserves as the school director. The school servesover 200 students (grades 1—6) in two shifts, onefrom 08:00 hours until 11:00 hours and the otherfrom 14:00 hours until 17:00 hours.

The System: Soluz Honduras installed thePV system and wiring in February 1999. The sys-tem consists of a 50-Wp, pole-mounted PV panel,a controller with high and low voltage discon-nects and a 12-volt, 90 Ah battery. The battery,warranted for 18 months, is an imported modelpurchased through a local dealer. The applica-tions consist of six (two per classroom) 9-watt PLcompact fluorescent bulbs and one DC outlet.

Institutional/Financial Arrangements: SoluzHonduras is executing this project within theframework of its existing fee for service business.In this model, the customer pays Soluz Hon-duras a fixed monthly fee; Soluz Hondurasretains ownership of the system and is responsi-ble for system maintenance. Prior to the schoolinstallation, Soluz had performed about 20 homeinstallations in the area on a full-cost recoverybasis. The school project is similarly organizedwith Soluz owning the system, but in this case,waiving the monthly fee.

The PV modules were donated to Soluz toaid in the post-Mitch rebuilding effort. Soluz isdonating the lights, wiring, and use of the con-troller. The school purchased the battery withfinancing provided by Soluz. The school directorplans to use the proceeds from the adult literacyclasses to repay the loan and pay for replacement

batteries. Since Soluz retains ownership of thesystem (except for the battery), it can remove andrelocate the system if the grid is extended to thevillage or the school proves incapable of replac-ing/maintaining the battery.

The battery requires the most frequent opera-tor attention. School ownership of the batteryprovides an incentive to the school to properlymaintain it in order to minimize replacementcosts. This reduces the maintenance burden onSoluz and represents a tangible contribution bythe school and community towards the creationand maintenance of the system.

Soluz performs maintenance on the remain-der of the system, including replacement oflights. Because Soluz already has a maintenanceinfrastructure in the area, it expects the incre-mental cost of servicing the school system to bevery low.

Soluz has enough PV panels to replicate thisproject at another dozen schools using the samedonation arrangement. Soluz expects to performother school installations over the next year.


Figure 6.7. PV installation at Santa Cruz Minas.

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AcknowledgmentThe information was provided by:

Richard Hansen, President, Soluz, Inc.John Rogers, Vice-President for Engineering,

Soluz, Inc.55 Middlesex Street, Unit 221N. Chelmsford, MA, USA 01863-1561

CASE STUDY #5 — Biogas Plant in a Rural School in Bangladesh

Details of School LocationFaridpur Muslim Mission,Shah Farid Madrasah Building,Court Compound, Faridpur,Bangladesh.

The energy system at the school consists oftwo biogas plants of the fixed dome type (onlyone is currently in operation). Biogas is used forcooking only, and the sludge from the plant isused as a fertilizer.

The SchoolThe school consists of three tin-roofed shed

buildings with south-facing open verandas.They are 118 m2, 164 m2, and 170 m2 in area. The

buildings house a maximum of 400 orphans. Inaddition, there is a technical training center.

Students/StaffCurrently, the number of students/orphans

is 350 and there are 50 staff members (teachersand custodians, etc.) The normal school yearruns from January to December, with breaks during the summer and at the end of the year,plus religious holidays. The school week runsfive days a week, six hours per day.

This is a boarding school. Students reside atthe school all year long. In addition, 50 staffmembers reside at the school. The technicaltraining center is open to both the orphans and tooutside students.

Energy End Use in the SchoolA hand pump is used to pump tube well

water.

The largest energy use is for cooking. Thereare four burners, with one using biogas and theother three using wood fuel, cow dung, jutestalks etc.

Educational Aids: There are four computersand a printer.


Figure 6.8. Entrance to the Faridpur MuslimMission, Bangladesh.

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Figure 6.9. Biogas plant digester.

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The Biogas PlantThe biogas plant consists of: an inlet cham-

ber, where sludge is collected from the toilets; afermentation chamber; and a hydraulic chamberfor the residue. It is based on a design of a house-hold biogas plant using human excrement pro-vided by the Local Government EngineeringDepartment (LGED).

The plant is of the fixed-dome type originallydeveloped in China. The feedstock is primarilyhuman excrement. The biogas plant produces sixhours of gas per day, which is enough for oneburner only, and does not meet the entire cook-ing needs of the school. The second plant, whichis incomplete, was designed to operate on a feed-stock of cow dung, water hyacinth, and agricul-tural wastes.

Local masons, under the direct supervisionof LGED, constructed the plant. The plant wasconstructed from brick and cement that are pro-duced locally in Bangladesh. The constructiontook two to three months to complete in 1993.The plant has been in continuous operation sincethat time and is in good condition.

The total cost for the operational plant is Taka17,000 (U.S. $351), the non-operational plant costis Taka 30,000 (U.S. $619). LGED paid for the sys-tem and handled the financial arrangements forthe capital investment. The school pays for oper-ation and maintenance. In practice, O&M costshave proved to be negligible.

The cost of replacing the operational planttoday would be Taka 25,000 (U.S. $515) and thenon-operational plant would be Taka 40,000(U.S.$825).

Operation and Maintenance of the Renewable Energy System

The school superintendent and secretaryoperate the plant. Local staff does maintenanceand repairs. No major repairs have been under-taken in the first five years of the operation,except for a minor repair to the collection pit in1998. No specific training programs for custodi-ans or teachers have been instituted in the

operation and maintenance of the RES. Thoughschool administrators believe that proper train-ing would be desirable, they consider operationand maintenance to be quite adequate. No per-formance change has been noted over the years.System malfunctions are reported to the schoolsecretary who in turn notifies the Thana(precinct) engineer of the LGED.

Education and SocioculturalConsiderations

Since the installation of these biogas plants,no new RE systems have been installed at theschool. There has been no effort to use the plantfor educational purposes at the school. Therehave been successful installations of additionalbiogas systems in the local community. The prin-cipal barrier to the uptake of this technology inthe community is the cost and lack of financing.

The potential exists for the school to buildadditional biogas plants for lighting as well asfor additional cooking fuel. This would dependon the availability of feedstock to run the plant.There are no seasonal or climatic limitations tousing of the biogas plant on a daily basis. TheBangladesh Center for Scientific and IndustrialResearch (BCSIR) Dhaka is the national andregional support structure for this technology.

School officials have noted that it takes 50%less time to cook food on the biogas burner thanon a comparable wood-fuelled burner. As theraw material is human excretion, there are no


Figure 6.10. Oven fueled by biogas.

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costs involved for its collection. They find thebiogas is cleaner and more efficient than otherfuels and it is definitely socially acceptable.

AcknowledgmentsSylvia Mortoza and Amimur RahmanHouse 6Road 2/CSector 4Uttara M.T.Dhaka 1230Bangladesh

CASE STUDY #6 — A Renewable Energy Training Center in Lesotho

BackgroundThe Bethel Business and Community Devel-

opment Centre, (BBCDC) is a private agencywhose main goal is to develop the human, eco-nomic and technical potential of the area throughpractical education.

Details of TrainingTotal number of staff: 6.

Total number of students: 30 full time (2-yearcourses), 100 per annum (1-week courses).

Solar technology is taught as a core subject inthe two-year rural development curriculum.

BBCDC can accommodate 10 to 16 guests forshort courses, conferences, meetings, or retreats.It can also arrange for visits of several months by researchers and academics professionallyengaged in RE research or other aspects of ruraldevelopment.

Energy System Types/Services:Photovoltaics, solar ovens, solar water

heaters, underfloor solar mass heating systems,water tank mass heating system, solar green-house, radiative nocturnal cooler, passive solardesign, daylighting, hydraulic ram pumps, andbiomass for fuel wood coppice.

Renewable Energy System DescriptionPhotovoltaics: Four staff houses, a guest flat, aconference center, and a library-office buildingare each fitted with 12-volt, stand-alone photo-voltaic systems. Installed PV capacity is as follows:

• One-staff house: 220 watts, used for lights, 60-liter fridge/freezer, fan for solar underfloor heat-ing, small spin washer, desktop computer,printer, satellite telephone, and small powertools. The house is also wired for 220 volts andhas a 600-watt inverter.

• Two-staff house: 20 watts each, used for lightsand radio.

• One-staff house: 55 watts, used for lights andradio.

• One guest flat: 10 watts, used for lights.

• Conference Center: 150 watts, used for lightsand fans for underfloor heating, and 220 volts,used for the inverter for such equipment asvideos and an overhead projector.

• Library-office building: 220 watts, used forlights, television, satellite receiver, a 120-literfridge/freezer, and charging of cordless typepower tools.

Solar ovens: Household solar ovens are beingproduced at BBCDC on a commercial basis. Twolarge prototypes with glass area of 0.5 m2 and1.0 m2, respectively, are used in the schoolkitchen.


Figure 6.11. Main conference center showing REapplications.

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Solar water heaters: Two thermosyphon waterheaters are fitted on staff houses, each with 100-liter tanks and 1.2 m2 of collector area. The Con-ference Center is fitted with an integral designthermosyphon heater with 2 x 150-liter tanks,and a 6.4-m2 collector. One old batch-type waterheater is soon to be replaced by an upgradedthermosyphon model.

Underfloor mass heating systems: One staffhouse is built with rock storage beneath the floorslab that is ducted to a collector on a wall facingthe equator. A 12-volt fan is used to circulate air.The Conference Center is built with rock storagebeneath the floor slabs of the guestrooms. Hot air from clear glazed solar attics on the centralroof are ducted to the storage. Two 12-volt fanscirculate air.

Water tank mass heating system: An extensionto one of the staff houses has recently been com-pleted and includes an 8000-liter roof water col-lection tank. The tank is within the houseenvelope and is designed to thermosyphon inwinter to a ground mounted collector (4 m2). Thesystem is for space heating. It has not yet beenthrough a winter and is under testing.

Brace design greenhouse: Nocturnal tempera-tures of -10°C are common in Lesotho in winter.A 3 x 5 meter (Brace Research Institute design)greenhouse is built on the campus and used forseedling production. Thermal mass consists of

3 x 100-liter barrels of water. It remains frost-freeduring the winter months.

Radiative nocturnal cooler: The climate in thehighlands of Lesotho is suitable for radiativenocturnal cooling. A passive cooler is built on the Campus with eight cubic meters of interiorvolume. It is cooled by means of a roof pond and retractable roof. A 32-m3 cooler has recentlybeen built by BBCDC off-campus for a farmer'scooperative.

Passive solar design: The buildings are all welloriented and most of the residential buildingsare fitted with wall and ceiling insulation.

Daylighting: The Conference Center is builtwith daylighting in the main classroom and inthe bathrooms. Clear fiberglass panels are fittedon the outside, and a frosted glass panel is fittedon the inside ceiling. Light is tunneled usingordinary aluminized building paper. The interiorglass panel is hinged to allow cleaning. A recenthouse extension includes daylighting in thebathroom and a clerestory window. Recentbuildings have been fitted with double glazedwindow units built by BBCDC.

Hydraulic ram pumps: An old Blakes hydram isused to provide water for BBCDC and the BethelMission. BBCDC has also built ram pumps using5Omm and 80mm pipefittings and a few weldedcomponents.

Biomass for fuel wood coppice: the BBCDCcampus has been extensively landscaped withearthworks for storm water capture. The result isgreatly improved biomass production andpoplar bluffs are becoming rampant. Photosyn-thesis is after all, the ultimate energy creator onthe earth, and in arid climates water is the limit-ing factor.

Installation InformationPV panels and components have all been

purchased. All other solar energy systems are in-house products, assembled from raw materialsand basic components.


Figure 6.12. Staff house—note clerestorywindow.

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The following equipment has been used:

4 x 60-watt 12-volt panels: Solarex

4 x 55-watt 12-volt panels: Siemens

2 x 20-watt 12-volt panels (amorphous): Siemens

1 x 10-watt 12-volt panels: Arco

All other solar energy systems: BBCDC

Installations by: BBCDC staff and students.

Year Installed: incrementally, between Jan. 1,1993 to present.

Present condition of equipment: excellent; continuous process of upgrading and expansionis carried out.

System Costs (US$)10 watt Arco: U.S. $500.00 (1987)

20 watt Siemens: U.S. $75.00 (1993)

60 watt Solarex: U.S. $400.00 (1996)

55 watt Siemens: U.S. $300.00 (1997)

*The cost of all the other equipment is difficult to determine because it was all done in-house.Tanks for the solar water heaters, for example,were collected from scrap yards.

Who paid for the equipment? Some was pur-chased privately by staff members. Some waspurchased by BBCDC out of its general revenuefund earned through commercial operations.Some was part of a grant allocation from theIrish Consulate in Lesotho. For financing,BBCDC has secured a U.S. $25,000 loan fromE&Co., based in the United States, for solarenergy commercialization. In the first phase ofoperations, this is allowing BBCDC to commer-cialize solar oven manufacturing and to marketand install stand-alone PV systems.

Labor costs: BBCDC staff and students did allinstallation and fabrication.

Repairs and maintenance: All done by BBCDCstaff and students.

Maintenance costs: Covered by BBCDC com-mercial revenues.

Training in System Operationand Maintenance

No one at BBCDC has been trained specifi-cally for any of the above. In fact, none of thestaff have a formal technical qualification in anyfield. The staff are self-taught. One of the staffmembers has recently been to a three-weekcourse sponsored by the International Institutefor Energy Conservation.

Are there national/regional markets?These are in their infancy. The support struc-

ture is emerging, although little is being done topromote solar technology on a broad scale. Thebenefits to education are enormous, to say theleast. The main lesson is that all of the systems at BBCDC are affordable on a "Do It Yourself"basis where local enthusiasm and industry candesign, build, install, and maintain systems. It is extremely expensive on a "turn key" basis.Solar energy is an excellent way of using localresources, teaching general shop skills andapplied sciences, and of greatly augmentingfacilities.

AcknowledgmentThis information was supplied by:

Ivan YaholnitskyBethel Business and Community DevelopmentCentreBox 53, Mt. Moorosi 750 LesothoSouth Africa



CHAPTER 7: LESSONS LEARNED

Chapter IntroductionMany lessons have been learned from past

experiences. Lessons learned are a valuableresource for future success. These experiencesapply at all levels: institutional, operational, sys-tem design, technology, and development.

Institutional • A policy framework to integrate RE resourcesinto school buildings, both for improving effi-ciency and for educational purposes, must besupported with political will and commitment.

• Perceptions are often inaccurate or over simpli-fied. Common misperceptions are that RE powersystems are unaffordable, a future technology, orthat they require no maintenance.

• Donor funded programs often fail for lack ofoperating funds and inadequate local serviceinfrastructure.

• Existing local service infrastructures may beadapted to provide routine maintenance andtimely repair.

• Evaluation of system costs based only uponinitial cost discourages the choice for RE sources.

• Cost analysis often lacks consideration for non-comparable qualities of service.

• There are great potential benefits from cooper-ation with other human service sectors such aspublic health, agriculture, safe water supply, economic development, and communications.These links are in need of development.

• Energy supply in the local community can gen-erate income to support operating expenses.

• Energy supply in the local community hasneed for and the ability to economically supporta commercial service infrastructure.

Operational • Lack of maintenance is common and leads tosystem failure.

• Lack of installation standards of acceptanceleads to system failure.

• Users are often unaware of the proper opera-tion, care, or limitations of RE systems. Meteringis often not understood or is confusing to theuser.

• Training must be thorough and ongoing.

• Logistics are often underfunded and toobureaucratic.

• There is often a lack of spare parts, particularlywith special parts.

• Systems should be supplied as simple andcomplete as possible.

• Pilot projects must be replicable and useproven technologies.

• Pilot projects must be of a manageable scale forthose implementing them.

• Pilot projects must be monitored and evalu-ated prior to implementation of full-scale projects.

System Design• Lack of procurement standards leads to confu-sion on the part of suppliers and often results inthe least cost, least robust option.

• Although higher efficiency results in lowercosts, simplicity in system maintenance shouldalso be taken into account.

• Energy systems should be integrated with enduse applications.

• The energy system/application must be theleast expensive, highest benefit option to meetthe needs of the school system.

• Systems should be designed and provided ascompletely and detailed as possible.

• Adequate technical and user manuals mustaccompany RE systems and equipment.



• One size does not fit all. Systems must be prop-erly designed for particular site conditions.

• Sophisticated electronics may be vulnerable todamage by lightning.

Technology and Development Needs• There is a need for more reliable resource data.

• The implementation process may require sev-eral (4–6) years for full start-up. Implementationis then on going.

• Choices must be driven by programmaticneeds rather than technology.

• Program planners need reliable and under-standable information regarding energy choices.

• The fact that schools are often located inremote, poorly accessible areas, dictates that the technical designs for RE systems should be simple, robust, and easy to maintain; thisshould constitute an overriding system selectioncriteria.



REFERENCES

1. Gipe, P. (1993). Wind Power for Home andBusiness. Chelsea Green Publishing Company,White River Junction, Vermont.

2. Cowen, W.D.; Borchers, M.L.; Eberhard, A.A.;Morris, G.J.; and Purcell, C. de V. (1992). RemoteArea Power Supply Design Manual. 2 vols. Energyfor Development Research Center, University ofCape Town, Cape Town, South Africa.

BIBLIOGRAPHY

Cabraal, A.; Cosgrove-Davies, M.; and Schaeffer,L. (1996). Best Practices for Photovoltaic HouseholdElectrification Programs. World Bank TechnicalPaper #324, Asia Technical Department Series,Washington, D.C.

Cardinal, J.; Flowers, L.; Taylor, R.; and Weingart,J. (1997). Proceedings of Village Power ’97.NREL/CP-440-23409. National RenewableEnergy Laboratory. Golden, Colorado.

Cowen, W.D.; Borchers, M.L.; Eberhard, A.A.;Morris, G.J.; and Purcell, C. de V. (1992). RemoteArea Power Supply Design Manual. 2 vols. Energyfor Development Research Center, University ofCape Town, Cape Town, South Africa.

Cross, B., ed., (1995). The World Directory ofRenewable Energy Suppliers and Services 1995.James & James Sciences Publishers, Ltd., London, United Kingdom.

Duffie, J. A., Beckman, W.A. (1991). Solar Engi-neering of Thermal Processes. 2nd edition, JohnWiley & Sons, Inc., New York.

Fowler Solar Electric Inc. (1991). Battery Book forYour PV Home. Worthington, Massachusetts.

Gipe, P. (1993). Wind Power for Home and Business.Chelsea Green Publishing Company, WhiteRiver Junction, Vermont.

Gregory, J.; Silveira, S.; Derrick, A.; Conley, P.;Allinson, C.; Paish, O. (1997). Financing Renew-able Energy Projects: A Guide for DevelopmentWorkers. Intermediate Technology Publications,London, United Kingdom, and The StockholmEnvironment Institute 1997. 157 pp.

Hankins, M. (1993). Solar Electric Systems forAfrica: A Guide for Planning and Installing SolarElectric Systems in Rural Africa. rev. ed.; Common-wealth Science Council & AGROTEC; London,United Kingdom, and Harare, Zimbabwe.

Hankins, M. (1993). Solar Rural Electrification inthe Developing World, Four Country Case Studies:Dominican Republic, Kenya, Sri Lanka, Zimbabwe.Solar Electric Light Fund; Washington D.C.



Hunter, R. and Elliot, G., ed. (1994). Wind-DieselSystems: A Guide to the Technology and it’s Implementation. Cambridge University Press,Cambridge, United Kingdom.

McNelis, B.; Derrick, A.; and Starr, M. (1992).Solar Powered Electricity: A Survey of PhotovoltaicPower in Developing Countries. Intermediate Tech-nology Publications, London, United Kingdom.

Nelson, V. (1996). Wind Energy and Wind Turbines.Alternative Energy Institute, West Texas A&MUniversity, Canyon, Texas.

Risser, et al. (1995). Stand Alone Photovoltaic Sys-tems: A Handbook of Recommended Design Practices.Report # SAND87-7023, Sandia National Labora-tories, Albuquerque, New Mexico.

Solar Energy International (1998). PhotovoltaicDesign Manual. 2nd ed., P.O Box 715, Carbondale,Colorado, 81623.



GLOSSARY

Alternating Current (ac)—Electric current inwhich the direction of flow oscillates at frequent,regular intervals.

Altitude—The angle between the horizon (a hor-izontal plane) and the sun, measured in degrees.

Amorphous Silicon—A thin film PV silicon cellhaving no crystalline structure.

Ampere (A)—Unit of electric current measuringthe flow of electrons per unit time.

Ampere-Hour (Ah)—The quantity of electricalenergy equal to the flow of current of one amperefor one hour.

Angle of Incidence—Angle that references thesun's radiation striking a surface. A "normal"angle of incidence refers to the sun striking a sur-face at a 90° (or perpendicular) angle.

Annualized Cost—The equivalent annual costof a project if the expenses are treated as beingequal each year. The discounted total of theannualized costs over the project lifetime is equalto the net present cost (NPC) of the project.

Array—A mechanically integrated configurationof modules together with support structure,designed to form a DC power-producing unit.

Azimuth—Angle between true south and thepoint directly below the location of the sun. Mea-sured in degrees.

Battery—Two or more "cells" electrically con-nected for storing electrical energy.

Battery Capacity—Generally, the total numberof ampere-hours that can be withdrawn from afully charged cell or battery. The energy storagecapacity is the ampere-hour capacity multipliedby the battery voltage.

Battery Cell—A galvanic cell for storage of elec-trical energy. This cell after being dischargedmay be restored to a fully charged condition byan electric current.

Battery Cycle Life—The number of cycles, to aspecified depth of discharge, that a cell or batterycan undergo before failing to meet its specifiedcapacity or efficiency performance criteria.

Battery Self Discharge—Self-discharge is theloss of otherwise usable chemical energy byspontaneous currents within the cell or batteryregardless of its connections to an external circuit.

Battery State of Charge—Percentage of fullcharge or 100% minus the depth of discharge(see depth of discharge).

Charge Controller—A device that controls thecharging rate and/or state of charge for batteries.

Charge Rate—The current applied to a cell orbattery to restore its available capacity.

Concentrator—An optical component of a photovoltaic array used to direct and increasethe amount of incident sunlight on a solar cell.

Conversion Efficiency (PV)—The ratio of theelectricity energy produced by a photovoltaiccell (under full sun conditions) to the energyfrom incident sunlight on the cell.

Cost of Energy—The cost per unit of energy that,if held constant through the analysis period,would provide the same net present revenuevalue as the net present cost of the system.

Crystalline Silicon—A type of PV cell madefrom a single crystal or polycrystalline slice ofsilicon.

Current—The flow of electric charge in a con-ductor between two points having a difference inpotential (voltage).

Cut-In Speed—The minimum wind speed atwhich a particular wind turbine will produceenergy.

Cut -Out Speed—The speed at which a particu-lar wind turbine will reduce its power output in order to protect itself from excessive windspeeds. Most small wind turbines do this by tilting out of the wind.



Days of Autonomy—The number of consecutivedays a stand-alone system will meet a definedload without energy input.

Deep Cycle Battery—Type of battery that can bedischarged to a large fraction of capacity manytimes without damaging the battery.

Depth of Discharge (DOD)—The amount ofampere-hours removed from a fully charged cellor battery, expressed as a percentage of ratedcapacity.

Design Month—The month having the lowestRE energy production to load ratio.

Direct Current (dc)—Electric current flowing inone direction.

Discharge Rate—The current removed over aspecific period of time from a cell or battery.

Disconnect—Switch gear used to connect or disconnect components in a stand-alone system

Duty Cycle—The ratio of active time to totaltime. Used to describe the operating regime ofappliances or loads in stand-alone systems.

Efficiency—The ratio of output power to inputpower. Expressed in percent.

Electric Circuit—A complete path followed byelectrons from a power source to a load and backto source.

Electric Current—Magnitude of the flow of electrons.

Electrolyte—A conducting medium in which theflow of electric takes place by migration of ions.The electrolyte for a lead-acid storage cell is anaqueous solution of sulfuric acid.

Equalization—The process of mixing the elec-trolyte in batteries by periodically overchargingthe batteries for a short period.

Grid—The network of transmission lines, distri-bution lines, and transformers used in centralpower systems.

Insolation—The solar radiation incident on anarea. Usually expressed in Watts per squaremeter (W/m2).

Inverter—A solid state device that changes a dcinput to an ac output.

IV Curve—The graphical representation of thecurrent versus the voltage of a photovoltaic cell,module, or array as the load is increased fromzero voltage to maximum voltage. Typically normalized to 1000 watts per square meter ofsolar insulation at 25°C.

KiloWatt (kW)—One thousand Watts.

KiloWatt Hour (kWh)—One thousand Watthours.

Life-Cycle Cost—An estimate of the cost ofowning and operating a system for the period of its useful life; usually expressed in terms of the present value of all costs incurred over thelifetime of the system.

Load—The amount of electrical power beingconsumed at any given moment. Also, anydevice or appliance that is using power.

Maximum Power Point—The operating pointon a PV array current vs voltage curve wheremaximum power is delivered.

Module (Panel)—A predetermined electricalconfiguration of solar cells laminated into a protected assembly.

NEC—An abbreviation for the National ElectricCode which contains safety guidelines for alltypes of electrical installations. Article 690 pertains to solar photovoltaic systems.

Net Present Cost (NPC)—The value in the baseyear (usually the present year) of all expensesassociated with a project.

Nominal Voltage—A reference voltage used to describe batteries, modules, or systems (i.e., a12-Volt or 24-Volt battery, module or system).

Ohm—A unit of electrical resistance measurement.

Open Circuit Voltage—The maximum possiblevoltage across a photovoltaic array.

Orientation—Placement according to the directions, N, S, E, W; azimuth is the measure in degrees from true south.



Panel—See module.

Parallel Connection—The method of intercon-necting electricity-producing devices or powerconsuming devices, so that the voltage is constant but the current is additive.

Peak Load— The maximum load or electricalpower consumption occurring in a period oftime.

Peak Watt (Wp)—The amount of power a photovoltaic device will produce during peakirradiance.

Photovoltaic (PV) Cell—A photo-electric cellthat generates electrical energy when irradiancefalls on it.

Photovoltaic (PV) System—An installed aggregate of solar array, power conditioning and other subsystems providing power to agiven application.

Power Conditioning—The electrical equipmentused to convert power from a photovoltaic arrayinto a form suitable to meet the power supplyrequirements of more traditional loads. Loosely,a collective term for inverter, transformer, volt-age regulator, meters, switches, and controls.

Power Curve—A graphical representation of awind turbine’s power output as a function ofwind speed.

Renewable Energy (RE)— Energy produced bynon fossil fuel or nuclear means. Includes energyproduced by PV, wind turbines, hydro-electric,biomass, and solar thermal sources.

Series Connection—A method of interconnect-ing electricity producing devices or power usingdevices so that the current remains constant andthe voltage is additive.

Short Circuit Current—Current measured whena PV cell (module) is not connected to a load orother resistance and is shorted.

Single-Crystal Silicon—A material formed froma single silicon crystal.

Solar Cell—see Photovoltaic cell.

Solar Thermal Electric—Method of producingelectricity from solar energy by concentratingsunlight on a working fluid which changesphase to drive a turbine generator.

Stand-Alone System—A system that operatesindependently of the utility lines.

Standards of Acceptance—A set of characteris-tics, attributes, features and performance criteriawhich establishes the minimum acceptable quality and value of products and services. Inthe context of health care, these standards areadopted by the purchaser or authority responsi-ble for procuring health care systems.

State-of-Charge—The available capacity in a cell or battery expressed as a percentage of rated capacity. For example, if 25-ampere-hourshave been removed from a fully charged 100-ampere-hours cell, the new state of charge is75%.

Sun Hours—A unit of measure of solar insola-tion: 1 sun-hour = 1000 watt-hours/m2.

Surge Capacity—The ability of an inverter orgenerator to deliver high currents for short periods of time such as when starting motors.

Temperature Compensation—An allowancemade in charge controller set points for changingbattery temperatures.

Tilt Angle—Angle of inclination of collector asmeasured in degrees from the horizontal.

Volt, Voltage (V)—A unit of measurement of the force given to electrons in an electric circuit;electric potential.

Watt, Wattage (W)—Measure of electric power.Watts = Volts x Amps.

Watt-Hour (Wh)—A quantity of electrical energywhen one Watt is used for one hour.

Wind Turbine—A device that converts theenergy of moving air into electricity.



ABOUT THE AUTHORS

Tom LawandTom Lawand has been with the Brace

Research Institute of McGill University, Montréal, Canada, since its inception in 1959.The Institute is a pioneer in the use of renewableenergy resources in meeting the water andenergy scarcities in arid and semi-arid areas ofthe world. He has worked with a variety ofrenewable energy systems in design, testing,installation as well as meeting the educationalneeds in these fields of engineers, techniciansand scientists. He is also President and Founderof Solargetics Limited, a design-consulting firm.He has travelled extensively in all continents of the world and has written several hundredreports and publications on a wide variety ofrenewable energy and water related subjects.

Antonio "Tony" C. JimenezA graduate of the University of Colorado

(B.S. Engineering Physics 1990) and ColoradoState University (M.S. Mechanical Engineering1998), Tony Jimenez has worked in NREL’s Village Power Team since 1995 performing system-sizing analysis on many proposedhybrid installations. He has also worked onrenewable and hybrid system applications, such as this guide, and on the development of hybrid system sizing and analysis tools.

Contact InformationTony JimenezNREL/NWTC1617 Cole BoulevardGolden, Colorado 80401-3393Fax: [email protected]



ACKNOWLEDGEMENTS

The authors could not have completed this publication without the generous help of many colleagues. Our thanks goes first to Larry Flowers, who conceived the idea of publishing a series of applications guides and has supported our efforts to produce this guide. Next, we wish to thankRon Alward who in addition to assisting in writing chapter five, provided a thoughtful review of the entire manuscript that greatly improved the final product. We offer many thanks to our otherreviewers, Jay Burch, Robert Foster, Silverio Navarro and Alfredo Rapallini. Their generous sharingof expertise and experience has resulted in a greatly improved publication. In addition, we wish to thank those who contributed the material for our case studies, Graciela Pedro, Pierre Rieszer, Arturo Kuntsmann, Richard Hansen, Sylvia Mortaza, Amimur Rahman, Ivan Yaholnitsky, andGyani R. Shakya. Finally, we thank the Agency for International Development (AID) for providingthe funds used to print this publication.

Antonio C. JimenezTom Lawand


Notice:This report was prepared as an account of work sponsored by an agency of the United States government. Nei-ther the United States government nor any agency thereof, nor any of their employees, makes any warranty,express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness ofany information, apparatus, product, or process disclosed, or represents that its use would not infringe privatelyowned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark,manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favor-ing by the United States government or any agency thereof. The views and opinions of authors expressed hereindo not necessarily state or reflect those of the United States government or any agency thereof.

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Renewables for SustainableVillage Power

This is the second in a series of rural applications guidebooksthat the National Renewable Energy Laboratory (NREL) VillagePower Program is commissioning to couple commercialrenewable systems with rural applications. The guidebooks arecomplemented by NREL Village Power Program developmentactivities, international pilot projects, and the visitingprofessionals program. For more information on the NREL VillagePower Program, please visit the Renewables for SustainableVillage Power Web site:

http://www.rsvp.nrel.gov/rsvp/

Produced for the U.S. Department of Energy1000 Independence Avenue, SWWashington, DC 20585

by the National Renewable Energy Laboratory,a DOE national laboratory

with support from the U.S. Agency for International Development

NREL/BK-500-26222November 2000

Printed with a renewable-source ink on paper containing atleast 50% wastepaper, including 20% postconsumer waste


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