Duke University Photovoltaic Solutions Task # 2 Advisor ... · The LightAware Module The LightAware monitoring system is housed in a durable plastic shell with openings to expose

Page 1 of 23

Duke University

Photovoltaic Solutions

Task # 2

Advisor: Dr. David Schaad

Adam Dixon

Eric Fails

Lee Pearson

Steven Worrell

Page 2 of 23

WERC Environmental Design Competition

Task 2:

Photovoltaic System Performance Indicator

Duke University


WERC 2008

WERC Environmental Design Contest

New Mexico State University

Las Cruces, NM

April 6-9, 2008


Page 3 of 23

Table of Contents

Executive Summary ........................................................................................................................ 4

Task Identification .......................................................................................................................... 6

Problem Statement: ..................................................................................................................... 6

Global Photovoltaic Marketplace: .............................................................................................. 6

United States Photovoltaic Marketplace: .................................................................................... 7

Existing PV Monitoring Systems................................................................................................ 7

Motivation ................................................................................................................................... 8

Full Scale Design Description ........................................................................................................ 9

The LightAware Module............................................................................................................. 9

Data Processing ......................................................................................................................... 10

User Interface ............................................................................................................................ 11

Full Scale Diagram ................................................................................................................... 12

Bench-scale Diagram .................................................................................................................... 12

Bench-scale Lab Results ............................................................................................................... 13

Technical Evaluation of the Bench Scale ..................................................................................... 14

Signal Acquisition ..................................................................................................................... 14

Signal Processing ...................................................................................................................... 15

Display ...................................................................................................................................... 16

Waste Generation ...................................................................................................................... 16

Components of Performance Indicator System: ........................................................................... 16

Installation Instructions & Safety Warnings ................................................................................. 21

User instructions & Maintenance .................................................................................................. 22

References ..................................................................................................................................... 23

Page 4 of 23

Executive Summary

Current monitoring systems are difficult for most consumers to use, resulting in widespread

underperformance of photovoltaic systems. Photovoltaic Solutions addresses this problem by

displaying key diagnostics on both a wireless display unit and on the user’s computer. Because

consumers demand maximum system efficiency, and the monitoring system is the interface

between the consumer and the photovoltaic system, photovoltaic suppliers are under increased

pressure to provide state of the art monitoring systems.

Currently rated at nearly 2.3 billion dollars, the global photovoltaic market has experienced 25%

growth annually for the last decade due to strong technology adoption in European and Asian

marketplaces. The environmentally friendly aspect of solar energy cannot be understated when

assessing the future growth of the photovoltaic marketplace, and the total global market is

expected to grow 30-40% annually for decades.

The LightAware system combines simple technology to produce innovative monitoring statistics.

By measuring the intensity of incident sunlight using phototransistors, the LightAware System

can calculate the optimal expected power output. Using this metric the LightAware system

calculates the instantaneous efficiency of the solar panel system on the user’s home and tracks

this information over time. Competitor’s monitoring systems fail to monitor efficiency, instead

preferring only to monitor instantaneous power output. Monitoring power output is certainly

important, however, basic users cannot diagnose underperforming solar panels because they do

not know what they should be expecting. In our price range, no competitors offer the results and

ease of use that we can for our customers.

The information that the LightAware System collects is transmitted wirelessly to the user’s home

computer and is then rebroadcast over the internet. This allows for the user to check up on

his/her PV system at home, at work, or in the car listening to some tunes on their Ipod Touch.

LightAware also includes a digital display that can be mounted in a convenient location within

the home. In the event of a PV system malfunction, the user is notified via email and alert on

their home computer. With a click of a button, the user can send a help request to one of

Photovoltaic Solutions qualified service staff who can work through the issue via communication

Page 5 of 23

over the internet, or can arrange a service visit if the problem cannot be fixed remotely. As the

number of users of our system expands in a neighborhood, users can compare their efficiency

against their neighbors as another check to monitor performance. This capability also helps our

technicians and will decrease service time.

At Photovoltaic Solutions we are convinced that our LightAware monitoring system is a viable

alternative to existing monitoring systems. For such a small price, we offer the most capability,

flexibility, and ease of use for users of any ability. We have effectively solved the problem of

communicating solar panel performance to the user in a cost effective way.

Page 6 of 23

Task Identification

Problem Statement:

Develop and demonstrate a system to determine that a residential utility-interactive PV system is

operating properly and that the ac power output is following the solar power available to the PV

array.

Global Photovoltaic Marketplace:

Currently rated at nearly 2.3 billion dollars, the global photovoltaic market has experienced 25%

growth annually for the last decade due to strong technology adoption in European and Asian

marketplaces. Japan and Germany account for over half of all photovoltaic power production

globally, and still experience some of the fastest industry growth patterns. Accordingly, the

marketplace is dominated by foreign producers, mostly located in Western Europe and Japan.1 In

2006, photovoltaic systems produced by Sharp, a Japanese company, generated 18% of all

residential photovoltaic power world wide.2

International success has been driven by an expanding marketplace and generous government

subsidy programs. Aggressive tax incentives along with mandated energy ‘buy-back’ programs

for large energy producers have made solar technology available to on-grid consumers regardless

of income level.1 While solar energy production is not cheaper than traditional fossil fuels, the

technology appeals to many consumers in Western Europe, which is well ahead of the United

States and much of the world in environmental consciousness.

Off-grid photovoltaic production is an emerging marketplace that accounted for roughly 7% of

total sales last year. Off-grid systems, as the name implies, are not tied into the power grid, and

do not participate in energy ‘buy-back’ programs. However, consumers in regions of both

developed and developing nations who lack dependable energy sources have found solar to be a

reliable electricity source.3

The environmentally friendly aspect of solar energy cannot be understated when assessing the

future growth of the photovoltaic marketplace, and the total global market is expected to grow

Page 7 of 23

30-40% annually for decades. As producers continue to market solar energy as a mainstream

technology and are able to secure government reimbursements, photovoltaic system production

will continue to quickly expand internationally.

United States Photovoltaic Marketplace:

Perhaps the most unique aspect of the photovoltaic industry is that, until very recently, nearly all

of its growth has occurred without the participation of the United States. Widespread adoption of

photovoltaic technologies is inevitable, and as the environmental consciousness of consumers in

the United States increases, the market will quickly expand. In fact, many reports suggest that the

United States’ potential for photovoltaic energy production is more than twice that of already

well established markets, suggesting that when the United States does enter the marketplace, the

total international market could be buoyed up to well beyond 25 billion dollars.2

However, until the United States adopts energy subsidy programs similar to those in Germany

and Japan, photovoltaic energy production will be limited to wealthy and environmentally

conscious consumers who are willing to purchase the systems on their own. The total United

States photovoltaic market is rated close to 300 million dollars, with the residential component

comprising nearly half of the total marketplace. First Solar, the leading United States based

manufacturer, accounted for roughly 25% of total United States sales in 2006, and is actively

lobbying state legislatures to subsidize photovoltaic energy production.3

Even without active government support behind the solar movement, the United States

photovoltaic market has experienced 20% growth annually since 2000, due largely in part to

decreased photovoltaic production costs and an increased interest in green technologies.2

Existing PV Monitoring Systems

Systems are already available that offer similar monitoring capabilities. High end monitoring

systems (used more institutionally) monitor the PV Array and the environmental factors that

affect it. These systems are also equipped with real time displays that are easy to understand and

are typically hooked up to a kiosk or computer internet LAN setup. They range from simple to

complex so anyone can use them and they cost between $2,000 and $15,000. Intermediate

monitoring systems (used both institutionally and residentially) monitor energy, occasionally

Page 8 of 23

power, and some environmental factors that affect the system. These systems are typically

connected directly to the internet and their ease of use varies greatly. They cost between $500

and $3,000. Low end monitoring systems (used more residentially) monitor energy and

sometimes also power. These systems may use kilowatt hour meters, direct inverter read-outs

and, remote LCD displays. They cost between $0 and $600.4 The price of our system will be in

the low end price range, however, the capabilities our system offers will exceed the existing mid

range products. As such we believe that our system gives a competitive advantage to our

company and a useful service for our customers.

Motivation

Current monitoring systems are difficult for most consumers to use, resulting in widespread

underperformance of photovoltaic systems. Photovoltaic Solutions addresses this problem by

displaying key diagnostics on both a wireless display unit and on the user’s computer. Because

consumers demand maximum system efficiency, and the monitoring system is the interface

between the consumer and the photovoltaic system, photovoltaic suppliers are under increased

pressure to provide state of the art monitoring systems. As the United States market expands to

serve individuals with less technical know-how, more efficient and consumer friendly

monitoring services must be developed to better serve this marketplace. Accordingly, this

consumer base can be expected to pay more for a more user-friendly monitoring system capable

of conveying complicated technical metrics of photovoltaic function through clear and easily

interpreted graphs and language.

A problem with current photovoltaic systems is undiagnosed underperformance, and consumers

who are not technically inclined have little hope of noticing underperformance of their

photovoltaic system, especially if they are still tied into on-grid power sources that can make up

for lack of solar production. Hence, monitoring systems that clearly indicate optimal

performance levels are in high demand, but technologies capable of delivering these metrics are

very rudimentary.

As a whole, however, both the domestic and international marketplace for photovoltaic systems

is poised for rapid growth in the coming decades, especially with the emergence of major

consumer bases in the United States and elsewhere. As populations become increasingly aware

Page 9 of 23

of the detrimental affects of traditional nonrenewable fuel sources on the environment, a strong

push on national and local governments to help subsidize solar power will further help to drive

the marketplace.

Full Scale Design Description

System indicators currently on the market provide information relating the current amount of

power being generated by the PV system to the theoretical maximum power. This measure of

efficiency is only useful when the panel is directly aligned with bright sunlight, and is of almost

no use during cloudy or overcast days or in the morning or evening. Our design instead measures

incident sunlight striking the panel, and uses empirical data to determine if the amount of power

being generated is consistent with the amount of power that should be generated for that much

sunlight. The LightAware Module is used as described below to determine how efficiently the

PV system is converting available sunlight into power. This measure of efficiency then

determines if the PV array is functioning properly, and communicates to the user through the

various interface possibilities described.

The LightAware Module

The LightAware monitoring system is housed in a durable plastic shell with openings to expose

the phototransistors to light. The plastic housing is white so that solar radiation is reflected to

keep the temperature of the module as low as possible. The NPN phototransistors produce an

output voltage proportional to the intensity of the incident sunlight. This output voltage is then

sent to the Microchip PIC 18F4250 microcontroller and undergoes a 10-bit analog to digital

conversion. The PIC 18F4250 is contained in a separate protective housing that is placed on the

underside of the solar panels to protect it from light and precipitation. Both the LightAware

Module and the PIC 18F4520 are mounted on the solar panel. The LightAware system

communicates with the data processing software using a wireless radio frequency protocol used

with PIC cards (rfPIC technology).

Page 10 of 23

Figure 1: The Light Aware Module which has three phototransistors: two imbedded at 45 degrees from the

vertical phototransistor.

Data Processing

The digital signals from the PIC 18F4520 are transmitted to the computer wirelessly for

processing using the rfPIC wireless transmission protocol. The rfPIC system is composed of an

RF transmitter on the solar panel and a receiver by the processing unit. The digital signals from

the rfPIC are fed into a Texas Instruments Digital Light Processing (DLP) device to convert the

signals into universal serial bus (USB) format. The DLP is a plug-and-play device, and is readily

recognizable by the signal processing software. The processing software will be written in C++

to perform the calculations on the data received from the DLP device.

The output from the inverter relays the amount of power generated by the panels at any given

time. This output is run through a voltage and current transformer and is fed into another PIC

18F4520 near the inverter. The PIC 18F4520 will perform a 10-bit analog to digital conversion

on this signal and will relay it to the DLP device.

The processing software will calculate metrics such as current power output, optimal power

output, instantaneous efficiency, and total power generated over the course of a day, month,

season, and year. These metrics will be saved on the computer and will be consulted to make

sure that the system is maintaining its optimum efficiency. If efficiency is progressively

decreasing, the system will alert the user through e-mail that the system is not performing at its

maximum efficiency. The user should seek the help of a professional electrician in this

circumstance.

Page 11 of 23

User Interface

Once the inputs from the LightAware sensor and PV system are processed in the owner’s

computer, there are many potential options for the use of this data. For the least involvement

from the user, the system will essentially operate in the background, and only notify the user

when there is a problem with the PV’s functionality. This notification can be done via email,

SMS text message, or notifications on the home computer. This would serve to alert the user to

potential problems, and would also contain information that can be accessed by a technician to

diagnose and solve the problem. A more in depth approach would involve daily monitoring of

solar power conversion efficiency, with monitoring available through the same means outlined

above. Similar to currently available monitoring systems, our design also includes a wireless

display that can be placed anywhere in the dwelling. Unlike current displays that give

efficiencies based on the total possible output of the system, our novel LightAware sensor allows

for calculation of an efficiency based on the amount of sunlight on the system. Because of the

large temporal variation in incident sunlight (both daily and monthly) this measure of efficiency

will be a great deal more revealing of how well the PV system is operating.

For added capabilities, the results of the signal processing can be transmitted wirelessly on the

user’s home wireless network (typically 802.11g). This will enable the user to check the status of

the solar panels from any computer with an internet connection. We will also supply a wireless

display device that can be mounted in a convenient location in the user’s home. This device will

communicate with the home’s wireless network to display metrics of the solar panel’s

performance.

The system will send self diagnostic information to the user through email. If, for some reason,

the monitoring system malfunctions and the signals cannot be adequately processed, the system

will alert the user to seek help from a professional electrician.

Page 12 of 23

Full Scale Diagram

Bench-scale Diagram

Figure 2: Schematic diagram of bench scale experiment. Photovoltaic array (1) with our ‘LightAware’

sunlight detection unit (2). The LightAware unit detects incident sunlight and transmits data to a

microprocessing unit (3), which then sends data for analysis and storage to a computer (6). Our system also

detects how much electricity is output from the inverter (5) through the use of a data acquisition card (4).

The 120 VAC line power (7) is transformed to 5 VDC to power the LightAware unit and the MPU.

Page 13 of 23

Bench-scale Lab Results

Table 1: Recordings for solar panel performance and LightAware module performance

Data from 3/17/08

Solar Panel Transistor Readings

Time Voltage Current Power Morn Noon After

1:30 PM 20.4 0.16 3.264 0.053 0.103 0.044

4:00 PM 20.3 0.44 8.932 0.039 0.12 0.86

4:15 PM 19.5 0.45 8.775 0.012 0.102 0.972

4:30 PM 19.4 0.13 2.522 0.015 0.08 0.324

4:45 PM 19.46 0.14 2.7244 0.011 0.082 0.292

5:00 PM 20.8 0.27 5.616 0.003 0.12 0.43

Data was collected on March 17th, 2008 in Durham, NC at Duke University’s Smart Home

residence on Faber Street. A BP 10-watt solar panel was used as the solar panel of interest and

voltage and current readings were taken using digital multimeter. A bread-boarded LightAware

unit was placed next to the solar panel and readings were taken concurrently with the solar panel

readings using a digital multimeter. This data was collected over the course of the day and

plotted using Microsoft Excel with linear regression tools. This allowed for the power of the

solar panel to be related to the transistor voltage readings from the bread-boarded LightAware

module.

As shown in Figure 3 a linear relationship exists between solar panel power and transistor

voltage from the LightAware unit. However, it is very likely that the constant of relation that is

found will vary from solar panel to solar panel since sizes and efficiencies will be slightly

different. As such, each module sold will have to be calibrated on site to ensure that it will give

reliably information to the user throughout its use.

Page 14 of 23

Figure 3: Relation of solar panel power output to transistor voltage from the LightAware Module

Technical Evaluation of the Bench Scale

The photovoltaic monitoring system contains three primary technical components, all of which

will be discussed in their own sections:

• Signal Acquisition

• Signal Processing

• Display

Signal Acquisition

The LightAware monitoring system gauges the intensity of the incident sunlight using NPN

phototransistors produced by PerkinElmer Optoelectronics. The NPN phototransistors were

chosen because they have highly modifiable internal gains and direct current output responses

that vary differentially based on incident sunlight. The VTT1015H model was specifically

chosen because it exhibits a similar spectral response as most solar panels. The NPN

phototransistors must be powered with a +5 VDC bias voltage at the collector, and the output

Page 15 of 23

voltage is read from the emitter. Photodiodes were also considered because they are passive

elements, but they have no capability for internal gain, which could affect the fidelity of the

acquired signal.

The monitoring system also monitors the output from the inverter. The inverter’s output is

typically 120 or 240 VAC at various amperages. Our system transforms the output from the

inverter to roughly 6.3 volts (at 0.6 mA) using a Stancor transformer for acquisition by a

National Instruments DAQ card. (Note that the Full Scale design uses another PIC card instead

of the DAQ card).

Signal Processing

The Microchip PIC 18F4520 takes the outputs from the NPN phototransistors and performs a 10-

bit analog to digital conversion. The PIC 18F4520 is programmed in C language using

hardcoded analog to digital functions. The PIC 18F4520 is powered by the same +5 VDC power

source as the NPN phototransistors. The maximum voltage from the NPN phototransistors on a

bright day has been calibrated to be +1V, so the PIC is able to convert the analog signal with a

resolution of approximately 1mV. Analog to digital conversion is necessary because the values

must be transmitted over very long distances, and weak analog signals are subject to attenuation

and distortion. The digital signals from the PIC 18F4520 are fed into a Texas Instruments Digital

Light Processing (DLP) device to convert the signals into universal serial bus (USB) format. The

DLP is a plug-and-play device, and its outputs are readily recognizable by the LabVIEW

software.

The digital signals from the PIC and the DAQ are fed into a computer for analysis using

LabVIEW software. This software takes the data from the NPN phototransistors and calculates

how much power the photovoltaic system should be producing based on the incident sunlight.

This calculation is performed using calibration constants determined during the testing of the

bench scale. The optimal power output is then compared to inverter output to calculate system

efficiency.

Page 16 of 23

Display

The display for the bench scale is part of the LabVIEW software interface. This display was

chosen because it is a cost effective way to simulate a real display device. However, in the full

scale product, the computer performing the data analysis will broadcast the results over the

internet using FTP protocol.

Waste Generation

The largest component of the waste stream in a combined PV system and indicator is that of the

main system itself. Current research suggests that in the near future recycling of PV systems will

be standard practice, which ensures that the potentially hazardous materials involved will not

only be removed from landfills but will be reused as raw materials.5 The additional electronics

and wiring implemented in our proposed design would insignificantly change the overall waste

generated at the end of the system lifetime. In terms of individual components, the

phototransistors are made of aluminum and silicon, and are no more toxic than any other

electrical component. It may not be as economically feasible to recycle the materials in these

components as it is for entire PV systems, but because the entire system will be sent to a

recycling facility it can be assumed that the monitoring system will at least be disposed

properly.

Components of Performance Indicator System:

Component Description Cost Picture

Microchip

PIC 18F4520

A PIC is a Programmable Intelligent

Computer which is a microcontroller capable of performing simple analog to digital conversions using C language code.

$2.36

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=13

35&dDocName=en010297 http://www.voti.nl/common/18f452.jpg

Schematic

Page 17 of 23

SOURCE: http://ww1.microchip.com/downloads/en/DeviceDoc/39631D.pdf


National Instruments DAQ USB-6008

The National Instruments USB-6008 multifunction data acquisition (DAQ) modules provide reliable data acquisition at a low price. With plug-and-play USB connectivity, these modules are simple enough for quick measurements but versatile enough for more complex measurement applications.

$159

http://sine.ni.com/nips/cds/view/p/lang/en/nid/14604

Schematic

Page 18 of 23

SOURCE: http://www.ni.com/pdf/manuals/371303k.pdf


Stancor Power

Transformer P-6465

A transformer transforms voltage from high to low. Transformer; Chassis; Pri:117V; Sec:6.3VCT; Sec:0.6A; Lead; 50/60Hz; 2.38In.In.W; 1.38In

$9.44

http://www.alliedelec.com/Search/ProductDetail.asp?SKU=928-3027&SEARCH=&MPN=P-6465&DESC=P-6465&R=928-3027&sid=47CC9100396C617F

Schematic

SOURCE: http://www.alliedelec.com/catalog/pf.aspx?FN=974.pdf


Page 19 of 23

Perkin Elmer phototransistor VTT1015H

An NPN phototransistor produces an output current when exposed to photons. The collector receives a 5VDC bias voltage and the output voltage is read from the emitter.

($2.76) x (20) = $55.14

http://www.alliedelec.com/Search/ProductDetail.asp?SKU=980-

0102&SEARCH=&MPN=VTT1015H&DESC=VTT1015H&R=980%2D0102&sid=4796838071E3617F&tab=specs#tab

Schematic

SOURCE: http://www.alliedelec.com/catalog/pf.aspx?FN=1864.pdf


Microengineering LabsLAB-X2 Experimenter Board

The development board powers the PIC. The LAB-X2 contains the circuitry required by the PICmicro® MCU to operate: 5-volt power supply, oscillator, reset circuit, as well as an RS-232 serial port and basic analog and digital I/O. Both 40 and 28-pin DIP microcontrollers are accommodated. All of the pins on the MCU are wired to a 40 pin connector which can be used to connect your prototype circuitry.

$79.95

http://www.microengineeringlabs.com/products/labx2.htm http://www.microengineeringlabs.com/ima

ges/Detail_JPGs/LABX2A_detail.jpg

Schematic

Page 20 of 23

SOURCE: http://www.microengineeringlabs.com/downloads/labx2sch_06.pdf


Mouser DLP USB Device DLP-USB245M-G

The DLP USB Device converts the digital signal from the PIC to a USB signal which is then sent to the computer for signal processing.

$28.75

http://www.mouser.com/search/ProductDetail.aspx?qs=CoW5K%2FMp%2F73t5w3WDhf9Ow%3D%3D

Schematic

Page 21 of 23

SOURCE: http://www.ftdichip.com/Documents/DataSheets/DLP/dlp-usb245m13.pdf

Installation Instructions & Safety Warnings

Installation of the monitoring unit would ideally be performed at the time of installation of the

overall PV system, and done by qualified electricians. The most important aspect of installation

is the alignment of LightAware system along an east-west axis, such that it closely mimics the

sun’s pattern. The system wiring should done according to the provided circuit diagrams. The

PIC card should be located in such a way as to reduce the possibility for weather damage,

similarly it should be located out of direct sunlight so as to reduce the possibility of thermal

damage to the unit.

The following safety precautions will be taken:

• When unplugging the power supply cord, be sure to grasp the power supply plug; never

pull on the cord itself.

• Never plug in nor remove the power supply plug with wet hands, as doing so may cause

electric shock.

• To prevent a fire or electric shock, never open nor remove the unit case as there are

sensitive components inside the unit that can be damaged or cause harm to operator.

Page 22 of 23

• Do not insert nor drop metallic objects or flammable materials in the ventilation slots of

the unit's cover, as this may result in fire or electric shock.

• Use the unit only with the voltage specified on the unit. Using a voltage higher than that

which is specified may result in fire or electric shock.

• Do not cut, kink, otherwise damage nor modify the power supply cord. In addition, avoid

using the power cord in close proximity to heaters, and never place heavy objects --

including the unit itself – on the power cord, as doing so may result in fire or electric

shock.

• Install the unit only in a location that can structurally support the weight of the unit and

the mounting bracket. Doing otherwise may result in the unit falling down and causing

personal injury and/or property damage.

• Do not use other methods than specified to mount the bracket. Extreme force is applied to

the unit and the unit could fall off, possibly resulting in personal injuries.

User instructions & Maintenance

Our system software is designed for flexibility in terms of the amount of technical data offered

by the display. For the most basic level, the user would only know of the monitoring system if

the PV is not working properly, and would be notified via email. For the more technology savvy,

information on the daily efficiency of the system would be available. In either case, when the

system is not operating at peak efficiency, a visual inspection of the system would be the first

step. If this does not reveal the problem (for example, if an object is blocking the solar array)

then a qualified PV system electrician should be contacted to perform a system analysis.

Page 23 of 23

References

1 “Trends in Photovoltaic Applications: Survey report of selected IEA countries between 1992 and 2005.” International Energy Agency.

Accessed September 14, 2007. www.suterdruck.ch

2 “The Global PV Industry: Technologies, Applications, and Drivers for Future Growth.” Interstate Renewable Energy Council (IREC).

Presentation given July 19, 2007.

3 First Solar, Inc. 2006 Annual Report to Investors. 4 Heliotronics, Residential Monitoring, http://www.heliotronics.com/papers/CH_ResMonitoring.pdf

5 J.R.Bohland,et al. : :Possibility of Recycling of Silicon PV Modules, 26" IEEE PVSC( 1997)

Duke University Edmund T. Pratt, Jr. School of Engineering

DEPARTMENT OF CIVIL AND ENVIRONMENTAL TELEPHONE (919) 660-5200

ENGINEERING FAX: (919) 660-5219

BOX 90287 HTTP://WWW.CEE.DUKE.EDU

DURHAM, NORTH CAROLINA 27708

March 17, 2008

Memorandum To: Professor David Schaad From: Professor Jeff Peirce Re: Financial Audit of WERC Contest: Task 2 “Photovoltaic Solutions” The strengths and weaknesses of the financial plan for “Photovoltaic Solutions” are listed below. Strengths: Throughout the text the authors show an appreciation for and an understanding that:

• recent decreases in production costs of photovoltaic systems have led to technical

solutions that otherwise would not be available (page 6); • consumers currently demand systems that operate at maximum efficiency (page

6); • both the US and international markets (supplies and demands) for photovoltaic

systems could be entering a period of rapid expansion (pages 4 and 6); • full-scale design incorporates many aspects of bench scale studies but also can

include important changes to take advantage of economies of scale and thus provide the systems at lower costs (page 7);

• the LabVIEW software interface display was selected in a cost effective manner (page 10);

• the marketplace may not find it economically feasible to recycle the materials in the individual components of the photovoltaic systems (page 11); and,

• the costs of the system components are well documented and available in the literature (page 11, 12, 13, 14 and 15).

Weaknesses and Suggestions: 1. All considerations of the very important economic analysis and financial plan,

including those topics mentioned above but sprinkled throughout the document, should be included in a separate section of this report. This Economic Analysis and Financial Plan section must be thoroughly developed and thoroughly referenced, and the title of this section must be included in the Table of Contents; and,

2. Engineering economic analysis including estimates of present worth and/or equivalent annual worth could be used as part of this discussion to benchmark the relative value of the total cost of the proposed solution.






March 17, 2008

Memorandum To: Professor David Schaad From: Professor Claudia Gunsch Re: Legal Audit of WERC Contest: Task 2 “Photovoltaic Solutions” Beyond the design and manufacture liability of the PV system and indicator, this product’s production and disposal will need to be performed in accordance with the Resource, Recycling, Conservation, and Recovery Act (RCRA). As duly pointed out by the research team, at the present time, “the largest component of the waste stream in a combined PV system and indicator is that of the main system itself”. Because many solvents, metals and other hazardous components are incorporated into electronic manufacturing, it is important to think about the disposal of such items. RCRA was enacted to protect the public from harm caused by waste disposal, to encourage reuse, reduction and recycling and to clean up spilled or improperly stored wastes. All of these aspects are pertinent to this project and need to be addressed. The individual components indicated in the proposal are rather cheap, however their disposal costs should be taken into consideration. The team indicates that in the future many of the components will be recycled and if this were the case, the requirements under RCRA are likely to be lessened. The design and manufacture of the system for implementation could expose the design professional and the manufacture to legal liability. Because the proposed use for the indicator is to provide users with information as to the efficiency of an installed PV system, the liability should be low. It does not appear that there would be substantial expenses associated with such system failing and limited adverse health effects can be expected from its operation. Thus, the legal liability should be low. Nonetheless, it would be worthwhile to incorporate an automatic shutoff mechanism if the system and/or indicator were to become wet or improperly operate beyond specific limits. In addition, it would be prudent for the manufacturer to insure themselves.






March 17, 2008

Memorandum To: Professor David Schaad From: Professor Helen Hsu-Kim Re: Safety Audit of WERC Contest: Task 2 “Photovoltaic Solutions” The team covered most of the important environmental health and safety items related to the implementation of their system design.