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Chapter 10

Hybrid Power Systems

10.1 Introduction

Electrical energy requirements for many re-mote applications are too large to allow thecost-effective use of stand-alone or autono-mous PV systems. In these cases, it may prove

more feasible to combine several differenttypes of power sources to form what is knownas a "hybrid" system. To date, PV has beeneffectively combined with other types ofpower generators such as wind, hydro, thermo-electric, petroleum-fueled and even hydrogen.The selection process for hybrid power sourcetypes at a given site can include a combinationof many factors including site topography, sea-sonal availability of energy sources, cost ofsource implementation, cost of energy storageand delivery, total site energy requirements,

etc.

10.2 Petroleum-fueled engine generators(Gensets)

Petroleum-fueled gensets (operating con-tinuously in many cases) are presently themost common method of supplying power atsites remote from the utility grid such asvillages, lodges, resorts, cottages and a variety

of industrial sites includingtelecommunications, mining and loggingcamps, and military and other government-operated locations.

Although gensets are relatively inexpensive ininitial cost, they are not inexpensive tooperate. Costs for fuel and maintenance canincrease exponentially when these needs mustbe met in a remote location. Environmentalfactors such

as noise, carbon oxide emissions, transport andstorage of fuel must also be considered.

Figure 10.1 Hybrid PV/Generator System Example;

Courtesy Photron Canada Inc.,

Location: Sheep Mountain

Interpretive Centre, Parks Canada

Kluone National Park, Yukon

Territories, Canada, 63 North

Latitude; Components shown include:

generator (120/240 V), battery (deep

cycle industrial rated @ 10 kWh ca-

pacity), DC to AC stand-alone

inverter (2500 W @ 120 V output),

miscellaneous safety + control

equipment including PV array

disconnect, PV control/regulator,

automatic generator start/-stop

control, DC/AC system metering etc.;

-Components not shown: PV array

(800 W peak).

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Figure 10.2 Genset fuel efficiency vs. capacity utilized.

Fuel to power conversion efficiencies maybe as high as 25% (for a diesel fueled unitoperating at rated capacity). Under part loadconditions, however, efficiencies may de-cline to a few percent. Considerable wasteheat is therefore available and may be uti-lized for other requirements such as spaceand/or water heating.

10.3 Why a PV/genset hybrid?

PV and genset systems do not have muchin common. It is precisely for this reasonthat they can be mated to form a hybridsystem that goes far in overcoming thedrawbacks to each technology. Table 10.1lists the respective advantages and

disadvantages.

As the sun is a variable energy source, PVsystem designs are increased in size (andtherefore cost) to allow for a degree ofsystem autonomy. Autonomy is requiredto allow for provision of reliable powerduring "worst case" situations, which areusually periods of adverse weather,seasonally low solar insolation values oran unpredicted increased demand forpower. The addition of autonomy to the

system is accomplished by increasing thesize of the PV array and its

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requisite energy storage system (the battery).

When a genset is added, additional batterycharging and direct AC load supply capabili-

ties are provided. The need to build in sys-tem autonomy is therefore greatly reduced.When energy demands cannot be met by thePV portion of the system for any reason, thegenset is brought on line to provide the re-quired backup power. Substantial cost sav-ings can be achieved and overall system reli-ability is enhanced.

PV/genset hybrid systems have been utilizedat sites with daily energy requirementsranging from as low as 1 kWh per day to as

high as 1 MWh per day, which illustratestheir extreme flexibility. They are a provenand reliable method for efficient and cost-effective power supply at remote sites.

10.4 PV/genset hybrid system description

The PV/genset hybrid utilizes two diverseenergy sources to power a site's loads. ThePV array is employed to generate DC

energy that is consumed by any existing DCloads, with the balance (if any) being usedto charge the system's DC energy storagebattery. The PV array is automatically online and feeding power into the systemwhenever solar insolation is available andcontinues to produce system power duringdaylight hours until its rate of productionexceeds what all existing DC loads and thestorage battery can absorb. Should thisoccur, the array is inhibited by the systemcontroller from feeding any further energy

into the loads or battery.

A genset is employed to generate AC energythat is consumed by any existing AC loads,with the balance (if any) being used by thebattery charger to generate DC energy thatis used in the identical fashion to thatdescribed for the PV array above.

Figure 10.3 Block diagram of a hybrid

PV-Genset system.

At times when the genset is not running,all site AC power is derived from thesystem's power conditioner or inverter,which automatically converts system DCenergy into AC energy whenever AC loadsare being operated.

The genset is operated cyclically in directresponse to the need for maintaining asuitable state of charge level in thesystem's battery storage bank.

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Figure 10.4 Hybrid PV/Generator System

Example. Courtesy Photron

Inc., Location: Caples Lake,

California, USA; 65 kVA 3 0 @

480 V generator which includes

co-generation equipment (i.e.

heat exchangers to utilize thethermal energy created by unit

operation).

10.5 Other PV/hybrid types

Certain specific site locations may offeraccess to other forms of power generation.Access to flowing water presents the poten-tial for hydro power. Access to consistentwind at sufficient velocity presents the po-tential for wind power. PV/hydro andPV/wind hybrid systems have been utilizedat sites with daily energy requirementranges similar to those described forPV/genset hybrids. Their use, however, ismuch more site dependent, as their energysource is a factor of that locations'topography.

PV/Thermoelectric generator hybridsystems have been used effectively at siteswhose daily energy requirement isrelatively low, ranging from 1 to 20 kWhper day. Propane is the fuel source for thethermoelectric process, and conversionefficiencies of up to 8% can be achieved.Considerable waste heat is thereforeavailable which may be utilized for otherrequirements. In cold climates, this heat isoften used to maintain the battery storage

system at desired temperature levels.

Table 10.1 Relative Advantages of Energy Sources: Genset vs. PV

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Section C

Architectural Integration

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Principal ContributorsChapter 11: Introduction to Architecture and Photovoltaics

Ingo HagemannSteven Strong

Chapter 12: Photovoltaic Modules Suitable for Building Integration

Peter ToggweilerCinzia Abbate-Gardner

Chapter 13: Design Concepts

Cinzia Abbate-GardnerPeter ToggweilerGregory KissTony SchoenHeinz Hullmann

Chapter 14: Integration Techniques and Examples

Peter ToggweilerHermann LaukampChristian Roecker

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Chapter 11

Introduction to Architecture andPhotovoltaics

11.1 Motivation

The last two decades have brought significant

changes to the design profession. In the wakeof traumatic escalations in energy prices,shortages, embargoes and war along withheightened concerns over pollution, environ-mental degradation and resource depletion,awareness of the environmental impact of ourwork as design professionals has dramaticallyincreased.

In the process, the shortcomings ofyesterday's buildings have also becomeincreasingly clear: inefficient electrical and

climate conditioning systems squander greatamounts of energy. Combustion of fossilfuels on-site and at power plants addgreenhouse gases, acid rain and otherpollutants to the environment. Inside, manybuilding materials, furnishings and finishesgive off toxic by-products contributing toindoor air pollution. Poorly designed lightingand ventilation systems can induce headachesand fatigue.

Architects with vision have come to under-

stand it is no longer the goal of good designto simply create a building that isaesthetically pleasing - buildings of the futuremust be environmentally responsive as well.They have responded by specifying increasedlevels of thermal insulation, healthierinteriors, higher-efficiency lighting, betterglazing and HVAC (heating, ventilation andair conditioning) equipment, air-to-air heatexchangers and heat-recovery ventilationsystems. Significant ad-

vances have been made and this progress is avery important first step in the right direction.

However, it is not enough. For the developedcountries to continue to enjoy the comforts ofthe late twentieth century and for the deve-loping world to ever hope to attain them,sustainability must become the cornerstone ofour design philosophy. Rather than merely us-ing less non-renewable fuels and creating lesspollution, we must come to designsustainable buildings that rely on renewableresources to produce some or all of their ownenergy and create no pollution.

One of the most promising renewable energytechnologies is photovoltaics. Photovoltaics(PV) is a truly elegant means of producingelectricity on site, directly from the sun,without concern for energy supply or en-vironmental harm. These solid-state devicessimply make electricity out of sunlight,silently with no maintenance, no pollutionand no depletion of materials. Photovoltaicsare also exceedingly versatile - the sametechnology that can pump water, grind grainand provide communications and village

electrification in the developing world canproduce electricity for the buildings anddistribution grids of the industrializedcountries.

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Figure 11.1 HEW, Hamburg, Germany: 16.8

kWp facade-integrated PV system.The polycrystalline PV modules

are installed as fixed shading

devices.

There is a growing consensus that distributedphotovoltaic systems which provide electricityat the point of use will be the first to reachwidespread commercialization. Chief amongthese distributed applications are PV powersystems for individual buildings.

Interest in the building integration of photo-voltaics, where the PV elements actually be-come an integral part of the building, oftenserving as the exterior weathering skin, isgrowing world-wide. PV specialists from some15 countries are working within the Interna-tional Energy Agency's Task 16 on a 5-yeareffort to optimize these systems and architectsare now beginning to explore innovative waysof incorporating solar electricity into theirbuilding designs.

This chapter presents the reasons behindbuilding-integrated PV and some examples ofthis early work. View these PV-powered buil-

dings as a first glimpse into the coming newera of energy-producing buildings where thiselegant, life-affirming technology will becomean integral part of the built environment.

11.2 Building envelope

More than any other building component, theroof and especially the facade, have to facechanging and also often unpredictable de-mands. Facade materials, building components

and construction techniques that are visible onthe inside and outside of the building have tofulfill numerous requirements:

Figure 11.2 SOS Kinderdorf, Zwickau, Ger-

many: 2.9 kWp roof-integrated

PV system. Frameless archi-

tectural laminated glass with

amorphous silicon cells.

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Figure 11.3 Building envelope performance requirements.

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11.3 Planning context of an energy con-scious design project

The possibilities of an active and passive so-lar energy use in buildings is greatly in-fluenced by the form, design, constructionand manufacturing process of the buildingenvelope. A promising possibility of activesolar energy use is the production ofelectricity with photovoltaics. This technol-ogy can be adapted to existing buildings aswell as to new buildings. It can be integratedinto the roof, into the facade or intodifferent building components, such as aphotovoltaic rooftile.

Such an integration makes sense forvarious reasons:

The solar irradiation is a distributed en-ergy source; the energy demand is distri-buted as well.The building envelopes supply sufficientarea for PV generators and thereforeadditional land use is avoided as well ascosts for mounting structures and energytransport.

Table 11.1 Active and Passive Solar De-sign Principles ( Ingo

Hagemann).

Figure 11.4 Laukaa autonomous house,

Finland.

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Figure 11.5 Commercial building (A. Wild)

in Innsbruck, Austria.

In order to use PV together with other availa-ble techniques of active and passive solarenergy, it must be considered that sometechniques fit well together and others ex-clude each other. For example: As a kind ofa "passive cooling system", creepers areused for covering the south facade of abuilding. The leaves evaporate water andprovide shade on the facade. This helps toavoid penetration of direct sunlight andreduces the temperature in the rooms behindthe facade. At the same time the leaves

create shading on PV modules that may bemounted on the facade resulting in a farlower electricity production.

To avoid such design faults it is necessary tocompare and evaluate the different tech-niques that are available for creating an en-ergy conscious building. An overall energyconcept for a building should be made at thebeginning of the design process. Therefore,the architect and the other experts involvedin the design and planning process need to

work together right from the beginning ofthe design and planning process. All togetherthey have to search right from the beginningfor the best design for a building project.

11.4 Photovoltaics and Architecture

Photovoltaics and Architecture are a

challenge for a new generation of buildings.Installations fulfilling a number of technicalapproaches do not automatically representaesthetical solutions. A collaboration be-tween engineers and architects is essential tocreate outstanding overall designs. Thisagain will support the wide use of PV. Thesesystems will acquire a new image, ceasing tobe a toy or a solar module reserved for amountain chalet but becoming a modernbuilding unit, integrated into the design ofroofs and facades. The architects, together

with the engineers involved are asked to inte-grate PV at least on four levels during theplanning and realisation of a building:

Design of a building (shape, size, orienta-tion, colour)

Mechanical integration (multifunctionalityof a PV element)

Electrical integration (grid connectionand/or direct use of the power)

Maintenance and operation control of thePV system must be integrated into the

usual building maintenance and control.

The photographs illustrate some examples ofPV facades and PV house designs.

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Figure 11.6 Planning Responsibilities and Lay Down of Energy Consumption.

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Chapter 12

Photovoltaic Modules Suitable forBuilding Integration

12.1 Introduction

A PV module is basically designed and ma-

nufactured for outdoor use. All products avail-able are suitable to be exposed to sun, rainand other climatic influences. Thesecircumstances make possible the use of PVmodules as part of the building skin. Manydifferent types of module technologies areavailable. However, not all of them are usefulfor building integration. In the past, modulesused to be specifically designed for energygeneration and the building element functionwas neglected. Future considerations aim atdesigning building elements which also

deliver electrical energy. The moduleconfiguration is described in Chapter 5. Thevarious module types such asmonocrystalline, polycrystalline and amor-phous silicon have differing aestheticconsiderations. The colour of monocrystallinecells varies from uniform black to a dark greywith a uniform surface structure. In contrast,the structure of polycrystalline cells showsirregular grey to blue coloured crystals. Inboth types, the current gathering grid lines arewell visible as a silver or black metallic

colour. This may change in the future, as thegrid colour is better matched to the colour ofthe cells. Many types of modules andlaminates are available with mono- orpolycristalline cells. For semitransparentmodules the space between the single cells isenlarged to let light pass through. Custom-designed modules allow an individual qualityof the light transmission. In addition, thecolour of the back sheet for non-transparentmodules can be selected.

Amorphous silicon is deposited on metal,glass or plastic films, meaning different kindsof modules are available. These modulesusually have a dark brown colour. For semi-transparent modules of amorphous silicon thecells themselves are pervious to light. Sincethe cells absorb a part of the spectrum, thecolour of the passed light is changed.

Today's technology of module design haslead to several solutions for building-integrated PV systems. The following tableshows the advantages and disadvantages ofdifferent types of PV modules.

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Table 12.1 Suitability of different module types for building integration.

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Figure 12.1 Standard module.

Figure 12.2 Standard laminate (APS).

Figure 12.3 Large glass-glass module with predefined transparency (Flagsol).

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Figure 12.4 Glass module with predefined

transparency.

Figure 12.5 Module with metal back sheet

and plastic cover (USSC).

Figure 12.6 Swiss Solar Tile (Newtec).

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Figure 12.7 Custom-designed module (here: triangular shape) (Solution).

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Chapter 13

Design Concepts

13.1 Design as multidisciplinary approach

The design and construction of buildings hasshifted away from the creation of a"dwelling", moving towards the interpretationof the multi-functionality of the various

construction typologies, as well as thecomponents of architecture. The tendency toindustrialize building construction hasrevealed the need to clarify the designprocess; which controls the growingcomplexity of the project, and the need tocombine the technical-scientific role of theengineer with the technical and compositerole of the architect, and with the new indu-strial technologies. The problem of archi-tecturally integrating photovoltaic technologyrequires an interdisciplinary design approach.

This not only imposes collaboration and thepresence of highly specialized professionalson the project team, but also introduces asensitivity to problems that go beyond thebuilding itself. These inhabit a sphere that iseven broader, including social, economic,environmental, energetic and ecologicalissues.

As an example, a building facade must notonly keep out water and regulate heat loss, itmust also regulate the entry of light, provide

a sound barrier, offer ease of technical main-tenance and also must be aesthetically and ar-chitecturally satisfying.

The study of the elements and componentsinvolved in photovoltaic application systemsis of great importance in the final quality ofthe product. On this level, a PV buildinginstallation is a typical industrial designproblem. Each project for the architecturalintegration of

photovoltaics may require both the revisionof the type and the dimensions of thephotovoltaic panel, and the study of newframing and mounting systems. Individualspossessing the skills that are specific to thissector will be involved as well. These people

range from the architects and engineers tophotovoltaic cells manufacturers and to allthe technicians and the producers of thematerials employed in the construction.

13.2 The role of photovoltaics in building

It has been mentioned before that a building isa combination of many complex systems:structural mechanical, electrical, and others.Changes to the parameters of one system affect

the others. An assessment of the performanceof a building-integrated PV system as an ele-ment of a building skin therefore requires amultidisciplinary approach. A building- inte-grated PV system in fact adds another role tothis program: power generation. A buildingsurface can usually be classified as a roof or awall, with significant differences in function,construction, and thermal and solar loading.

Architects are turning into industrial

designers and project energy managementconsultants in order to address PVconstruction as more than just a buildingmaterial. The value of PV can besignificantly enhanced by collateral energybenefits. As PV cells capture sunlight and con-vert it to electricity, they also convert it toheat which can be used or discarded asnecessary.

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13.3 Considerations in designing buildingenvelopes for PV

During the design stage, both the technicaland aesthetic characteristics of the PVmodule must be considered in order to arriveat a satisfactory integration of PV into thebuilding as a whole.

Central to the study of PV building design isthe conflict between PV solar considerationsand contemporary building conventions. Theprimary goal in the layout of PV powersystems is to maximize the amount of powergenerated through optimum array orientation,

but this goal is tempered in the case ofbuilding design by considerations ofconstruction costs, optimum building floorarea, daylight control, thermal performance,and aesthetics. In addition, buildingenvelopes are often designed to deflect andminimize the amount of radiation falling on abuilding's surface, since cooling is often thelargest consumer of energy in a building. Bycontrast, photovoltaics require the greatestpossible radiation in order to maximizeperformance. Also, the envelope system must

be designed to resist any water which maypermeate the skin and infiltrate not only theframework, but also the photovoltaic panelinterlayer. In addition, electrical connectionswhich penetrate the weather seal must also bedesigned for reliable performance. Inclimates where clear/cold days bringsubstantial and immediate temperaturechanges to building surfaces, the PVenvelope system needs to resist or eliminatethe condensation.

Both mild and extreme climates require goodinsulating properties at the envelope. PV pa-nels may be directly laminated withinsulation or may be incorporated into multi-layer air or gas-filled insulating units.Electrical connection design will also need totake into account thermal bridging.

The impact of lightning on PV building enve-

lopes is another important environmentalissue. PV structures will need to be groundedand circuited to prevent a possible powersurge which may result in damage to thepanels or a hazard to their occupants.

The issues of building-integrated PV designare not exclusively technical. The balance be-tween the issues of PV building design andconstruction will vary greatly according tothe circumstances of each project (climate,budget, client priorities, aesthetics, etc.).

13.4 Outline for the design procedure

The following discussion attempts to identifya possible outline for the design procedure ofa building-integrated PV system.

13.4.1 Climatic considerations and orienta-tion

Locations, climates, latitude, average cloudi-ness, average temperatures, precipitation, hu-midity, dust/dirt, wind loads, and seismic con-

ditions will all affect the economics of a PV-integrated building system by virtue of howthey are addressed in the envelope design.

South-facing unobstructed PV panels are usu-ally oriented at a tilt equivalent to the locallatitude in order to receive maximum solarradiation, while building walls are generallyvertical for reasons of economy, efficiencyand traditional construction technology. Eastand West-facing facades perform relativelywell at steep angles or vertical orientation

due to the low angle of the sun at thebeginning and end of the day. The building'selectrical load profile and the utilility time-of-use rate structure are important parameters inestablishing optimum PV orientation.

The inherent flexibility of PV compared toother types of solar collectors (wiring is in-

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herently easier to run than plumbing), com-bined with anticipated low material cost (thin-film PV on glass substrates are basically si-milar to coated architectural glass), raises thepossibility of considering PV a building ma-terial first, and a PV device second. Thus, anarchitect desiring a monolithic appearancefor a building may choose to clad all of a buil-ding's surfaces with PV, even those that willnever see the sun. If the economics permit,PV can be used in any number of buildingcomponent configurations and without anoverriding demand for optimal orientation. IfPV orientation is not perceived as a designrestriction, architects will be much moreopen to their use.

13.4.2 The site

The characteristics of the site and its orienta-tion will influence the design in order to de-termine where and how to integrate PV in thebuilding.

Building floor area can be a precious commo-dity. In some cases, sloped PV panel configu-rations will reduce the amount of occupiableperimeter floor area because the wall effecti-vely 'cuts back' on floor area as the buildinggets taller. Any reduction in usable floor areaneeds to be considered when evaluating thelife-cycle costs of a PV system.

High rise structures are usually built in an ur-ban environment where real estate costs arehigh and the surrounding landscape is dense.Shadows cast by other tall buildings reducethe performance of the panels. It may be that

for certain high rise projects only the upperstories will be clad in PV with only someareas active during the course of a day. Insuch cases, the designer can chose toarticulate or camouflage the active andinactive portions of the facade by usingcontrasting or matching cladding next to thePV.

13.4.3 Zoning regulations and buildingcodes

Sometimes zoning regulations regarding co-lors, building shape, and building codes, willalso have an impact on the selection of thedifferent kind of photovoltaic material to use.

Another parameter is certainly the identifica-tion of technology, or which type of panels(single crystal or polycrystalline cells) shouldbe used. This decision should be made inaccordance with the dimension of thebuilding, its possible overall configuration,the economical restraints (some technologies

are more expensive than others) and theenergy demand.

13.4.4 Type of panels

The selection of the PV panels, theiraesthetic characteristics in terms of modulargeometry, dimension, color, mounting system(with exposed frame or without frame), willinfluence the overall appearance of thebuilding and the architectural character of theintervention. The modules are the mostimmediately recognizable and distinguishingcomponents of the various PV systems. Theyare most visible from outside the buildingand will most probably be placed in aprominent position to avoid the shadowcones of nearby buildings that could reducethe efficiency of the system and the desiredelectric energy output. PV panels mayprovide energy benefits beyond the electricitythey generate by providing passive solarheating or cooling load reduction.

The modular geometry, the colors and the tex-ture of both the cells and the glass of the pho-tovoltaic panels constitute the main aestheticcharacteristics of the panels. The balance be-tween the amount and quality of glass and thequantity and type of cells used in the panel ispart of the design process and will berelevant to both the panel and the space. Thisdevice can be used to exploit a sort ofdecorative and

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functional texture formed by the natural lightthat filters through the cells. In fact, this trans-parent grid of light created by the glass spacebetween the cells is a significant contribution

to the enrichment of the architectural qualityof the indoor spaces. Very different are thosecases in which the panel is interpreted as realconstruction material. Here it acquires consi-derable functional and aesthetic validity, par-ticularly when we analyze the very interestingdialectic taking place between PV and tradi-tional construction materials.

The photovoltaic cell presents its most inte-resting aesthetic aspects on the exterior face

which is exposed to the sun. By varying theselection and positioning of PV cells in themodule, it is possible to obtain a wide varietyof color, brilliance, reflectivity and transpa-rency effects.

The cables, the junction box and the batteryof a PV module might be visible, dependingupon the type of installation and the type ofmodule. This should be taken intoconsideration during the design stage, so thatthe overall spatial configuration is controlled.

13.4.5 Installation

For both new construction and retrofit, themethod of installation is important to the costeffectiveness of the system. For example, glaz-ing installation from the interior does not re-quire exterior scaffolding. Interior glazing is acommon method of contemporary curtainwall installation today, accomplished bysplitting the mullion and muntin extrusionsinto separate elements which snap into placein the field.

Shop labor is usually cheaper and moreprecise than field labor. Whenever possible,panelized or prefabricated wall or roofsections will save money, especially incomplex PV wall profiles. Prefabricatedsystems could also include some

electrical balance of systems or PV-powereddevices such as fans or lights.

It is important to recognize that the integratednature of applied architectural PVinstallations (curtain wall framing, glazingsystems, PV and electrical connections, etc.)will require the combined efforts of a numberof different building trades and jurisdictions.Conventional construction sequences andresponsibilities must be considered in thedevelopment of PV products if they are to fitpresent construction industry practice.

13.4.6 Structure, engineering and details

The mechanical and electrical systemsrequired to maintain and operate a building ofsubstantial scale are often complex and canrequire a tremendous amount of energy.Photovoltaics add both benefits andadditional levels of complexity to theengineer's task. PV buildings will challengearchitects and engineers to develop innovativesolutions for integrating a building's supportsystem with PV supplied power. Critical

issues to consider for engineering systemsintegration will be, among others, safety,durability and economy.

13.5 Configurations for PV building inte-gration

Before starting to design a PV building, it isvery important to analyze each possible ap-plicable solution of application to determine

its overall impact on the building's energy bal-ance and the energy efficiency performanceof the overall system.

The following diagrams offer a panorama ofconfigurations for PV integration, selected bythree main architectural application typolo-gies:

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walls and facades, roofs and large coverings, light filtration and screening elements.

13.5.1 Walls and facades (Figures 13.1 - 13.7)

There are two basic curtain wall framingsystems in common use: pressure plate andstructural silicone glazing. In pressure platesystems, the glazing unit is mechanically heldfrom the front by a plate with an extrudedcover or 'cap'. Structural silicon glazing gluessome or all of the glazing edges to theframing systems. In pressure plate systems,the mullion cap depth must be kept to aminimum to avoid adverse shadowing on PVcells. Alternatively, flush application of astructural silicon seal between PV glazingunits eliminates shadowing effects butincreases weather seal and durabilityproblems for PV panel edges.

To minimize sealing problems, or to captureheat from the PV modules, it may make senseto fabricate a double wall envelope, where thePV glazing is the external, unsealed layer and

the inner layer may be the weather tight en-closure.

Optimizing PV panel performance in buildingwall applications may require complex detai-ling and therefore higher construction costs inorder to accommodate optimal orientations tothe sun. For wall applications, these complexconfigurations may take on a sloped or "saw-tooth" profile (see Figures 13.3, 13.4, 13.13)or the PV may be applied independent of thebuilding's skin as awnings or light-shelves

(Figures 13.14, 13.15).

13.5.2 Roofs and large coverings (Figures13.8 - 13.13)

For roof applications, installations generallyrequire little compromise in solar orientationbut may create structural or weather-proofing

problems. Horizontal roof configurationsmust be structured to accommodate othertypes of loading such as snow and water.This issue requires different solutions

depending upon the location of the building.In climates with considerable snowaccumulation, skylights and roof systemsincorporating PV may need to be designedwith a slope sufficient to shed snow whichmay be steeper than the optimal slope forsolar gain. Partial PV skylight enclosureswill shade interior spaces from directsunlight while simultaneously harnessingpower from the sun's rays. PV roof monitorscould also reduce or eliminate the need fordaytime electric lighting by providing

indirect daylight.

Flexible substrates such as sheet metal or fab-ric would open up large new markets. PV de-vices that mimic traditional buildingmaterials (such as clay roof tiles) may alsoincrease their market.

13.5.3 Light-filtration and screening ele-ments (Figures 13.14, 13.15)

Opaque PV panels installed as PV windowawnings (Figure 13.14) or PV light shelves(Figure 13.15) can shield direct sun whileproviding diffuse, indirect light to interiorspaces. The portion of these light shelveswhich are exposed to sunlight would be PV;the portion in shade could be any reflectivematerial. The panels' surface would bouncelight onto the ceiling inside.

Another PV device with some passive solarbenefits is the semi-transparent photovoltaicpanel, or PV window, designed to admit aspecific amount of light and/or view to aspace. Some thin-film PV devices areinherently semi-transparent, if produced withclear conductive coatings on glass substrates.Alternatively, opaque PV devices may berendered effectively transparent by thecreation of a pattern of clear areas where theopaque materials have been removed. Itshould be possible to

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incorporate semi-transparent PV into insulatingor high-performance multi-pane glazing units.With less active PV area, the solar performanceof these semi-transmissive panels will be less

than with opaque PV. But the passive benefitsand vision area produced in some cases willoutweigh the reduction in efficiency.

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Figure 13.1 Diagram A: Vertical curtain wall.

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Figure 13.2 Diagram B: Sawtooth vertical curtain wall.

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Figure 13.3 Diagram C: PV sawtooth curtain wall.

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Figure 13.4 Diagram D: PV accordion curtain wall.

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Figure 13.5 Diagram E: PV sloping curtain wall.

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Figure 13.6 Diagram F: PV sloping/stepped curtain wall.

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Figure 13.7 Diagram G: PV structural glazing.

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Figure 13.8 Diagram H: PV roof panels.

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Figure 13.9 Diagram I. PV atriums.

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Figure 13.10 Diagram J: Flexible/metal PV substrates.

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Figure 13.11 Diagram K: PV skylights.

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Figure 13.12 Diagram L: Independent PV rooftop array.

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Figure 13. 13 Diagram M: PV sawtooth roof monitors.

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Figure 13.14 Diagram N: Hybrid PV awning systems.

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Figure 13.15 Diagram O: Hybrid PV awning/light shelf systems.

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13.6 IEA Task 16 Architectural Ideas Competition

The following examples have been extracted from the IEA Architectural Ideas Competition"Photovoltaics in the Built Environment". The initiative for this competition, launched in 1993,lies with Task 16 of the IEA Solar Heating and Cooling Programme.

13.6.1 South East South South WestB.J. van den Brink,

The Netherlands

Environmental-friendly building means buil-

ding as little as possible, and therefore aswell building as compact as possible. A com-pact layout reduces the amount of neededbuilding material. A compact buildinglayout reduces as well the need for energywhen the building is in use. Finally, acompact urban planning reduces need fortransportation.

The detached houses have a compact layout(they approximate a sphere), but cannotmatch these principles completely becauseof a lack of urban compactness. Tocompensate this, the facades can absorb alot of solar energy, and futuristic flaps onthe roof can open during the day to collectsolar energy and close during the night toinsulate the building.

Figure 13.16 IEA competition entry by B.J. van den Brink, The Netherlands.

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13.6.2 PV in single dwelling unitD. Mizrahi, Switzerland

The design of a single dwelling unit using PV

is a very delicate question which demands ahigher grade of sensibility. The perceiving ofthe social implications of technological deve-lopment and the responsibility for our envi-ronment are indispensable for that. To avoid'architectural pollution' it is necessary to ap-proach PV as self-defined design and con-struction element of architecture. In this way,PV becomes an obvious part of the building.

Figure 13.17 IEA competition entry by

D. Mizrahi, Switzerland.


D. Mizrahi, Switzerland.

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13.6.3 A conference and cultural centreG. Kiss, USA

Figure 13.19 IEA competition entry by G. Kiss, USA.

Large-area, thin-film photovoltaics are usedthroughout. Uniform appearance, large sizeand low cost are the principle advantages ofthis type of PV. In each application in this de-sign, collateral energy benefits (daylighting,thermal) are maximized while initial costs areminimized by multifunctional construction.The conference centre roof sawtooth isdirectly supported by box trusses tilted tosupport the photovoltaics while providing

drainage sufficient to keep the modules clean,and providing clerestory area for fulldaylighting. Heat buildup (not needed forspace heating in this climate) is circulatedbelow the trusses and exhausted outside.

The hotel curtain wall is internally ventilatedfrom floor to floor by convention dampers atthe head and sill of each window. Hot airfrom the wall cavity is directed in or outaccording to demand. This avoids the costs ofa full double wall system while providing theflexibility of operable windows.

Figure 13.20 IEA competition entry by G. Kiss, USA.

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13.6.4 An Energy-Conscious OfficeBuilding in AnkaraC. Elmas, USA

There is no example of photovoltaics integra-tion to buildings in Turkey. In order to makethis technology acceptable, this project usesthe PV modules as sunshades that are remi-niscent of traditional mashrabiyas (woodlattice screens). PV modules are used withdifferent configurations, transparencies andpatterns at each facade in order to respondto the sun, views from the offices, characterand scale of the particular facade.


C.Elmas, USA.

Figure 13.22 IEA competition entry by C. Elmas, USA.

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13.7 German Architectural IdeasCompetition 1994

The architectural ideas competition "Photo-voltaics in Buildings" was initiated to encou-rage architects in cooperation with engineersto tackle the technically and aestheticallychallenging problem of building integrationof photovoltaic systems. It was supported bythe Federal Ministry of Education, Science,Research and Technology under a grant tothe Fraunhofer Institute for Solar EnergySystems (FhG-ISE) in Freiburg, Germanyand organized by the Institute for Industrial-ization of Building Construction (Institut IB)

in Hannover, Germany.

Using a building that was in planning and/orunder construction anyway, possibilities forthe integration of photovoltaic systems withhigh architectural quality were to be shown.The conditions for and the consequences ofthe integration were to get special attentionwith respect to the building. The buildingscould be of any size and location within Ger-many, e.g. office and administration buil-dings, traffic facilities, sports facilities, con-

vention halls, industrial buildings, schools orresidential buildings.

The jury met in September 1994 to evaluatethe 30 competition entries. The entries wereudged in three rounds according to the fol-

lowing criteria:

The overall architectonic concept, the overall energy concept, the integration of the photovoltaic ele-

ments, the transferability of the solution, the expense and the gain from the photo-

voltaic systems used.

Seven entries have been awarded and men-tioned:

13.7.1 Zentrum fr Kunst und Medien-technologie, Karlsruhe (Schweger +Partner, Hamburg)

An industrial area from the turn of the cen-tury will be modernized and prepared for theCenter for Arts and Media Technology. Thephotovoltaic generators will be integrated inthe transparent roof of the patios. This gives amultiple effect:

Reduction of energy entry and air con-ditioning power by about 90 kW,

a photovoltaic generator with a nominalpower of about 100 kW,

direct feeding of the electrical power intothe overhead line of the Karlsruhe trolleycars (no batteries or current inverters).

Figure 13.23 Visible photovoltaic panels

above the entry hall.

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13.7.2 Exhibition building "Haus desWaldes", Stuttgart (Dipl.-Ing. Mi-chael Jockers, Stuttgart)

The pavilion contains an exhibition halland supporting facilities. It is located in theStuttgart city forest close to the televisiontower. The photovoltaic generator (14.5kW) is used in addition to other energysaving measures (passive heat gains,daylighting, high insulation of opaquecomponents, use of wood as load-bearingmaterial, solar collectors for hot watersupply).

Figure 13.24 Cube of music studio outside

the existing building.

Figure 13.25 PV array on top of the musicstudio.

Figure 13.26 Section of the glass roof

Figure 13.27 Model view of

"Haus des Waldes".

Figure 13.28 Detail of roof integration

("Haus des Waldes").

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13.7.3 Housing project with nine apart-ments in Aalen (Kerler-Amesder-Braun, Fellbach)

The terrace-shaped apartment building showsan interesting way of integration of the pho-tovoltaic generator in combination with win-d o w s a n d l o g g i a s . T h e s y s t e m i sdimensioned to cover approximately twothirds of the yearly electrical energy con-sumption. Even during the summer months,almost all of the energy generated is thusconsumed within the building. Excess energyis fed into the mains.

Figure 13.29 Section terrace. Figure 13.31 Section room.

Figure 13.30 Bird's eye view.

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13.7.4 Administration building forNrnberger Versicherung, Nrn-berg (P. Dirschinger, F. Bifang,

Ammerndorf)

This is a large administration building (about4500 employees) with photovoltaicgenerators integrated into differentcomponents (among others noise-absorbing walls, shading devices and anadvertising sign). The total nominalelectrical power is 366 kW. Othermeasures related to the energy con-sumption are transparent insulation, thermalcollectors, daylighting, cold buffering, heatrecovery and optimal insulation of all

outer walls.

Figure 13.32 Model view.

Figure 13.33 Section of sound protection wall

with PV array.

Figure 13.34 Section with shading PV ele-

ments.

Figure 13.35 Section of ventilated facade.

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13.7.5 Office building Luxemburger Stra-Be, Wirth (Elkin + Hvels,Cologne)

This building is planned for a private inves-tor on the outskirts of Cologne on a cornersite with good traffic connections. Severalenergy-relevant measures are planned:

High-insulating glass facade, ventilation with heat recovery, integrated photovoltaic generators

("saddleback roof', "great sun shovel","little sun shovel").

13.7.6 Ecological housing estate, Hamm-Heessen (H.F. Bltmann, Bielefeld)

This project, which will be built in two pha-ses, will provide about 100 housing units ofdifferent types. The authors plan to approxi-mately cover the yearly electrical energyconsumption of the estate with aphotovoltaic system of about 196 kW.Excess electrical energy will be fed into themains.

Figure 13.36 View from east. Figure 13.38 Integration details.

Figure 13.39 Western and eastern facade.

Figure 13.37 Facade section.

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13.7.7 Radio relay station Tabarz I, Bot-terode/Thringen (StreckebachArchitekten, Kassel)

In this pilot project, a photovoltaic generatorand batteries are used as backup to increasethe reliability of the power supply. It is in-vestigated as a possible way to replace dieselgenerators in environmentally sensitive ar-eas. An architectonically interesting way ofmounting the photovoltaic generator to theexisting tower was found.

Figure 13.41 Tower with PV array.

Figure 13.40 Existing tower.

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Chapter 14

Integration Techniques and Examples

14.1 Introduction

The following selection of examples aims atpresenting basically two key issues. One isthe demonstration of a significant number ofrealised examples: facades, roofs and othersshow clearly that the architectural andtechnical integration of PV in buildings isfeasible. And as a second message, theexample descriptions show how the systemsare mounted. Each mounting method isexplained by a set of drawings. In addition tothese example presentations, some generalrecommendations for module integration aregiven as follows.

Use of non-corrosive materials: On PV faca-des there are always small leakage currentsaround. In order to avoid corrosion caused bythe leaking DC currents, it is essential to usenon-corrosive construction materials. Theoints and holding points require special con-

cern.

Exchange of modules: The exchange ofsingle modules should be possible withouttaking away a large part of the facade or roof.

Flat surfaces: To avoid shading, dust accu-mulation and to ease clearing by rain, protru-

ding elements over the solar modules shouldbe avoided. Fixation points for an unframedmodule may only little just out the module sur-face.

Easy cabling: Before the solar roof or facadeelements are placed, the electricalconnections have to be prepared. The use ofreliable plug connectors makes a rapid andeasy installation possible. During mounting ofthe modules no

electricians should be required.

Minimum module handling on site: Asmost of the current solar modules consist of aglass surface, they require careful handlingduring transportation. Once being installed,the risk of damage is very low. This

circumstance leads to the recommendationthat module handling on the construction siteshould be reduced as far as possible. Themodule should go from the transportationcontainer directly to a place along the roof orfacade.

Module matching and string layout: De-pending on the electrical layout and the mo-dule characteristics, they have to be assignedto a certain position in order to form groupsor strings of modules with similar electrical

characteristics. This can be done in thefactory before shipping. The packing shouldthen be accordingly in order to ease modulehandling on site.

Ventilation: As long as modules based oncrystalline cells are used, it is an advantagewhen the modules' rear side is ventilated aswith curtain walls. With amorphous modulesthe difference is negligible because the effi-ciency depends only little on temperature.

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14.2 Stadtwerke Aachen, Aachen, Germany

Figure 14.2.1 General view.

Key data

Nominal power: 4.2 kWGross Area: 87 m2Module manufacturer: Flachglas

SolartechnikInverter: 2 PVWR 1800Start of operation: 1991Owner: Stadtwerke

Aachen AG

Short descriptionThe south-facing glass facade of the 20-year-

old administration building of the StadtwerkeAachen (Utility of Aachen) was replaced by asolar facade during the renovation of the hea-ting services. Light-diffusing modules develo-ped especially for this south-southeast frontdirect daylight into the staircase behind. Thechessboard type combination of glass elementsand the modules with dark-blue crystallinesilicon cells between the compound glazingoffers surprising patterns outside as well asinside.

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Figure 14.2.2 Detail of mounting structure.

This example was one of the first so-called

multipurpose applications with PV modules.The PV modules act as semitransparentfacade, as wall element including thermalinsulation and as power production device.The wiring is integrated in the structureholding the modules.

Figure 14.2.3 View of the facade from the

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14.3 Scheidegger Metallbau, Kirchberg, Switzerland


Key dataNominal power: 18 kWGross Area: 170 m2Module manufacturer: SolutionInverter: Solar MaxStart of operation: 1992Owner: Scheidegger Me-

tallbau, AG

Short descriptionJust as important as the energy productionwas here the ability to gain knowledge aboutnew architectural possibilities in facadedesign with PV modules. Besides theproduction of electricity and the aestheticdesign, the weather protection of the building,the shading of workplaces near windows insummer and the combination of theproduction of electricity and hot air are othergoals of this installation.

To make a better use of the PV modules, apart of the facade is built with reflectingelements. The whole installation is workingproperly, but there are high expenditures forattachment. Cheaper PV modules could beused effectively for the whole facade area.The multifunctional design of the facade issketched in Figure 14.3.3.


Figure 14.3.3 Multifunctional design of the PV

facade.

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14.4 ISET, Kassel, Germany


Key dataNominal power: about 0.5 kWModule manufacturer: ASE GmbHInverter: 3 x NEG 1600

3 x SLD 224Start of operation: 1993

Owner: ISET e.V., Kassel

Short descriptionThe main idea of this project is the realisationof an experimental photovoltaic (PV) facade at

an existing building at the University ofKassel. The facade consists of a PV array of 50

m2 (75% south, 15% west and 10% east orien-

tation) and is used for testing different compo-nents (modules or inverters) and concepts(mounting and electrical installation) in prac-tice. Since July 1st, 1993, five different PVgenerators are in operation, their conditions aremeasured and recorded.

The project is funded by the Ministry of En-vironment of Hessia. The industrial project

Figure 14.4.2 Detail view of the installation

behind the facade.

partners are ASE GmbH (DASA and NU-KEM) and SCHCO International.

Detail of mounting structureIn this project existing industrial componentsare used for building up the PV facade. So afacade system was modified to integrate thePV modules. Three different sizes of modulesare inserted: 1780 x 1180 mm, 1180 x1180 mm and 580 x 1180 mm. The modulescontain 160, 80 or 40 photovoltaic cells in or-

der to be electrically connectable.

Main research aspectsThe PV facade is exclusively designed for thefollowing research aspects which enables an-swers to the questions and concerns of modulemanufacturers, facade builders, architects andenergy industries. These are:

edging quality of frameless PV modules,

defect recognition to detect defects in thesystem,

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measuring technology, e.g. reference mea-suring,

safety of persons and the system, energy processing, test of different types

meteorology - recording of weather data installation - mechanical and electrical con-cepts,

shadowing and the influence of HOT-SPOT-effect,

mechanical tests - behaviour under extremewind conditions,

electrical tests - efficiency and isolation re-sistance.

Figure 14.4.3 Detail view of the mechanical

construction.

Figure 14.4.4 Energy input of reference PV module (refering to 1 kW).

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14.5 kotec 3, Office building, Berlin


Key dataNominal Power: 4.2 kWGross area: 64 m2Module manufacturer: Flachglas Solartechnik

GmbHInverter: 2 x PV-WR 1800 SStart of operation: 1994Owner: Triangel Grund-

stcksverwaltungs-gesellschaft

Short descriptionThe goal to be achieved is to integrate a solarfacade of the most progressive technical stateinto a new industrial building of the latest ar-chitecture. Special attention should be paid toobtain a good efficiency of the installationand to integrate the PV generator properlyinto the architecture.

The industrial building created by the archi-tects Aicher, Jatzlau von Lennep and Schulerin Berlin-Kreuzberg, with a floor surface of8100 m2 was equipped with a grid-connectedphotovoltaic generator integrated in its southfront. The 44 solar facade elements are inte-grated as cold facade elements into the frame-work system of a reflecting whole glassfacade with interwork side ventilation.

Figure 14.5.2 Detail of PV element.

The new "SJ" facade system used for thefirst time for a solar facade project stands outfor its easy mounting system for glasspanels. The solar facade modules aredesigned as blue glistening, partly reflectingdouble pane laminated glazing unit toharmonize best with the remaining reflecting"structural glazing" facade. The electricalconnection is done by a standardized plugsocket system.

With regard to the module configuration andproduction, the connection system - thoughtas a standard for future projects - as well asthe aesthetic successful architectonicintegration, this project sets an innovativeexample.

The facade system is particularly suitable forthe integration of PV facade modules, as itholds frameless facade panes of any kind bya minimum of 4 fastening points through pa-tented, star shaped stainless steel parts withelastic EPDM coating and is thus able tocarry the frameless OPTISOL moduleassembly. Electrical connection: Thecollecting line is attached to the interior panecovered with solar control reflectiveinsolating coating. The bypass cables comingfrom the panel board through standardsockets are connected with the modules.These modules are interconnected with asocket/plug system, the junction box beingstuck to the glass back side of the module.The whole connection system makes

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the installation work easier and, if necessary,enables easy replacement of each individualmodule.

Figure 14.5.3 Module design drawing.

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14.6 LRE building EPFL, Lausanne, Switzerland


Key DataNominal power: 3 kW

Gross area: 28.5 m2Module manufacturer: Flagsol AGInverter: Top Class 3000Start of operation: 1993Owner: EPFL Lausanne

Short descriptionOn the outer wall of the Electric Power Sy-stems Laboratory the metallic thermo-lacque-red cladding was replaced by photovoltaicpanels in sheeted glass.

As existing elements were replaced, particularattention was given to the following details:

identical dimensions through made-to-mea-sure photovoltaic modules;

uniform color due to the use of polycristal-line cells aligned edge to edge without visi-ble electrical connections; within the panelitself a frame painted the same blue as themetallic structure to hide the main electric

connections; minimum specularity due to acid treatment

of the glass (reduced reflection) to producean effect as similar as possible to that of theformer cladding and differenciate the facadeelements from the windows.

The panels were mounted in a traditional wayby VEC-glueing and recessed fitting of themetal sections.

Mounting techniqueAs can be seen on the drawing of Figure 14.6.2

the mounting technique is quite traditional forglass panels:

a metal frame is anchored into the wall, inthis case using existing fixing points (Figure14.6.3);

two Z-shaped aluminium profiles are scre-wed onto the frame, over a protective sheetfor the thermal insulation (Figure 14.6.4).

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Figure 14.6.2 Cross-section of mounting de-

sign.

Figure 14.6.3 Detail: Metal frame.

Figure 14.6.4 Detail: Z-shaped profile.

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14.7 Northumberland Building, University of Northumbria, England


Key dataNominal power: 39.5 kWGross Area: Laminate area

293m2 Clad area(covered) 442 m2

Module manufacture: BP SolarInverter: SMA PV-WR-T

40 kW

Start of operation: December 1994Owner: University of

Northumbria

Short descriptionThe aim of this project is to provide a de-monstration of an architecturally integratedphotovoltaic (PV) facade on an existing buil-ding at the University of Northumbria in North-East England. The project will demonstrate thefeasibility of PV cladding in a northern

European climate and allow investigation ofthe installation details and supply profile ofthe electricity generated. This project willsupply the first example of integrated PV clad-ding in the UK, in order to stimulate interest inthis technology and to provide information forfuture integration into appropriate buildings.

Figure 14.7.2 Sectional view of mounting

structure.

The project partners are IT Power Ltd,Newcastle Photovoltaics Applications Centre,Estate Services Department of the University ofNorthumbria, Ove Amp & Partners and BPSolar.

The project is to fit rainscreen overcladding tothe south facade of the Northumberland build-ing. PV elements are integrated into this clad-ding system. This provides a total installedcapacity of more than 39 kW. The claddingpanels are approximately 3m x 1.4m, and eachcontains five PV laminates. There are 465 PVlaminates used in the whole array, each rated at85W.

The Northumberland building is a typical ex-ample of a 1960s construction for which the

cladding has provided protection for over 20years before refurbishment is required. Manysimilar buildings exist across Europe whichwill all require recladding within the next de-cade. The Northumberland building suffersfrom shading for some portions of the day andcan therefore be used to study the effect of par-tial shading on such a system.

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14.8 House Weiss, Gleisdorf, Austria


Key DataNominal power: 2 kWGross Area: 18 m2Module manufacture: Siemens M50LInverter: Siemens PV V 2500Start of operation: 1992Owner: private owner

Short descriptionWithin the framework of the Austrian "200 kWRooftop Programme" Mr. Weiss installed aphotovoltaic system on the roof of a buildingnear his low energy house in 1992. The singlefamily house has a living area of 150 It islocated close to the small town of Gleisdorf inthe Southern Austria. The heating load of thewell insulated building was calculated to be 7kW.

Mr. Weiss and his family already use veryenergy efficient household appliances. Data ofthe last years indicate, that only 2135 kWh ofelectric energy is annually consumed. This can

only be achieved by using an 8m2

solar thermalcollector system providing hot water for thedish washer and the washing machine. An aux-iliary electric heating element is used to supplydomestic hot water in wintertime (it consumes335 kWh annually). The house is heated by awood stove and some passive solar gains areutilized.


For better integration of the solar modules inthe wooden roof structure the house owner de-cided to use Siemens M50L laminates. TheSolar generator consists of 4 strings with 10modules each.

Figure 14.8.3 Sectional view of the horizontal

structure.

Figure 14.8.4 Sectional view of the vertical

structure.

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14.9 BOALsolar profile system for PV laminates

Figure 14.9.1 Detail of mounting structure. Figure 14.9.2 Detail.

Short descriptionThis profile has been developed by R&S,Ecofys and Boal (a large manufacturer of pro-files for greenhouse constructions). The mainobjective of the system is to provide a standardPV mounting system for slanted roofs.

The profile has been applied successfully in anumber of projects, including the 250 kWproof integrated PV system in Amsterdam and a100 kWp roof integrated system in Amersfoort(both in cooperation with the local utility).

The mounting system has been tested in ac-cordance to general Dutch standards for roo-fing materials (including water tightness, ro-bustness and fire protection).

The system consists of vertical and horizontal

aluminium profiles. The vertical profiles arescrewed to the battens (which are slightlyhigher than standard battens, in order to pro-vide enough ventilation). Horizontal profilesare glued to the PV laminate (prefab) andfitted into notches in the verticals. A plasticprofile, placed over the vertical profiles, holdsthe laminates down and provides absolutewater tightness.

Compared to mounting PV modules above thetiles, this system offers the following ad-vantages:

Avoidance of tile and tiling costs: High aesthetic value; Easy mounting technique;

Well-proven construction system; Highly standardized, leading to lower costs; In-factory preparation of mounting (glueing

of profiles).


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Figure 14.9.4 View, front view, side view.

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14.10 Solar Tile, Mnchaltorf, Switzerland


Key dataNominal power: 3 kWGross Area: 36 m2Module manufacturer: Plaston-NewtecInverter: Solcon 3300Start of operation: 1992Owner: PMS Energie AG

Short descriptionNew solar roof tiles represent a real photovol-taic integration: the system is not installed onthe roof, rather, the roof itself is the system.The roof elements installed on an old resi-dential house in Mnchaltorf, made of glass,were developed and produced in Switzerland.


Each one of the 76.6 x 50.5 cm2 lage, rainproof resin boards with integrated photovoltaiccells replaces five conventional tiles.

Under the guidance of Alpha Real AG, a groupof three companies has developed a Solar Tile

to cover inclined roofs in one step. The tile isbased on a standard laminating technologyequipped with a special frame and newly de-signed module interconnections. Particularly,this new solar tile design had to employ thefollowing functions:

easy mounting like ordinary clay tiles; the essential function of the clay tile (i.e.

weatherproof building material) has to besubstituted by the solar tile;

the sealing of the roof has to employ age oldroof sealing techniques, as they are function-ing on clay tiles without silicon or rubbersealant;

the interconnection among solar tiles andbetween solar tiles and clay tiles has to besimple, easy to install, and absolutely reliab-le;

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to speed up installation time, theelectrical connection from module tomodule has to be made with plug

connectors; roofmg professionals have to be able to

do the installation and wiring work on theroof without extended training;

every solar tile has to be easily exchange-able;

the life assessment of the plastic framehas to be at least as long as the minimalexpected life time of a solar module;

it has to incorporate existing frameless so-lar modules of different thickness and tobe able to adapt to future solar module de-velopment such as thin film technology orsimilar.

Figure 14.10.3 Front view, sectional views.

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14.11 Pietarsaari Solar House, Finland

Figure 14.11.1 General view. Figure 14.11.2 Detail of mounting structure.

Key dataNominal power: 2.2 kWGross area: 55 m2Module manufacturer: APSInverter: SMA 1800System design: NAPSStart of operation: 1994Owner: private owner

The aim of the Pietarsaari Solar House, con-structed in the Pietarsaari House Fair 94 area,is to demonstrate to a wide audience that withcurrent commercial technology energy con-sumption of houses can be dramaticallyreduced. During the House Fair exhibitionmore than 100,000 people visited the SolarHouse. In contrast to a conventional averageFinnish house, which needs purchased energyof 160-250 kWh/m2 for space heating, water

heating and electricity, the corresponding en-ergy demand has been reduced to roughly 20-30 kWh/m2 in the Pietarsaari low energyhouse. The low energy consumption has beenachieved with a combination of improvedinsulation, heat recovery from ventilation,heat pump with ground pipes, super windowsas well as by utilizing solar energy. The househas 10 m2 solar thermal collectors and a 2.2kW grid-connected PV system.

The aim of PV integration into this house wasto develop and test a simple and inexpensivewatertight photovoltaic roof structure and totest it. The system has been constructed byusing frameless large area amorphous photo-voltaic modules and glass fibre profiles.

Amorphous modules were chosen to be able tocover the whole roof with the chosen 2.2 kWarray and thus to achieve a uniform appearan-ce.

Figure 14.11.3 Construction detail.

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By using large area modules the number ofconnections and mounting profiles could beminimized. Also the short energy paybacktime of amorphous technology was

considered to be meaningful. The benefits ofcomposite profiles are:

similar thermal expansion to that of glass; good electrical and heat insulation charac-

teristics; good corrosion resistance and good mechanical strength.

The watertight PV roof was achieved by

mounting the frameless modules over the exis-ting vertical wooden roof substructure withrubber seals and long vertical glass fibre pro-files going from the top of the roof down to

the bottom of the roof. The horizontal seambetween the modules has been sealed with afork-shaped profile and elastic silicon mass.This type of simple integration method wasplanned in order to reduce the cost of materialas well as the installation time.

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14.12 Office Building, Utility of Meilen, Switzerland

Figure 14.12.1 General view. Figure 14.12.2 Detail of mounting structure

Key dataNominal power: 3 kWGross Area: 30 m2Module manufacturer: HeliosInverter: SolconStart of operation: 1992Owner: Utility Meilen

Short descriptionSchweizer Metallbau AG has developed aroof-integrated system that is able to carry PVmodules or thermal collectors. Theinstallation area is completely covered by theconstruction, conventional tiles are onlynecessary to cover the remaining area of theroof. A combination of photovoltaic andthermal use of solar energy is possible.

A relatively large space on the backside of themodule allows a sufficient air circulation for

module cooling and/or use of the low temper-ature heat. All current dimensions of PV mod-ules or laminates are possible to apply, butthere are some restrictions regarding the mod-ules' edges. In order to not cover solar cells byrubber profiles, the distance between theedges and the first cells shall be at least 15mm. The thickness of the module in the edgezone must be within 4 to 5 mm.

The laminate is completely kept by rubberprofiles. There is no direct join to the alumini-um profile. The top rubber profile is made ofEPDM.

Figure 14.12.3 Aerial view, sectional views.

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14.13 Integrated Solar Roof, Boston, USA


Key dataNominal power: 4.3 kWGross Area: 40 m2Module manufacturer: Mobil SolarInverter: American Power

ConversionStart of operation: 1984Owner: private owner

Short description

In 1984, 10 million viewers watched a TVprogramme introducing the latest technologyin the area of photovoltaics at that time; itpresented this one-family house in the northeast of the US. The roof facing south is tiltedby 45 degrees and divided into three sections.Twelve photovoltaic modules are located ineach of the left and right sections, while themiddle section contains roof-integrated solarcollectors.

The well-insulated house was designed as amodel for a country-wide energy-saving pro-gramme. The private residence meets high de-mands in terms of both aesthetics andcomfort. The frameless PV modules are thefinished weathering skin and are mounteddirectly over the wooden roof trusses withoutstructural roof sheating or additionalweatherseal. Free air circulation behind themodules is encouraged with generous inletand outlet vents designed

Figure 14.13.2 Detail of mounting.

to achieve maximum air flow. The PV lami-nates were designed specially for direct roofintegration and the thermal collector uses thesame glass cover. The result is a fully inte-grated appearance for both systems.

Figure 14.13.3: Aerial view

Figure 14.13.4: Sectional views

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14.14 Norwegian Solar Low Energy Dwelling

Figure 14.14.1 General view. Figure 14.14.2 Detail of PV modules mountedon the roof.

Key dataNominal power: 2.52 kWGross Area: 22.6 m2Module manufacture: BP SolarInverter: SMA PV-WR 1800Start of operation: 1994Owner: Hamar Building

Society

Short descriptionAs this was the first grid-connected, roof inte-grated PV system in Norway, there existed noready-to-use mounting structures for PV mo-dules on the market. Therefore, a safe andsimple method of integration was adopted.

The PV panels were fitted on the south facingroof of the middle apartment of the 3-unit rowhouse. Prior to being mounted on the roof, thePV modules were fixed onto aluminium pro-

files in units of two, as shown in the figure. Inthis way, a quick and simple mounting proce-dure was obtained.

Aluminium profiles were placed in betweenthe PV modules to prevent the accumulation ofsnow. This solution is not watertight, andtherefore requires a complete, finished roofunderneath. An alternative solution (labelled Ain the figure) is to let the PV panels replace the

conventional roof tiles. Thus, one would sim-ply need a conventional sub-roof construction.

Figure 14.14.3 Mounting procedure.

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14.15 Single Family House, Schauenbergstrasse, Zrich, Switzerland

Figure 14. 15. 1 General View.

Key dataNominal power: 3 kWGross Area: 25 m2Module manufacturer: SiemensInverter: SolconStart of operation: 1990Owner: private owner

Short descriptionThe applied mounting technology can beadapted for facades. The use of trapezoidalsheet metal with modules glued on leads to alow cost, safe and flexible installation.


Figure 14.15.3 Front view, sectional views.

Detail of mounting structureAs glueing technique, a special rubber tape(acrylic foam) is applied. Glueing is a compe-titive mounting technique compared to me-chanical attachment. Glueing does not penetra-te the material nor causes it corrosion.

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14.16 Shopping Centre, Stockholm


Key dataNominal power: 9.9 kWGross area: 76 m2Module manufacturer: GPV SwedenSystem design: NAPSInverter: 2 x Solcon 3400 HE

2 x PV-WR 1800Start of operation: 1993Owner: Stockholm Energi

AB

Short descriptionThis photovoltaic project was the contributionfrom Stockholm Energi AB to the Swedishparticipation of Task 16. The system is alsothe Swedish "Demobuilding" and the largestPV installation in Sweden. The 90 modulesare divided into three separate systems, eachequipped with its own inverter. Two of thesystems are mounted on the 45 tilted roof of

a shopping centre in Stockholm City. Thethird part is installed on the vertical wall of aroof space on top of the building. Themodules are standard GPV 110, framedmodules, with black tedlar on the back side tomake the array visually well integrated intothe traditional black roofing sheet.

One of the tilted arrays and the vertical oneare connected to Solcon inverters. The othertilted

Figure 14.16.2 View of the PV generator.

system is connected to two PV-WK1800 in-verters operating in a master-slave configura-tion.

Detail of mounting structure

The modules are mounted in groups of threeinto a framework of black anodisedaluminium U-profiles that are fixed to the

roof or the wall in case of the vertical array. Acable duct is attached to one of the horizontalprofiles. Each module is lifted up in the upperU-profile and then slid into the lower U-profile. By tightening screws on both theupper and the lower profile the modules arefixed into the structure. This method makes itvery easy to remove any module for service.The cabling was laid out in the cable ductbefore installing the modules. The moduleswere delivered with cables and quick-coupling connectors which made the

electrical installation work safe and relativelyfast. The connectors were then sealed byshrinking tubing.

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Figure 14.16.3 The upper part of the moun-

ting frame.

Figure 14.16.4 The lower part of the moun-

ting frame with the cable duct

attached below.

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14.17 Fensterfabrik Aerni, Arisdorf, Switzerland

Figure 14.17.1 General view. Figure 14.17.2 View of the facade.

Key dataNominal power: 8 + 53 kWGross Area: 86 + 505 m2Module manufacturer: SolutionInverter: Solcon + Eco

PowerStart of operation: 1991

Owner: FensterfabrikAerni AG

Short description

Shed roof

Besides the production of electricity, the heatbehind the sheds is used with an airstream on alow-temperature niveau. Goal of the combinedsolar system is to produce 70% of the totalenergy used.

The mounting into the shed with large areamodules was done with a special mountingsystem. Two modules are fixed on a metal sub-structure with rubber profiles. The horizontaloin is realised with silicon sealant. Behind the

modules, an air channel allows to use the hotair for space heating. In summer time, the heatis stored in the ground.

Figure 14.17.3 Partial view of shed roof

FacadeThe drawings show the details of a standardfacade cladding system. It is designed for theuse with different materials such as glass,

metal and composite panels including also PVmodules. For large panels, the clip holding themodules has to be doubled. This depends alsoon the strength of the glass. Each single mod-ule can be exchanged.

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Figure 14.17.4 Detail drawing of ALUHIT, a system to attach frameless PV modules on

facades.

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14.18 Solarzentrum Freiburg, Germany


Key dataNominal Power: 18.5 kWGross area: 153 m2Module manufacturer: DASAInverter: SKN402 /SKN 301Start of operation: 1993Owner: SST GmbH

Short descriptionFour PV generators are integrated into thefacade and roof of this office building. Thefacade is of special interest, since it is a struc-tural glazing (SG) facade.SG is a construction method using a specialtype of silicone adhesive to glue window andparapet elements, also made from glass, di-rectly onto the statically bearing support struc-ture. Additional fixtures, which are possiblyvisible from the outside are in many cases notnecessary. The silicone adhesive performssealing function and it takes all mountingforces as well as wind loads transferring theseto the support structure. The support structureconsists of thermally decoupled aluminiumprofiles, which are anchored to the building atthe various storey ceilings.

Figure 14.18.2 Facade detail.

Figures 14.18.3 and 14.18.4 show details ofthe sophisticated support structure, which haveto fulfil very different functions: staticsupport, thermal decoupling, accommodation

of window elements, accomodation of parapetelements and accommodation of regular wallinsulation.

A SG facade is turned into a PV facade by re-placing the glazing material by customizedframeless PV modules. The whole facade isdivided into segments. Each segment, whichmay reach up to 8 m height, is completelyfactory-mounted including thermal insulationand a lining which eventually makes the inner

wall cover. PV modules, regular wall elementsas well as windows, all can be mounted in onesegment.

Factory preconstruction of segments includingPV modules offers a high production quality atvery low tolerances. Thus cable glands etc. canbe placed exactly in the area of installationchannels or hollow ceilings. Preconstruction

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minimizes the risk of damaging the valuablePV modules in a harsh construction site envi-ronment.

Figure 14.18.3 Horizontal cut through facade

construction.Figure 14.18.4 Vertical cut through facade

construction.

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14.19 SOFREL, Solar Flat Roof Element

Figure 14.19. 1 General view.

Figure 14.19.3 Aerial view, sectional views of

a SOFREL with sheet metal or

a composite material such as

Alucobond.

Short descriptionSOFREL (Solar Flat Roof Elements) is a flat

roof integrated PV system.

This new project has recently started in Swit-zerland which aims to develop a Solar FlatRoof Element (SOFREL). PMS Energy Ltd.,Alpha Real Ltd., Swiss Institute of Technologyin Lausanne (EPFL) and the Union Bank ofSwitzerland (SBG/UBS) are developing a flatroof integrated PV system. The main goal is tocombine the function as building skin and PVelement in one unit for flat or nearly flat roofs.

As shown in Figure 14.19.3 the solar modules

Figure 14. 19.2 Detail of mounting structure.

are integrated in composite materials such asAlucobond which results in a watertight rooftogether with the drainage system. The differ-ence between watertight and non-watertightSOFREL is explained Figures 14.19.5 and14.19.6.

Non-watertight versions are made of steel rein-forced concrete. In such a case, the flat roof is

sealed with a conventional method.

Figure 14. 19.4 Aerial view, front view, side

view of a SOFREL element

based on concrete.

The SOFREL system starts to enter the marketduring 1995. A patent is pending; production is

not focused on a certain product, it can be real-ised by several companies.

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Compared to a conventional PV structurewith weight foundations the main advantagesare:

Improved flat roof design High aesthetic value Saving in material, therefore less dispo-

sal and improved energy and raw mate-rial balance

Fewer planing costs Less installation effort Easy roof maintenance

Figure 14. 19.7 PV array with concrete SO-

FREL on the building of the

"Berufsschule Wattwil" in

Wattwil, Switzerland.

Figure 14.19.5 Watertight SOFREL. The water is drained on the SOFREL into a special drain

channel. The SOFREL element serves as module substructure and as main part

of the roof sealing. The main advantage is the longer life span to be expected and

the possibility of checking the status of the roof sealing and the easy access for

exchange of single elements.

Figure 14.19.6 Non-watertight SOFREL. The water is drained beyond the module substructure

by a standard flat roof sealing. The SOFREL element serves as module substruc-

ture and as weathering protection for the flat roof sealing.

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14.20 Demosite, Lausanne, Switzerland


Key dataNominal power: approximately 8 kWGross Area: 300 m2Module manufacturer: severalInverter: severalStart of operation: 1992Owner: EPFL, Suppliers

Short descriptionDEMOSITE is an international exhibition anddemonstration centre for photovoltaic buildingelements, located at the Ecole Polytechnique aEcublens. The goal of this centre is to informpotential users (architects, project managersauthorities...) of the various forms andfunctions photovoltaic elements can take itorder to thus propagate their use in architecture.

In creating a link between manufacturers from

various countries (at printing time: Switzerland, Germany, USA, France, Japan, UKand users, DEMOSITE serves to promote theintegration of photovoltaics on buildings andto stimulate demand for these new elements.

Figure 14.20.2 Facade element of Demosite.

Figure 14.20.3 Marketed Solar Tile at Demo-

site.

Each pavilion is more than a simple display asit shows various solutions to problems of im-plementation and measures real on-site per-formance.

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Objectives:

to display construction elements thatproduce electricity from sunlight;

to show different methods of imple-mentation, including architectural andconstructional details, at one location;

to gather elements from different coun-tries;

to publicize these elements and to sti-mulate the development of new productsand methods;

to measure the energy produced by thevarious systems;

to provide experimental data from en-ergy measurements including climatic

data; to stimulate architects to integrate pho-

tovoltaics into constructions; to offer public relations service, inclu-

ding guided tours with information pa-nels on display and newsletters.

Figure 14.20.4 "Pyramides" at Demosite

combining sun protection, nat-

ural lighting and electricity

production.

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14.21 Eurosolare photovoltaic roof system, Nettuno (Rome), Italy

Figure 14.21.1 General view. Figure 14.21.2 Detail.

Key dataNominal power: 30 kWGross area: 300 m2Module manufacturer: under negotiationInverter:Start of operation: 1995Owner: Eurosolare s.p.a.Designers: Architects Cinzia Abbate and

Corrado Terzi

Short descriptionThe new roof will cover the central bay of thefactory which is currently used for the assem-bly line of the photovoltaic cells, the officespace and the conference room of the compa-ny. The project proposes a new roof made oftwo lenticular steel beams; two depressedarches, one counterpoised against the other,placed on both sides of the e

Documents

Task 16 Photovoltaics in Buildings p2