Integrating Thin­Film Photovoltaics Onto Building Envelope Surfaces

Michael Gumm Corporate Roof Consultants, LLC Seminole, Florida

Proceedings of the RCI 23rd International Convention Gumm ­ 101 ABSTRACT This paper covers design and installation methods for Building Integrated Photovol­ taics (BIPV) using the new thin­film photovoltaic module technologies with conven­ tional construction products over the following building envelope surfaces: • Single­ply, modified bitumen, and metal roofs • EIFS and concrete and masonry wall surfaces • Concrete surfaces, such as parking lots and architectural elements

Installation methods include thin­film photovoltaic modules laminated to single­ply membranes; flexible photovoltaic modules combined with elastomeric coatings applied over roofs, concrete, and walls; and re­deployable photovoltaic systems with magnetic membranes for metal roof applications and self­ballasted insulated roof panels. The subject matter covers new construction and building restorations. Information for array design and the various finance options available to owners is also provided.

SPEAKER Michael Gumm has been actively involved in the roofing industry for the past 25 years in manufacturing, sales, contracting, and consulting. He is the founder and president of SolarPower Restoration Systems Inc. and SolarSeal Technologies Inc. Both companies are engaged in developing new building­integrated photovoltaic (BIPV) application technologies. Mr. Gumm is a BIPV pioneer and inventor with five patents pending covering a number of BIPV application technologies using conven­ tional building products with photovoltaic systems to create new building envelope surfaces that both weatherproof and generate renewable energy from the sun Contact Information: Phone – 727­230­3269; E­mail – [email protected]

Gumm ­ 102 Proceedings of the RCI 23rd International Convention Integrating Thin­Film Photovoltaics Onto Building Envelope Surfaces

INTRODUCTION: Crystalline Silicon The industry standard for We are all familiar with the solar technology since photovolta­ basic photovoltaic glass module ic systems have been installed on mounted on racks or posts. buildings has been glass­mount­ Glass­encapsulated photovoltaics ed, silicon­based solar panels. are the most common type of Today, a new type of photovoltaic solar module. Most rack­mounted technology called thin­film photo­ PV modules consist of crystalline silicon – either as a single or as a voltaic technologies is ready to Figure 1 – Crystalline sili­ poly­crystalline wafer to generate change the way photovoltaics are con array on the New York electricity. installed on buildings. This paper State Energy Research & is written to give our industry a Development Authority’s • Silicon­based photovol­ broad overview of both old and Voorheeville, NY, school. taics have the highest new solar technology plus insight electrical output of any on designing and applying these photovoltaic material per photovoltaic systems. According sq ft. to the Solar Energy Industry These newer technologies, called

Association, solar power in 2006 • Typical power production thin­film photovoltaics, include represented only one­tenth of one is between 12 to 15 watts very thin layers of photovoltaicly percent of the added electrical per sq ft. active material placed on a glass power capacity to the U.S. power • Silicon wafer photovoltaics superstrate, flexible metal, or grid. In three years, solar will are more expensive and plastic substrates. Flexible thin­ grow to 15 percent of added require large amounts of film PV modules are made by capacity and by 2018, solar is energy to manufacture. depositing semiconductor materi­ expected to contribute 50 percent Silicon modules costs als on stainless steel foil or a plas­ of the annual U.S. power increase. $4.85 per watt on aver­ tic carrier and encapsulating with If you have not seen solar on a age.1 a solar transparent plastic poly­ project in the past, chances are • In 2006, solid silicon pho­ mer. you will in the near future. tovoltaic modules repre­ Semiconductor materials used

PHOTOVOLTAIC BASICS sented about 95% of all in thin­film photovoltaics include: solar panels installed.

Photovoltaics (PV) are one of • Amorphous silicon (a­Si) : Uni­solar and MWOE­ the most promising sustainable Other building system appli­ solar energy technologies. Solar PV cations include semi­transparent modules produce electricity on photovoltaic glass modules for • Copper indium gallium site, directly from the sun, with windows and skylights using diselenide (CIGS): Mia the least environmental harm. crystalline silicon, and one PV solé, NanoSolar and

Solar has the smallest environ­ manufacturer has integrated thin Global Solar mental impact of any of the silicon wafers into a single­ply • Cadmium telluride (CdTe): renewable energy systems. Photo­ roofing product. Leading silicon First Solar voltaic modules are solid­state panel manufacturers include devices that simply make electric­ SunPower, Sharp, Schott Solar, Other new solar technologies ity from sunlight. They require lit­ Sharp Corporation, and Canon Inc. tle maintenance, produce no pol­ in development include dye­sensi­ lution, and don't deplete any non­ Thin­Film Photovoltaics tized solar cells using a dye­ impregnated layer of titanium renewable fossil energy resources A number of new photovoltaic dioxide to generate electricity. such as oil, natural gas, and coal. technologies have begun to Dye­sensitized solar cells will be

emerge into the marketplace. printed onto various polymer

Proceedings of the RCI 23rd International Convention Gumm ­ 103 films with equipment resembling The power storage system computer printers. Thin­film pho­ is essentially free. tovoltaic materials are used in • Both the building owner both glass­encapsulated and flex­ and the utility benefit with ible­membrane solar modules. grid­tied BIPV, as on­site

Thin­film photovoltaics' differ­ solar power production is ence over traditional silicon mod­ typically greatest during a ules include: building and power com­ pany's peak energy needs.

• Thin­film photovoltaics • The photovoltaic system Figure 2 – Flexible, thin­ generate less power per sq reduces energy costs for film photovoltaic module ft than crystalline silicon, the building owner, and at Grand Valley State but produce more overall the exported surplus solar University, displaying Uni­ total power output over energy provides additional Solar thin­film solar cells. the solar day compared to power to the utility grid silicon­based photovol­ during the time of its taics. Thin­film photo vol­ greatest energy demand. taics do this because they because rebates and incentives produce more power in low • The utility company can are priced out in watts. and overcast light condi­ maintain needed power

tions compared with crys­ production capacity with­ BUILDING INTEGRATED PHOTO­ talline silicon. Most power out the capital investment VOLTAICS (BIPV) SYSTEMS measurements for silicon of building new power gen­

are taken during peak Building­Integrated Photovol­ eration plants.

power production times at taics (BIPV) is a new sustainable­ • The building owner can

midday. energy­source building technolo­ draw back the net­metered

gy. Photovoltaics are one of the power at night, typically • Thin­film photovoltaics on most promising renewable ener­ when electrical costs are average produce 6 to 10 gy­source building technologies. A lower, helping to reduce watts of power per sq ft, BIPV system consists of integrat­ the cost of utility­generat­ depending on the type of ing photovoltaic modules into the ed power. semiconductor material building envelope with conven­ used. • Photovoltaic systems can tional building products, such as • Thin­film solar photovol­ become the building's pri­ the roof, windows, or walls. BIPV taics' power production is mary energy source in the is simultaneously both the build­ not affected by higher en­ event of a power failure ing envelope surface and the vironmental operating and energy can be stored building energy source. temperatures. Silicon­ onsite for emergency back­

based modules start drop­ BIPV Advantages up using batteries.

ping power output once • A building owner's BIPV BIPV systems are available for

module temperature ex­ system is connected with a number of building­envelope

ceeds 25 degrees C. the local utility grid, and surfaces, including roofs, walls,

• Solar shading does not with net metering, can windows, and concrete. lower the entire thin­film export surplus energy to module power output. the utility for use later, ROOFING AND BIPV when the building requires Placing rigid solar photovolta­

Thin­film photovoltaics cost utility energy. ic roof panels as a stand­alone or less than silicon modules. Aver­ • The building becomes a roof­top, equipment­mounted age cost, depending on the type of power distributor at the power module array has been semi­conductor material used point of use by net meter­ around since the invention of and if the module substrate is ing the building's surplus solar­photovoltaic cells. The cre­ glass or polymer­encapsulated, is power production. Think ative idea of integrating thin­film between $3.00 and $4.24 a watt.2 of net metering as a PV modules into a roofing system Power production per sq ft varies method to bank or deposit dates back to the 1980s. Only between manufacturers; the solar surplus solar energy pro­ recently, with the commercial industry tends to price product duction during the day development of newer, structural­ cost by watt rather then per sq ft, with a utility company. ly flexible PV thin­film modules,

Gumm ­ 104 Proceedings of the RCI 23rd International Convention have we seen the integration of tem. PVC single­ply is the mem­ PVs into traditional roofing mate­ brane polymer of choice and TPO rials. Today there are a number of can be used. Both flexible PV roofing systems and products on modules and single­ply mem­ the market using laminated PV branes are manufactured in simi­ flexible films, including shingles, lar fashion into long sheets. The roof tile, metal roofs, modified factory­laminated, single­ply bitumen, and single­ply roof membrane and PV panels are membranes. These are dual­func­ shipped to the roof project site in tional products, both weather­ Figure 3 – Uni­solar metal large, pre­manufactured rolls. proofing the building and generat­ panels with thin­film pho­ The PV laminated single­ply roof ing renewable energy from the tovoltaics. system is installed over an exist­ sun. ing compatible roof membrane or thin­film modules and coatings is installed as a new roofing sys­

Metal Roofs and Photovoltaics that both waterproofs the metal tem using traditional roof con­ Uni­Solar pioneered the appli­ roof and generates renewable struction methods and labor tech­ cation of flexible thin­film PV energy. niques. modules to architectural metal Flexible thin­film modules With the SIT system, a new roof panels. The Uni­Solar's flexi­ offer the best options for adding a single­ply roofing system is ble thin­film module has a pres­ photovoltaic array to a metal roof applied to the roof. The new sin­ sure­sensitive peel­and­stick ad­ system. Rigid glass silicon PV gle­ply roof system can be hesive on the back surface of the modules can be used on metal mechanically fastened or fully flexible modules and can be facto­ roofs, but require some type of adhered. The factory­laminated ry laminated to metal roof panels mechanical surface attachment. single­ply membrane and flexible for new construction. The Uni­ Surface­mounted or rack­mount­ PV module is then installed Solar self­adhesive flexible thin­ ed silicon PV modules or arrays directly over the new single­ply film PV modules can be applied to do not keep the existing metal roof system and hot­air welded in existing snap­lock and batten roofs watertight, and should the place. On partial roof installa­ standing­seam metal roofs if the metal roof leak in the future, the tions, photovoltaic laminated sin­ metal panels have a flat profile attached PV array may have to be gle­ply membranes can be ad­ between seams. removed for roof repairs. It is hered to the existing roof sub­ Another company, Dawn important to determine how the strate using polyurethane foam as Solar, has gone a step further and additional weight of the heavier an adhesive, double­sided tape or combined flexible solar modules glass modules and rack attach­ bonding adhesive. In most cases, with metal roofing and a con­ ment system will affect the metal­ these partially attached system cealed radiant­heating system roof system. Silicon module sys­ applications are not waterproofed. under the metal panels, produc­ tems can be quite heavy. The SIT system patent ended last ing both electricity and hot water year, and several other commer­ from the sun. LOW­SLOPE ROOFS AND PHOTO­ cial roofing manufacturers are VOLTAICS expected to bring similar solar Metal roof R­panel roof sys­ single­ply roof systems into the tems with overlapping seams and Solar and single­ply systems market over the next two years as exposed fasteners or metal roof The most common BIPV panels with stiffener beads or stri­ low­slope roof system today ations have been limited to tradi­ is a factory­laminated, flex­ tional equipment­mounted glass ible, thin­film PV module to modules. SolarSeal Technologies a single­ply membrane created a new solar roof system by sheet. This concept was combining certain elastomeric patented by Solar Inte­ coatings and different inter­ply grated Technologies over 20 construction elements with flexi­ years ago. Working with ble thin­film photovoltaics to Uni­Solar and Sika­ bridge the metal­roof profile and Sarnafil, the Solar Inte­ exposed fasteners while creating a grated Technologies (SIT) flat substrate for the PV modules. created the first single­ply Figure 4 – Solar Integrated Tech­ The SolarSeal System creates a BIPV photovoltaic roof sys­ nologies’ thin­film laminated roofs. monolithic membrane with the

Proceedings of the RCI 23rd International Convention Gumm ­ 105 additional heat load will affect the The SolarSeal System is the only long­term performance of the roof universal roof­integrated photo­ membranes. voltaic system that can be applied to either new or existing roofs, Most white single­ply roofs are including asphalt­based roof sys­ known to be cool roofs, with a typ­ tems and single­ply roof systems. ical surface temperature not more than 10­15 degrees hotter then ambient air temperature. Now they will be subjected to long­ Figure 5 ­ Open­energy photo­ term temperature exposure 30­40 voltaic module and single­ply degrees higher. Good insulation in membrane system. the roof system is important in reducing heat transfer from the the roofing industry starts em­ PV modules to the building interi­ bracing solar roof systems and or. Thin­film modules with plastic renewable energy. carriers should be cooler, but as

of today are still in development Figure 6 – SolarSeal system Silicon wafers can be used and will not be deployed for over SBS membrane with Uni­ with a single­ply membrane sys­ another two or three years. Solar PV module. tem. The Open Energy SolarSave PV module is a single­ply mem­ Solar and BUR­Modified Bitumen brane and photovoltaic composite Photovoltaic systems integrat­ SLOPED ROOFING SYSTEMS panel using thin silicon crys­ ed with standard asphalt roofing talline wafers covered with a solar and modified­bitumen roof­sys­ Glass photovoltaic modules transparent polymer on top of an tem BIPV has lagged behind in have been used on high­slope res­ aluminum substrate with a sin­ development. With a surface­ idential roofs for years. The flat gle­ply PVC or TPO membrane operating temperature up to 165 panels are easy to install and only laminated to the back side. Like degrees, attaching a thin­film require a few roof penetrations to the SIT flexible PV membrane, the photovoltaic module directly onto run the wiring. However, glass PV

Open Energy module can be hot­ an asphalt­based roof membrane modules are considered by some air welded to a new or existing with a lower softening point has to be unattractive roof systems. single­ply membrane. The Open proven to be difficult. SBS­modi­ With an expected service of 30

Energy panel, with its crystalline fied membranes tend to have years and higher, surface­temper­ silicon, generates twice the elec­ lower softening points compared ature glass modules will outlast trical power per sq ft compared to to APP and standard 90­pound many surfaces, especially shingle the Uni­Solar panel. The Open cap sheets. The difference in ther­ roof systems. These days, there

Energy panels cost more per watt mal expansion between the mod­ are a number of alternative photo­ than the SIT solar single­ply sys­ ules, adhesive, and asphalt roofs voltaic roofing products in which tem. The higher energy cost of the makes direct adhesive attachment the solar active materials have

Open Energy module can be offset challenging. been incorporated into the roof when more power production is products to create true BIPV roof­ needed with limited roof area or Recently, SolarSeal Technolo­ ing products. gies developed a new PV roof sys­ when more power is wanted over a tem for asphalt­based roof sys­ These new shingle and tile larger roof area. tems. The SolarSeal PV Roof products use either thin­film or

Photovoltaic modules get hot System first applies high­perfor­ crystalline silicon for a solar­ on a hot summer day. We have mance elastomeric roof coatings active surface. Uni­Solar makes a seen surface temperatures up to to the asphalt­based roof mem­ flexible solar shingle module that

165 degrees. Many thin­film pho­ brane, creating a continuous integrates into a regular shingle tovoltaic modules use a stainless­ waterproof roof surface. The flexi­ roof. The Uni­Solar module is steel carrier to deposit their solar ble PV module is embedded onto dark blue in color, is 12 in x 86.5 active materials; these stainless the first elastomeric coatings with in long, and produces 17 watts carriers absorb heat. We will need additional elastomeric coating per module run. There are a num­ to pay attention to the heat build and textile interply components to ber of Solar Tile modules available up and heat transfer from the form a monolithic, weatherproof today that interface with flat con­ modules to the roof membrane membrane that both protects the crete tiles. The SunPower SunTile systems and monitor to see if the building and generates electricity. is a high­efficiency solar panel

Gumm ­ 106 Proceedings of the RCI 23rd International Convention that blends invisibly into concrete Right now, wall and window • Conventional silicon­ tile roofs. GE Solar makes 18 sin­ systems are very specialized. As based PV­glass module gle­crystal cells connected in a the pricing of solar systems con­ rack­ and post­mounted series module with a peak power tinues to drop, more building wall systems. of 55 watts at 8.4 volts and has a and window systems will start to • Protective Roof Membrane unique interlocking design for incorporate solar into more tradi­ (PMR) self­ballasted pho­ concrete tile applications. Sharp­ tional wall and window building tovoltaic tile systems,

Solar offers polycrystalline silicon products. such as Powerlight's modules with 62 volts of output. PowerGuard panels or the

Open Energy makes a poly­crys­ SolarSeal Surface OverLay talline tile type module that comes System. in brown, red, and black colors. Atlantis Energy Systems makes a • PVC or TPO single­ply membrane and thin­film slate type tile that works well with flat tiles and slate roofs. PV module composites by Solar Integrated Technolo­ Figure 8 ­ Solar wall at the gies and Open Energy. main elevation of OpTIC, show­ • Proprietary elastomeric ing the cantilevered business coatings and thin­film PV­ center and 1,000m2 PV wall module composite systems array. for asphalt­based roof and single­ply roof systems PHOTOVOLTAIC ROOF DESIGN developed by SolarSeal Technologies. Figure 7 ­ Solar shingles by Designing a photovoltaic sys­

Open Energy. tem for BIPV is a complex process,

especially for roofing. The solar Thin­film photovoltaics are a

industry for the most part has new roofing and building material WALL AND WINDOW SOLAR SYS­ grown up independently of the technology and a number of appli­ TEMS roofing industry. Installing rack­ cation technologies for installing

There are a number of new mounted glass photovoltaics on a these thin­film modules are under wall and window photovoltaic sys­ roof requires few roofing skills development as these products tems. The key limiting factor with other than drilling a few holes in leave the laboratories and become wall and window application is the roof and caulking around the commercialized. the building placement in rela­ wiring penetration or flashing There are a number of con­ tionship to the sun. Southern­ around the support mounts. tractor and installation options. exposure walls produce the most With the introduction of new • Roofing contractor – de­ power. Window systems are typi­ roof systems that combine tradi­ sign and estimate – cally a silicon wafer or thin­film tional roof products with photo­ installer cell laminated between two sheets voltaics, roof designers and roof­ of glass and are semi­transparent. • Roofing contractor and so ing contractors are learning a new Solar window applications include lar contractor subcontrac­ set of technical skills. Solar inte­ window glazing, curtain walls, tor – hybrid atriums, and skylights. grators and solar design consul­ tants are becoming more educat­ • Solar contractor and roof Solar wall systems vary from ed about roofing technologies. ing subcontractor – hybrid integrating glass modules into With photovoltaic building sur­ • Manufacturer design – curtain walls, to thin­film mod­ faces becoming more common­ roofing contractor esti­ ules with adhesives to adhere the place and the need to create more mate – installer module to a wall surface. Another energy­efficient and sustainable • Roof consultant design – solar application system created buildings, both the solar industry contractor estimate – by SolarSeal Technologies uses and the conventional construction installer thin­film, semi­flexible modules product industry need to be able with elastomeric coating systems to work with and learn from each • Solar consultant design – for integrating solar modules onto other. contractor estimate –

EIFS walls system, tilt­wall con­ installer Today, there are four BIPV crete wall panels, and masonry • Architectural design – con­ application options for low­slope wall systems. tractor estimate – installer roof systems:

Proceedings of the RCI 23rd International Convention Gumm ­ 107 • Solar integrator – roofing 50 states, less than half have Financial Options

contractor subcontractor – attractive enough incentive pro­ • Direct Purchase. Owners

hybrid grams for solar energy to make purchase the photovoltaic

real economic sense. The Data­ system using internal base of State Incentives for The design and sales process cash flow and utilize the Renewables and Efficiency timeline for specifying and selling tax credits, state and local (DSIRE) is the best source for photovoltaic roof systems is much rebates, utility rebates, looking up any state and regional longer and far more complex com­ and RECs, or they can go tax credit and incentive based pared to selling standard roof sys­ to their existing lending/ state programs and can be found tems. The cost of a roof system leasing institutions. at www.dsireusa.org/. with a photovoltaic system is • Finance lease. This is expensive; the average installed Determining what financial similar to a bank loan, and cost of a commercial low­slope options are available to building the lessee is considered roofing and photovoltaic system owners is an important part of the the owner of the equip­ before tax credits and rebates can design and sales package. ment for both accounting average between $72 and $110/ and tax purposes. sq ft, depending on the photo­ Financing Options • Operating Lease. The voltaic system used. The solar It is important to understand lessor is considered the industry uses cost­per­watt for and identify the owner's special owner for the tax credits, pricing, due to the variation in needs for financing the project. depreciations, and re­ power output with different solar The designer and contractor must bates. The lessee is rent­ technologies. The tax credits and be knowledgeable and communi­ ing the roof/equipment rebates tend to be stated in cost­ cate to the building owner, the dif­ and can write off the cost per­watt. The average cost per ferent financial options available of the lease. watt installed on low­slope com­ to them. A key part of selling pho­ mercial applications is between • Tax­Exempt Lease. These tovoltaics is having access to $8 and $9 per watt DC. Photo­ lease types can meet the established lease programs from voltaic systems and components needs of schools, universi­ leasing and capital investment are priced per watt, so the roofing ties, state, and local gov­ groups. Capital leases, power pur­ cost must be estimated and then ernments. The public chase agreements (PPAs) and translated into cost­per­watt. agency pays for the cost of bond options are very important the roof and photovoltaics The incentives, grants, feder­ for selling to state, local govern­ from current utility cost. al­ and state­tax credits and ments, school districts, and other The lessor, depending on rebates make BIPV affordable. public agencies. These leases can the lease package struc­ Unfortunately, there is no uni­ become another revenue stream, ture, takes the tax bene­ form system of tax credits and tax­credit source, depending on fits, and in some cases, rebates. The federal government investment packages the contrac­ can have a tax­exempt provides a 30% tax credit and tor or solar integrator has set up package on the earned five­year accelerated depreciation with the financial companies. interest. on a commercial BIPV system With the commercial owner, it is • Power Purchase Agree­ cost. While this helps to reduce important to explain the tax bene­ ment. An outside invest­ the overall cost, what makes a fits, state utility rebates, perfor­ ment group owns and solar system cost­effective is the mance incentives, and renewable operates the solar equip­ additional state, local, and utility energy credits to show the owner ment, and sometimes, the credits, rebates, and perfor­ their real cost, plus monthly ener­ roof. The building owner mance­based incentives. Many gy savings and payback period for pays the solar array owner varied rebate programs are their investment. With commer­ for the electricity produced offered throughout the United cial owners, the recent trend is by the solar array. The States. Some states have such a going towards either commercial array owner, in effect, is a large number of rebate options leases or the power purchase mini­utility company. The that one must calculate the per­ agreements. array owner may sell back formance­based incentives, utili­ surplus power by net ty, and state rebate costs by zip metering to the local utili­ code. There are still 12 states with ty company. no net­metering laws. Out of the

Gumm ­ 108 Proceedings of the RCI 23rd International Convention • Google satellite photo of (photos). building and surrounding Preliminary roof information buildings collection • Building­site location Information Processing and Designing a low­slope roof and Preliminary Design • Building solar orientation photovoltaic system starts out like The above information is used (what direction does it face a conventional roofing system, to the sun) to calculate the following informa­ and in the case of a re­roof, will tion to design the PV system. require the following information • Identify shadow obstacles to determine if the building is a (roof­top equipment, sur­ • Electrical load: Determine suitable candidate for a BIPV roof rounding roofs, buildings, building power require system. and trees can affect the ments (total peak KW). overall effectiveness of the • Array sizing: Calculate • Type of existing roof(s) photovoltaic system) . array size requirements

• Number of existing roofs • Identify solar access (solar (KW). insolation). Insolation is a • Age of roof(s) • Array layout: (module size measure of solar radiation • Deck type based on roof size and incident on a surface. It is equipment locations) and • Structural load capacity the amount of solar energy pricing • Insulation type received over a given area

in a given time. • Wiring system design: • Perimeter details (voltage drop, safety build • Ceiling space and wall • Core cuts ing code, NEC code, and structure access for wiring environment) • Photos of roof and major system to the utility ser­

roof elements and site vice • Combiner box: (size and conditions locations) • Moisture survey may be • Controller specifications required Preliminary power analysis [(size) battery back­up sys

• Existing roof coating, test data tem only] for adhesion and compati­ It is important to determine • Inverter specifications bility the electrical energy consumption (size)

for the building when designing a • Utility­interactive system PV system. The following informa­ If the roof is suitable for a design tion is needed on existing build­ BIPV system, on the next phase, ing. New buildings must calculate either get an existing roof plan of this information. Contractor information the building, or be prepared to requirements for estimating create an accurate roof plan with • Utility bills (highest bill all curbs, HVAC, drains, and per quarter minute) for the Provide installation contrac­ scuppers on the roof. All of these past two years. tor(s) with the following informa­ tion so they can price out the sys­ items must be pinpointed and • Usage pattern with peak, tems. measured. part­peak, and off­peak usage; summer and winter 1. Approved roof plan and Preliminary Roof Information demand charges. roof specifications for Photovoltaics

• Current and future elec­ 2. Approved PV array plan The building's orientation, tric rate schedule. Factor and specifications solar shadowing, and solar insola­ in tiered rates and time­of­ 3. Approved wiring plan and tion are important design ele­ use utility pricing and specifications ments used to determine what annual rate inflation type of PV system can be used 4. Approved controller plan • Inventory list of major and how large a photovoltaic sys­ and specifications (battery appliances and other high­ tem can be installed on the roof. systems only) ampere drawing equip­

Create a roof plan with all ment (seasonal/non­sea­ 5. Approved inverter plan roof­top elements (drains, curbs, sonal). and specifications ) pipes, etc.) • Locate and inventory 6. Utility­interactive system

existing electrical services design

Proceedings of the RCI 23rd International Convention Gumm­ 109 incentive process is critical for direct attachment to the roof getting one's client and the con­ membrane or onto the elastomer­ Photovoltaic estimating soft­ tractor the cost savings that make ic coating system. These thin­film ware is available from several the solar system economically fea­ modules can last longer then the sources. Input all data into solar sible. These rebate and backsides roof systems. The single­ply solar sales and Estimating tool soft­ vary. Some states even require the composite system or solar elas­ ware. Software packages will gen­ PV system to be installed first, tomeric coating composite system erate the PV system cost. Andy then the credit applied for, and can be coated and recoated again Black's OnGrid software system is the state will pay out only if is has with compatible elastomerics one of the best. The software pro­ allocated funds in the account at coatings at some future time, syn­ vides all the financial information the time of filing. Others require chronizing the service life of the needed to explain the following. owners to reserve the rebates by roof and thin­film modules. • System cost first filing and then there is a set You should also contact the amount of time to get the system • Operating cost roof manufacturer if the existing installed and commissioned. Per­ • Operating profits formance­based incentives, means roof is still under warranty. Major modification or changes in roof • Operating losses just that: over time, the array sys­ use can void the existing roof war­ • Net power savings tem is monitored and is expected to perform as designed. So be ranty if the manufacturer is not • Lifecycle power savings contacted and agrees to the solar careful with power production • Tax credits estimates when designing a solar installation. It is important to monitor any photovoltaic rack array system • Capital depreciation installation on any existing or new

• Rebates DESIGNING AHEAD: LIFE CYCLES, roof for damage due to construc­

• Return on investment ROOFS, WARRANTIES tion and foot traffic. (ROI) Photovoltaic manufacturers In the roofing industry, we are

• Equity/property value say their photovoltaics will have a used to specifying and getting a

increases long service life. Glass­module single­source roof warranty cover­

• Property resell value manufacturers claim their mod­ ing all roof components, material

ules will produce energy for 30­50 replacement, and workmanship • System payback period years. Many thin­film photovolta­ for 10, 15, or 20 years. Photovol­

• REC (green tag) income ic manufacturers routinely say taic system warranties do not

• PBIs (performance­based their modules will be guaranteed exist.

incentives) for 80% of the modules' installed The photovoltaic module will

power production at year 20 or have two warranties. One warran­

Most software packages will 25. ty is for material and workman­ generate charts and graphs, so When designing a roof, it is ship defects for manufacturing

ROI and payback cycles are clear important to keep the long service the PV modules. This warranty and easy to understand. Some life of photovoltaics in mind. can be as short as 18 months, software packages will fill out the Chances are the roof will have to and the average warranty is five forms needed for state and utility be replaced long before the photo­ years for PV module replacement rebates and the forms for com­ voltaic modules are. One has to due to defective materials/labor. missioning the PV array system ask oneself, does it make econom­ The second warranty is for power with the utility company. ic sense to install a rack or pole­ production. Most manufacturers will guarantee their modules will Completing the necessary mounted array system over an generate 90% of the rated in­ paperwork for the rebates and tax existing roof system with a limited stalled power production at year credits and being aware of the performance life? What are the ten and 80% of the installed rated deadlines related to these rebates options to maintain the roof? power production at year 20. On is very important. A contractor or What can you do to extend the average, a PV module will lose designer can incur substantial roof's service life? Have you fac­ 0.5% to 1.0% of its installed rated cost and liabilities if he or she tored in the cost of removing the power production a year. fails to complete the rebate and PV modules for roof repairs or performance­based utility incen­ replacement at some future time Photovoltaic inverters, the tives paperwork and forms in a and is the owner aware of this devices that convert DC power to timely fashion. Understanding the future cost? Flexible, thin­film PV AC power, typically are warranted rebate and performance­based systems have the advantage of for five to ten years, and over the

Gumm ­ 110 Proceedings of the RCI 23rd International Convention course of the photovoltaic array's One of the best resources for American National Stan­ service life, will have to be the NEC 2005 and wiring photo­ dards Institute (ANSI) replaced. On wiring and cabling, voltaics is John Wiles at New ANSI C2­1990 code requires UV­rated cable. Mexico State University. He may Institute of Electrical and E­ Most cables are warranted for 10 be contacted via e­mail at to 20 years (material only), and it [email protected], and a PV Sys­ lectronic Engineers (IEEE) makes good sense to install cables tems Inspector/Installer Check­ IEEE 519 (2004) Recom­ in a pre­manufactured cable list will be sent via e­mail to those mended Practice and Re­ channel to protect the wiring. requesting it. An e­mailed copy of quirements for Harmonic With an average roof system and the 100­page “Photovoltaic Power Control in Electrical Power PV system, therefore, one will Systems and the National Elec­ Systems have a roof warranty from one trical Code: Suggested Practices,” manufacturer and several war­ published by Sandia National IEEE 928 (2004) Recom­ ranties from the PV­module com­ Laboratories and written by John mended Criteria for Ter­ ponent manufacturers. Over time, Wiles will be sent at no charge to restrial PV Power Systems as traditional roofing manufactur­ those requesting a copy. The IEEE 929 (2004) Recom­ ers create standardized PV roof Southwest Technology Develop­ mended Practices for Util­ systems, we will eventually get a ment Web site (www.nmsu.edu/~tdi) ity Interface of Residential single­source warranty package. maintains all copies of the "Code and Intermediate PV Sys­ Corner” columns written by John tems Basic Design Resources Wiles and published in Home Creating a small 2­ or 3­KW Power Magazine over the last ten IEEE 1374 (2004) Guide for 3 residential array system is not years. Terrestrial PV Power Safe­ very difficult; most PV module ty Systems SUMMARY manufacturers can help with the International Electronic E­ basics. A good resource for under­ The solar industry grew up lectrotechnical Commis­ standing and learning the solar largely independent of the tradi­ sion (TEC) installation process can be found tional construction trades and in the photovoltaic Design and product industry. New solar tech­ IEC 1173 (2000) Overvoltage

Installation Manual published by nology companies are just start­ Protection for PV Power

Solar Energy International. A ing to explore the application pos­ Generating Systems number of hands­on schools with sibilities with their new solar IEC 1277 (2000) Guild­Gen­ week­long classes can be found products in development. Solar eral Description of PV through the American Solar power systems will become more Power Generating Systems Energy Society (ASES) that can common in the future. These new provide the knowledge and skills solar products will become inte­ IEC 61646 (1996) Thin­Film for residential projects. grated into many traditional Terrestrial Photovoltaic

Commercial roof applications building systems. Today is a good Modules are far more complex. Besides time for our industry to start National Fire Protection As­ array layout design, cabling lay­ learning more about solar tech­ sociation (NFPA) out, running the wiring to the nologies and how these new tech­ combiner boxes, and incorporat­ nologies will affect the design and NFPA 70 (2005) National ing lighting protections, discon­ installation of building systems Electrical Code with which we work. nect switches, and grounding can Underwriters Laboratories be challenging. While DC current SPECIFICATION REFERENCES (UL) UL 1703 (2002), In­ is safer than AC current, most terconnected Electrical commercial systems array strings Photovoltaic specification ref­ Power Production Sources will be running voltages up to erences can be found in CSI around 525 volts DC, so the sys­ Specification Section 13625 ­ UL 1741 (1984, R 2004), tems must be carefully designed. Photovoltaic Energy Systems. Key Flat Plate PV Modules and Photovoltaic wiring is controlled photovoltaic standards can be Panels primarily by Article 690 of the found in the following: 2005 National Electrical Code. With commercial systems, it is 1990 National Electrical best to collaborate with an experi­ Code enced solar integrator or electrical engineer with solar experience.

Proceedings of the RCI 23rd International Convention Gumm ­ 111 FOOTNOTES 1. Silicon PV module cost only: SolarBuzz www.solarbuzz.com/ on 08/25/2007 2. Silicon PV module cost only: SolarBuzz www.solarbuzz.com/ on 08/25/2007 3. Taken from IAEI (Electrical Inspectors Magazine), March/April 2005 www.iaei.org/subscriber /magazine/05_b/wiles.htm.

Gumm ­ 112 Proceedings of the RCI 23rd International Convention