Solar Tech Ref Guide

8/2/2019 Solar Tech Ref Guide

1/30

Solar Technology Reference Guide

Aaron Binkley

Prepared for and Funded by

the NAIOP Research Foundation

January 2012


2/30

Help ensure that the NAIOP Research Foundationcontinues to promote industry success.

Thank you for your choosing to download this report. Foundation research and analysis gives industry

professionals unique insights in to the current business environment and emerging trends that lead to successful

development and communities.

Traditional sources of revenue cover only a portion of the costs of producing these reports. Additional support,

provided by end users of this research through the Foundations Sustainer Fund, helps to ensure that the Foundation

will have the funds to continue to proactively address the many research project requests it receives each year.

Donate to the Sustainers Fund today!

Learn how to become involved in the work of the Foundation.

Contact Information

Amount:

Gift Levels

Benefactor Gifts of $2,500 and above

Leader Gifts of $1,000-$2,499

Donor Gifts of $500-$999

Sustainer Gifts of $250-$499

Yes, I am interested in ways I can

support the work of the Foundation.

Please call me to discuss

Please send me information about

Becoming a Foundation Governor

Underwriting a Foundation project, or major initiative

Area of interest __________________________

Making an annual gift

How to apply for a research grant

*Make checks payable toNAIOP Research Foundation

NAME COMPANY TITLE

ADDRESS CITY STATE ZIP

PHONE E-MAIL

Contribution Information

CARD HOLDER NAME CREDIT CARD TYPE

NUMBER EXPIRATION DATE

(Contributions to the NAIOP Research Foundare tax deductible to the extent allowed by la

Please see below for contribution informat

Call Bennett Gray at (703) 674-1436 to make a contribution by telephone.

Mail or fax your donation to: NAIOP Research Foundation(Sustainers Fund)2201 Cooperative WaySuite 300

Herndon, VA 20171-3034Fax: (703) 674-1486


3/30

About NAIOP

NAIOP, the Commercial Real Estate Development Association, is the leading organization for developers,owners and related professionals in ofce, industrial and mixed-use real estate. NAIOP comprises 15,000members in North America. NAIOP advances responsible commercial real estate development and advo-cates for effective public policy. For more information, visit www.naiop.org.

The NAIOP Research Foundation was established in 2000 as a 501(c)(3) organization to support the workof individuals and organizations engaged in real estate development, investment and operations. The Foun-dations core purpose is to provide these individuals and organizations with the highest level of researchinformation on how real properties, especially ofce, industrial and mixed-use properties, impact and benetcommunities throughout North America. The initial funding for the Research Foundation was underwritten byNAIOP and its Founding Governors with an endowment fund established to fund future research. For moreinformation, visit www.naioprf.org.

2011 NAIOP Research Foundation

There are many ways to give to the Foundation and support projects and initiatives that advance the com-mercial real estate industry. If you would like to do your part in helping this unique and valuable resource,

please contact Bennett Gray, senior director, at (703) 904-7100, ext. 168, or [email protected].

Requests for funding should be submitted to [email protected]. For additional information, please contactSheila Vertino, NAIOP Research Foundation, 2201 Cooperative Way, Herndon, VA, 20171, at (703) 904-7100, ext. 121, or [email protected]

About the Author

Aaron G. Binkley is Director, Sustainability Programs for Prologis. Binkley is an expert throughout the Pro-

logis organization on matters associated with sustainable design and construction such as LEED Certi-cation, renewable energy, energy conservation, carbon emissions and environmental sustainability. Hisresponsibilities include working closely with operations and development teams globally to further Prologissustainability initiatives, including carbon strategy, customer and investor education programs, energy ef-ciency and retrot initiatives and renewable energy projects.

Binkley was previously Director, Sustainability Programs for AMB Property Corporation. Binkley led theAMB renewable energy program which was responsible for the development of 4 megawatts of rooftopsolar projects and planning and due diligence for 60 megawatts. Binkley was also responsible for customeradvisory on renewable energy for new construction projects and existing buildings. Other responsibilitiesincluded energy conservation programs, sustainable building advisory, carbon footprint benchmarking, sus-tainability reporting and customer education on sustainability topics.

Binkley is a member of the Real Estate Roundtable Sustainability Policy Advisory Committee and was apast appointee to the NAIOP Sustainable Development Committee. As a member of the USGBC (U.S.Green Building Council) Warehouse and Distribution Center Adaptation Working Group, Binkley co-authored revisions to the renewable energy credit (EAc6), now available in the LEED pilot credit library.Binkley has published articles and white papers on renewable energy and energy conservation.

Binkley previously worked as an architect, specializing in sustainable design and renovation projects. Bin-kley is a Registered Architect and a LEED Accredited Professional. He has a master of science degreefrom MIT in Real Estate Development and an architecture degree from Carnegie Mellon University.

i


4/30

ii

Acknowledgements

I would like to thank Andy Brown, John Williams and Adam Parr for their valuable input on this document.I would also like to thank Elizabeth Sherrod and the NAIOP Foundation for their support of this referenceguide and other resources that foster and support efforts to educate the real estate profession.


5/30

About NAIOP i

About the Author i

Acknowledgements ii

Table of Contents iiiExecutive Summary 1

Solar Market Overview 4

Solar Basics 4

Classifying Solar Technologies 5

Rack-Mounted PV Module Systems 6

Composite Frame PV Module Systems 7

Adhered Building-Integrated PV Module Systems 8

Structural Building-Integrated PV Module Systems 9

Product Characteristics 10

Module Composition 11

Manufacturers, Market Share and Distribution 11

Physical Characteristics 12

Building Impacts, O&M and Climate Considerations 13

Performance, Cost and Design Characteristics 14

Solar Module Efciency 14

The Angle of Racking 15

Net-to-Gross Layout 15

Solar Array Weight 16

Roof Area Requirements 16Designing an Efcient Roof Layout 17

Inspecting Roofs 18

Construction Considerations 18

Warranties 20

Connecting to the Grid 20

Conclusion 21

Glossary of Terms 22

End Notes 23

List of Figures 24

List of Tables 24

Table of Contents

iii


6/30

1

Executive Summary

The Solar Technology Reference Guideprovides realestate decision-makers with the information neededto evaluate a range of solar technologies and theirimpact on the buildings supporting them. Solar tech-

nologies can be dened in four categories basedon their interaction with the host building. These

categories generally group products according

to weight, installation process and method of at-

tachment to buildings.

This makes it possible to make side-by-side compar-isons and evaluate the pros and cons of solar prod-ucts. Selecting and installing the most appropriatesolar technologies for a given building helps ensurethat projects are completed quickly, protably andwithout undesired structural or operational impacts.

This guide provides recommendations such as bestpractices for building design to:

Identify suitable building sitesDesign a building that maximizes the spaceavailable to support solar modulesManage project costsMinimize construction risksPrevent roof damageIdentify solutions suited to local climate condi-tions.Know what to look at in solar product warranties

This enables real estate industry professionals tomake informed decisions that reduce project costsand minimize operational risks.

Categorizing Solar Products

The key to choosing appropriate products for a spe-cic project is understanding the similarities and dif-ferences between available solar photovoltaic (PV)technologies. This makes it possible to recognizerelevant risk factors and make better choices of tech-nology. Current solar products on the market canbe grouped into four broad categories based on

their interaction with the host building:

Rack Mounted Glass PV Module SystemsComposite Frame Glass PV Module Systems

Adhered Building-Integrated PV Module Sys-tems (Adhered BIPV)Structural Building-Integrated PV Module Sys-tems (Structural BIPV)

Rack Mounted Glass PV Module Systems are themost common type of solar solution. They tend tobe the heaviest solutions, but they enable optimumenergy production and they can be customized for

almost any roof condition. Racking systems are de-signed to accommodate nearly all standard solarmodule sizes. These systems represent more than90 percent of the solar market and are supported byan experienced base of installers.

Composite Frame Glass PV Module Systems offermodular and pre-assembled solar module designsthat support fast installation and lower total systemweight. There are a limited number of manufactur-ers of composite frame systems. These types ofproducts are becoming more popular on commercialroofs where there is a need to both minimize weight

and expedite the installation process.

Adhered Building-Integrated PV Module Systemsaddress weight-constrained rooftops and metal roofsthat are difcult to accommodate with traditionalsolar module systems. These technologies are thelightest solar products on the market today. They areadhered to the roof without racking or ballast. En-ergy production tends to be lower because they areinstalled at to the roof, not angled to maximize theenergy they capture from the sun. Modules can beinstalled close together because they do not castshadows on one another.

Structural Building-Integrated PV Module Systems

offer solutions that are integrated into building com-ponents such as curtain wall facades, carports andoverhead canopies. These systems are highly engi-neered for custom applications and they tend to bethe most expensive type of solar project. The aes-thetics of these projects can be carefully controlled.

How Solar Products Affect Cost

The physical characteristics of each category interactwith economic considerations to determine whetherthe technology is appropriate for a given building, in-cluding:

Cost of solar module technologiesElectrical production of solar arrayCosts to install, including labor and balance-of-system costsBuilding preparation, including structural up-grades and roof coatings/replacements


7/30

Roof protection and warranty maintenanceTypes of climates conditions that can be accom-modated (i.e., High wind zones)Net area suitable for coverage of solar modulesThe angle at which modules can be positioned

The best economics on a solar project result from

more than simply selecting the most energy-produc-tive solar modules or the least expensive products.While all solar modules perform best when per-

pendicular to the sun, higher module efciency

ratings do not always mean greater electricity

output. Each technology produces electricity in dif-ferent amounts depending on sunlight and projectconditions. Less efcient modules may achieve simi-lar energy output -- when compared to higher ef-ciency modules -- by producing electricity for morehours throughout the day or in cloudy conditions.

Planning and Constructing Projects

The type of solar technology selected has an impacton the construction process. Rack mounted modulesystems often require large amounts of space on-site for staging and prep areas. Composite systemsand adhered BIPV systems are pre-assembled andcan be loaded directly onto a rooftop, minimizingconstruction disruptions. Structural BIPV systemsare integrated into the existing construction processfor other building elements, plus the additional workto connect the solar array.

Only a portion of a roofs total area can be cov-

ered with solar modules. Panels should not beplaced in areas shaded by tall HVAC equipment,adjacent buildings, penthouses or trees. Modulesshould also be spaced adequately so they do notcast shadows on each other. The perimeter of theroof should also be kept clear to facilitate workersafety, roof inspections and the placement of non-solar equipment on the roof.

The location of existing rooftop equipment such asHVAC units, skylights and shaded areas can affect

the layout of a solar array. On a small or clutteredroof, as little as 50 percent of the roof may be avail-able for solar modules. On a large open roof the suit-able area may approach 90 percent. An array thatis efciently laid out is easier to maintain, will t

more solar panels and therefore generate more

electricity. It can also reduce solar project costs

by simplifying design and speeding installation.

Solar modules typically weigh between 25 and 70

pounds and are designed to be carried by two work-ers on the job site. Module products can be larger,but those are designed primarily for ground-basedapplications where they can be craned into place.

Solar array weight can become a driving factor

in the choice of which solar product is the most

suitable. Few existing buildings were designedwith solar in mind, so there is often little ex-

cess structural capacity to support solar equip-

ment on rooftops.Array weight can vary from lessthan one pound per square foot to nine pounds persquare foot. This range exists due to the technologyselected, local wind conditions that may necessitatemore ballast to resist wind forces, system designand method of attachment to the building.

Before installing any solar products on a build-

ings roof, it is essential that you determine

whether the roof is suitable for the project. Theroof should be in good condition and have sufcientlongevity that it will not need replacing during the op-erational life of the solar project. Pay special atten-tion to areas of poor drainage. Standing water candamage solar equipment as well as over-stress theroof. For roofs that are nearly new, the addition ofa white roof coating can extend the roofs life, helpresist wear from construction trafc and reduce per-formance-robbing high roof temperatures.

During the contruction process, care is needed toavoid unnecessary roof wear or damage. Perform-

ing a pre-construction roof inspection and apost-installation inspection provide a way to pro-

actively identify and resolve potential problems.

Care should be taken during construction to en-

sure that adequate roof protection is in place to

avoid jeopardizing roof warranties or causing

preventable damage.

The construction process for each type of solar tech-nology can affect the suitability of that product for aparticular building. Where staging areas are limited,it may be advantageous to specify a solar productthat can be delivered directly to the site ready-to-in-

stall. For sites where there is no large open expanseof roof, a rack mounted system may provide morecustomization. On buildings with a much greaterfacade area than roof area, structural BIPV facadeproducts may be advantageous.

There are two types of warranties that concern thereal estate professional. These are materials andworkmanship warranties and energy output warran-ties. A materials and workmanship warranty will vary

2


8/30

3

based on the type of equipment. Modules, invertersand racking are typically warranted for 10 years,

while racking is often warranted for ve years.

The energy output warranty typically covers 25

years and provides solar project investors pro-

tection against the loss of revenue due to under-

performance of the solar modules. For newer

module technologies, manufacturers may provideinsurance policies to protect investors until there issufcient track record of adequate performance.

Connecting to the utility grid is a factor that can affectthe economic viability of a solar project. Solar proj-ect owners often need to undertake interconnectionreviews in order to get approval from the local utility.

At times the utility may require upgrades to the localgrid system to accommodate the solar facilitys newcapacity. Depending on the scope of these costs itmay affect the economics of the solar project.

Conclusion

The solar industry in the U.S. is poised to continueits upward trajectory of growth in the years that comeas more states adopt solar programs. Combined withglobal growth in the scale of solar module manufac-turing, costs for solar modules and equipment can beexpected to continue to decline over time.

It is widely acknowledged that not every solar tech-nology will achieve commercial success. There will

be success stories and failures along the way but itwill ultimately lead to better products that meet theneeds of commercial property owners and drive evenwider adoption.


9/30

The global solar industry is supportedby growth in the United States and hasgrown rapidly in the past decade, re-cording 27-fold growth between 2000and 2010.1 In the United States thereis currently enough solar capacity in-stalled to power more than 600,000

homes.2

The United States is current-ly the third largest solar market in theworld, behind the European Union andJapan.

To put the United States market in con-text, Germany has installed solar ca-pacity more than ten times greater thanthe United States; Germany alone ac-counts for 56 percent of European de-mand.3 It is projected, however, that theU.S. could become the worlds largestsolar market as soon as 2013 if growth

in the United States continues whilethe German market slows.4 That is, ofcourse, if China does not overtake bothcountries as it seeks to ramp up its do-mestic solar projects.

A growing number of states have is-sued regulations and funded incentiveprograms that support solar projects oncommercial buildings. This has contrib-uted to signicant growth in the solarindustry in recent years (Figure 1).

Within the United States, California hasthe largest solar market, accounting for45 percent of national demand.5 Othersouthwestern states such as Arizonaand Nevada have also begun to de-

velop substantial solar portfolios. Solaris not constrained to sun-drenched lo-cations. States not traditionally knownfor their sunshine such as New Jersey,

Pennsylvania and Massachusetts havecreated programs that support solarprojects on commercial buildings. Assupport for solar projects on commer-cial buildings grows, property ownerswill see more opportunities for solarprojects throughout the United States.

The real estate industry is increasinglyeyeing rooftop solar projects as a wayto generate additional revenue and im-prove sustainability. However, manyproperty owners are wary of pursuingsolar until they become familiar with so-lar products on the market.

Solar manufacturers and installers caninadvertently contribute to this wari-

ness. Vendors may have expertise witha limited number of solar products sotheir proposals often tailor these solutions to most projects. As such, the im-

pact on the building can only be minimized to the extent it is feasible withthe limits of that technology. Withouknowing the range of product solutionsavailable, property professionals mayaccept a solution thats not appropriatefor their building site. They may also re

ject solar altogether as a viable solutionwhen a suitable solution may exist witha different solar technology.

Real estate professionals consideringsolar have valuable knowledge aboutheir buildings condition and suitabilityfor solar. When they can evaluate whichsolar technologies align best with theseconditions, the projects are more likelyto be successful.

Electricity is created by solar panelsand delivered to the building or utilitygrid in the following steps:

1. Sunlight hits a solar module

(also referred to as a solar panel).Semi-conducting materials in themodule convert the suns energyinto electricity.

2. Electricity from each panel iscombined with many other solarmodules. An assembly of intercon-nected solar panels is referred toas a solar array.

3. Specialized electrical devices

such as charge controllers, in-verters and transformers take theraw electricity from the solar arrayand condition it to become usableelectricity.

4. This electricity is then deliveredto the building to offset electricloads, or is returned to the localelectric utility.

Solar arrays on buildings can be al-most any size, from a few kilowatts --to power signage and other inciden-tal electricity use -- to multi-megawattsystems capable of powering thehost building and its neighbors.

The rules that determine the feasi-bility of solar projects vary from oneutility to another, as well as from onestate to another. As a result, the eco-nomic value of a given solar project

will vary based on the projects loca-tion. In some markets, it may makesense to produce electricity for usein the host building. In other markets,it may be more cost-effective to sellenergy to the utility.

Solar companies and local utilitiescan help identify suitable marketswhere a commercial property portfo-lio overlaps with solar-friendly regu-lations.

Solar Basics

4

Solar Market Overview

0

375

750

1,125

1,500

2005 2006 2007 2008 2009 2010 2011(projected)

Figure 1: Megawatts (MW) of Solar Capacity Installed

Each Year in the United States6

MW


10/30

Solar technology literature typicallygroups solar panels based on the com-position of the electricity-producing ma-terials in solar cells. Accordingly, thereare four predominant solar cell compo-sitions in commercial production:

Crystalline silicon (C-Si) Amorphous silicon (A-Si)Cadmium telluride (CdTe)Copper Indium Gallium Selenide(CIGS)

This type of classication is used bythe solar industry because manufac-turing requirements, cost, installationmethods, nancing potential and per-formance varies with each technology.There are also sub-classications with-in these groups (such as mono-crystal-

line and polycrystalline within the C-Sigroup).

Other classications for solar technolo-gies exist for specialized applications,such as those used to power satellites.These technologies tend to be manytimes more expensive and are not a tfor commercial building projects. In ad-dition, innovative research in academiaand start-up companies are developingnew solar technologies for the future.

Classication based on solar cellcomposition is not the most use-

ful way for real estate profession-

als to categorize technologies. Thisis because one type of solar cell canbe assembled to create modules thathave very different shapes, weights, ordimensions depending on its manufac-ture. Conversely, nearly all solar cellcompositions are being used in rectan-gular glass modules even though theirperformance varies widely.For example, amorphous silicon is asolar cell composition used by sever-

al solar panel manufacturers, and theform of solar panel they produce hasvery different physical characteristics.Some modules are thin and exible,while others are sandwiched betweenrigid glass panels.

A more useful way to classify solartechnologies for commercial prop-

erty owners is to group them by the

way they interact with the host build-

ings. This classication depends ontheir physical attributes such as formfactor, weight, installation process andmethod of attachment to the building.

This way when a project encountersolder buildings with limited load-bear-ing capacity, lightweight solar productscan be selected. A building with a metal

roof would use a different solution thanone with a gravel-ballasted built-uproof, and so on.

Categorizing modules this way is notscientic; it is practical. This makesit possible to sort solar technologiesbased on their impacts on buildingsrather than their inner workings.

There are four main categories:Rack Mounted Glass PV Module

Systems (Page 6)

Composite Frame Glass PV Mod-ule Systems (Page 7)

Adhered Building-Integrated PV

Module Systems (Adhered BIPV)(Page 8)Structural Building-Integrated PV

Module Systems (Structural BIPV)(Page 9)

Both rack-mounted and compositesolar products use similar rectangularglass modules. These systems alsogenerally use ballast, typically masonryblocks or gravel used for its weight to

hold the array on the roof and resistwind forces.

The key difference for the real estate

owner is that rack-mounted solar ar

rays are assembled from many com

ponents in the eld. They generally

require more ballast and are heaviethan the other technologies, but they

tend to produce more electricity be

cause modules of high efciency

can be specied and they can be

positioned optimally to absorb the

suns energy.

Both rack mounted and compositeframe module categories can be anchored to the building to resist windand seismic forces. This can reducesystem weight by reducing the need

for ballast. These are typically discreteconnections that can be disassembledwithout affecting the integrity of the roofor the building structure.

In contrast, adhered BIPV systems arephysically attached to building roof ofacade components such as the exist-ing roof membrane. These products cannot readily be removed without removing the entire roof or facade. Patchingand repairs are typically required.

Structural BIPV systems are similato adhered BIPV systems in that theyare attached to the building. The keydifference is that BIPV systems are integrated into the building in a way thamakes them integral to the function ofthe building.

For example, curtain wall glazing canbe replaced by solar modules. Without the modules, the curtain wall system would not be able to keep out theweather unless the modules were subsequently replaced with window glass.

Classifying Solar Technologies

Rack Mounted ModuleSystems

Composite FrameModule Systems

Adhered Building-Integrated Modules

Structural Building-Integrated Modules

Crystalline Silicon P P P P

Amorphous Silicon P P P P

Cadmium Telluride P

Copper Indium Gal-lium Selenide

P P

Table 1: Solar Cell Composition by Product Category

5


11/30

Rack-mounted glass modules are used in the most commontypes of rooftop solar arrays. Rows of solar panels are heldat an angle atop the roof on a metal frame composed of rails,braces and trays for ballast. Rack-mounted systems can behighly customized to accommodate varying roof conditionsand can be adjusted to hold the solar panels at almost anyangle to optimize energy production.

These racks can accommodate nearly all rectangular glasssolar panel makes and models. They can be anchored to the

Rack-Mounted PV Module Systems

Figure 3: Example Rectangular Solar Modules

Rack-mounted array with masonry ballast blocks on a gravel ballasted

roof. Image: Aaron Binkley

Figure 4: Example Rack-Mounted Solar Installations

Field-assembled racking system under construction on an asphalt built-up

roof. Image: Aaron Binkley

Solar racking permanently attached to roof structure. Note post with bolted

connection. Image: Aaron Binkley

Rack-mounted array with masonry ballast blocks on an asphalt built-up

roof.Notealuminumwinddeectoratright.Image:AaronBinkley

roof structure with standard pipe ttings and ashing bootsused throughout the roong industry. These racks are metaso they require grounding, an added step in the constructionprocess.

Image: ZEP Solar

Figure 2: Racking System Detail

Ballast blockon ballast tray

Aluminum or

stainless steelrack frame

Solar module

Winddeector

6


12/30

Image: Solon





Weight (typical range) 4 to 9 PSF 2 to 6 PSF 1 to 1.5 PSF n/a

Method of Attachment Ballasted; afxed Ballasted Afxed Integrated into build-ing component

Table 2: Added Weight and Method of Attachment

Image: SunPower

Composite Frame PV Module Systems

Composite frame glass module systems are designed to

meet the needs of low-slope commercial roofs.Compos-ite frame products use similar solar modules as rack-mount-ed arrays. The key differences are:

They are installed in a reinforced composite berglass orplastic frame, usually at the factory before being shipped

to the job site;The frames snap together without tools;The module and frame are installed at the same time;The installation process is expedited;The impact of construction activity on the roof is re-duced.

Composite frames are designed to hold the solar moduleseither parallel to the roof or at a shallow angle up to about10 degrees. This is a compromise between a low prolethat minimizes wind forces and reduces ballast needs, anda higher angle that increases electricity production but re-quires more ballast to resist wind forces.

Each project will vary based on local conditions anddesign requirements, but in general, rack mounted sys-

tems are heavier than composite frame systems. This isdue in part to the higher angle of the solar panels, which in-creases wind forces that must be counteracted with ballast.

Alternatively, the racking may be anchored to the roof, butthis introduces roof penetrations to the project that may ormay not be desirable from the property owners standpoint.

Composite systems may also require ballast, but their shal-lower angle reduces wind forces. In contrast, neither adheredBIPV nor structural BIPV systems require ballast because

they are integrated into existing building elements. Thismakes them lighter when compared to glass module sys-tems. The table below compares the relative added weightof the four solar technology categories.

7

Image: Solon

Figure 5: Composite Frame Module Detail

Image: SunPower

Compositeframe bonded

to solar module

Wind deector

Solar module

Connectionto adjacent

module

Note: PSF = Pounds per square foot


13/30

Adhered building-integrated photovoltaic modules (adheredBIPV) are products that are attached directly to existingbuilding elements, most commonly the roof. These prod-ucts do not need a racking system for support. This class ofproducts is adhered directly to the roof surface and does notneed ballast to hold them in place.

Adhered BIPV products can be used ona wide range of roof types, from stand-

ing seam metal roofs to membrane roof-

ing. These products are only suitable

on gravel-ballasted roofs if the gravel

is removed and the roof is thoroughly

cleaned. This is necessary for adequatebonding of the solar module product to theroof surface.

Although not recommended, adheredBIPV modules can be walked on (withcare), so they do not create obstructions

on the roof. While they can be removed,they are bonded in place with adhesives.This may require patching the roof wherethe panel has been removed.

Adhered BIPV modules lie parallel to the roof and are notangled to face the sun. This can reduce energy production.Conversely, more density of modules can often be installedbecause the modules will not cast shadows on one other.

Adhered Building-Integrated PV Module Systems

Image: Solon

Figure 6: Adhered BIPV Installation Details

Adhered BIPV Arrays on Membrane Roofs

Image: Lumeta

Image: Solon

Image: Uni-Solar

BIPV modulesbonded to secondaryroof membrane

Existing roof mem-brane prepped forsolar modules

BIPV modulesbonded to ridges ofmetal roof

Adhered BIPV Solar Arrays on Metal Roofs

8

Image: Uni-Solar

Image: Uni-Solar

Image: SoloPower


14/30

Structural Building-Integrated PV Module Systems

Image: Aaron Binkley

Image: SuntechImage: Yingli Americas and Borrego Solar

Solar Carports

Carports are a structural BIPV solution that is becoming more common, particularly in warm climates where shadedparking is a building amenity. Modules are attached to a supporting steel structure and form the roof of the carport.This application can be considered structural BIPV because the solar modules make up the roof of the carport itself.

Structural building-integrated photovoltaic modules (structur-al BIPV) are integrated into a buildings facade, roof or otherbuilding element. These products differ from adheredBIPV in that they completely replace building compo-

nents, such as curtain wall or atrium glazing. BIPV prod-ucts become integral to the function of the building system,and the modules rely on the existing facade elements (such

as the curtain wall frame) to provide structural support. Be-low is a list of common structural BIPV applications, althoughothers can be engineered:

Curtain wallsWindows

AwningsSunshadesCarports

Atrium glazingPanelized metal wall systems

Structural BIPV products are specialized solutions engi-

neered to be integral with the building facade. Their aesthet-ics can be carefully controlled. They can be more challeng-ing to service because they are built into the building.

Aluminum

curtain wallframe

Solar module

Curtain wallglazing

Figure 7: Structural BIPV System Detail

Image: Aaron Binkley

9


15/30


Composite Frame Mod-ule Systems

Adhered Building-Inte-grated Modules

Structural Building-Inte-grated Modules

Characteristics Rectangular glasssandwich panelsSupported by a

metal rackRack is assembledin the eldWide variety ofshapesMany modulemanufacturers

Rectangular glasssandwich panelsSupported by a

composite rein-forced plastic rackModular shapeFew manufacturersFrame designed tot specic moduletype and size

Flexible panelsencapsulated ina wear-resistant

polymerLays at on roofFew productsFew manufacturers

Adhered to roofNo racking required

Solar cells encap-sulated in glass orinsulated glazing

unitIntegrated intobuilding systemsuch as curtain wallor atrium glazingSpecialized productFew manufacturers

Pros Many modules tochoose fromCompatible withmost racking sys-tems

Mature technology Large number ofsuppliersExperienced install-ersHigh efciencymodules

Designed for low-slope commercialroofsLight weightModular

Requires few or no tools for installationReduces amountof ballast requiredcompared to rackmounted system

Designed for low-slope commercialroofsLight weightRequires few or no

tools for installationNo ballast requiredDoes not restrictroof travelNot affected bywindLittle impact onbuilding structure

Designed to be builtinto building com-ponentsSimilar weight totraditional glazing

systemRequires special-ized installationNot affected bywindLittle impact onbuilding structureColor options

Cons Requires separateracking system andballastHighest weightDifcult to remove

Extensive roof traf-c for installationSnow removal incold climates

Few manufacturersSingle prole - notadjustable or cus-tomizableSnow removal in

cold climates

Few manufacturersLimited installerexperienceDifcult to removeNot suitable for

use in conditions ofstanding water

Proprietary technol-ogyLimited installerexperienceDifcult to remove

Aesthetics vary

CommonApplications

Commercial roof-topsCarports

AwningsGround-basedsystemsResidential rooftops

Commercial roof-tops

Commercial roof-tops

Curtain wallWindows

AwningsSunshadesCarports

Atrium glazingPanelized metalwall systems

Table 3: Product Characteristics

Product Characteristics

The product characteristics (Table 3) listed below providea side-by-side comparison on the four product categories.Characteristics are dened by their physical features, shape,composition, manufacturer adoption and racking require-ments.

The table provides a list of pros and cons for each product.

This list identies major considerations and common factorsthat can be used to help determine which product catego-ry is better-suited to a particular application. The pros andcons focus on product availability and substitutes, as wellas building impacts related to the installation of the solar ar-

ray. The installation process can accelerate roof wear andlead to damage if not planned for and monitored carefullythroughout the construction process.

The structural impacts of each category are also consideredbased on a typical range of installed system weights. Themost common applications for each category are provided

to further assist in targeting the right product to the right application on commercial buildings. These characteristics aregeneral for each category, and do not represent an exhaus-tive feature-set for every product on the market.

10


16/30

11





Manufacturers Hundreds; examples

include:SunPowerYingliSuntechSanyoBP SolarTrinaFirst SolarQCells

SunPower

SolonRenusol (compositeframe only)Solyndra (see page21 for additionalinformation)

Thin lm:

Uni-SolarSoloPowerGlobal Solar

Ascent Solar

Crystalline:SolonLumeta

Canadian Solar

BP SolarSuntechPythagorus SolarZytech SolarVoltarlux

Market Share +/-90 percent of com-mercial solar market

+/-8 percent of commer-cial solar market

+/-2 percent of commer-cial solar market

Niche;


17/30

Physical Characteristics





Width 24 to 48 inches typi-cal; up to 86 inches

43 to 54 inches Thin lm: 14 to 25inchesCrystalline: 48 inches

Varies according toframe of supportingbuilding system

Length 48 to 75 inches tyical;up to 102 inches

78 to 90 inches Thin lm: 188 to 216inchesCrystalline: 93 inches


Aspect Ratio Varies; 1:1 to 2:1 bymanufacturer

2:1 Thin lm: 14:1Crystalline: 2:1

Varies; similar to cur-tain wall glazing

Thickness 0.25 to 2 inches withframe

10 to 12 inches includ-ing integrated frame

Thin lm: 0.25 inchesCrystalline: 0.5 inches

0.25 inches to 1 inch

Module Weight Varies; 3 to 5 PSFtypical

2.5 to 3.0 PSF Thin lm: 0.5 to 1 PSFCrystalline: 2.1 PSF


Racking and BallastWeight

Varies; 1 to 4 PSFtypical

0.5 to 2.0 PSF none required none required

Total System Weight Varies; 4 to 9 PSFtypical

3.0 to 5.0 PSF Thin lm: 0.5 to 1 PSFCrystalline: 2.1 PSF


Physical characteristics help to dene each solar category. Table 5 provides indicative ranges for the products dimensionscomponent weight and total installed system weight. The data in the table provides a typical range for products you canexpect to encounter as a general comparative guide; it does not represent all products on the market.

While there is variation within each category, many manufacturers products have been somewhat standardized to facilitateeasier handling, installation, and integration with common racking systems. Consult manufacturers data for detailed specications for the modules that are being considered.

Table 5: Physical Characteristics7

The size of solar modules can vary considerably dependingon the type of panel and its intended use. Solar modulesintended for rooftop applications are designed to behandled by two workers at a time, and weigh in at 25 to70 pounds per module.8

Solar modules can be larger for applications wherethey can be craned into place such as curtainwall glazing or carport canopy roofs. The largest

module for these applications weighs morethan 200 pounds and is intended primarily forground-based applications.9

Flexible thin lm modules like the oneshown at the far right, are longer andnarrower than typical solar modules.This form factor allows them to beused on metal roofs and on appli-cations where glass panels aretoo wide. Their exible steelbase sheet allows them to beapplied to curved surfaces.

Figure 10: Scale Comparison of Module Sizes

Note: PSF = Pounds per square foot

5ft.

9in.

12


18/30

13





Building Impacts Weight can havesignicant effect onbuilding structureIncreases wind

loads on buildingstructureIncreases seismicload on buildingstructureDifcult to removeonce installedSuitable for lowslope roofs andpitched roofs withsuitable rackingsystem

Weight can havemoderate effect onbuilding structureNo increase in wind

loads on buildingstructureIncreases seismicload on buildingstructureEasy to removeonce installedSuitable for lowslope roof types

Weight has littleeffect on buildingstructureDifcult to remove

once installedSuitable for all lowslope roof typesRequires littlesetback from roofedge or obstruc-tionsCan be walked onDoes not obstructmaintenance paths

Weight has littleeffect on buildingstructureDifcult to remove

once installedSuitable for build-ing systems whenproperly engi-neeredSolar cells visiblein the installedproduct can haveaesthetic impacts

O&M Inspections 2X per

yearCleaning 1X-2X peryear

Inspections 2X per


Inspections 2X per


Inspections 2X per


Climate Consid-erations

Suitable for allclimate regionsUse in high-windzones requiresadditional ballastor fastening to roofBest performancein direct sunlight

Suitable for allclimate regionsSuitable for use inhigh-wind zoneswith additional bal-lastBest performancein direct sunlight

Suitable for allclimate regionsSuitable for use inhigh-wind zones(some are Miami-Dade approved)Suitable for directand indirect sun-light

Suitable for allclimate regionsSuitable for use inhigh-wind zones(can be engineeredto meet Miami-Dade regulations)Best performancein direct sunlight

Building Impacts, O&M and Climate Considerations

The impact that the solar array has onthe building host is often a determin-ing factor that makes one solar productmore suitable than another for com-mercial building applications.

An important consideration is the

weight of the solar equipment (solarmodules plus racking and ballast).Astructural engineer should inspect thebuilding and calculate the allowableweight of the solar array. Exceeding thissafe limit could result in roof ponding,difculty accommodating other rooftopequipment in the future due to weightconstraints, or in a worst case scenariocontribute to roof damage. This is aparticular concern in climates subjectto heavy rain or snowfall that may bedifcult to remove from the roof.

The ease of roof maintenance with

solar installed is another consider-

ation. BIPV products have little impact

on roof or facade access for mainte-nance purposes. Rack-mounted andcomposite module systems need to beworked around or temporarily removedto gain access to roof or building areas.Pathways must be included in the de-sign to service rooftop equipment as

well as the solar array itself (see pages15 to 17).

Roof repairs underneath all solar

product types may require tempo-

rary removal or repositioning of so-

lar panels, racking and ballast in or-

der to access the roof. Rack-mountedsystems may have tilt-up features thatallow limited access to the roof under-neath. Even with this feature, roof re-pairs that extend underneath severalsolar panels may require temporary

removal of the array for convenienceand safety.

Operations and maintenance (O&M)

is minimal for most solar products

All panels lose performance due to dusand dirt accumulation, in the range of1.5 percent to 6 percent under normaconditions.10 Periodic rain is usuallysufcient to clean the modules and re-store output. Semi-annual inspections

should identify and repair damagedequipment. Inspections should also beconducted immediately after extremeweather events.

Solar panels are designed to withstanda broad range of climates and temperatures. Products installed in high-windzones may require additional ballast toresist wind forces. With proper engineering, BIPV systems can be used inhurricane zones. Special care must betaken when selecting products in corro

sive coastal and marine environmentsto prevent premature module deterioration, racking system corrosion, andeven damage from birds.

Table 6: Building Impacts, O&M and Climate Considerations


19/30





Cost per kWh

(relative)

$ $ Thin lm: $ to $$

Crystalline: $ to $$

$$$$

Power Density 8 to 16 watts/SF 8 to 16 watts/SF Thin Film: 6 to 10 w/SFCrystalline: 13 w/SF

6 to 13 watts/SF

PracticalEfciency

8% to 17.5% 8% to 17.5% Thin Film: 5% to 7%Crystalline: 10% to 12%

5% to 12%

Net-to-GrossLayout14

50% to 80% 50% to 80% Thin Film: 70% to 90%Crystalline: 60% to 90%

20% to 40%

Performance, Cost and Design Characteristics

Solar module performance varies widely among products.

Practical efciency -- the real world conversion of sunlight

into electricity -- varies from 5 percent to more than 17 per-

cent. However, efciency is not the only factor. Less efcientproducts may produce as much energy as high efciency mod-els by operating more efciently in different lighting conditions,or by generating energy for more hours throughout the day.

Solar module prices have declined by more than 50 per-

cent since 2008 (Figure 11), and continue to drop as global

production rises to meet growing demand.Project costs, ex-pressed in $ per watt, can vary widely based on design param-eters. Project costs (modules, balance-of-system plus installa-tion) can be in the $3 to $5/watt range on large projects.11

Table 7: Performance and Design Characteristics13

6.0

5.0

4.0

3.0

2.0

1.0

0.0

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

$

perWatt

Figure 11: Retail Module Price Index (2001-2011)12

Solar Module Efciency

Solar technologies have a wide range of efciencies - the percentage of sunlight striking the module that is convertedinto electricity. On the low end of the spectrum you will nd efciencies in the single digits; at the high end, efciencies

are in the high-teens in percentage.

Higher module efciency does not always mean greater electricity output. Each technology produces electricity in dif-ferent amounts depending on sunlight and project conditions. Some modules produce best in bright, direct sunlightbut output falls off quickly in cloudy conditions. Less efcient modules may achieve similar energy output by producingelectricity earlier in the morning and later in the evening when the sun is less intense, a trade-off that offsets lowermodule efciency.

Solar modules perform best when perpendicular to the sun.This delivers the greatest amount of sunlight to the module.For some modules, shallower angles quickly reduce energyoutput because the suns energy is not absorbed as ef-ciently. For other technologies, performance is not impacted

as greatly. These modules may have an advantage at siteswhere it is not feasible to install solar modules at the anglethat would allow modules to produce at optimum efciency.

Because of these factors, it is essential to look at more thanjust the efciency of the solar modules when comparing dif-ferent solar technologies. Solar project designers can pro-vide expected annual kilowatt-hour production projectionsbased on the performance characteristics of the technologythey propose. This will allow you to see how different tech-nologies compare in terms of energy output, not just energyconversion efciency.

Figure12:TypicalSolarModuleEfciencyRange

19

17

15

13

11

9

7

5

Efciency(%)

CrystallineSilicon

Copper IndiumGallium Selenide

Cadmium Tel-luride

AmorphousSilicon

14


20/30

15

The Angle of Racking

Solar modules produce the greatest amount of energy whenthey are positioned perpendicular to the sun. This is why,in large ground-based systems, modules are installed onmotorized frames that track the sun throughout the day tomaximize energy production.

It is rarely feasible to install solar tracking systems on build-ings due to cost and installation constraints. Instead, racking

systems hold the solar modules at a xed angle that bal-ances energy production with cost, aesthetic and structuralconsiderations.

Where modules can be positioned at a near-optimal angle,traditional high-efciency solar modules often make sense.If this is not possible due to height, wind uplift or aestheticconsiderations, solar technologies that produce more energygiven the practical constraints of that site may be a prefer-able solution.

Space must be maintained between rows of solar mod-

ules to avoid casting performance-degrading shadows

on adjacent modules. The steeper the angle of the so-lar modules, the greater the distance required between

rows of modules.

Space-constrained sites face a trade-off between:1) optimum output from fewer modules, or2) installing a greater number of modules in total, but accept-

ing that the output of each module will not achieve its peaklevel of performance.

Determining what solution is best for your project requiresanalysis by the solar project designer as they experimentwith module spacing angle, module type, cost and weight ofthe project. With the number of variables at play, there isno one-size-ts-all solution for maximizing power out

put and economics of a solar system design.

Figure 13: Racking Angle Comparison

0 degree angle to minimize visibility, weight, wind uplift

10 degree angle to maximize array coverage

30 degree angle to maximize module output

Only a portion of a roofs total area can be covered with solar modules. Panels should not be placed in areas shadedby tall HVAC equipment, adjacent buildings, penthouses or trees. Modules should also be spaced adequately so theydo not cast shadows on each other. The perimeter of the roof should also be kept clear. This ensures there is sufcient

distance from the roof edge to support worker safety. It also allows access to the perimeter of the building to facilitateroof inspections, load equipment onto the roof, and provides a place to store panels if portions of the solar array needto be moved temporarily.

Walkways are needed for maintenance, inspection and re department access. Keep a clear area around rooftopequipment such as skylights, HVAC equipment, roof hatches and exhaust fans. Consider reserving a portion of the rooffor HVAC equipment that future buildingtenants may require.

Once these space requirements are fac-tored into the design, you can determinethe net-to-gross solar layout. This is theroof area covered by solar panels com-

pared to the gross roof area. A number of70 percent means that 70 percent of theroof can be used by the solar array (in-clusive of walkways for solar equipmentaccess).

The net-to-gross ratio can be very lowon small cluttered roofs or it can be veryhigh on large unobstructed roofs. Thepercentages listed in Table 7 representa typical range for projects. Actual ratiosare likely to vary for any given site.

Net-to-Gross Layout

Perimeter setback

Maintenance and re dept. access

HVAC

setback

Solararrays(blue)

Figure 14: Example Roof Layout Indicating Setbacks

Skylights


21/30

The area required on a roof to host asolar array varies depending upon thetechnology selected. High-efcien-cy solar modules take up the least

amount of space, while low ef-

ciency adhered BIPV and structural

BIPV modules require a much great-

er area - as much as double that of

high-efciency modules to achieve

the same installed capacity.

Where space is limited and energyproduction per square foot needs tobe high, a high efciency product maysuit. But it is not always as simple as

choosing the highest efciency module. Weight constraints on the projecmay dictate a much smaller array whenusing highly efcient, but heavier rectangular glass modules. A lighter weighsolar array may help alleviate weighlimits and allow a larger system withgreater output to be installed.

Module cost can also affect the choiceof one technology over another. A highefciency module may be relativelymore expensive, making a larger, buless efcient solar array a more costeffective solution.

In other cases, it may be advisable touse a particular type of solar producwhether or not it is the most efcient, inorder to comply with zoning restrictionsor aesthetic requirements at the building. An adhered BIPV product may beneeded on a building with no parapet ithe solar array needs to be hidden fromview.

Roof Area Requirements

Figure 15: Roof Area Requirements for 100 kW Array

High-efciency rectan-gular glass modules12,000 to 14,000 SF

Avg. efciency rectan-gular glass modules14,000 to 18,000 SF

Low-efciency thin lmBIPV modules20,000 to 25,000 SF

Structural BIPV mod-ules30,000 to 40,000 SF

The weight of a solar array is a sig-nicant consideration for commercialbuildings. Few existing buildingswere designed with solar in mind, so

there is often little excess structural

capacity to support solar equipment

on rooftops. This limitation can be-

come a driving factor in the choiceof which solar product is the most

suitable. In some cases, only the mostlightweight products may work. A struc-tural engineer can determine the allow-able additional load criteria for a givenbuilding.

The weight of a solar array is a combi -nation of the solar panels, racking and

any ballast required to resist wind up-lift. Racking and ballast for rectangularglass panels often weigh more than thepanels themselves. Large at panelsare subject to signicant forces as windblows across them.

More ballast is required to resist windforces in higher wind zones. This weightcan become a limiting factor in the de-sign of rooftop solar projects, especiallyon buildings with little excess structuralcapacity. Extra weight also affects thebuildings structure by adding weightthat can be shaken in an earthquake.

Adhered BIPV products lie at on the

buildings roof. When properly installedthese products act as part of the roomembrane to resist wind forces withouthe need for ballast.

Structural BIPV products are integratedinto the buildings facade. The facade

element that the solar modules are anchored to is already designed to resiswind and seismic forces.

Solar array weights will vary basedon local requirements, choice of solatechnology and design parametersThe table below lists typical ranges ofsolar array weights for both moderateand high-wind zones.

Rack Mounted ModuleSystems Composite FrameModule Systems Adhered Building-Integrated Modules Structural Building-Integrated Modules

90 mph wind zone 4 to 7 PSF 2 to 4 PSF 1 to 1.5 PSF n/a

120 mph wind zone 5 to 9 PSF 3 to 6 PSF 1 to 1.5 PSF n/a

Solar Array Weight

Table 8: Solar Array Weights in Various Wind Zones

16


22/30

17

When planning a building that will havesolar on the roof, design the roof to fa-cilitate an efcient solar array layout.This will maximize the amount of solarpower that can be generated while alsoreducing solar project costs by simplify-ing design and installation. A solar ar-

ray that is efciently laid out is easier tomaintain, will t more solar panels andtherefore generate more electricity.

The location of rooftop equipment androoftop obstructions affects the amountof energy that can be produced by aroof. The illustrations on this page com-pare features of a roof that has beendesigned to support an efcient solarlayout (Figure 17) with a roof that hasnot (Figure 16). Designing for solar onthe roof of a building can be accom-

plished by considering where rooftopequipment such as HVAC units, sky-lights and roof hatches will be placed.This will allow the designers to optimizethe roof layout without adding costs orhaving to change designs in the eldduring construction.

Align skylights so they can be ac-cessed with direct walk paths thattake up a minimum amount of roofspace.Locate rooftop equipment, includ-ing roof hatches, toward the perim-eter of the roof. Most solar arrayswill have a 10- to 20-foot setbackfrom the roof perimeter that can beused for placing small equipment.Wherever possible, locate largerHVAC units to minimize the ex-

tent that they cast shadows on theroof.

Shaded areas are unsuitable for solapanels. Ideally, tall equipment shouldbe located on the northwestern cornerof the building so it does not cast shad

ows on open areas of the roof wherethe solar array could be located.

Solar projects can be designed for mosroofs, but incorporating a few simpleconsiderations during the design of abuilding can go a long way toward maximizing the area of the roof suitable foa solar array. This can often be donewithout affecting building costs, andthese changes also help to simplify solar project design and installation whenthe time comes.

Designing an Efcient Roof Layout

Figure16:InefcientRoofLayoutforSolar Figure17:EfcientRoofLayoutforSolarNorth

Skylight layoutrequires greater

amount of mainte-nance travel paths

Roof hatch and HVAC unitsdistributed across roof takes

up space usable for solar;reduces efciency of solar

panel layout

Arrangement of HVACequipment on roof pre-

vents adding solar panelsin this area. Shading fromlarge HVAC unit reduces

available area for solar

HVAC equipment groupedtogether and moved tocorner to minimize shadedarea on roof

Roof hatch and HVAC units movedinto perimeter setback area to maxi-mize usable roof space for solar

Skylight layoutaligned to minimizemaintenance paths


23/30

Construction of solar projects can beaffected by the choice of technologyand the project site. This in turn affectsthe projects cost. A large rooftop solarproject may require thousands of solarpanels, miles of cabling and conduits,and many tons of racking and ballast tobe delivered to the project site.

Solar projects installed as part of theconstruction of a building can read-ily be integrated into the contractorsschedule. Projects at existing buildingsrequire a high level of planning so con-struction does not interrupt occupants,block parking or otherwise interferewith the use of the building. Projects re-quire a work area to receive materials,lay down, sort, and assemble the com-ponents of the solar project. A crane isoften needed to deliver materials to theroof or installation location.

The time required for the installationof a solar project varies by technol-

ogy and site. Project installation

rates can vary considerably based

on project scope, manpower and

technology. This could range from a

few tens of kilowatts per day up to

100 kW per day on large, well-staffed

projects.

There are often days or weeks of prepwork before modules arrive. Electricalinterconnection, sitework, cleanup and

commissioning can also extend for daysor weeks after modules are installed.Roof work pertaining to the project,such as a roof coating or replacement,should be added to this schedule.

Roof warranties can be voided due

to wear from excessive foot trafc.

Rooftop projects should specify tem-

porary protection to prevent damage

from construction activity. Undernormal circumstances a roof may havea few people on it a few times a yearfor inspections and maintenance. A so-lar project could put dozens of workerson the roof for a month or more.

Inadequate roof protection such as notusing walk mats and slip-sheets couldvoid the roof warranty. Review the roofprotection plan with the roof warrantyprovider and roong manufacturer priorto construction. Get a sign-off at the

completion of construction stating thatthe roof manufacturer has inspectedthe roof and that their warranty remainsin force.

Rack-mounted systems -- where com-ponents including racking materials,ballast, conduits, wiring and modulesare delivered to the site and assembledin the eld -- can be the most time-inten-sive projects to install. However, theyare often the most exible and customi-zable, since the design can be modi-

ed to account for any site constraintAssembly of these systems requirestools and eld fabrication, which mayincrease the possibility of roof damageduring construction.

Composite frame products are usu

ally faster to install, and they cu

down on staging needs. The mod

ule and its racking unit are joined in

the factory, so they can be installed

quickly as a single unit in the eld

Composite systems have been designed for tool-less assembly and thereis little need for eld modications. Because there are fewer materials delivered to the site from different suppliersthe staging and construction processcan occur more quickly.

Both rack-mounted systems and com-posite frame systems require ballas- masonry blocks added to resist wind

uplift forces. The lower prole of thecomposite system typically requiresless ballast. To reduce the amount ofballast required, both categories of sys-tems can be anchored to the roof structure to resist wind uplift.

Adhered BIPV systems can be in

stalled quickly if the site is clean

and clear of obstructions.A numbeof thin exible modules are typically in-stalled on a secondary roof membraneThese membranes are laid out on the

Construction Considerations

18

Inspecting Roofs

Before installing any solar products on a buildings roof,it is essential that you determine whether the roof is suit-able for the project. The roof should be in good conditionand have sufcient expected life that it will not need re-placing during the operational life of the solar project.

Perform a roof inspection to identify maintenance needs.

Walk the roof with the solar project developer and yourroof maintenance contractor and agree on the conditionof the roof prior to construction commencement. Makeany needed repairs prior to construction.

Perform a post-construction roof walk to identify areasof construction-related roof damage or excessive weardue to the solar project. Performing a pre- and post-inspection alongside the contractor will help ensure asuccessful project and alleviate disputes about who isresponsible for roof damage.

When inspecting a roof, pay special attention to areasof poor drainage. Standing water can not only damagethe solar equipment over time, the weight of standingwater plus the solar equipment can over-stress the roofand produce an unsafe condition. In general it is best torepair areas where water ponds, and avoid them entirelyif that is not feasible.

For roofs that are new or nearly new, consider investingproactively in a white roof coating that will extend theroofs life, help resist wear from construction trafc, andreduce performance-robbing high roof temperatures.The white coating has the added advantage of reducingroof temperatures that can reduce solar module perfor-mance and degrade equipment.

These simple steps will help identify and resolve poten-tial roof issues before they become real problems.


24/30





Construction Over-view

Assemble rackingon-siteInstall ballastInstall solar mod-ules on rackingInstall conduitsand wiringConstruct electri-

cal roomInstall electricalequipment

Install solar mod-ules and rackingInstall ballastInstall conduitsand wiringConstruct electri-cal roomInstall electrical

equipment

Clean and preproofInstall solar mod-ulesInstall conduitsand wiringConstruct electri-cal room

Install electricalequipment

Install solar mod-ules with buildingelementsInstall conduitsand wiringConstruct electri-cal roomInstall electrical

equipment

Staging Requirements DeliveriesRacking pre-fabri-cationBallast storageModule storageand sortingConduit and wir-ing storage andpre-fabrication

Electric room gearCrane, lifts, scaf-foldingConstructiontrailer

DeliveriesBallast storageModule storageand sortingConduit and wir-ing storage andpre-fabricationElectric room gearCrane, lifts, scaf-

foldingConstructiontrailer

DeliveriesModule storageand sortingConduit and wir-ing storage andpre-fabricationElectric room gearCrane, lifts, scaf-folding

Constructiontrailer

DeliveriesModule storageand sortingConduit and wir-ing storage andpre-fabricationElectric room gearCrane, lifts, scaf-folding

Constructiontrailer

Roof Protection Walk matsSlip sheetsPads for materialsstaged onto roofBreak areas forconstruction staff

Walk matsSlip sheetsPads for materialsstaged onto roofBreak areas forconstruction staff

Walk matsSlip sheetsPads for materialsstaged onto roofBreak areas forconstruction staff

n/a

Install Time / 500kw 10 to 30 days 8 to 25 days 8 to 25 days 15 to 30 days

19

roof atop the existing roof surface. Thesecondary membrane is adhered to theexisting roof underneath and providesa good deal of additional protectionagainst damage or degradation.

Adhered BIPV products may be de-

livered to the site as large roong

rolls. Ballast is not required since the

membrane is adhered to the existingroof. This is one of the reasons ad-hered BIPV products are lighter thanother solar products. Installation doesnot require tools aside from those

used to bond the product to the ex-

isting roof.

Some adhered products such as exiblecrystalline BIPV modules are adhereddirectly to the existing roof membraneor metal roof. There is no sacricialmembrane. Ballast is not required for

this BIPV system either, which contrib-utes to its low installed weight. Installa-tion does not require tools.

Adhered BIPV products rely on a

strong bond to the existing roof of

the building. Careful roof prepara-

tion is critical to ensure proper in-

stallation. The existing roof must also

be assessed to ensure that it is suitableas a substrate for BIPV products. Theseproducts are not intended for areas ofthe roof that may have standing water.

Structural BIPV systems are often in-stalled at the time of building construc-tion due to their integration with thebuilding facade or roof. As a result thereis little additional staging area required.The installation process is similar to thetraditional building products they are in-tegrated into, save the additional effort

required to wire up the system. Thesesystems are usually customized for thebuilding system they are installed insuch as a curtain wall or roof canopymaking it difcult to replace or modifythe system once installed.

The construction process for each typeof solar technology can affect the suit

ability of a product for a particular building. Where staging areas are limited, imay be advantageous to specify a solarproduct that can be delivered directly tothe site ready-to-install, such as a composite frame product. For sites wherethere is no large open expanse of roofa rack mounted system may providemore customization. On buildings witha much greater facade area than rooarea, structural BIPV facade productsmay be advantageous.

Table 9: Construction Considerations


25/30

Warranties provide assurance for the quality and reliability of the components that are used in a solar array. The term andcoverage of warranties varies based on the type of equipment. Solar module warranties include materials and workmanshipas well as a warranty on energy output.

The materials and workmanship warranty typically extendsfor 10 years. Energy output warranties for solar modulestypically extend 25 years. Warranty terms are structured ina stepped manner such as: minimum output of 90 percentat 10 years and 80 percent at 25 years. Virtually all solarmodules offer this type of warranty, both in terms of durationand two-stage performance guarantee. The output warrantyprovides solar project investors protection against the loss ofrevenue due to downtime.

Warranties of 25 years require that the creditworthiness

of the company backing the product be considered.When working with companies that have a limited operating historyor a smaller balance sheet, it is becoming more common to provide a third party insurance guarantee that backstops thewarranty for their products. This helps to address concerns of the module purchaser that the manufacturer will be around toservice the warranty in the future. Companies with less-proven technologies may also purchase insurance policies to reducetechnology and performance risks.

Inverters are an electrical device that takes incoming direct current (DC) electricity from the solar array and turns it intoalternating current (AC) electricity for building use. Inverter warranties are typically 10 years. However, inverter reliability isimproving and warranties are steadily getting longer; extended warranties of up to 20 years exist. In time, inverter warrantiesmay align with solar module warranties so the major high-value components of the solar array can be expected to performfor the same amount of time. This can also add certainty to the operations and maintenance costs associated with solarfacilities. This makes projects more attractive to solar investors and operators because it reduces nancial risks.

Racking is made of non-corrosive materials such as aluminum, stainless steel, or composites and does not typically havemoving parts. This makes racking systems highly durable and largely maintenance free. Care should be taken to not letincompatible metals come into contact with one other. Racking equipment is typically warranted for 5 to 10 years.

Roof warranties should be closely matched to the solar arrays lifespan -- 20 to 25 years. Roong manufacturers are intro

ducing extended life roof membranes to provide greater compatibility with the anticipated lifespan of solar projects.

Solar projects on commercial build-ings need certain permits in order tobe connected to the utility grid. Thisis essential when the array is oper-ating as a small rooftop power plant(referred to as distributed genera-tion) by feeding its power to the gridand by-passing the building host.

The need for grid interconnectionalso applies if the building is the in-tended consumer of the power (re-ferred to as a net metered project).This is because it is possible for elec-tricity to back-feed to the power gridin cases where the solar array pro-duces more energy than the build-ing can use. This is the case evenwhere the output of the solar array issignicantly lower than the buildingsenergy needs.

Utilities are becoming increasinglycareful about where and how they al-low solar projects to connect to theirgrid in order to minimize the possi-bility of grid instability. Switches andbreakers are required on solar proj-ects to temporarily allow the array tobe physically isolated from the utilitygrid if needed for safety reasons.

Where the grid cannot readily ac-commodate the additional demandsplaced on it by a solar array, up-grades to feeders and sub-stationsmay be required. Depending on theutility and the solar project, thesecosts may need to be paid by the so-lar project sponsor. This can drasti-cally affect the projects economic vi-ability if upgrades are extensive andthe project cannot absorb the costs.

The process the utility goes throughto assess the grids ability to supportsolar capacity in a given location cantake weeks or months to determine.This can become a critical path itemfor solar project feasibility analysisby the solar developer.

Utility companies are working to up-

grade the grid and make it smarterso it can handle distributed and netmetered solar projects. This is not afast process because solar can af-fect the grid in various ways.

Utility interconnection plays a largepart in the cost and feasibility of solarprojects, and answers to these ques-tions are needed before a projectcan be underwritten accurately andplanned with certainty.

Warranties

Connecting to the Grid

20

Figure 18: Warranty Terms

Racking

0 5 10 15 20 25 30

Module - Output

Module - Workmanship

Inverter


26/30

21

As more states adopt solar programs, the solar industry inthe United States is poised to continue its upward trajectoryof growth. Combined with global growth in the scale of solarmodule manufacturing, costs for solar modules and equip-ment can be expected to continue to decline and drive evenwider adoption.

While established technologies compete for market share,new technologies are being researched and brought to mar-ket that promise higher efciencies and novel form factors.Many of these will not be successful, but a few will succeedand have a transformative effect on the industry. Many prom-ising advancements are focused on ever more cost-effectiveways to manufacture solar modules. Engineers and install-ers are working to improve the speed of installation, reduceweight and lower project costs for all solar technologies.

There have been several recent notable solar industry fail-ures that have cast a shadow on the entire solar industry.Evergreen Solar, a producer of rectangular crystalline sili-

con modules that used a proprietary manufacturing process,shuttered its operations because it was unable to competeon cost as the industry grew and module prices dropped pre-cipitously in the past few years.

Solyndra, a U.S.-based solar module producer, sought tocombine a promising new solar technology with a uniqueform factor tailored for commercial rooftop applications. Inthe face of massive declines in traditional rectangular PVmodule costs, they were unable to scale up manufacturingand reduce costs quickly enough to survive. Until recently,this product had been considered a potentially disruptivenew entrant for rooftop projects, best placed into this guides

category of composite frame PV module systems.

It is widely acknowledged that not every solar technology willachieve commercial success. Some of the failures will surelyprompt discussion about the pros and cons of the solar in-dustry. It is worth remembering that in any industry growthand innovation are essential elements to its ongoing suc-

cess. There will be both success stories and failures alongthe way but it will ultimately lead to better products that meethe needs of customers at ever-lower costs.

This is particularly true when it comes to the emerging recognition that tailoring solar products for commercial buildings serves an unmet need for many property professionalsThese advancements will deliver higher quality products andwill have fewer unwanted impacts on commercial buildings

At the same time costs will continue to decline, which wildrive ever-wider adoption in the real estate industry.

The level of innovation taking place in the solar industry today is encouraging. This focus on solar technologies thatpromise to deliver new and better solutions is particularlyinteresting to those in the commercial real estate industryThis guide provides a practical approach to understandingthe solar product solutions that can be used on commerciabuildings today and establishes a framework to allow a better understanding of the products that emerge tomorrow.

Conclusion

Solyndra tubular solar module.

Image: Solyndra


27/30

22

Alternating current (AC) = The type of electric current used in buildings and appliances.

Array = A group of solar modules. A solar project can contain one or many arrays.

Balance of System (BOS) = All the parts of a solar electric system excluding the solar panels and the

inverter. Balance of system often includes racking, wiring, conduits and raceways, sitework and roof

protection.

Ballast = A heavy material -- usually masonry, concrete blocks or gravel -- used to resist wind forces.

BIPV (Building Integrated Photovoltaic) = Solar modules that are permanently afxed to the exterior

of a building.

Cell = The smallest part of a solar panel that converts light into solar electricity.

Direct Current (DC) = The type of electrical current produced by solar cells. Direct current electricity

must be converted into alternating current before it is usable in a building.

Distributed generation = Generation of electricity near its point of use throughout a utility territory.

Interconnection = The process of connecting a solar electrical system to the electrical grid.

Inverter = An electrical device that converts direct current (DC) electricity into alternating current (AC)electricity.

Kilowatt = One thousand watts.

Kilowatt-hour (kWh) = 1,000 thousand watts produced or consumed over a period of one hour.

Megawatt = One million watts.

Miami-Dade = A set of building code requirements originating in Miami-Dade County, Florida that con-

tain stringent requirements for withstanding extreme wind and weather events such as hurricanes.

Module = A group of solar cells assembled into an electricity-generating device; also referred to as a

solar panel.

Monocrystalline = A solar cell composed of a large, single silicon crystal and has a patchwork pattern.

Multicrystalline = A solar cell composed of silicon oriented in various directions. Also referred to as

polycrystalline.

Net meter = Regulatory requirements that allow an electric utility to measure electricity based on en-

ergy consumed minus energy produced. In simple terms it refers to an electricity meter that spins both

forward and backwards.

Net-to-gross = The percentage of a typical roof that can be used for a solar array, after accounting for

perimeter setbacks, shaded areas, access walkways and other limiting conditions.

Panel = A group of solar cells; also referred to as a solar module.

Photovoltaic = The conversion of light into electricity.

Power purchase agreement (PPA) = A contract between a power consumer and a power producer.Racking = The support structure for a solar modules.

Roof protection = Measures taken during solar array construction to minimize damage to the roof.

Staging = A part of construction where materials are sorted, prepped and organized for installation.

Watt = A unit of power equal to amps times volts.

Wind zone = A designation in building structural codes describing the wind forces a structure (or solar

project) must be designed to withstand.

Glossary of Terms


28/30

Global Solar Power Growth Doubled in 2010: Study. February 14, 2011. Reuters.com. Accessed Sep-1.

tember 2, 2011: http://www.reuters.com/article/2011/02/14/us-energy-solar-idUSTRE71D4WJ20110214

http://www.whitehouse.gov/blog/2011/07/27/fastest-growing-industry-us-solar-energy2.

EPIA Global Market Outlook for Photovoltaics Until 2015. Europe Photovoltaic Industry Association.3.

2011. Page 11.

2010 U.S. solar industry explosion will lead to U.S. becoming largest market in world by 2013. Clean4.

Energy Authority.com. March 10, 2011. Accessed August 12, 2011: http://www.cleanenergyauthority.

com/solar-energy-news/report-says-us-slated-to-become-world-leader-in-solar-031011/

U.S. Solar Market Insight; 1st Quarter 2011 Executive Summary. Solar Energy Industry Association.5.

2011. Page 2.

U.S. PV Market Growth. SolarCellcentral.com. Accessed September 3, 2011:6. http://solarcellcentral.

com/markets_page.html#tf_mkt_share

Examples include: Rack mounted module systems: First Solar FS3, Yingli Panda 265 Series, Sun-7.

Power E20, Suntech STP280, TSolar TS390. Composite frame module systems: SunPower T5, SolonSolxx. Adhered BIPV modules: UniSolar PVL144, Ascent Solar WaveSol Light 5 meter, Lumeta Pow-

erply 400, Solon SOLbond. Structural BIPV modules: Canadian Solar BIPV, BP Solar BIPV, Pythago-

rus Solar PVGU, Zytech ZT60 DS.

Examples include: First Solar FS Series 3 module (26 lb.); Yingli Panda 265 series module (42 lb.);8.

Suntech STP 280 module (59.5 lb.) Solyndra Series 200 module (69 lb.)

TSolar TS390 solar module (200 lb., 86 in., x102 in.)9.

Kimber, A and L. Mitchell et al. The Effect of Soining on Large Grid-Connected Photovoltaic Systems10.

in California and the Southwest Region of the United States. Powerlight Corporation. 2006. Page. 6.

Accessed September 21, 2011: http://ericwalstad.com/portfolio/images/IEEE_2006_Full_Paper_r3.pdf

German Small Solar Cheaper Than U.S. Big Solar. Cleantechnica.com. September 28, 2011. Ac-11.

cessed October 9, 2011: http://cleantechnica.com/2011/09/28/german-small-solar-cheaper-than-u-s-

big-solar/

Solarbuzz Retail Module Price Index. Solarbuzz.com. Accessed August 30, 2011.12. http://solarbuzz.com/

facts-and-gures/retail-price-environment/module-prices

Examples include: Rack mounted module systems: First Solar FS3, Yingli Panda 265 Series, Sun-13.

Power E20, Suntech STP280, TSolar TS390. Composite frame module systems: SunPower T5, Solon

Solxx. Adhered BIPV modules: UniSolar PVL144, Ascent Solar WaveSol Light 5 meter, Lumeta Pow-

erply 400, Solon SOLbond. Structural BIPV modules: Canadian Solar BIPV, BP Solar BIPV, Pythago-

rus Solar PVGU, Zytech ZT60 DS.The term Net-to-gross layout describes the percentage of a typical roof that can be used for a solar14.

array after accounting for perimeter setbacks, shading setbacks, access walkways and other limiting

conditions. For example, a 60,000 square foot roof may accommodate a 500kW of solar array if 100

percent of the roof could be covered with modules. This is the gross area. This would be impractical

in most cases as it would prevent access to the roof for maintenance, inspections and other operation-

al needs. Accounting for these needs reduces the amount of space on the roof where solar modules

can be installed. This is the net area. See page 15.

End Notes

23


29/30

Figure 1: Megawatts (MW) of Solar Capacity Installed Each Year in the United States 4

Figure 2: Racking System Detail 6

Figure 3: Example Rectangular Solar Modules 6

Figure 4: Example Rack-Mounted Solar Installations 6Figure 5: Composite Frame Module Detail 7

Figure 6: Adhered BIPV Installation Details 8

Figure 7: Structural BIPV System Detail 9

Figure 8: Cutaway of Glass Solar Module 11

Figure 9: Cutaway of Flexible BIPV Solar Module 11

Figure 10: Scale Comparison of Module Sizes 12

Figure 11: Retail Module Price Index (2001-2011) 14

Figure12:TypicalSolarModuleEfciencyRange 14

Figure 13: Racking Angle Comparison 15

Figure 14: Example Roof Layout Indicating Setbacks 15

Figure 15: Roof Area Requirements for 100 kW Array 16

Figure16:InefcientRoofLayoutforSolar 17

Figure17:EfcientRoofLayoutforSolar 17

Figure 18: Warranty Terms 20

List of Figures

Table 1: Solar Cell Composition by Product Category 5

Table 2: Added Weight and Method of Attachment 7

Table 3: Product Characteristics 10

Table 4: Manufacturers, Market Share and Distribution 11

Table 5: Physical Characteristics 12

Table 6: Building Impacts, O&M and Climate Considerations 13

Table 7: Performance and Design Characteristics 14

Table 8: Solar Array Weights in Various Wind Zones 16

Table 9: Construction Considerations 19

List of Tables

24


30/30

NAIOP RESEARCH FOUNDATION

Were Shaping the Future

2201 Cooperative Way, Suite 300Herndon, VA 20171

tel 703.904.7100

Documents

Solar Tech Ref Guide