building a solar future: repowering america’s homes, businesses and industry with solar energy

7/31/2019 Building a Solar Future: Repowering Americas Homes, Businesses and Industry with Solar Energy

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Building aSolar FutureRepowering Americas Homes, Businesses

and Industry with Solar Energy


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Building a Solar FutureRepowering Americas Homes, Businesses

and Industry with Solar Energy

Environment TexasResearch & Policy Center

Tony Dutzik and Rob Kerth,Frontier Group

Rob Sargent,Environment America

Research & Policy Center

Bernadette Del Chiaro,Environment California

Research & Policy Center

March 2010


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Environment Texas Research & Policy Center thanks Jigar Shah, CEO o the CarbonWar Room; Carrie Hitt, president o the Solar Alliance; Justin Baca, manager o marketresearch and analysis or the Solar Energy Industries Association; Adam Browning, execu-tive director o Vote Solar; Larry Chretien, executive director o the Energy Consumers

Alliance o New England; Wilson Rickerson, executive vice president o Meister Consul-tants Group; DeWitt Jones, president o DCC Solar Energy Advantage; and Bill Powerso Powers Engineering or their thoughtul review and insightul suggestions. Thanksalso to Elizabeth Ridlington, Susan Rakov and Travis Madsen o Frontier Group or theireditorial support.

Environment Texas Research & Policy Center thanks the John Merck Fund, the EnergyFoundation, the Richard and Rhoda Goldman Fund, the Arntz Family Foundation, theMeadows Foundation, the Cynthia and George Mitchell Foundation, the Park Founda-tion, Fred Stanback, and the Kresge Foundation or making this report possible.

The authors bear responsibility or any actual errors. The recommendations are those

o Environment Texas Research & Policy Center. The views expressed in this report arethose o the authors and do not necessarily reect the views o our unders or those whoprovided review.

2010 Environment Texas Research & Policy Center

The Environment Texas Research & Policy Center is a 501(c)(3) organization. We arededicated to protecting Texas air, water and open spaces. We investigate problems, cratsolutions, educate the public and decision-makers, and help Texans make their voices heardin local, state and national debates over the quality o our environment and our lives. Formore inormation about Environment Texas Research & Policy Center or or additionalcopies o this report, please visit www.environmenttexas.org.

Frontier Group conducts independent research and policy analysis to support a cleaner,healthier and more democratic society. Our mission is to inject accurate inormation andcompelling ideas into public policy debates at the local, state and ederal levels. For moreinormation about Frontier Group, please visit www.rontiergroup.org.

Cover photos: Top row (l to r): VELUX/ESTIF; Kevin Dooley, reprinted under Creative Commons license;Alex Snyder, Wayne National Forest; Gregory Kolb, Sandia National Laboratory; Sacramento Municipal Util-ity District; Solar panels: istockphoto.com, Daniel Schoenen Fotografe

Layout: Harriet Eckstein Graphic Design

Acknowledgments


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Table of Contents

Executive Summary 1

Introduction 6

Why Solar? Why Now? 8

Building a Solar Future for America: The Tools 11Photovoltaic Power 11Concentrating Solar Power 12Solar Water Heating 13Passive Solar Lighting and Heating 14Active Solar Heating and Cooling 15

A Solar Future for America 17Solar Homes 17Solar Businesses 20

Solar Factories 21Solar on Farms 24Solar in Transportation 26Solar in Communities 28Solar Grid 32

Mapping Out a Solar Vision 36Americas Solar Potential 36A Near-Term Goal 38

Achieving a Solar America 41Understanding the Barriers to a Solar America 41Policies to Build a Solar America 44

Notes 52


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Executive Summary

America has virtually limitless po-tential to tap the energy o the sun.Solar energy is clean, sae, proven

and available everywhere, and the price omany solar energy technologies is declin-ing rapidly. By adopting solar energy ona broad scale, the nation can address ourbiggest energy challengesour depen-dence on ossil uels and the need to ad-dress global warmingwhile also boost-

ing our economy.America has the potential to obtain a

large and increasing share o our energyrom the sun. In the near term, Americashould set the ambitious goal o ob-taining 10 percent or more o our to-tal energy consumption* rom the sunby 2030, using a wide variety o tech-nologies and tools.Achieving that targetwould result in the sun providing us withmore energy than we currently produceat nuclear power plants, more than hal as

much as we currently consume in our cars

and light trucks, or nearly hal as much aswe currently obtain rom burning coal.

A comprehensive suite o public policystrategies can remove many o the com-mon barriers to solar energy developmentand help to make this vision a reality.

There are many ways to take advan-tage o the suns energy. Solar energycan be converted to electricity, or used

or lighting, heating and cooling. It canreplace the ossil uels we burn at electricpower plants, in actories, in our homes,and even in our cars. Solar energy tech-nologies include:

Photovoltaics (PV) Photovoltaicsdirectly convert solar radiation intoelectricity. PV can take the ormo panels or be incorporated intobuilding materials. PV is scalable,generates electricity anywhere

the sun shines, including in coldclimates, has no essential movingparts, uses virtually no water, andis one o the ew power generationtechnologies well suited or use inurban areas.

* Note: This goal reers to total energy consumptionrom allsources in the United States, not just electric-ity consumption.

Executive Summary 1


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Concentrating solar power (CSP) CSP plantsuse mirrors to ocusthe suns energy to harness heat thatcan be used directly or to generateelectricity. Because heat is cheaperand easier to store than electricity,

CSP plants with thermal storagecan be designed to provide energyrom the sun even at night. CSPplants have been reliably generatingpower in desert areas o the West ordecades and are now experiencinga resurgence due in part to allingcosts and increasing demand orutility-scale renewable electricity.

Solar water heaters Rootop-mounted collectors capture solarenergy as heat and produce hotwater. Solar heat collectors can beextremely efcient; low-temperatureheaters can capture up to 87 percento the solar energy that reachesthem. Solar water heaters can alsobe adapted or uses ranging romresidential water heating to large-scale industrial use.

Solar space heating and cooling

Collectors similar to those usedor hot water can also be usedto heat air in place o urnacesor boilers. These systems cancontribute 50 percent or more o theenergy needed to heat a building.Solar energy can even be used tocool buildings through the use oabsorption chillers.

Passive solar design Forcenturies, skilled builders have

designed homes and other buildingsthat take the best possible advantageo solar energy. Passive solardesign can contribute to the overallefciency o a building, reducing theneed or energy or lighting, heatingand cooling.

Solar energy can help power virtual-ly every aspect o Americas economy.

Solar Homes

New homescan be built to maximize

use o the suns energy throughpassive solar design and the use osolar PV panels and water heatingsystems. Solar energy can be pairedwith advanced energy efciencytechniques to create zero net energyhomes, which produce as muchenergy as they consume. Zero netenergy homes have already been builtin parts o the country, are possible inall climates, and oten save money orconsumers over time.

Many existing homes can alsoincorporate solar technologies.Photovoltaic panels can be installedon the roos o 35-40 percent ohomes nationwide, and solar heatcollectors on 50 percent o residentialroos.

Solar Businesses

Commercial buildingssuch asbig-box stores, strip malls andofce complexesalso have manyopportunities to take advantage osolar energy. About 60 to 65 percento commercial roo space nationwideis suitable or photovoltaics. Large-scale commercial photovoltaic andsolar water heating installations arealso cheaper per unit o energy than

smaller residential installations.

Many businesses present uniqueopportunities to tap solar energy:

o Walmarts use o skylights insome its big box stores has cut

2 Building a Solar Future


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energy costs by 15 to 20 percentby reducing the need or electriclighting.

o Laundry acilities, hotels, hospi-tals and even baseballs Boston

Red Sox have adopted solarwater heating to reduce theirconsumption o natural gas orwater heating.

Solar Factories

Manuacturing acilities consume vastamounts o energy to create heat, mucho it at temperatures that could be sup-plied by solar water heating systems. Foodprocessors, chemical companies and tex-tile plants are among those that are goodcandidates or solar energy. For example,a Frito-Lay plant in Caliornia uses solarconcentrators to provide heat or cookingsnack oods. At ull capacity, the systemreplaces as much natural gas as is used by340 average American homes.

Solar Farming

Solar photovoltaics can provide a largeshare o the electricity needed to operatea arm and keep harvested crops cool, andare especially useul or pumping water,providing irrigation and meeting otherneeds in remote areas that arent easilyreached by the electric grid. Many armscould also take advantage o solar energyor heating greenhouses, ventilating barnsor drying crops.

Solar in Transportation

The development o plug-in vehi-clesboth plug-in hybrids and ullyelectric vehicleswill allow renew-able energy to play a larger role in

powering our transportation system.Toyota, or example, is developingsolar charging stations or its ToyotaPrius plug-in hybrid vehicle, dueon the market in 2011. In addition,Americas vast areas ohighways and

parking lots could house solar panels.

New transportation technologiescreate new opportunities to usesolar power. Caliornias high-speed rail authority has committedto powering the states new railsystem with renewable energy,while major shipping companies areexperimenting with the use o solarsails to reduce the environmentalimpact o shipping.

Solar Communities

Government acilities such as ofces,schools and wastewater treatmentplants, as well as community insti-tutions such as churches, are otenexcellent candidates or solar energy.

New policy tools enable members

o a community to work together tofnance solar energy installations,enabling even individuals withoutsuitable roos to take part in expand-ing solar power.

Housing developments in Europeand elsewhere have created neigh-borhood-wide solar district heatingsystems that reduce ossil uel con-sumption or space heating and waterheating by 25 percent or more.

Building the Solar Grid

Concentrating solar power plants canreplace coal and other ossil uels orbase load electricity generation.

Executive Summary 3


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Since photovoltaics generate energybest when demand is highestonhot, sunny summer daysthey canreduce the eective peak demandthat utilities have to meet, provid-ing stability to the grid, reducing the

need or expensive new power plantsand transmission lines, and curbingair pollution.

Photovoltaic cells and solar waterheaters distributed on buildingsaround the country will reduce theamount o energy that needs to owrom central power plants or energyproviders to consumers.

Investing in orms o smart gridtechnologies can expand the amounto electricity the nation can generaterom distributed solar power whilemaintaining reliable electricitysupplies.

America can obtain a large share oits energy rom the sun. But it will nothappen on its own. Local, state andederal governments must implementpublic policies that remove the barriers

currently impeding the spread o solarenergy and adopt policies to make solarenergy an important part o Americasenergy uture.

Financial incentives, such as grants,tax credits and eed-in taris helpto compensate homeowners andbusinessowners or the benefts theirinvestments in solar energy deliver tosociety and can create a robust earlymarket or solar technologies, build-

ing the economies o scale neededto lower the price o solar energy.To create a stable market, fnancialincentives should be applied con-sistently over a long period o time,instead o as intermittent, on-againo-again programs.

Renewable electricity standards(RES), such as those now in placein 29 states, can ensure that utilitiesintegrate solar into their energy pro-fles. Solar carve-outs, which requirethat a share o the RES be met with

solar energy, can ensure a diversifedmix o renewable resources and en-courage the development o distrib-uted renewable resources.

New fnancing tools can help in-dividuals and businesses absorb thelarge upront costs o solar instal-lations and begin reaping beneftsimmediately. Municipalities can usetheir power to borrow at low inter-est rates to fnance residential solarinstallations, which can be paid backthrough assessments on property taxbills. Utility on-bill fnancing canachieve similar aims, while low-in-terest loans and loan guarantees canhelp reduce the payback time or so-lar energy investments by businesses.

Advanced building codes and stan-dards can ensure that builders takemaximum advantage o passive solar

heating and lighting in new build-ings and create new opportunities orintegrating solar energy into existingbuildings. Solar-ready building stan-dards guarantee that new homes arebuilt with solar energy in mind, andcan be broadened to require that so-lar energy be oered as an option onnew homes. Some states and coun-tries have gone so ar as to requirethe use o solar energy (specifcally,solar water heating systems) on new

residential buildings.

Consistent rules to ensure ac-cess to solar energyare needed toovercome bureaucratic barriers thatcan prevent individuals and busi-nesses rom using solar power. Solar



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access laws prevent homeownersassociations and municipalities romadopting rules that eectively ban theuse o solar energy, while revisions topermitting rules and utility regula-tions can reduce the hassle and cost

o installing solar energy and ensurethat people are compensated airlyor the solar power they supply to thegrid.

Public education and workorcedevelopmenteorts are critical toexpanding the use o solar energy.Public education programs can helpanswer consumers questions aboutsolar energy and make it easier togo solar. Workorce training canexpand the number o workers withthe skills needed to partake in thedramatic growth o Americas solarenergy market. Meanwhile, energy

labeling requirements or buildingscan ensure that the energy-sav-ing value o passive and active solarenergy systems is ully understoodwhen properties change hands.

Investments in a solar grid will beneeded to ully tap Americas solarenergy potential. A well-designedsmart grid can ensure that solarpower is an asset to the electric grid,while limited investments in newtransmission capacity can help to tapthe nations best solar resources.

Research and development pro-grams can help ease the integrationo existing solar technologies, urtherdevelop emerging technologies withgreat promise or the uture, and in-vestigate new potential uses or solarenergy.

Executive Summary 5


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Americas energy system is all-impor-tant to our economy, but it is so in-tegrated into our daily lives that it

has become all but invisible to most o us.Few o us ever stop to marvel at the

path that a drop o oil must take rom aSaudi Arabian well to the gas tanks o ourcarsthe drilling technology that allowsthe crude oil to be pumped rom deep be-neath the earth, the pipelines that carry

that oil to a port, the military power thatkeeps the shipping lanes open or the tank-ers to transport that oil halway aroundthe world to our shores, the giant refner-ies that convert the crude oil into gasoline,and the extensive distribution inrastruc-ture that gets the gasoline into our tanks.

Similarly, ew o us see the immenseinrastructure that turns a lump o coalmined in Montana into the electricity thatpowers a computer in Alabamathe gi-ant machines that mine the coal, the trains

that carry it across the country, the mas-sive power plants that convert it into elec-tricity, the ubiquitous web o wires thattransmit that electricity across great dis-tances and through neighborhoods to ourhomes.

Even ewer o us see the environmental

damage let behind by our consumptiono ossil uels. Some o that damage isinvisible, such as the health-threateningpollutants that oul our air and infltrateour lungs or the leaking underground oilstorage tanks that slowly pollute drinkingwater. Sometimes the damage is inictedar away rom where most Americans live,appearing as the melting o Arctic icedue to global warming, or the flling in

o a remote Appalachian hollow resultingrom mountaintop mining. As people inAmerica and worldwide have awakenedto the environmental dangers posed byossil uels, we have built even moreinrastructure to mitigate those dangersrom installing scrubbers on coal-fredpower plants to training hazmat teams toclean up oil spills.

Over the course o more than a century,and with the investment o untoldbillions o dollars, America has built

an energy system that does a masteruljob o unlocking the energy stored inunderground deposits o ossil uels andtransorming that energy into the heat,electricity and kinetic energy that powerour economy. However, that same systemdoes a poor job o taking advantage o the

Introduction



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powerul renewable energy sources allaround usespecially the sun.

Indeed, as America has built its econ-omy around the expectation o continuedaccess to cheap ossil uels, we have turnedour backs on centuries o received wisdom

about how to use the suns energy to ourbeneft. Once upon a time, skilled buildersoriented homes to take maximum advan-tage o the sun and wind, installed awningsand deciduous trees to block the suns raysin summer, and used light-colored build-ing materials to reect solar energy in hotclimates. Today, many o these practiceshave been eschewed in the quest or mass-produced cookie cutter homes that arecheaper to build but more expensive tooperate, solidiying our dependence onossil uels.

Cheap ossil uels have also caused usto turn our backs on newer technologiesto tap the power o the sun. Solar waterheaters have been standard equipment onhomes in some parts o the world or de-cades (and were common in parts o theU.S. in the early part o the last century),yet are rare in the United States today. Foryears, technologies such as solar photovol-taic panels and concentrating solar power

plants have stood ready to play an impor-tant role in supplying us with energy, onlyto alter or lack o consistent governmentsupport o the kind enjoyed by the ossiluel industry.

Today, America is experiencing thedownsides o our dependence on ossil u-els as never beore. The ominous spectero global warming, the continued pollu-tion o our air and water that results romossil uel use, and worries about the cost

and availability o ossil uels in an era ogrowing worldwide demandall o theseare powerul reasons to look or alterna-tives. And never beore have so many goodalternatives been available.

Solar energy has the potential to dra-

matically reduce our use o ossil uels invirtually every area o our economy. It isclean, sae, ubiquitous and exible. It isalso increasingly cost competitive withconventional sources o energy.

Taking advantage o Americas limitlesssolar energy potential would deliver greatrewards to the nation, but it wont be easy.It will take creativity to transorm our en-ergy system rom one based on ossil uelsand centralization to one that efcientlyreaps solar energy at the places where thatenergy is used. Realizing a solar utureor America will require new habits othinking, new policy tools, and, most oall, a roadmap o where we are headed.

The immense inrastructure that bringsossil uels to our homes is a potentialobstacle to that transormation, but it isalso an inspiration. I America and theworld can surmount the challenge o us-ing a drop o oil rom a desert hal a worldaway to power a trip to the grocery store

in Omaha, how much easier must it be toharness the heat and light that strikes ourhomes every day?

The time has come or America to em-brace a vision o a clean energy uture,with solar energy as a key contributor, andto lay the groundwork or that uture byadopting smart public policies that cantransorm our economy and preserve ourenvironment.

Introduction 7


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America urgently needs to reduce ourconsumption o ossil uels to pro-tect our environment and ensure

our continued economic prosperity. Solarenergy can replace many o the ossil u-els we currently use to power our homes,communities, arms, businesses, actoriesand cars.

Americas Dependence onFossil Fuels: Harming OurEnvironment andThreatening Our FutureThe vast majority o the energy Americauses each year, 84 percent o it, comesrom ossil uels.1 Coal, oil and natural gasare inherently limited resources, requiring

tremendous eort and expense to discover,extract, process and distribute. Fossil uelsrepresent one o the most important day-to-day expenses or American amilies andbusinessesin 2006, the United Statesspent nearly 7 percent o its gross domes-tic product, or $921.2 billion, on ossil

uels or home, business and transporta-tion use.2 For every dollar that an Ameri-can household spends each year, about 9cents goes toward the purchase o energy,most o it or ossil uels.3

Perhaps the greatest challenge posed byour dependence on ossil uels is the dam-age those uels do to our environment andour health. Fossil uel combustion contrib-utes to the ormation o smog and soot,

which damage the lungs and make the airin areas housing 186 million Americansunhealthy to breathe.4 The burning ocoal contributes to the ormation o acidrain and contaminates our waterways withmercury, a neurotoxin that makes fsh inmany waterways unsae to eat.

The toll o ossil uel extraction onour environment is widespread and se-vererom oil spills o our coast to theragmenting o natural habitat or naturalgas drilling. Coal mining in the 19 th and

20th centuries ouled approximately 9,000miles o rivers in Appalachia with acid minedrainage.5 Mountaintop removal miningin many o these same areas threatens newenvironmental damage in the 21st century.

No issue, however, poses as great along-term threat to our environment as

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global warming. Global warming is un-derway, and its impacts can already be eltin the United States and worldwide. Al-ready, plants and animals are being orcednorthwards by rising temperatures, put-ting populations at risk.6 In the oceans,

rising temperatures and acidity are rap-idly destroying coral rees and threateningother ecosystems.7

Disturbing though these changes are,they are only a raction o what will takeplace i we ail to rein in our emissions.In the ew years since the Intergovern-mental Panel on Climate Change issuedits most recent report, global warmingsharmul eects have already outpaced thescientists worst predictions.8 Worse yet,scientists report that we are approachingtipping points at which the eects oglobal warming will accelerate, and eortsat mitigation become more and more di-fcult.9

I global warming emissions continueunabated, global temperatures may in-crease by as much as 11.5 F and sea levelscould rise 6.5 eet by the end o the centu-ry, causing massive ooding and displace-ment.10 I global warming is allowed to takeplace on this scale, the consequences will

likely include the extinction o as much as70 percent o all species on earth, intenseheat waves with temperatures reaching120 F in large parts o the United states,and droughts across as much as a third othe globe.11

In 2008, our nation emitted more than7 billion metric tons o global warmingpollution, the vast majority o it result-ing rom the production and use o ossiluels.12 In order to preserve a reasonablechance o keeping the increase in global

average temperatures below 2 C, emis-sions o global warming pollutants mustpeak soon and be cut by roughly hal bymid-century. The United States, as theworlds second-largest emitter o globalwarming pollution, and the country re-

sponsible or more o the global warmingpollutants in the atmosphere than anyother, must go arther and aster than theworld as a whole.

Achieving these emission reductionswill require us to use every resource avail-able to us to decrease our use o ossiluels. While energy efciency will likelyaccount or the frst major steps we taketowards averting a climate crisis, we willalso need to replace existing dirty energysources with new clean uels. Solar ener-gyin the orm o solar power plants, so-lar panels and collectors on our homes andbusinesses, and new buildings that take ad-vantage o the suns energy through theirdesignwill be a critical tool or achiev-ing this goal.

Solar Energy:A Powerful SolutionSolar energy technologies are a power-ul solution to reduce the environmentaldamage caused by our dependence on os-sil uels.

Lie-cycle analyses o solar photovoltaic(PV) systems show that they dramaticallyreduce emissions o global warming pollut-ants and smog- and soot-orming pollut-ants compared with ossil uels, even whenthe emissions created in the manuacturing

The decision to install solar PV yields 26 to 27 years of true

fossil fuel-free electricity.

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o the PV systems are included. For somePV technologies, lie-cycle emission reduc-tions are as high as 89 to 98 percent.13

According to the U.S. Department oEnergy, the energy payback time or aPV systemthe amount o time it takes

to save as much energy as was used to pro-duce the systemranges rom three toour years and is decreasing over time. As-suming a system lietime o 30 years, thedecision to install PV yields 26 to 27 yearso true ossil uel-ree electricity.14

Concentrating solar power plants also

dramatically reduce ossil uel use andemissions. According to one analysis, aconcentrating solar power plant generatesenough energy in its frst fve months inoperation to repay the energy used tobuild the plant.15

Solar energy can dramatically reduceour use o ossil uels and our emissionso global warming pollutants. There aremany solar technologies that can play arole in Americas energy system, and manyways to use those tools to help power oureconomy.



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When most people think about so-lar energy, they think o solarpanels sitting on rootops, or, less

requently, mirrors spread out across thedesert. While these technologies are im-portant, they represent only part o thepotential or solar energy to transorm ourenergy system.

The sun is a ubiquitous and tremen-dously exible source o energy. Solar en-

ergy can be converted directly into elec-tricity, stored as heat or later conversion,or used in the ormslight and heatinwhich it arrives. It can be captured cen-trally and then distributed to users, or col-lected right where it will be used. Thereare many technologies and tools that canbe used to harness solar energy.

Photovoltaic PowerPhotovoltaic (PV) cells use the suns radia-tion to generate a direct ow o electric-ity. The two most common orms o PVare crystalline silicon PVthe traditional,sel-contained PV panels most Americans

envision when considering solar powerand thin flms, inexpensive sheets omaterial that can be used in panels or bespread across roos and other architecturaleatures. Crystalline silicon PV panels arerequently more expensive, but are moreefcient at converting sunlight into elec-tricity, and can be mounted on a roo orcan stand alone on top o a pole or piece omachinery. Thin flms, while less efcient,

cost less and require less silicon to pro-duce. They can also be integrated unob-trusively into buildingsrolled out acrossrootops or walls as a barely visible sheet.

PV systems are easily transportable andinstallable, and can be used to generateelectricity where it will be used, even atlocations the electric grid doesnt reach.16PV is also modular, so installations can bescaled to the appropriate size or a givenuse.17 PVs scalability allows it to be usedor both large-scale power plants and to

power handheld calculators, and it dis-tinguishes PV rom almost every otherpower generation technologyimagine,or instance, a coal-powered calculator,or a nuclear-powered roadside cell phonecall-box.

PV has other advantages as well. PV

Building a Solar Future for America:The Tools

Building a Solar Future for America: The Tools 11


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is one o the ew power-generating tech-nologies that is a good ft or urban ar-easit produces no air pollution and canbe installed on buildings, parking lots andother developed areas without intereringwith human activities. As a result, thereis no additional land required or siting adistributed PV system. PV systems, un-like steam generators, do not use wateror anything other than routine cleaningo the panels, making them a good ft orareas with low water availability. And PVsystems generate the greatest amount oelectricity at the times when it is mostneeded, particularly hot, sunny summer

days.Photovoltaic installations are increas-ing rapidly in the United States. Between1998 and 2008, the amount o installed PVcapacity increased by a actor o more than10, rom 100 megawatts (MW) to 1,173MW.18 (See Figure 1.) But the potential

or PV systems ar outstrips the numberinstalled today. Americas residential andcommercial rootops, or example, couldhost as much as 712 gigawatts o solarpanels (roughly 700 times the capacity oall solar installations today) i every incho suitable rootop were to be covered,enough to produce roughly a quarter oAmericas electricity using current tech-nologies.19 Central-station photovoltaicsystems in sunny areas, PV systems alongroads or over parking lots, and PV instal-lations at actories could add to this total.

Concentrating Solar PowerWhereas PV technologies produce elec-tricity only when the sun is shining onthem, concentrating solar power (CSP)can provide a steady and uninterrupted

Solar photovoltaics help to power the Indian Pueblo Cultural Center in Albuquerque, New Mexico, one o many

community buildings that can make good use o solar energy . Credit: Sandia National Laboratories



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stream o power by storing the suns heatand using it to power a generator. These

systems are particularly suitable or largepower stations, but can also be deployedor smaller scale on-site generation.

All concentrating solar power technol-ogies use mirrors to ocus light on a re-ceiver to heat a uid. Once heat has beencaptured, it can be stored until it is needed,or it can be used immediately to power asteam generator or heat engine.

Large-scale concentrating solar plantscan take several ormseither ocusingheat on a single central tower, or on longpipes that carry heated uid to a centralcollector. These technologies are versa-tile enough to use as a stand-alone powerplant, as a preheating system or the wa-ter used in ossil-uel plants, or in a hy-brid confguration alongside existing ossiluel generators.21 CSP plants in Caliornia

have been reliably producing power ordecades, while at least six new plants have

come on line since 2006. 22Concentrating solar can also be used

on a smaller scale, with satellite dish-likemirrors ocusing energy on a small receiv-er that contains a heat exchange engine.These systems have less storage capability,but are also more modular, requiring lessaccess to vast open spaces.

Solar Water HeatingSolar water heating systems are amongthe simplest uses o sunlight or energy.In solar water heating systems, water (or aheat transer uid) is piped to the roo oa building, where it is heated by travelingthrough sunlight-absorbing pipes. Because

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1,000

1,200

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1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

CumulativeInst

alledPhotovoltaicCapacity,U.S.

(Me

gawatts)

Figure 1. Installed Photovoltaic Capacity, United States20



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capturing heat rom sunlight is simple andefcient, solar water heating systems canabsorb as much as 87 percent o the energyradiated at a given section o roo.23 Solarwater heating can be used or swimmingpools, to replace conventional residentialand commercial hot water heaters, and inlarger-scale industrial settings.

A range o collector types is avail-able or heating water with solar energy.The least expensive systems raise watertemperatures only about 18 F above theambient air temperature and are typicallyused to heat swimming pools.24 A slightlymore expensive collector can heat waterto temperatures suitable or a home hotwater system.25 These collectors can unc-tion in all climates, and in warm climatesthey can be made less expensive by storing

water on the roo near the collector. Themost expensive collectors are designed orapplications requiring extremely hot wa-ter, or or heating large volumes o wateror commercial or industrial use. Solarwater heating systems should have a con-ventional uel backup to provide heat on

Solar power towers such as this one in Caliornia use arrays o mirrors to ocussunlight on a central receiver, and can incorporate thermal storage, which enables the

plant to deliver electricity even at night. Credit: Sandia National Laboratory

cloudy days. Overall, solar collectors cantypically provide or 50-80 percent o abuildings water heating needs.26

Solar water heating has already becomewidely used in some countries. In Israel,or example, 90 percent o homes current-

ly use solar water heating and Hawaii hasrecently adopted a standard requiring so-lar water heating on all new homes built inthat state, though with some exceptions.27

Passive Solar Lightingand HeatingFor most o human history, skilled build-ers designed buildings to take advantageo the sun or lighting and heating. Thatchanged in the mid-20th century as build-ers began to rely on cheap energy to makeup or defciencies in a buildings design.A renewed ocus on energy conservation,however, has brought the practice o day-lighting and passive solar heating back intothe oreront o architectural thought.

In its simplest orm, daylighting is theart o bringing a comortable amount o

light into living and work spaces duringthe day, without causing excessive glareor heat transer through windows.Lighting designers can use windows,skylights, reective suraces, and exterioreatures that direct or diuse light toilluminate rooms and decrease the needor artifcial lighting.28 A well daylit spacewill have comortable levels o light in alldierent areas, throughout the day, andall year round. Daylighting can reducetotal building energy costs by as much

as one third.29

Solar lighting systemscan be augmented by electric lights thatare controlled automatically by dimmerswitches and that supplement sunlightwhen necessary. Advanced systems,meanwhile, can use fber optic cables todeliver light rom collectors on the roo



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to fxtures that also hold electric lights,automatically decreasing the amount oelectricity used as appropriate.30

Passive solar heating, much like pas-sive solar lighting, aims to admit solar en-ergy to a building when it is needed, while

keeping it out when it is not. South-acingwindows that admit winter sunlight (usu-ally positioned so as to be shaded duringthe summer), skylights, and air circulationeatures that move solar heat through thehouse all assist in reducing the need oractive heating.31 Passive solar eatures canalso include sunspaces such as enclosedporches, which provide a pocket o warmair outside the building envelope. Thermalstorage walls (dark-colored walls behindglass that can conduct heat to the interior)can store solar energy during the day andrelease it at night.32

Active Solar Heatingand CoolingSolar heat can also be captured through ac-tive systems, either or heating residentialand work spaces or or industrial purpos-es. The collectors used or these systemsgenerally resemble those used or solarhot water heaters; either glazed plates (ormost home space heating applications) orevacuated tubes (or commercial, industri-al, or solar cooling applications) are used.33In some cases, solar space heating and wa-ter heating systems can be combined.

When used or home heating, activesolar systems generally provide or 40-80percent o a buildings heating needs.34

While solar heating is airly intuitive, itmay be more surprising to learn that solarenergy can also be used to cool buildings,even without being converted into elec-tricity. In a solar cooling system, air is cy-cled through a dessicant material that pullsthe humidity out o the air. That materialis then baked dry by solar heatcapturedjust as in a solar heating systemallow-ing it to be reused. The dry air can thenevaporate water rom another source, suchas an indoor ountain, which cools theairjust as the evaporation o sweat coolsa human body. Such systems can save ap-proximately 50 percent o the energy usedto air condition a building.35 They are alsoat their most eective on sunny days whenthe need or air conditioning is likely to begreatest.

Passive solar design techniques such as daylighting cancreate attractive living spaces while reducing electric-ity consumption. Credit: U.S. Department o En-ergy Solar Decathlon, reprinted under CreativeCommons license



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Solar water heating systems, which are common in parts o the world, can provide 50 to 80 percent o a buildings

hot water needs. Credit: VELUX/ESTIF



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Solar energy can be integrated into vir-tually every part o American liethehomes we live in, the ofces where

we work, the arms and actories that pro-duce the products we buy, and the schoolswhere our children learn. With creativityand sound public policy, solar energy canmake a major contribution to Americasenergy uture.

Solar HomesThere are more than 128 million hous-ing units in the United States, includ-ing more than 80 million single-am-ily homes.36 Virtually all o these homesconsume ossil uels or heating, lighting,air conditioning and other purposes, yetonly a tiny raction currently produce en-ergy rom the sun. Tapping Americas ull

potential or powering our homes withthe sun could dramatically reduce ourdependence on ossil uels and our emis-sions o global warming pollution whilealso creating thousands o installationjobs that cant be outsourced.

What a Solar Home Looks LikeSolar homes use the energy o the sun toavert the need to burn ossil uels or tapelectricity rom the grid. New homes havethe greatest potential to take advantage osolar energy, but solar technologies canalso be integrated easily into many exist-ing homes.

New Homes

New homes are the easiest places to takemaximum advantage o the suns energy.Solar energy can play an important role inthe construction o zero-energy homes,which produce as much energy as they useover the course o a year.

Most o the eatures that distinguisha solar home are subtle. Well-posi-tioned windows and skylights decreasethe amount o time that electric lightingis needed each day. Thoughtul buildingorientation and the proper use o shading

elementssuch as overhangs, awnings ordeciduous treesallow warming sunlightin during the winter while keeping it outduring the summer. Thermal mass ele-ments, such as stone walls or oors, canbe used to store the suns warmth during

A Solar Future for America

A Solar Future for America 17


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the day and release it at night. Replacingconventional wood-rame walls with ther-mal mass walls made o concrete, or ex-ample, could reduce whole-house energyconsumption by 6 to 8 percent.37

Not only are many o these design el-

ements energy savers, but many o themalso add to the beauty and comort o anew home.

New homes also provide an opportu-

nity to take ull advantage o active solarenergy technologies such as photovoltaicsand solar water heating systems. Insteado having to retroft a buildings electricityor plumbing systems to accommodate so-lar energy, solar technologies can be builtinto new homes right rom the start, andthe home and surrounding vegetation canbe deliberately designed to maximize thesolar energy potential o the home.

Installing a solar water heater in a newhome, or instance, can cost just hal o

what it would to install one in an existinghome.39 Photovoltaics, meanwhile, can beincorporated into building materials sothat they require little technical expertiseto install. In October 2009, Dow Chemi-cal announced that it would be rolling outa line o solar shingles that it expects to

generate $5 billion worth o revenue by2015, and which will take less than hal aslong to install as conventional solar pan-els.40 Other companies are developingsimilar products.

Home builders with standardized so-

lar home designs can incorporate solarenergy eatures less expensively than theowner o an existing home, and may beable to shave costs urther by orderingsolar components in volume and devel-oping a trained workorce. Caliornia, orexample, has seen the development o newresidential subdivisionsamounting tohundreds o homesthat incorporate so-lar technologies either as an option or astandard eature.41

Residents o solar homes have generallybeen happy with their purchase. A 2006survey o Caliornia solar home ownersound that 92 percent would recommendthe purchase o a solar home to a riend.42Builders o solar homes also beneft be-cause solar homes sell aster than con-ventional homes.43 When combined withadvanced energy efciency technologies,passive and active solar energy can dra-matically reduce ossil uel consumption inhomes, while saving homeowners money.

A study in the U.S. Southwest estimatedthat zero-energy homes could reducenet energy consumption by 60 percent ormore. These homes would cost an added$15,000 to $20,000 or construction, butin all cases the homeowner would savemore in energy bills than was spent on theenergy-saving eatures.44

Nor do solar homes only work in theSouthwest or other sunny regions o theUnited States. A Massachusetts state taskorce, or example, concluded that the en-

ergy savings o a zero-energy home in thatcold-weather state more than compensateor the additional upront cost. In act, in-corporating passive solar eatures can ac-tuallyreduce some o the costs associatedwith building a new home by allowing orthe installation o smaller, less expensive

Figure 2. Elements of a Passive Solar Home38



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heating and air conditioning systems.45

Some building design experts are con-templating Energy-Plus building de-signs that make homes net energy produc-ers. These homes are built using extremelyairtight construction materials and tech-

niques and use designs that take optimaladvantage o sunlight. The internationalPassive House design standard, or ex-ample, saves up to 90 percent o the en-ergy used in home space heating.46 Thesebuildings could be paired with active so-lar systems to be net sources o energy totheir communities.

Existing HomesExisting homes may not have been builtto take advantage o the sun, but many aregood candidates or incorporating solarenergy.

Photovoltaic panels can be installed onalmost any roo, but they are most eectiveon at or lightly-sloped roos acing the

equator, which receive direct sunlightthroughout most o the day. Currentestimates suggest that 35-40 percento residential buildings are suitable orphotovoltaic panels.47

Solar water heaters typically decrease

the amount o natural gas or electricityrequired or water heating by 50 to 80percent.48 A National Renewable EnergyLaboratory study estimated that 50 per-cent o residential buildings nationwidecould use solar water heating systems.49 Aswith solar photovoltaic panels, solar waterheating systemsin which a rootop col-lector is used to pre-heat water or house-hold usecan be installed in any climate,although dierent types o systems workbetter in dierent parts o the country.Solar water heating systems are smaller,technologically simpler, less expensive,and more efcient at capturing the energyat sunlight than solar PV panels. Installinga solar water heater in an existing home

Solar homessuch as those in this Caliornia developmentare increasingly common and sell more rapidly thanconventional homes. Credit: Sacramento Municipal Utility District



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costs about $6,000.50 State and ederal in-centives can deray some o the cost o in-stalling solar water heaters.

Solar BusinessesAmericas commercial buildingsitsbig-box stores, strip malls, hotels, ofcebuildings, and the likeare just as depen-dent on ossil uels as our nations homes.Commercial buildings are responsible ornearly roughly 14 percent o the nationsenergy consumption.51 For certain typeso businesses, ossil uel expenditures canbe a major business expense. A growing

number o frms nationwide are comingto recognize that adopting solar energymakes good business sense, as well as goodenvironmental sense.

What a Solar Business Looks LikeAmericas commercial sector is extraor-dinarily diverse, with businesses o manytypes ranging in size rom mom-and-popstores to giant ofce complexes. Dier-ent kinds o commercial buildings present

dierent kinds o opportunities or usingsolar energy. Businesses that use a particu-larly large amount o energy or any onepurpose have the potential to take advan-tage o the economies o scale describedor homes in osetting that need with so-lar energy.

Big box stores are single-story build-ings and use a great deal o electricityor indoor lighting during the day-time. By installing just one skylight

per 1,000 square eet o store spaceand using dimmable indoor lights,Walmart has been able to save 15-20percent o total building energy costsin many o its superstores.52 In addi-tion, Walmart has installed solar PVsystems on 20 o its stores and plans

to expand its production o solarelectricity in the years to come.53

Warehouses also use a great deal oenergy on lighting, and can beneftrom incorporating passive solar

lighting eatures. Temperature-con-trolled warehouses can save energyby incorporating appropriate passivesolar heating or cooling eatures.54

Laundromats use a great deal oenergy to heat both water or washersand air or dryers, and can use solarenergy or both o these purposes.For example, the Worlds LargestLaundromat in Berwyn, Illinois,installed a solar water heating systemdesigned to produce 2,400 gallons ohot water every day ater natural gasprices spiked in 2001.55 Other kindso businesses and institutions withlarge laundry acilities, such as pris-ons and hotels, can use solar energyin a ashion similar to laundromats.

Restaurants and other businesses thatserve ood to many customers can usesolar water heating or their water

heating needs. Baseballs Boston RedSox, or example, installed solar waterheaters on the roo o Fenway Park,reducing consumption o natural gasor water heating at the acility bymore than one-third.56

Businesses and institutions with largepublic meeting spaces or other openspaces can use 50 percent or moreo their total energy on heating, andcould use solar heating systems to

oset their need or conventionalheating.57

As with solar homes, newly built com-mercial buildings can be designed to in-corporate passive and active solar ea-tures rom the very beginning, reducing



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their cost. A 2007 assessment o severalcategories o green buildings (some owhich incorporate passive or active solarenergy systems), or example, ound thatthere was no signifcant dierence in thecost o building green versus non-green

buildings.58 A similar analysis o buildingsmeeting the Leadership in Energy andEnvironmental Design (LEED) standardsound that buildings meeting the criteriao the lowest three tiers o the LEED pro-gram cost an additional 2 percent or lessto build, while cutting energy consump-tion by 28 to 48 percent.59

Commercial buildings are much morelikely than residential buildings to haveat roos, meaning that many o them canplay host to properly oriented photovoltaicpanels or solar water heating systems. Areport or the National Renewable EnergyLaboratory estimated that 60-65 percent ocommercial roo space nationwide wouldbe suitable or PV panel installation.60

Many businesses have larger roos, anduse more energy, than residential energycustomers. This makes it possible or themto take advantage o the signifcant econo-mies o scale that come with purchasingand installing active solar installations o

larger sizes. Large photovoltaic systemswith between 500 and 750 kilowatts (kW)o capacity, or instance, cost about 30 per-cent less per Watt o capacity than smallresidential systems.61 The high-efciencyheat collectors oten used or commercialsolar heating applications, meanwhile, canbe installed in large numbers and coupledwith mirrors to enhance their eective-ness. These measures can reduce the per-square-oot cost o these high-efciencycollectors to 50 percent or more below the

average cost o residential units.62One potential barrier is that commer-

cial establishments are disproportionatelylikely to rent their buildings, creatingpotential split incentive problems, inwhich builders bear the cost o installingsolar energy systems but tenants reap the

benefts in reduced energy costs. Feed-intaris and third-party fnancing tools canhelp to surmount these obstacles. (Seepage 43.)

Solar FactoriesHistorically, manuacturing acilities havebeen thought o as environmental pollut-ers, not potential contributors to a greenuture. But Americas manuacturing sec-tor has a great deal to gain rom a transi-tion to cleaner sources o energy.

Manuacturing is extremely energy in-tensive. Food processing acilities, cementplants, steel mills and other industrial a-cilities use energy on a vast scale. They are

responsible or roughly 28 percent o theglobal warming pollution emitted in theUnited States.63 Reducing ossil uel con-sumption in actories is not just a matter oenvironmental concern. American manu-acturers ace the challenge o internationalcompetitionreducing energy costs is just

Workers install solar panels on the roo o the supervisors ofce at Wayne NationalForest in Ohio. Many ofce buildings can take advantage o solar energy. Credit:

Alex Snyder, Wayne National Forest



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one way to remain competitive.Solar energy cannot replace all the en-

ergy that is used by Americas manuactur-ing sector, but it can make an importantcontribution to meeting the energy needso many o Americas actories.

What a Solar Factory Looks LikeAmericas manuacturers use energy or awide array o purposes. Electricity is usedto light shop oors and power machinery,ossil uels are burned in boilers to createsteam and process heat and to generateelectricity. Solar energy can help to alle-viate energy demand in several o theseareas.

The creation o process heat usesmore energy in Americas manuacturingsector than any other single activity.64Melting iron in a mill or cooking cement

in a kiln obviously requires process heat,but so does distilling ingredients in a phar-maceutical plant, pasteurizing milk in aood processing plant, or bleaching clothat a textile mill.

Uses o process heat are classifed by

the temperatures required. Some pro-cesses take place at temperatures wellabove what can be achieved economicallyusing solar energy, but many others takeplace at lower temperatures. About 30percent o process heat is used at lowtemperaturesbelow the boiling pointo waterand another 27 percent is usedat medium temperaturesbetween 100and 400 C.65 Solar heat is most useul orprocesses occurring at less than 250 C.66In certain key industriessuch as ood,textiles, and paper60 percent or more oprocess heat is needed at these tempera-tures.67 Solar water heating is potentially

Audi installed a solar cooling system (above) at its training center in Ingolstadt, Germany. Credit: Solahart/ESTIF.



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well-suited to several uses o industrialheat, including cleaning, drying, preheat-ing o boiler water, and sterilization.68

Industrial plants that use large amountso process heat at low and medium tem-peratures can potentially install large ar-

rays o solar thermal collectors to providethat heat. Worldwide, approximately 90solar process heat systems are currentlyin place, including several in the UnitedStates.69 The largest solar process heatsystem in operation in the United Statesis located at a Frito-Lay actory in Cali-ornia. It uses a 5-acre feld o solar con-centrators to create steam, which is usedto heat the oil used to cook the companysSunChips brand o snack oods.70 At ullcapacity, the system can produce 14.7 bil-lion BTU o energy per year, equivalent tothe annual natural gas use o 340 averageAmerican homes.71

The industries with the most existingsolar process heat plants are ood, chemi-cals, transport and textiles.72 The kinds osolar heat collectors used can vary with thetemperatures needed, and with the scale othe application. Rootop collectors similarto those used or residential hot water areappropriate or some industrial applica-

tions, while large-scale collector arrayssimilar to those used or concentratedsolar power plants can serve large scale,high temperature uses. For airly low tem-perature uses, process heat can actually begenerated at the same time as electricitythrough the use o photovoltaic/thermalcollector arrays, which capture the wasteheat generated by sunlight striking photo-voltaic panels.73

Solar process heat is just one o manyopportunities to tap solar energy in indus-

try. The Steinway & Sons piano actoryin New York City, or example, recentlyinstalled the worlds largest solar coolingsystem. During the summer, the systemcools and dehumidifes the actory, pre-venting moisture rom aecting the preci-sion parts o the companys world-amous

pianos, while during the winter the systemhelps heat the acility.74

Solar photovoltaics can be used to helpmeet the electricity needs o actories.Like commercial buildings, large actoriesare likely to have at roos and be exposed

to sunlight. Installing photovoltaics onactories can reduce demand or electric-ity, provide power to drive motors andindustrial machinery, and deliver electric-ity back into the grid during peak demandtimes on hot summer days.

Passive solar design can also reduce en-ergy demand in actories. About 5 percento the energy used in the manuacturingsector is actually used or lighting and cli-mate control in workspaces.75 Passive solardesign elements such as daylighting can re-duce the need or artifcial light. Ford Mo-tor Companys Rouge Center truck plantin Dearborn, Michigan, or example, wasredesigned to incorporate daylighting owork areas, augmented by well-controlledelectric lights.76

The use o solar energy in industry canavert the consumption o ossil uels, whileproviding a hedge against volatile ossiluel prices or energy-intensive industries.The vast amount o energy used in indus-

try means that the potential or energysavings and emission reductions is large. Astudy by the International Energy Agency,or example, estimated that solar processheat could provide or roughly 4 percento industrial heat demand, reducing con-sumption o ossil uels.77

The expansion o solar energy use inindustry aces unique hurdles, however.Solar process heat, or example, seems likea perect ft or many industries that relyon hot waterindustrial acilities are hun-

gry or options to reduce energy costs andthe technology to provide solar hot wateris relatively cost-eective and technologi-cally proven.

However, industrial acilities, like otherbusinesses, are oten driven by short-termeconomics, rather than the potential to



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generate energy savings over the longterm. A mid-1990s review o cancelled so-lar process heat projects in the U.S. oundthat two projects were rejected by com-panies because they sought a three-yearpayback time, while the proposed projects

delivered payback in 4.4 and 5.2 years, re-spectively.78

In addition, integrating solar waterheating into an existing industrial plantcan be technologically challenginges-sentially requiring the re-engineering okey processes. Resolving those issues re-quires the existence o experts trained inintegrating solar energy into industrialprocesses. Unortunately, the solar processheat industry in the United States is rela-tively undeveloped. The European Unionis working aggressively to develop marketsor and expertise in the solar process heat

sector, and the United States could ollowsuit.79

Solar on FarmsIn the 1930s, the United States broughtelectricity to remote towns and dwellingsacross the country through rural electrif-cationone o the signature accomplish-ments o the New Deal. Access to cheapenergy, however, has also resulted in manytasks that were once carried out using so-lar energysuch as crop dryingbeingshited to ossil uels.

Agriculture represents only a small por-tion (approximately 1 percent) o Americastotal energy consumption.80 But, or indi-vidual armers, ossil uel costs can repre-

P-R Farms in Caliornias San Joaquin Valley uses the electricity created rom a photovoltaic system to power its coldstorage and packing operations, resulting in a dramatic reduction in monthly energy bills. Credit: PowerLight



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sent a large share o their total expenses.Farmers spent $28.8 billion on energy in2003, about 14 percent o their produc-tion expenses.81

The distributed, modular nature osolar energy makes it uniquely suitable

to provide electric power and heat onarms and ranches around the country.Farms and ranches may need electricityor pumps and ences and on-site pro-cessing operations, space heating orbarns and greenhouses, and hot wateror cleaning at locations where runningelectric wires rom the grid or requent-ly reflling uel tanks can be inconve-nient and expensive. Photovoltaic panelsand solar heat collectors, which requireminimal maintenance, no reueling, andno connection to a grid, can provide asimple and economical solution.

What a Solar Farm Looks LikeSolar energy is already commonly used onarms or remote applications. Photovol-taic panels, or instance, are oten used orpowering water pumps in remote pastures.These PV-powered pumping systems costa total o $2,500 to purchase and install,

and operate completely independent o thegrid.82 Solar electricity can also be used topower electric ences, irrigation systems,and building machinery. These remote so-lar systems, while small, can deliver out-sized environmental benefts, since theyoten replace inefcient and highly pollut-ing diesel generators.

There are, however, many other poten-tial applications or solar energy on arms.Space heating and ventilation, or exam-ple, are important on many arms, pro-

viding winter heat or animal barns andgreenhouses and keeping the air in animalenclosures ree o dust, gases and odors.Farmers also use heat to dry cropsa tra-ditional role or solar energy that is nowsometimes perormed by heat rom ossiluels. Passive solar heat can displace ossil

uels or some greenhouse and crop dryingapplications. Many greenhouses that derivegrowing light rom the sun, but heat romgas or propane, could be replaced withbuildings that rely on passive solar heat-ing or much o their needs. These passive

solar greenhouses are oriented to capturemore direct sunlight rom the south, anduse thermal mass and insulation to storeheat rom the day through the night.83 Inwarmer climates, crop drying can be per-ormed in sheds with glazed south-acingwalls that admit heat, requiring no activeheating system.84

Active solar heating is most useul onarms or heating barns. Barns contain alarge volume o air, and also need moreventilation than many large buildings,because o the dust and livestock emis-sions that quickly build up in them.85Solar heating systems can replace gas orpropane heaters in barns, and can also beused to promote air circulation during thesummer. Active heating systems can alsobe used or crop-drying applications, butare most cost-eective or this purposewhen the solar collector provides heatboth to a drying shed and other build-ings, as needed.86

Farmers who need to clean barns ormachinery use a signifcant amount oenergy or heating water. Dairy armsin particular (which have both barns andmilking machines to clean on a regularbasis) need large energy inputs or waterheatingas much as 40 percent o thearms total energy use.87 A solar waterheater can replace hal the ossil uel usedor water heating, preventing emissionsand saving money.88

Some arms are adopting photovolta-

ics to provide electricity to keep harvestedcrops cool and to run equipment. As oearly 2009, more than 50 Caliornia win-eries had installed solar panels, with doz-ens more planning to ollow suit, takingadvantage o Caliornias abundant sun-light to help power their operations.89



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Solar in TransportationThe phrase solar cars brings to mindimages o toy-store science projects andexperimental, Batmobile-style vehicles.But any transportation vehiclea car,

truck, train or even boatcan be a solarvehicle, so long as it is capable o beingpowered by electricity, and that electricitycomes rom solar power.

America has many reasons to look oralternative sources o energy or its trans-portation system. The nations dependenceon petroleum has severe environmental,economic and national security implica-tions. Shiting more o Americas trans-portation system to operate on electricitywould enable the nation to use a wider

variety o uels, including solar power andother orms o renewable energy.

Americas transportation system alsorepresents a powerul, i less obvious, seto opportunities or the utilization o solarpower. The nations transportation systemtakes up a tremendous amount o land.According to one estimate, approximately43,000 square miles o land in the UnitedStatesan area roughly the size o Ohiois covered by impervious suraces, most o

them roads and parking lots.90 Most othis area is unshaded and has little currentuse other than or storing or transportingcars, meaning that it could easily be usedor generating solar energy.

Finally, the hundreds o millions o

cars on Americas roads could somedayhelp expand the use o renewable energysources such as solar energy. Plug-in carscan allow or the short-term, distributedstorage o electricity in vehicle batteries,providing a source o emergency power tosmooth out the peaks and valleys o elec-tricity supply and demand.

What Solar TransportationLooks Like

Small solar panels are increasingly com-mon sights along highways across theUnited States, providing electricity orroadside signs, emergency call boxes andother roadside equipment without theneed to operate generators or run wiresto distant locations. States such as Oregonare going urther by installing photovolta-ic arrays designed to power all o the lightsat a highway interchange.91

But these applications account or onlya tiny portion o the energy used in power-

ing the nations transportation system, thevast majority o which goes toward movingvehicles. The introduction o plug-invehicleselectric vehicles and plug-in hy-bridscould enable solar power to make ameaningul contribution toward poweringour transportation system.

Plug-in vehicles are similar to todayshybrid-electric vehicles, which store theenergy captured by regenerative brakingand use that energy to help power the ve-hicle. However, plug-in vehicles have larg-er batteries that can also store electricitydrawn rom the grid. In a plug-in hybrid,grid electricity augments energy rom aossil uel-powered internal combustionengine. In an electric vehicle, there is nointernal combustion engine at all; the

Solar garages, such as this one at Arizona State University, shade ve-hicles while providing power to the grid, and could someday be usedto charge plug-in vehicles. Credit: Kevin Dooley, reprinted underCreative Commons license.



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vehicle is powered entirely by electricitydrawn rom the battery.

Plug-in vehicles are currently a rarity inthe United States, but that could changewithin the next couple o years. Several

major automakers are working to developplug-in hybridsGeneral Motors Chev-rolet Volt is scheduled to enter the marketin late 2010, and Toyotas Prius plug-inhybrid will be put out or testing in early2010 with a ull release in 2011.92 Severalother automakers are exploring plug-intechnologies, including the potential orully electric vehicles, with the NissanLea all-electric vehicle to be introducedin late 2010.93

Plug-in vehicles make environmen-

tal sense virtually regardless o how theelectricity that powers them is generated.Electric motors are inherently more en-ergy efcient than internal combustionengines. Even with the very dirtiest elec-tricity, electric cars are about equivalent totodays conventional cars in terms o glob-

al warming pollution. Powering plug-invehicles with renewable energy, however,dramatically increases their environmen-tal benefts.94

Plug-in vehicles also provide new op-

portunities or tapping solar energy andor integrating renewable energy into theelectric grid. Almost all vehicles spend themajority o their day sitting stilloten inexposed parking lots at a place o work. So-lar powered charging stations in parkinglots would enable drivers to charge theirvehicles during the day, while also pro-viding a source o shade to keep vehiclescool. Toyota is developing solar chargingstations or plug-in vehicles in Japan, andseveral companies in the United States

have built solar parking lots that eed cleanenergy into the grid.95 Solar charging hasthe potential advantage o channeling thedirect current produced by solar panelsinto a vehicle battery without the need toconvert to alternating currenteliminatingthe loss o energy that occurs when DC

Oregons solar highway project involves the installation o solar panels along roadsides in the state. Credit: Gary

Weber, Oregon Department o Transportation photo/video services



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power is converted to AC and vice versa.In any case, pairing the expansion o plug-in cars with solar power installations cangive plug-in hybrid owners the option ocharging up during the daytime withoutadding strain to the electric grid.

In addition to parking lots, highwaysprovide another possible location or so-lar panels. Oregon is considering the ex-pansion o its solar highway programand solar panels have been installed alongroadsides in Europe or decades.96

Airports are also proving to be ertileground or solar panel installations. Nu-merous airports across the countryin-cluding acilities in Denver, San Franciscoand Austinhave installed solar arrays thatprovide a share o the power or airport op-erations.97 Buer land surrounding runwaysalso provides large swaths o unshaded areathat could be used to house solar panels.

While electric cars are in the early stag-es o deployment, parts o Americas trans-portation system are already powered byelectricity. Subway and light rail systems,along with many commuter rail lines andsome intercity train lines, are powered byelectricity. The recent expansion o lightrail systems in cities such as Los Angeles,

Salt Lake City, Phoenix and Denver prom-ises to shit more travel away rom gaso-line-powered vehicles and toward electrictransportation. In addition, the nation isbeginning to invest in creation o a high-speed rail network that would likely bepowered by electricity, and leading statesare working to ensure that the electricitythat powers the system is renewable. Cali-ornias High Speed Rail Authority, or ex-ample, has committed to generating 100percent o the power or the states high-

speed rail system rom renewable energyand has evaluated the potential role o so-lar power in achieving that target.98

Solar energy can even help alleviate emis-sions rom the global shipping industry. Theshipping industry is estimated to have pro-duced just over 3 percent o the worlds

global warming pollution in 2007.99 Amajor Chinese shipping frm, or example,is experimenting with the use o solarsailslarge arrays o photovoltaic pan-elson some o its ships, while a smallnumber o solar erries already ply the wa-

ters o harbors around the world.100

Solar in CommunitiesGoing solar has traditionally been an in-dividual aair, with pioneering homeown-ers or businessowners deciding to installtheir own solar energy systems. The ben-efts o solar energy, however, can be evengreater when entire communities work to-gether to build solar energy systems.

Some orms o solar energy technol-ogysuch as neighborhood solar heatingsystems with seasonal heat storageareonly practical on the community level.Community involvement can also createnew opportunities or individuals to adoptsolar energy, even i their homes are poorcandidates or solar panels. Meanwhile,many community buildings are good can-

didates or solar energy.Moreover, broad adoption o solar en-ergy in a community can create importanteconomies o scale. The greater the lo-cal market or solar photovoltaics or hotwater systems, the greater the base o ex-pertise that can develop among the manyindividuals and businesses involved in theprocesssolar system installers, electri-cians, builders, banks, utilities, etc. In themany American cities, particularly on theEast Coast, that ace challenges in meet-

ing electricity demand, intense develop-ment o solar power can help alleviate theneed to build new power plants in denselypacked urban areas or build expensivetransmission lines to bring in power romelsewheresaving money or ratepayersas a whole.



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What a Solar CommunityLooks Like

Solar communities can take many orms.A ew potential ways that solar energy canbe integrated into communities are dis-cussed below.

Solar District HeatingA district heating system is one in whichsteam or hot water rom a central plant ispiped to residential and commercial build-ings in a city, neighborhood, industrialpark or college campus. In other words,

instead o each individual building havinga urnace or boiler, all the buildings in adistrict heating system receive heat romone central power plant.

District heat has a long history in theUnited States. District heat systems werebuilt in many American cities to provide

a proftable use or the steam let overater generating electricity. New York

Citys system is the largest in the UnitedStates.101 Denver, Los Angeles, Boston,Chicago and Kansas City are among themany other cities with downtown heatingsystems.102 Nationwide, more than 300universities and 120 hospitals also use dis-trict energy in the orm o heat, coolingor both.103

Solar energy can help to power districtenergy systems. In Europe, several hous-ing developments have been built withsolar district heating systems. In these sys-

tems, rootop solar collectors heat water,which is then piped to a central storagetank. The storage tank is typically de-signed with thick concrete walls and bur-ied underground to retain heat or use intimes o day when the sun is not shining oreven, with the installation o seasonal stor-

This solar thermal array, installed at Arnold Schwarzenegger Stadium in Graz, Austria, provides heat or thetowns district heat system. Credit: SOLID/ESTIF



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age, colder months o the year.104 The solardistrict heating system in Friedrichshaen,Germany, which uses seasonal storage tosupply heat and hot water to more than500 apartments, covers approximately 25percent o the neighborhoods space heat-

ing and water heating energy needs; othersolar district heating installations in Ger-many provide an even greater raction ohome heating or hot water.105 Such systemsare even viable in extremely cold climates.A 52-unit housing development in Alber-ta, Canada, will use solar energy to supply90 percent or more o the complexs spaceheating and hot water needs.106

Solar district heating has gotten thegreatest traction in Europe, but the largestsuch project is currently being built in theUnited States. The 900,000-square-ootFletcher Business Park in western NorthCarolina will be heated and cooled by asolar district energy system.107

Solar energy collectors can also be usedto augment steam production in existingdistrict heat systems, reducing the need toburn ossil uels.

Community-Owned Solar Energy SystemsTwo o the biggest hurdles to the installa-

tion o household solar power systems arethe upront cost o the system and the lacko an appropriate rootop. Homeownerswho wish to go solar have another op-tion or using solar power, howevertogo in with their neighbors on a commu-nity-owned solar system.

Across the nation, recent years havebrought a growing movement towardcommunity-owned renewable energy. Re-newable energy installations can be builtby institutions controlled by local resi-

dents, such as municipal utilities, munici-pal governments or electric cooperatives.For example, in Colorado, an electric co-operative oers its customers the ability tolease a solar panel installed on the utili-tys property. The homeowner receives acredit on the monthly bill or the value o

the solar power generated by his or herpanel.108 A similar program was recentlylaunched in Utah.109

Some states are working to create newopportunities or community-based solarpower. Colorado legislators have intro-

duced a solar gardens bill that wouldenable individual homeowners to partnerto build, and receive the benefts o, so-lar energy systems not located on theirproperties.110 Massachusetts has adopteda neighborhood net metering policy inwhich groups o 10 or more individuals ina single town can share in the benefts o asolar power installation.111

Solar in Community BuildingsCommunity institutionsschools, church-es, municipal buildings and the likeareamong the largest and most visible build-ings in any city or town. Many o thesebuildings also have unique characteristicsthat make them particularly well-suitedto take advantage o solar energy. Con-sider schools, which are primarily occu-pied during daylight hours and devote onequarter o their total energy consumptionto lighting.112 Schools, thereore, providean excellent opportunity to take advantage

o daylighting, reducing electricity needsand creating a more pleasant learning en-vironment. Most schools also have largeamounts o available roo space, and coulduse rootop solar collectors or much otheir heating needs.

Other community institutions presentsimilar opportunities:

Churches and other large communityspaces use as much as 60 percent otheir energy or heat.113 Solar heat

collectors could provide much o thisenergy, particularly during daytimeservices. Church ofce buildingsrequently have large, at roos.

Libraries, museums, and other publicbuildings use signifcant amounts



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o energy on heat and lighting, andoten have large at roos availableor PV panels or solar heat collectors.Skylights and other passive designeatures can be used to daylight thetop stories o these buildings.

Wastewater treatment plants are alsogood candidates or solar energy,with large open spaces that can easilyhost solar panels to help meet theacilities energy needs.

One advantage that churches, schools,and other public buildings have over ho-meowners in installing solar technologiesis that they generally expect to remainin the same building or decades, whichgives them greater certainty that they willreceive the ull lietime beneft o any so-lar project. Additionally, schools, librar-ies, and government ofce buildings areowned and operated by the same localgovernments that are oten responsibleor extending credit and incentives to ho-meowners or solar projects. By taking ad-vantage o their ability to issue municipalbonds at low interest rates, local govern-ments can fnance solar projects in a way

that spreads the costs and benefts o so-lar improvements out over the same timerame.

The Benefts o Solar CommunitiesWhen many homeowners and institutionsin a community go solar, the benefts areoten magnifed.

For example, as a vigorous market orsolar energy develops in a community, thedemand or trained solar energy installersincreases and the amount o experience

gained by those installers grows. Instal-lation costs can represent a large shareo the total cost o a solar energy systemand reducing those costs is a key step inmaking solar energy cost competitive. Re-search suggests that, as solar installers gainexperience and learn by doing, the cost

o installations decline.114 Moreover, thiseect is local, meaning that the develop-ment o a vigorous solar market in a com-munity or state can help bring costs down,creating a virtuous circle that makes solarenergy accessible to a greater number ohomeowners and businesses.

Installing large amounts o solar powerin an area can also reduce peak demandor electricity in areas where the grid isstrainedreducing the need to constructexpensive new power plants or transmis-sion lines. Because solar photovoltaicsgenerate the most electricity at preciselythe times when electricity demand is high-est (hot, sunny summer days), they canplay a major role in reducing peak demandon the electricity system. In New Jersey,or example, 10 megawatts (MW) o solar

power capacity can be counted on to oset4 to 7 MW o conventional peak genera-tion, meaning that careully located solarpanels can dramatically reduce the needto run expensive peaking power plants,build new power plants, or expand trans-mission lines to serve peak demand.115

President Obama and Vice-President Biden inspect solar panels on theroo o the Denver Museum o Nature & Science, one o many com-munity buildings that can beneft rom solar energy. Credit: White

House, Pete Souza



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Solar GridSolar energy, as we have seen, can be cap-tured in American homes and business-eseven entire communitiessharplydecreasing ossil uel consumption. These

solar technologies are distributed theyare implemented at or near the placeswhere energy is used. Distributed re-sources have many advantages over thecurrent centralized system o generatingand distributing electricity: they do notrely on the expansion o expensive long-distance transmission networks, they aremore energy efcient, and, with properintegration, they can make a large contri-bution to the resiliency o the electric gridand reduce the need or expensive peaking

power plants and transmission lines.But our existing electric grid can also

play a role in moving America toward asolar uture. The grid enables us to movepower rom places where it is not beingused to places where it is in demand,

supplying electricity to our homes attimes when the sun is not shining anddelivering solar electricity to places whereit is needed. The grid also enables us totake advantage o excellent solar resourcesthat are ar removed rom any source o

demand.Centralized solar power acilitiessuch

as photovoltaic arms and concentrat-ing solar power plantscan augment orreplace many ossil uel resources in ourelectricity system, while investment insmart grid technologies can help Amer-ica better tap the solar resources in ourown backyards.

Utility-Scale Solar Resources

Americas desert Southwest and othersunny areas o country possess some o thebest solar resources in the world. The so-lar radiation striking just a small portiono the southwestern U.S. contains enoughenergy to power the entire nation. There

Parabolic trough concentrating solar power plants, such as this one in Caliornia, have the potential to generatelarge amounts o power in sunny areas o the Southwest and elsewhere. Credit: Gregory Kolb, Sandia National

Laboratory



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are several ways to harness that resource.Concentrating solar power (CSP) plants

use mirrors to ocus the suns rays on acentral collector uid, with the capturedheat used to generate electricity (or, lesscommonly, to provide heat or industrial

processes or space heating). CSP plantshave been providing reliable electricityin Caliornia or decades, and a new gen-eration o plants is currently in operation,under construction, or in the early stageso approval. Six new CSP plants have be-gun operation in the United States since2006, with many moreand largerproj-ects in the pipeline.116 In Caliornia alone,developers have proposed more than 10gigawatts o concentrating solar powerprojectsan amount roughly comparableto 1 percent o Americas current electric-ity generating capacity.117 Similar levels osolar development have been proposed inArizona and Nevada.

The potential or CSP development isvirtually limitlessCSP plants coveringjust 9 percent o the area o Nevada couldpower the entire country.118 The mostimportant limitations on the technologystem rom its surroundingsspecifcally,the difculty o fnding adequate water

supplies in desert areas, potential conictswith sensitive desert ecosystems, and thechallenge o transporting electricity longdistances to population centers.

But while CSP has some disadvantagescompared with distributed solar power,it also has some advantages. One majorbeneft o CSP is that the heated uidproduced by the system can be easily andcost-eectively stored (as opposed to elec-tricity, which requires costly batteries orstorage). CSP plants with thermal storage

can deliver electricity even when the sunis not shining, enabling them to competedirectly with base load sources o powersuch as coal and nuclear power, therebyexpanding the share o electricity demandthat can be satisfed by solar power.

Ultimately, the nation will need to take

advantage o both distributed and centralsolar resources such as CSP to take a seri-ous bite out o our dependence on ossiluels. Careul location o CSP systems tominimize environmental impacts, the useo air-cooled systems that reduce water

consumption, and limited investments inexpanded transmission capacity can ensurethat CSP delivers the maximum beneftsto our environment.

In addition to stand-alone plants, CSPalso has the potential to be used in con-junction with ossil uel power plants. InFlorida, a 75 megawatt CSP acility is be-ing built as part o a hybrid power plantwith an existing natural gas fred genera-tor.119 Pairing solar energy with conven-tional power generation can reduce os-sil uel consumption and global warmingemissions while ensuring a steady and reli-able source o electricity to the grid.

In addition to the potential or distrib-uted use on rootops, photovoltaic (PV)modules can also be used in solar armsto generate electricity or the grid. Large-scale PV installations can be built quicklyto respond to emerging power needs, canbe located optimally in areas with

building a solar future: repowering america’s homes, businesses and industry with solar energy

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