building a solar future

8/9/2019 Building a Solar Future

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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 OhioResearch & 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 Ohio Research & Policy Center thanks Jigar Shah, CEO o the Carbon War 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 thought ul review and insight ul suggestions. Thanksalso to Elizabeth Ridlington, Susan Rakov and Travis Madsen o Frontier Group or theireditorial support.

Environment Ohio Research & Policy Center thanks the John Merck Fund, the Energy Foundation, the Richard and Rhoda Goldman Fund, the Arntz Family Foundation, the Meadows 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 thoseo Environment Ohio Research & Policy Center. The views expressed in this report arethose o the authors and do not necessarily re ect the views o our unders or those whoprovided review.

2010 Environment Ohio Research & Policy Center

Environment Ohio Research & Policy Center is a 501(c)(3) organization. We are dedi-cated to protecting Ohios air, water and open spaces. We investigate problems, cra t solu-tions, educate the public and decision-makers, and help Ohioans make their voices heardin local, state and national debates over the quality o our environment and our lives. Formore in ormation about Environment Ohio Research & Policy Center or or additionalcopies o this report, please visit www.environmentohio.org.

Frontier Group conducts independent research and policy analysis to support a cleaner,healthier and more democratic society. Our mission is to inject accurate in ormation andcompelling ideas into public policy debates at the local, state and ederal levels. For morein ormation 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 FotografeLayout: Harriet Eckstein Graphic Design

Acknowledgments


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Table of Contents

Executive Summary 1

Introduction 6

Why Solar? Why Now? 8Building 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, sa e, provenand available everywhere, and the price o many 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 alarge and increasing share o our energy

rom 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 sun by 2030, using a wide variety o tech-nologies and tools. Achieving that target would result in the sun providing us withmore energy than we currently produceat nuclear power plants, more than hal asmuch as we currently consume in our cars

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

A comprehensive suite o public policy strategies 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 energy can 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 anywherethe 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 re ers to total energy consumptionromall sources in the United States, not just electric-

ity consumption.

Executive Summary 1


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Concentrating solar power (CSP) CSP plants use 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 energy

rom 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 Roo top-mounted collectors capture solarenergy as heat and produce hot water. Solar heat collectors can beextremely e fcient; 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 o absorption 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 overalle fciency 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 homes can be built to maximizeuse o the suns energy throughpassive solar design and the use o solar PV panels and water heatingsystems. Solar energy can be paired with advanced energy e fciency techniques to create zero net energy homes, which produce as muchenergy as they consume. Zero netenergy homes have already been builtin parts o the country, are possible inall climates, and o ten save money orconsumers over time.

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

Solar Businesses Commercial buildingssuch as

big-box stores, strip malls ando fce complexesalso have many opportunities to take advantage o solar 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 unique

opportunities 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 BostonRed Sox have adopted solar water heating to reduce theirconsumption o natural gas or water heating.

Solar Factories

Manu acturing 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 Cali ornia uses solarconcentrators to provide heat or cookingsnack oods. At ull capacity, the systemreplaces as much natural gas as is used by 340 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 use ul or pumping water,providing irrigation and meeting otherneeds in remote areas that arent easily reached by the electric grid. Many armscould also take advantage o solar energy

or heating greenhouses, ventilating barnsor drying crops.

Solar in Transportation

The development o plug-in vehi-clesboth plug-in hybrids and ully electric 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 o highways andparking lots could house solar panels.

New transportation technologiescreate new opportunities to usesolar power. Cali ornias 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 o fces,schools and wastewater treatmentplants, as well as community insti-tutions such as churches, are o tenexcellent candidates or solar energy.

New policy tools enable members

o a community to work together tofnance solar energy installations,enabling even individuals withoutsuitable roo s 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 energy best when demand is highestonhot, sunny summer daysthey canreduce the e ective peak demandthat utilities have to meet, provid-ing stability to the grid, reducing theneed 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 ow

rom central power plants or energy providers to consumers.

Investing in orms o smart gridtechnologies can expand the amounto electricity the nation can generate

rom distributed solar power whilemaintaining reliable electricity supplies.

America can obtain a large share o its energy rom the sun. But it will not happen on its own. Local, state and

ederal governments must implement public policies that remove the barriers

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

Financial incentives , such as grants,tax credits and eed-in tari s helpto compensate homeowners andbusinessowners or the benefts theirinvestments in solar energy deliver tosociety and can create a robust early market 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 withsolar 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 up ront 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 back through 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 o ered 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 energy are 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 e ectively ban theuse o solar energy, while revisions topermitting rules and utility regula-tions can reduce the hassle and costo installing solar energy and ensurethat people are compensated airly

or the solar power they supply to thegrid.

Public education and work orcedevelopment e orts are critical toexpanding the use o solar energy.Public education programs can helpanswer consumers questions aboutsolar energy and make it easier togo solar. Work orce 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 understood when 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 investigate 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 ithas become all but invisible to most o us.

Few o us ever stop to marvel at thepath 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 hal way aroundthe world to our shores, the giant refner-ies that convert the crude oil into gasoline,and the extensive distribution in rastruc-ture that gets the gasoline into our tanks.

Similarly, ew o us see the immensein rastructure that turns a lump o coalmined in Montana into the electricity thatpowers a computer in Alabamathe gi-ant machines that mine the coal, the trainsthat 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 le t 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 drinking water. Sometimes the damage is in icted

ar away rom where most Americans live,appearing as the melting o Arctic icedue to global warming, or the flling ino a remote Appalachian hollow resulting

rom mountaintop mining. As people in America and worldwide have awakenedto the environmental dangers posed by

ossil uels, we have built even morein rastructure to mitigate those dangers

rom 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 builtan energy system that does a master ul job o unlocking the energy stored inunderground deposits o ossil uels andtrans orming 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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power ul 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 wisdomabout 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 re ect 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, solidi ying our dependence on

ossil uels.Cheap ossil uels have also caused us

to 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. For years, 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, only to alter or lack o consistent governmentsupport o the kind enjoyed by the ossil

uel industry. Today, America is experiencing the

downsides o our dependence on ossil u-els as never be ore. The ominous spectero global warming, the continued pollu-tion o our air and water that results rom

ossil uel use, and worries about the cost

and availability o ossil uels in an era o growing worldwide demandall o theseare power ul reasons to look or alterna-tives. And never be ore have so many goodalternatives been available.

Solar energy has the potential to dra-matically reduce our use o ossil uels in virtually every area o our economy. It isclean, sa e, 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 trans orm our en-ergy system rom one based on ossil uelsand centralization to one that e fciently reaps solar energy at the places where thatenergy is used. Realizing a solar uture

or America will require new habits o thinking, new policy tools, and, most o all, a roadmap o where we are headed.

The immense in rastructure that bringsossil uels to our homes is a potential

obstacle to that trans ormation, but it isalso an inspiration. I America and the world 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 by adopting smart public policies that cantrans orm 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 ensureour 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 Future The vast majority o the energy Americauses each year, 84 percent o it, comes

rom ossil uels.1 Coal, oil and natural gasare inherently limited resources, requiringtremendous e ort 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 by our 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 o coal contributes to the ormation o acidrain and contaminates our waterways withmercury, a neurotoxin that makes fsh inmany waterways unsa e to eat.

The toll o ossil uel extraction onour environment is widespread and severe rom oil spills o our coast to the

ragmenting o natural habitat or naturalgas drilling. Coal mining in the 19th and20th 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 ree s 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 warmingsharm ul e ects have already outpaced thescientists worst predictions.8 Worse yet,scientists report that we are approachingtipping points at which the e ects o global warming will accelerate, and e ortsat 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 o the 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 ossil

uels.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 by mid-century. The United States, as the worlds second-largest emitter o global warming pollution, and the country re-sponsible or more o the global warmingpollutants in the atmosphere than any other, must go arther and aster than the world as a whole.

Achieving these emission reductions will require us to use every resource avail-able to us to decrease our use o ossil

uels. While energy e fciency will likely account or the frst major steps we taketowards averting a climate crisis, we willalso need to replace existing dirty energy sources 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 advantage 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.

Li e-cycle analyses o solar photovoltaic(PV) systems show that they dramatically reduce emissions o global warming pollut-ants and smog- and soot- orming pollut-ants compared with ossil uels, even whenthe emissions created in the manu acturing

The decision to install solar PV yields 26 to 27 years of truefossil fuel-free electricity.

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

According to the U.S. Department o Energy, the energy payback time or aPV systemthe amount o time it takesto save as much energy as was used to pro-duce the systemranges rom three to

our years and is decreasing over time. As-suming a system li etime 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 many ways 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 roo tops, or, lessrequently, mirrors spread out across the

desert. While these technologies are im-portant, they represent only part o thepotential or solar energy to trans orm 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 heatin which 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 PV are crystalline silicon PVthe traditional,sel -contained PV panels most Americans

envision when considering solar powerand thin flms, inexpensive sheets o material that can be used in panels or bespread across roo s and other architectural

eatures. Crystalline silicon PV panels arerequently more expensive, but are more

e fcient at converting sunlight into elec-tricity, and can be mounted on a roo orcan stand alone on top o a pole or piece o machinery. Thin flms, while less e fcient,cost less and require less silicon to pro-duce. They can also be integrated unob-trusively into buildingsrolled out acrossroo tops 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.16 PV is also modular, so installations can bescaled to the appropriate size or a givenuse.17 PVs scalability allows it to be used

or both large-scale power plants and topower 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


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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 inter ering with human activities. As a result, thereis no additional land required or siting adistributed PV system. PV systems, un-like steam generators, do not use water

or anything other than routine cleaningo the panels, making them a good ft orareas with low water availability. And PV systems generate the greatest amount o electricity 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 PV capacity increased by a actor o more than10, rom 100 megawatts (MW) to 1,173 MW. 18 (See Figure 1.) But the potential

or PV systems ar outstrips the numberinstalled today. Americas residential andcommercial roo tops, or example, couldhost as much as 712 gigawatts o solarpanels (roughly 700 times the capacity o all solar installations today) i every incho suitable roo top were to be covered,enough to produce roughly a quarter o Americas 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 Power Whereas 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 macommunity 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. Thesesystems are particularly suitable or largepower stations, but can also be deployed

or 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 ossil

uel generators.21 CSP plants in Cali ornia

have been reliably producing power ordecades, while at least six new plants havecome on line since 2006.22

Concentrating solar can also be usedon 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 trans er uid) is piped to the roo o a building, where it is heated by travelingthrough sunlight-absorbing pipes. Because

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Figure 1. Installed Photovoltaic Capacity, United States 20



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capturing heat rom sunlight is simple ande fcient, solar water heating systems canabsorb as much as 87 percent o the energy radiated at a given section o roo .23 Solar water 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 typically used to heat swimming pools.24 A slightly more expensive collector can heat waterto temperatures suitable or a home hot water 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 water

or commercial or industrial use. Solar water heating systems should have a conventional uel backup to provide heat on

Solar power towers such as this one in Cali ornia use arrays o mirrors to ocus sunlight 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 become widely 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-20 th 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 ore ront o architectural thought.

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

light into living and work spaces duringthe day, without causing excessive glareor heat trans er through windows.Lighting designers can use windows,skylights, re ective sur aces, and exterior

eatures that direct or di use light toilluminate rooms and decrease the need

or artifcial lighting.28 A well daylit space will have com ortable levels o light in alldi erent 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 sunlight when 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 o electricity 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, whilekeeping it out when it is not. South- acing windows that admit winter sunlight (usu-ally positioned so as to be shaded duringthe summer), skylights, and air circulation

eatures 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.33 In 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 heatcaptured just 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 e ective 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 buildihot water needs.Credit: VELUX/ESTIF



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Solar energy can be integrated into vir-tually every part o American li ethehomes we live in, the o fces where we work, the arms and actories that pro-duce the products we buy, and the schools where our children learn. With creativity and sound public policy, solar energy canmake a major contribution to Americasenergy uture.

Solar Homes There 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 ullpotential 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 installation jobs 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 o solar 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. Thought ul buildingorientation and the proper use o shadingelementssuch 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 energy consumption 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 com ort 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 electricity or 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 by 2015, 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 work orce. Cali ornia, 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 generally been happy with their purchase. A 2006survey o Cali ornia solar home owners

ound that 92 percent would recommendthe purchase o a solar home to a riend.42 Builders o solar homes also beneft be-cause solar homes sell aster than conventional homes.43 When combined withadvanced energy e fciency 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 task

orce, or example, concluded that the en-

ergy savings o a zero-energy home in thatcold-weather state more than compensateor the additional up ront cost. In act, in-

corporating passive solar eatures can ac-tually reducesome o the costs associated with building a new home by allowing orthe installation o smaller, less expensive

Figure 2. Elements of a Passive Solar Home 38



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heating and air conditioning systems.45Some building design experts are con-

templating Energy-Plus building de-signs that make homes net energy produc-ers. These homes are built using extremely airtight 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 Homes Existing 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 e ectiveon at or lightly-sloped roo s 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 decreasethe amount o natural gas or electricity required or water heating by 50 to 80percent.48 A National Renewable Energy Laboratory study estimated that 50 per-cent o residential buildings nationwidecould use solar water heating systems.49 As with solar photovoltaic panels, solar waterheating systemsin which a roo top col-lector is used to pre-heat water or house-hold usecan be installed in any climate,although di erent types o systems work better in di erent parts o the country.Solar water heating systems are smaller,technologically simpler, less expensive,and more e fcient at capturing the energy at sunlight than solar PV panels. Installinga solar water heater in an existing home

Solar homessuch as those in this Cali ornia 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 de ray some o the cost o in-stalling solar water heaters.

Solar Businesses Americas commercial buildingsitsbig-box stores, strip malls, hotels, o fcebuildings, 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 growingnumber o frms nationwide are comingto recognize that adopting solar energy makes good business sense, as well as goodenvironmental sense.

What a Solar Business Looks Like Americas commercial sector is extraor-dinarily diverse, with businesses o many types ranging in size rom mom-and-popstores to giant o fce complexes. Di er-ent kinds o commercial buildings present

di erent 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 described

or homes in o setting that need with so-lar energy.

Big box stores are single-story build-ings and use a great deal o electricity

or 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 PV systems 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 o energy on lighting, and can beneft

rom incorporating passive solarlighting eatures. Temperature-con-trolled warehouses can save energy by incorporating appropriate passivesolar heating or cooling eatures.54

Laundromats use a great deal o energy 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 o hot water every day a ter natural gasprices spiked in 2001.55 Other kindso businesses and institutions withlarge laundry acilities, such as pris-ons and hotels, can use solar energy in 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 gas

or water heating at the acility by more 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

o set 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 o which incorporate passive or active solarenergy systems), or example, ound thatthere was no signifcant di erence in thecost o building green versus non-greenbuildings.58 A similar analysis o buildingsmeeting the Leadership in Energy andEnvironmental Design (LEED) standards

ound 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 have

at roo s, meaning that many o them canplay host to properly oriented photovoltaicpanels or solar water heating systems. A report or the National Renewable Energy Laboratory estimated that 60-65 percent o commercial roo space nationwide wouldbe suitable or PV panel installation.60

Many businesses have larger roo s, anduse more energy, than residential energy customers. 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 systems with 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-e fciency heat collectors o ten used or commercialsolar heating applications, meanwhile, canbe installed in large numbers and coupled with mirrors to enhance their e ective-ness. These measures can reduce the per-square- oot cost o these high-e fciency collectors to 50 percent or more below the

average cost o residential units.62One potential barrier is that commer-cial establishments are disproportionately likely to rent their buildings, creatingpotential split incentive problems, in which builders bear the cost o installingsolar energy systems but tenants reap the

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

Solar FactoriesHistorically, manu acturing acilities havebeen thought o as environmental pollut-ers, not potential contributors to a green

uture. But Americas manu acturing sec-tor has a great deal to gain rom a transi-tion to cleaner sources o energy.

Manu acturing 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 o environmental concern. American manu-

acturers ace the challenge o internationalcompetitionreducing energy costs is just

Workers install solar panels on the roo o the supervisors o fce at Wayne Forest in Ohio. Many o fce 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 manu actur-ing sector, but it can make an importantcontribution to meeting the energy needso many o Americas actories.

What a Solar Factory Looks Like Americas manu acturers use energy or a wide 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 alleviate energy demand in several o theseareas.

The creation o process heat usesmore energy in Americas manu acturingsector than any other single activity.64 Melting 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 a

ood 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 economically using 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 use ul orprocesses occurring at less than 250 C.66 In certain key industriessuch as ood,textiles, and paper60 percent or more o process 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 currently in 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 average American homes.71

The industries with the most existingsolar process heat plants are ood, chemi-cals, transport and textiles.72 The kinds o solar heat collectors used can vary with thetemperatures needed, and with the scale o the application. Roo top 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 electricity through the use o photovoltaic/thermalcollector arrays, which capture the wasteheat generated by sunlight striking photovoltaic panels.73

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

try. The Steinway & Sons piano actory in New York City, or example, recently installed the worlds largest solar coolingsystem. During the summer, the systemcools and dehumidifes the actory, preventing moisture rom a ecting 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 roo s and be exposedto sunlight. Installing photovoltaics on

actories 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 manu acturingsector 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 o work 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 ossil

uel prices or energy-intensive industries. The vast amount o energy used in indus-

try means that the potential or energy savings and emission reductions is large. A study 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 per ect ft or many industries that rely on hot waterindustrial acilities are hun-

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

However, industrial acilities, like otherbusinesses, are o ten 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 projectsdelivered 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 o key processes. Resolving those issues re-quires the existence o experts trained inintegrating solar energy into industrialprocesses. Un ortunately, the solar processheat industry in the United States is rela-tively undeveloped. The European Unionis working aggressively to develop markets

or 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 many tasks that were once carried out using so-lar energysuch as crop dryingbeingshi ted to ossil uels.

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

P-R Farms in Cali ornias San Joaquin Valley uses the electricity created rom a photovoltaic system to power its storage 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 o solar energy makes it uniquely suitableto provide electric power and heat on

arms and ranches around the country.Farms and ranches may need electricity

or pumps and ences and on-site pro-cessing operations, space heating orbarns and greenhouses, and hot water

or 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 re ueling, andno connection to a grid, can provide asimple and economical solution.

What a Solar Farm Looks LikeSolar energy is already commonly used on

arms or remote applications. Photovol-taic panels, or instance, are o ten 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 they o ten replace ine fcient 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 per ormed by heat rom ossil

uels. 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 passivesolar greenhouses are oriented to capturemore direct sunlight rom the south, anduse thermal mass and insulation to storeheat rom the day through the night.83 In warmer climates, crop drying can be per-

ormed in sheds with glazed south- acing walls that admit heat, requiring no activeheating system.84

Active solar heating is most use ul onarms or heating barns. Barns contain a

large volume o air, and also need more ventilation than many large buildings,because o the dust and livestock emis-sions that quickly build up in them.85 Solar 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-e ective or this purpose when 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 o energy 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 the

arms total energy use.87 A solar waterheater can replace hal the ossil uel used

or 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 o early 2009, more than 50 Cali ornia win-eries had installed solar panels, with doz-ens more planning to ollow suit, takingadvantage o Cali ornias abundant sun-light to help power their operations. 89



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Solar in Transportation The 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 solar vehicle, so long as it is capable o beingpowered by electricity, and that electricity comes 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. Shi ting more o Americas trans-portation system to operate on electricity would enable the nation to use a wider

variety o uels, including solar power andother orms o renewable energy. Americas transportation system also

represents a power ul, i less obvious, seto opportunities or the utilization o solarpower. The nations transportation systemtakes up a tremendous amount o land. According to one estimate, approximately 43,000 square miles o land in the UnitedStatesan area roughly the size o Ohiois covered by impervious sur aces, most o

them roads and parking lots.90 Most o this area is unshaded and has little currentuse other than or storing or transportingcars, meaning that it could easily be used

or generating solar energy.Finally, the hundreds o millions o

cars on Americas roads could someday help expand the use o renewable energy sources 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 LikeSmall 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 only a tiny portion o the energy used in power-ing the nations transportation system, the vast majority o which goes toward moving vehicles. The introduction o plug-in vehicleselectric vehicles and plug-in hy-bridscould enable solar power to make ameaning ul 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 electricity drawn rom the grid. In a plug-in hybrid,grid electricity augments energy rom a

ossil 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 used to charge plug-in vehicles.Credit: Kevin Dooley, reprinted underCreative Commons license.



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vehicle is powered entirely by electricity drawn rom the battery.

Plug-in vehicles are currently a rarity inthe United States, but that could change within 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 early 2010 with a ull release in 2011.92 Severalother automakers are exploring plug-intechnologies, including the potential or

ully 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 e fcient 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-in vehicles 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 stillo ten inexposed parking lots at a place o work. So-lar powered charging stations in parkinglots would enable drivers to charge their vehicles during the day, while also providing 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 o charging 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 Bu er 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 by electricity. Subway and light rail systems,along with many commuter rail lines andsome intercity train lines, are powered by electricity. The recent expansion o lightrail systems in cities such as Los Angeles,

Salt Lake City, Phoenix and Denver prom-ises to shi t 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 electricity that 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 energy and 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 A major 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 a air, 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 hot water systems, the greater the base o ex-pertise that can develop among the many individuals 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 densely packed urban areas or build expensivetransmission lines to bring in power romelsewheresaving money or ratepayersas a whole.



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

Solar District Heating A 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 le t overa ter 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, roo top 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 Friedrichsha en,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 o home 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 supply 90 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 Systems Two o the biggest hurdles to the installa-

tion o household solar power systems arethe up ront cost o the system and the lack o an appropriate roo top. Homeowners who 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 o ers 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 recently launched 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 in which groups o 10 or more individuals ina single town can share in the benefts o asolar power installation.111

Solar in Community Buildings Community 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, there ore, providean excellent opportunity to take advantage

o daylighting, reducing electricity needsand creating a more pleasant learning environment. Most schools also have largeamounts o available roo space, and coulduse roo top solar collectors or much o their heating needs.

Other community institutions presentsimilar opportunities:

Churches and other large community spaces use as much as 60 percent o their energy or heat.113 Solar heat

collectors could provide much o thisenergy, particularly during daytimeservices. Church o fce buildings

requently have large, at roo s.

Libraries, museums, and other publicbuildings use signifcant amounts



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o energy on heat and lighting, ando ten have large at roo s available

or PV panels or solar heat collectors.Skylights and other passive design

eatures 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 easily host solar panels to help meet the

acilities 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 li etime beneft o any so-lar project. Additionally, schools, librar-ies, and government o fce buildings areowned and operated by the same localgovernments that are o ten responsible

or extending credit and incentives to ho-meowners or solar projects. By taking advantage 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 Communities When many homeowners and institutionsin a community go solar, the benefts areo ten 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, thise ect islocal , 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 o homeowners and businesses.

Installing large amounts o solar powerin an area can also reduce peak demandor electricity in areas where the grid is

strainedreducing the need to constructexpensive new power plants or transmis-sion lines. Because solar photovoltaicsgenerate the most electricity at precisely the 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 o set4 to 7 MW o conventional peak genera-tion, meaning that care ully 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: WhiteHouse, Pete Souza



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

solar technologies are distributed they are implemented at or near the places where 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 e fcient, 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 alsoplay 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 acilitiessuchas 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 Cali ornia, have the potential to generlarge amounts o power in sunny areas o the Southwest and elsewhere.Credit: Gregory Kolb, Sandia NationalLaboratory



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millions o homes and businesses. To keepthe grid running reliably, generators mustbe turned o and on to ensure a per ectbalance between the supply and demandat every second o the day.

The spread o solar photovoltaic power,however, will make the job o keeping thegrid in balance more complicated. Insteado homes and businesses being electricity consumers, many will also be electricity producers, eeding power into the grid. Inaddition, solar energy is variable in waysthat are both predictable (night versusday) and unpredictable (the passing o astray cloud).

America has a long way to go be oresolar energy begins to have a meaning ulimpact on the grid. The nation candramatically expand the amount o solarpower in todays grid without reliability problems, and an even greater raction canbe provided i thought ul steps are taken

to integrate solar energy into the existinggrid.122 But maximizing the share o ourelectricity that comes rom solar power will likely require changes in the way weproduce and deliver electricityas wellas investments in a well-designed smartgrid. With creativity and investment,experts suggest that as much as 20 to 30percent o our electricity could someday come rom photovoltaicsgreatly expanding the ability o solar energy toaddress the nations energy needs.123

A well-designed smart grid is onethat is much more sophisticated in manag-ing electricity supply and demand than thecurrent grid. It might include:

Smart invertersTechnology to en-able utilities to control the ow o power rom solar PV invertersthedevices that trans orm DC power

rom solar panels to the AC power

Plug-in vehicles, such as these plug-in hybrids, can contribute to stabilizing the grid by providing electricity storcapacity. Energy storage is a key technology that can enable renewable sources o energy such as solar energy ta larger role in Americas energy uture.Credit: Argonne National Laboratory



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used in the grid and in homes. Utili-ties could use these smart invertersto manage the ow o solar electricity into the grid to maximize grid stability.

Smart controlsHomeowners coulduse smart controls to make the maxi-mum use o solar electricity or ex-ample, by heating hot water, runningspace heating or cooling equipment,or (someday) charging plug-in ve-hicles at times when solar panels areproducing the maximum amount o electricity instead o , or example, theevening hours when solar panels donot produce electricity but demand

or power remains high.

Smart energy storage, including theinstallation and remote control o

batteries to provide quick backuppower during cloud passages and tostore excess solar power producedduring peak periods. There are many possible ways to incorporate energy storage into the grid, including theinstallation o batteries at variouspoints in the grid and the use o bat-teries in plug-in vehicles.124

These investments in smart grid tech-nologies have the potential to deliver largereturns. A recent study by Navigant Con-sulting ound that investment in a PV Smart Grid would deliver positive eco-nomic benefts, while improving the eco-nomics o investments in PV and dramati-cally increasing the amount o solar powerthat can be integrated into the grid. 125



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Americas potential or solar energy development is virtually limitless.Solar energy can meet a wide variety o energy needs, it is available everywherein the United States, and the prices o key solar technologies are decliningin somecases, rapidly.

The nation should set a course tomaximize our use o solar energy, putting America on a path toward an energy sys-tem that relies primarily on clean, renew-able sources o energy. A good place tostart would be to ensure that at least 10percent o all the energy used in Americain 2030and pre erably morecomes

rom the sun. (See Energy vs. Electricity: What Does the 10 Percent Target Mean?page 38.)

Americas Solar Potential The nations potential or solar energy dwar s our current consumption o ener-gy, as well as projected energy use in the

uture.

Distributed solar PV A 2004 study by Navigant Consulting estimated thetechnical capacity or PV

building a solar future

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