New photovoltaics change solar costs
First Sol ar, with permission from Beck Energy
Jose, Calif. The up-to-date processing data makes the work unique, she says. And the use of the same New photovoltaic technologies, make single-crystal, multicrystal, assumptions across the board, resuch as the recent introduction and ribbon silicon solar cells, all of garding yearly available sunlight, of thin-film cadmium–telluride which have different efficiencies in performance, and energy grids, (CdTe) materials, have nearly douconverting sunlight into electricity. means “you can easily compare” bled the efficiency of solar cells They also compared these prodall of the technologies. within the past few years. But the ucts with the thin-film CdTe phoBut the origin of the electricmethods of making the materials tovoltaic systems manufactured by ity used to manufacture solar cells used for photovoltaic cells, whethfast-growing Arizona-based First varies from place to place, Reicher from silicon, metal, or other Solar. Weiser points out. The current materials, have raised assessment, based on doubts about the enviidealized European and ronmental friendliness U.S. grids, “is not telling of these passive energy you exactly what your collectors. Purifying and impact is.” For example, producing silicon uses a impacts from compolot of water and energy, nents manufactured in and refining zinc and China, where the eleccopper ores to get Cd, Te, tricity grid is often powand other elements creered by coal, will differ ates metal emissions and from those produced by an energy sink—all of components made in the which increase the techU.S. or EU. She also notes nology’s environmental that emissions from the footprint. transportation of those A new life-cycle asFields of sunshine: this solar power array in Germany is comcomponents before proposed of thin-film photovoltaic modules. sessment (LCA) of some duction and assembly, of the leading photovolsuch as by rail or truck, taic technologies, published in The analysis took into account are only partly considered. “DeES&T (pp 2168–2174), shows that frames, cables, and other necespending on the amount of goods some may be better than others, sary support materials, based on transported throughout the supply particularly when it comes to their ground-mounted systems under chain, including every transporlifetime emissions. Overall, howevsouthern European light conditation leg may increase estimated er, replacing traditional electricity tions, for over 30 years. It also ingreenhouse gas emissions by 30– grids fueled by gas, coal, and other cluded the energy required for 50%,” she says. means with photovoltaics would manufacturing under three sceKen Zweibel, president of Colocut emissions of greenhouse gases, narios, each with a different prorado-based PrimeStar Solar, notes particulate matter, and other polportion of electricity coming from that even if China were to adopt lutants by 89–98%. Rooftop panels coal, natural gas, or other sources. photovoltaics wholesale, produced could further reduce emissions beIn the end, the CdTe photovolentirely with coal-powered eleccause of the resulting decrease in taics came out on top. With more tricity, new solar materials would transmission lines and other infraefficient energy conversion and the allow products with 30-year lifestructure. But each form of photolowest cost, the technology used times to make up for those emisvoltaics has a different LCA profile, less energy and had fewer emissions in several years. “The field is specific to heavy-metal emissions sions overall, despite some Cd changing fast,” adds Zweibel, who and electricity use in particular, emissions during the manufacturrecently coauthored a “solar grand the new analysis shows. ing process. However, emissions plan” with Fthenakis in Scientific Led by Vasilis Fthenakis of from fossil-fuel-powered electricity American (2008, 1, 64–73). Brookhaven National Laboratory dwarfed those Cd emissions by orMissing from the analysis, says and Columbia University, the LCA ders of magnitude. Fthenakis, are end-of-life and reincludes information from dataThe new assessment is “incycling data. “Those studies are bases of more than a dozen accredibly useful,” says Corinne not yet completed,” but “it’s a safe tive solar companies and provides Reich-Weiser, a graduate student assumption . . . that recycling will a complex snapshot of the state in mechanical engineering at the make the emissions profile better, of the solar industry up to 2006. University of California Berke[and] the feasibility of recycling is Fthenakis and co-workers comley who works part-time for sohere.” pared data from companies that lar manufacturer SolFocus in San —NAOMI LUBICK 1816 ■ Environmental Science & Technology / March 15, 2008
