Distributed solar produces electricity outside the grid and has become one of the more polarizing topics in the power industry. Solar is here to stay in the U.S. Although the sun’s rays have been a clean energy solution since photovoltaic panels arrived in 1979, solar remains barely a blip in the U.S. power market. In 2012, solar power provided a mere 0.11 percent of U.S. electricity generation. By comparison, coal delivered 37 percent, natural gas 30 percent, nuclear 19 percent, and wind 3.5 percent. And that percentage includes utility-scale projects, like the big solar farms in California and Nevada that feed into the electricity grid, as well as distributed solar. Until recently, utilities could ignore solar.
Distributed solar could disrupt the de facto monopoly long held by regulated utilities. The solar industry is growing fast, and much of the growth is distributed solar built “behind the meter” – that is, on commercial and residential rooftops, where electricity from solar panels eliminates the need for power that would otherwise be generated and sold by the utilities. Last year, nearly 90,000 businesses and homeowners installed rooftop solar projects totaling about 1.15 gigawatts, roughly the amount generated by a large coal plant. That represented a 46 percent growth over 2011, according to the Solar Electric Power Association. By the end of last year, the number of customer-sited photovoltaic systems in the U.S. topped 300,000, the association says.
Large solar power projects account for more than 4,700 megawatts of electricity-generating capacity in the United States. Another 27,000 megawatts of large-scale solar are under development, which means that the industrial-solar sector is on its way to providing enough electricity for more than 5 million homes. The Department of Energy's SunShot initiative project that costs will continue to drop dramatically and 329,000 megawatts of solar power are fed into the power grid by 2030, representing 13.8 percent of total electricity demand in the U.S. Of that, the Department of Energy estimates, 209,000 megawatts, or almost two-thirds, could be utility-scale solar if prices for solar technology continue to fall. "Ultimately the real beauty of solar is that every building, every car park is covered," says Dan Kammen, a professor of energy at the University of California, Berkeley. "In the decades ahead, we'll go to more and more distributed but, I think we will see more of these bigger facilities still being installed."
Emerging technologies will enable the production of photovoltaic solar shingles made from available elements rather than rare-earth metals, an innovation that would make solar panels cheaper. A team of researchers described advances in solar cells made with the metals copper and zinc. Solar shingles that convert the sun’s energy into electricity typically must use elements that are scarce and expensive, such as indium and gallium. Recent tests suggest that materials like zinc phosphide and copper oxide could be capable of producing electricity at competitive prices within two decades. Companies are racing to find new sources of rare earth minerals, which are used in everything from solar panels to smart phones. Improved technology also can help capture heat energy not used by photovoltaic cells that only utilize part of the light spectrum while the rest escapes as heat. Harnessing waste heat adds to the harvested energy from the sun. Reprocessing waste heat can be used to generate electricity. Such savings would be especially significant at large solar power farms, where the dissipation of heat is an enormous waste of energy.
