19th-century solar panels were made of selenium. Today, photovoltaic (PV) panels use thin wafers of silicon crystal. As photons strike them, they knock electrons loose and produce an electrical circuit. These subatomic particles are the only moving parts in a solar panel, which requires no fuel and produces clean energy.
Small-scale solar systems, typically sited on rooftops, accounted for roughly 30 percent of PV capacity installed worldwide in 2015. In Germany, a leader in solar, rooftops boast 1.5 million systems. In Bangladesh, population 157 million, more than 3.6 million home solar systems have been installed.
Rooftop solar is spreading as the cost of panels falls, driven by incentives to accelerate growth, economies of scale in manufacturing, and advances in PV technology. Innovative end-user financing, such as third-party ownership arrangements, have helped mainstream its use. Yet, costs associated with acquisition and installation can be half the cost of a rooftop system and have not seen the same dip.
In grid-connected areas, rooftop panels can put electricity production in the hands of households. In rural parts of low-income countries, they can leapfrog the need for large-scale, centralized power grids, and accelerate access to affordable, clean electricity—becoming a powerful tool for eliminating poverty.
Charles Fritts…“photoelectric” modules: Perlin, John. Let It Shine: The 6,000-Year Story of Solar Energy. Novato, California: New World Library, 2013.
first [coal] plant…Thomas Edison: Schobert, Harold H. Energy and Society: An Introduction. Hoboken: CRC Press, 2014.
a billion people [without electricity]: IEA and World Bank. Sustainable Energy for All 2015—Progress Toward Sustainable Energy. Washington, D.C.: The World Bank, 2015.
sun’s light [vs.] world’s total [energy] use: NOAA. “Energy on a Sphere.” http://sos.noaa.gov/Datasets/dataset.php?id=579.
photovoltaics…2 percent of…electricity: IRENA. Letting in the Light: How Solar PV Will Revolutionize the Electricity System. Abu Dhabi: International Renewable Energy Agency, 2016; IEA. Technology Roadmap: Solar Photovoltaic Energy. Paris: International Energy Agency, 2014.
distributed systems…percent of [total]: IHS Technology. Top Solar Power Industry Trends in 2015. London, 2015.
Germany…1.5 million systems: IRENA, Solar PV.
Bangladesh…3.6 million home solar systems: IEA and World Bank, Sustainable; IRENA, Solar PV.
16 percent of Australian homes: REN21. Renewables 2016 Global Status Report. Paris: REN21 Secretariat, 2016.
manufacturing boom in China…inexpensive panels: Goodrich, Alan C., Douglas M. Powell, Ted L. James, Michael Woodhouse, and Tonio Buonassisi. “Assessing the Drivers of Regional Trends in Solar Photovoltaic Manufacturing.” Energy & Environmental Science 6, no. 10 (2013): 2811-2821; Fialka, John. “Why China Is Dominating the Solar Industry.” Scientific American. December 19, 2016.
soft costs of…a rooftop system: Ardani, Kristen, Galen Barbose, Robert Margolis, Ryan Wiser, David Feldman, and Sean Ong. Benchmarking Non-Hardware Balance of System (Soft) Costs for US Photovoltaic Systems Using a Data-Driven Analysis from PV Installer Survey Results. Golden, CO: National Renewable Energy Laboratory, 2012.
cheap[er] than…the grid in some [places]: IRENA, Solar PV; REN21, Renewables 2016.
financial benefit of rooftop PV: Hallock, Lindsey, and Rob Sargent. Shining Rewards: The Value of Rooftop Solar Power for Consumers and Society. Washington, D.C.: Environment America, 2015: Muro, Mark, and Devashree Saha. Rooftop Solar: Net Metering Is a Net Benefit, Washington, D.C.: Brookings Institution, 2016.
investment in distributed solar: REN21, Renewables 2016.
Bangladesh…115,000 direct jobs: IRENA, Solar PV.