Chapter 10. Stabilizing Climate: Converting Sunlight to Electricity
Wind is not the only vast untapped source of energy. When a team of three scientists at Bell Labs in Princeton, New Jersey, discovered in 1952 that sunlight striking a silicon surface could generate electricity, they opened the door to another near limitless source of energy—photovoltaic (or solar) cells. “No country uses as much energy as is contained in the sunlight that strikes its buildings each day,” writes Denis Hayes, former Director of the U.S. government’s Solar Energy Research Institute. 37
Sales of solar cells worldwide jumped by a phenomenal 57 percent in 2004, pushing the generating capacity installed during the year to 1,200 megawatts. With this addition, world solar-cell generating capacity, which has doubled in the last two years, now exceeds 4,300 megawatts, roughly the equivalent of 13 coal-fired power plants. (See Figure 10–2.) A decade ago the United States had roughly half of the world market, but this has now dropped to 12 percent as Japan and Germany have surged ahead with ambitious solar programs. 38
Solar cells are used either in stand-alone systems or in systems that can feed into the grid. In its early years, the solar cell industry was dominated by non-grid uses to supply electricity to communication satellites and in remote sites such as national forests or parks, offshore lighthouses, summer homes in isolated mountain regions, or islands.
Over the last decade, solar cell installations that feed into the grid have grown rapidly in response to incentives offered by governments, and they now account for more than three fourths of all new installations. Two-way meters that enable utility customers to feed surpluses into the grid for a fixed rate have spurred rapid growth in solar cell use. The U.S. Energy Policy Act of 2005 established two-way metering for any customer requesting it. Some countries have established a fixed price for utilities to pay for electricity fed into the grid. In Germany, this has been set well above the market price to reflect the value of clean electricity and to get the fledgling solar cell industry off the ground. 39
The residential use of solar cells is expanding at a breakneck pace in some countries. In Japan, where companies have commercialized a solar roofing material, the idea of making the roof the power plant for the home is increasingly popular. This, combined with Japan’s 70,000 Roofs Program launched in 1994 to subsidize the installations, got the country off to a fast start, making it a world leader in solar-generated electricity. 40
In 1998, Germany initiated a 100,000 Roofs Program, which gave consumers 10-year loans for buying photovoltaic systems at reduced interest rates. This ended in 2003 when the goal of 100,000 solar roofs was reached. With this fast-growing market, solar cell costs now have fallen to where German manufacturers are quite competitive internationally. 41
Within the United States, California is also providing attractive incentives for the residential installation of solar cells. In a climate where peak capacity on hot summer days presses against the limits of the grid, solar cells are seen as an alternative to fossil fuel plants, mostly gas-fired, that operate only during the peak daytime demand. Happily, solar cells generate the most electricity during the hottest times of the day, making them ideal for satisfying peak power demands. 42
Solar cell installations may be even more economical in large buildings. In Manchester, England, a 40-story office building in need of renovation will be covered with photovoltaic material. With three sides of this 400-foot building covered with this material, the building has a huge generating surface. An official of the building owner and occupant, the Co-operative Insurance Society, noted with a smile that it would produce enough electricity each year to make 9 million cups of tea. 43
In recent years, a vast new off-grid solar cell market has opened up in developing-country villages, where the cost of building a centralized power plant and a grid to deliver relatively small amounts of electricity to individual consumers is prohibitive. With solar cells costs falling, however, it is now often cheaper to provide electricity from solar cell installations than from a centralized source.
In Andean villages, solar installations are replacing candles as a source of lighting. For villagers who are paying for the installation over 30 months, the monthly payment is roughly equal to the cost of a month’s supply of candles. Once the solar cells are paid for, the villagers then have an essentially free source of power—one that can supply electricity for decades. Similarly, in villages in India, where light now comes from kerosene lamps, soaring oil prices mean that kerosene from imported oil may now cost far more than solar cells. 44
Today more than 1 million homes in villages in the developing world are getting their electricity from solar cells, but this represents less than 1 percent of the 1.7 billion people who do not yet have electricity. The principal obstacle to the spread of solar cell installations in villages is not the cost per se, but the lack of small-scale credit programs to finance them. If this credit shortfall is quickly overcome, village purchases of solar cells will soar. 45
The future of solar cells is promising. Japan, for example, where residential installations exceeded 1,000 megawatts at the end of 2004, plans to get 10 percent of its electricity from solar cells by 2030. Germany now has 700 megawatts of installed capacity and is growing fast. The United States, a distant third, introduced a solar tax credit in the Energy Policy Act of 2005. The first such credit in 20 years, it promises to rejuvenate the U.S. solar industry. 46
The cost of solar cells has been dropping for several decades and is expected to continue falling for the indefinite future. With each doubling of cumulative production, the manufacturing economics of scale drop the price an additional 20 percent. In addition, technologies for producing solar cells that convert more sunlight into electricity and do so at a lower cost are being worked on at numerous research facilities in several countries. 47
In addition to generating electricity from solar cells, solar energy can also be concentrated to boil water and produce steam, driving a turbine to generate electricity. There are various designs used in solar-thermal power plants, including power towers, which consist of an elevated facility containing water that is heated by an array of mirrors, and solar troughs. Usually computer-controlled, the mirrors shift their position as the sun moves across the sky to maximize the sunlight focused on the boiler. Some 350 megawatts of generating capacity in California has been operating very successfully since nine solar trough plants were built in the mid-1980s and early 1990s. New initiatives to develop solar thermal power plants are now under way in Spain. 48
One of the most popular ways of harnessing solar energy is the use of rooftop solar thermal collectors for both water and space heating. Janet Sawin of Worldwatch Institute reports that the global installations of 150 million square meters, excluding the one fourth that is used for swimming pools, supplies water or space heating for 32 million households. 49
For years both Israel and Cyprus, countries rich in sunlight, have been encouraging solar water heaters as a way of reducing the need for imported fossil fuels. Germany, which has 5.4 million square meters of solar water heating panels, ranks second in installed capacity. This panel area totals 540 hectares or roughly 1,300 acres. 50
China, far and away the world leader in this technology, is planning to quadruple its current 52 million square meters of collectors by 2015, reports Sawin. Spain, a leading manufacturer of solar thermal panels, is making a bid for industry leadership by requiring the inclusion of rooftop solar water heaters on all new buildings, residential and commercial, beginning in 2005. A two-meter panel on a single-family residence can reduce annual water heating bills by 70 percent. In effect, Spain is substituting its abundant sunlight for imported oil. 51
The technologies for converting sunlight into electricity or using it to heat water and building space are now well developed. And the economics are falling into place. What is needed to accelerate this is a set of incentives in all countries that reflects the value to society of reducing dependence on oil and of reducing carbon emissions.
37. Denis Hayes, “Sunpower,” in Energy Foundation, 2001 Annual Report (San Francisco: February 2002), pp. 10–18.
38. Figure 10–2 shows cumulative solar installations with data compiled from Paul Maycock, “PV News Annual Market Survey Results,” Photovoltaic News, April 2005; Janet L. Sawin, “Solar Energy Markets Booming,” in Worldwatch Institute, Vital Signs 2005 (New York: W.W. Norton & Company, 2005), pp. 36–37; market share from Katharine Mieszkowski, “How George Bush Lost the Sun,” Salon, 25 October 2004; Michael Schmela, “This is a Sharp World,” Photon International, March 2004.
39. William J. Kelly, “German Renewables Law Portends Tight California Market,” California Energy Circuit, 18 May 2004; Office of Energy Efficiency and Renewable Energy (EERE), DOE, “Net Metering, Tax Credits for Solar Energy Included in Energy Act,” EERE Network News, 10 August 2005.
40. European Photovoltaic Industry Association and Greenpeace, Solar Generation (Brussels: September 2001); Paul Maycock, “Japanese PV Residential Dissemination Program Exceeds Goals,” Photovoltaic News, January 2004.
41. Paul Maycock, “German 100,000 Roofs Program Tops 130 MW in 2003,” Photovoltaic News, August 2004.
42. Kelly, op. cit. note 39.
43. “Manchester’s Tallest Building Gets Europe’s Largest Solar Array,” Environment News Service, 9 November 2004.
44. “Power to the Poor,” The Economist, 10 February 2001, pp. 21–23.
45. Bernie Fischlowitz-Roberts, “Sales of Solar Cells Take Off,” Eco-Economy Update (Washington, DC: Earth Policy Institute, 11 June 2002); population without electricity in World Summit on Sustainable Development, Department of Public Information, Press Conference on Global Sustainable Energy Network (Johannesburg: 1 September 2002).
46. Paul Maycock, “Japanese Issue ‘Roadmap to 2030,’” Photovoltaic News, December 2004, p. 1, and Mantik Kusjanto and Anneli Palmen, “Germany’s Solar World Seeks Place in the Sun,” Reuters, 13 January 2005, cited in Sawin, op. cit. note 38; EERE, op. cit. note 39.
47. Robert H. Williams, “Facilitating Widespread Deployment of Wind and Photovoltaic Technologies,” in Energy Foundation, 2001 Annual Report (San Francisco: February 2002), pp. 19–30.
48. Scott Sklar, “Sleepers That Are Coming to Light,” Earthscan, 7 February 2005; EERE, “Spain to Build an 11-Megawatt Solar Power Tower,” EERE Network News, 24 August 2005.
49. Sawin, op. cit. note 38.
50. Li Hua, “From Quantity to Quality: How China’s Maturing Solar Thermal Industry Will Need to Face Up to Market Challenges,” Renewable Energy World, January-February 2005, pp. 56–57, cited in Sawin, op. cit. note 38; Germany from David Sharrock, “Spain Makes Solar Panels Mandatory in New Buildings,” Times Online (U.K.), 9 November 2004.
51. Sawin, op. cit. note 38; Sharrock, op. cit. note 50.
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