In his new Book Plan B 3.0: Mobilizing to Save Civilization author Lester R. Brown writes on solar cells and collectors. Several technologies are now used to harness the sun’s energy, including both solar thermal collectors and solar photovoltaic cells. Solar thermal collectors, widely used to heat water, are now also used for space heating. Collectors, which concentrate sunlight to boil water and produce steam-generated electricity, and assemblages of solar electric cells are both used on a commercial power plant scale, with individual plants capable of supplying thousands of homes with electricity. Perhaps the most exciting recent development in the world solar economy is the installation of some 40 million rooftop solar water heaters in China. With 2,000 Chinese companies manufacturing rooftop solar water heaters, this relatively simple low-cost technology is not only widely used in cities, it has also leapfrogged into villages that do not yet have electricity. For as little as $200, villagers can have a rooftop solar collector installed and take their first hot shower. This technology is sweeping China like wildfire, already approaching market saturation in some communities. Even more exciting, Beijing plans to more than double the current 124 million square meters of rooftop solar collectors for heating water to 300 million by 2020.
The energy harnessed by these installations in China is equal to the electricity generated by 54 coal-fired power plants. Other developing countries such as India and Brazil may also soon see millions of households turning to this inexpensive water heating technology. This leapfrogging into rural areas without an electricity grid is similar to the way cell phones bypassed the traditional fixed-line grid, providing services to millions of people who would still be on waiting lists if they had relied on traditional phone lines. The great attraction of rooftop solar water heaters is that once the initial installment cost is paid, the hot water is essentially free.
In Europe, where energy costs are relatively high, rooftop solar water heaters are also spreading fast. In Austria, Europe’s leader, 15 percent of all households now rely on them for hot water. And, as in China, in some Austrian villages nearly all homes have rooftop collectors. Germany is also forging ahead. Janet Sawin of Worldwatch Institute notes that some 2 million Germans are now living in homes where water and space are both heated by rooftop solar systems. Inspired by the rapid adoption of rooftop water and space heaters in Europe in recent years, the European Solar Thermal Industry Federation (ESTIF) has established an ambitious goal of 500 million square meters, or one square meter of rooftop collector for every European by 2020, a goal that exceeds the 0.74 square meters per person today in Israel, the world leader. Most installations are projected to be Solar-Combi systems that are engineered to heat both water and space. In 2007, Europe’s solar collectors were concentrated in Germany, Austria, and Greece, with France and Spain also beginning to mobilize. Spain’s initiative was boosted by a March 2006 mandate requiring installation of collectors on all new or renovated buildings. ESTIF estimates that the European Union has a long-term potential of developing 1,200 thermal gigawatts of solar water and space heating, which means that the sun could meet most of Europe’s low-temperature heating needs.
The U.S. rooftop solar water heating industry has thus far concentrated on a niche market—selling and marketing 10 million square meters of water heaters for swimming pools between 1995 and 2005. Given this base, however, the industry is poised to mass-market residential solar water and space heating systems. We now have the data to make some global projections. With China setting a goal of 300 million square meters of solar water heating capacity by 2020, and ESTIF’s goal of 500 million square meters by 2020, a U.S. installation of 200 million square meters by 2020 is certainly within reach given the recently adopted tax incentives. Japan, which now has 11 million square meters of rooftop solar collectors heating water but which imports almost all its fossil fuels, could easily reach 80 million square meters by 2020. If China, the United States, Japan, and the European Union achieve their goals, they will have a combined total of 1,080 million square meters of water and space heating capacity by 2020. This would come to 0.45 square meters per person for the 2.4 billion people in these countries, still well below Israel’s figure today.
If the developing world’s 5 billion people in 2020 have 0.1 square meter of rooftop water heating capacity per person by 2020, roughly the same as in China or Turkey today, this would add 500 million square meters to the world total, pushing it over 1.5 billion square meters. If we assume that each meter provides 0.7 thermal kilowatts of power, then we are looking at a world solar thermal capacity by 2020 of 1,100 thermal gigawatts, the equivalent of 690 coal-fired power plants.
The huge projected expansion in solar water and space heating in industrial countries could close some existing coal-fired power plants and reduce natural gas use, as solar water heaters replace electric and gas water heaters. In countries such as China and India, however, solar water heaters will simply reduce the need for new coal-fired power plants.
Read more online. The book “Plan B 3.0: Mobilizing to Save Civilization” is published by W.W. Norton and Company, Earth Policy Institute, 2008.
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