Solar energy is very efficient and, like wind power, it produces no greenhouse gases. You can capture solar energy, even on cloudy days. And it's the most abundant type of energy available — far beyond civilization's needs. In fact, the World Energy Council reports that the amount of solar energy that reaches the earth is over 7,500 times that of civilization's current energy demand! Even if society only captured 0.1 percent of the sun's energy, and used it with just 10 percent efficiency, it could still meet its current energy demand four times over.
The downside, which many renewable energy sources share, is the high upfront cost of setting up new technologies to capture that energy. Presently, solar electricity generation is the most expensive form of renewable generation (while solar thermal energy for producing hot water is one of the cheapest). Oil and coal offer far cheaper alternatives, but at a great environmental cost. Meanwhile, fossil fuel prices are going up, while solar costs are dropping.
People can harness solar energy in three ways, each of which we investigate in the following sections.
When people think of solar power, they probably think of photovoltaic power sources, which use solar cells to convert sunlight into electricity (photo means light, and voltaic means voltage). You can use these solar cells on their own — to power things such as calculators, satellites, or flashing electric construction signs — or as a part of a power grid, in which they contribute to an area's energy source.
One of the most common ways to use this type of solar energy is on roofs — using solar panels, solar shingles, solar tiles, or even solar glazing on skylight windows. You can have them designed for any size building with varying energy needs. When Bill Clinton was president of the U.S., he set a goal of a "Million Solar Roofs." This effort helped the photovoltaic industry get off the ground in that country.
The one drawback to photovoltaic power sources is that the typical solar cell is relatively inefficient. For it to work at its best, it generally needs direct sunlight — though it does still work on cloudy days. Fortunately, solar energy developers are continually working to improve this efficiency.
While the use of photovoltaic power spreads, the price comes down. Japan, Germany, and the U.S. lead the world in widespread solar cell use. Some solar companies are now boasting that their sun-made electricity can cost-compete with coal.
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