Solar energy can be grouped into two categories: active and passive. Passive solar energy simply collects the energy of the sun. Solariums, houses with extra thermal mass, solar ovens and solar space heaters are all examples of passive solar technology. Active solar takes the energy of the sun and converts it into electricity or mechanical power. These include photovoltaic electric systems, concentrating solar power, systems that store energy or use mechanical means to apply energy to an application. Active solar energy has at least three strong advantages over other forms of power generation.
Solar Requires no Fuel but the Sun
Consider a coal-fired power plant. A seam of coal 7 feet thick and an acre in size will produce 14,000 tons of coal, enough to supply electricity to 4,500 American homes. In order for this coal to do its work it must be mined, either from underground mines or strip mines. It must be cleaned and processed to remove impurities. It's loaded onto trains or barges for the trip to the plant. Only then can it be burned to generate steam, which generates electricity.
Now consider the photovoltaic solar cell. Sunlight hits the cell, which generates electricity. Active solar energy, once the solar cell is in place, requires no fuel other than the rays of the sun.
Solar is Self Contained
An active solar system can be completely self contained. Florida State University has been building an experimental off-grid, zero emission building. The purpose of this building is to be a prototype for a completely sustainable home. To power the building they chose photovoltaic solar power cells. These cells allow the building to be completely independent of the power grid–and meet the zero-emission criteria.
Active solar energy is completely self-contained. It can bring clean electricity to remote locations. It can provide electricity during natural disasters when the power grid has gone down. And it can make a house a self-sufficient oasis surrounded by houses that must rely on an external power plant for electricity.
Solar has no Emissions
According to the U.S. Energy Information Administration, in 2008 power plants in the U.S. produced 2,477 million metric tons of carbon dioxide, 7.8 million metric tons of sulfur dioxide and 3.3 million metric tons of nitrogen oxide. Emissions from power plants were responsible for 38,200 nonfatal heart attacks and 554,000 asthma attacks in 2002. Power plants shorten 24,000 lives a year, including 2,800 deaths from lung cancer, reports the administration.
By contrast, the number of deaths from operation of solar power generation plants is zero. Carbon dioxide emissions are zero. Sulfur dioxide and nitrogen oxide emissions are zero and zero. Solar power has no emissions and so is much healthier than conventional power generation methods.
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