We usually think
of solar energy simply as sunlight, but the term includes many other
renewable resources available around us.
By heating the
earth and its atmosphere, the sun generates wind, waves, rainfall for
rivers and differences in ocean temperatures. The sun helps grow trees
for firewood and plants for conversion to alcohol.
Obtaining energy
is possible from these secondary sources of solar energy as well as from
the sun itself. The water resources for hydroelectric power, for
example, are completely renewable, with solar energy an important part
of the cycle. Heat from the sun evaporates water from ocean and
lake surfaces. Clouds store the water, and it returns to the earth as
rain and snow. Electric power
producers are working increasingly with the sun. They are evaluating and
improving methods that range from solar water heaters to photovoltaic
cells and from wind power to biomass conversion.
