1. Geothermal
energy: is heat
contained beneath the Earth's crust, and brought to the surface in the form of
steam or hot water. The five main sources of this geothermal reservoir are dry,
super-heated steam from steam fields below the Earth's surface; mixed hot
water, wet steam, etc., from geysers, etc.; dry rocks (into which cold water is
pumped to create steam); pressurized water fields of hot water and natural gas beneath
ocean beds; and magma (molten rock in or near volcanoes and 5 to 30 miles below
the Earth's crust). Most Iceland buildings are heated by geothermal energy, and
a few communities in the United States, such as Boise, Idaho, use geothermal home
heating. Electric power production, industrial processing, space heating, etc.,
are fed from geothermal sources. The California Geysers project is the world's largest
geothermal electric generating complex with 200 steam wells that provide some
1,300 megawatts of power. The first geothermal power station was built in 1904
at Larderello, Italy.
2. Solar
radiation: utilization
depends on the weather, number of cloudy days, and the ability to store energy
for night use. The process of collecting and storing is difficult and
expensive. A solar thermal facility (LUZ International Solar Thermal Plant), in
the Mojave Desert, produces 274 megawatts and is used to supplement power needs
of the Los Angeles utilities companies. Japan has 4 million solar panels on
roofs and 2/3 of the houses in Israel have them; 90% of Cyprus homes do as
well. Solar photo voltaic cells can generate electric current when exposed to
the sun. Virtually every spacecraft and satellite since 1958 utilizes this kind
of resource.
3. Tidal
and wave energy: contain
enormous amounts of energy to be harnessed. The first tidal powered mill was built
in England in 1100; another in Woodbridge, England, built in 1170, has
functioned for over 800 years. The Rance River Power Station in France, in
operation since 1966, was the first large tidal electric generator plant, producing
160 megawatts. A tidal station works like a hydropower dam, with its turbines spinning
as the tide flows through them. Unfortunately, the tidal period of 13 ½ hours
causes problems of integrating the peak use with the peak generation ability. Ocean
wave energy can also be made to drive electrical generators. (The Handy Science
Answer Book, compiled by the Science and Technology department of the Carnegie
Library of Pittsburgh)
