ENERGY: PRODUCTION AND CONSUMPTION
Renewable Energy
While supplies of fossil fuels and uranium are limited and irreplaceable, renewable energy
sources--such as the sun (solar), wind, water (hydropower), wood and other plant material (biomass), waste, and
the heat of the earth (geothermal)--are practically inexhaustible or can be regenerated or recycled. Some
renewable energy sources, such as wood and other biomass, can be burned directly to provide heat for homes or
fuel for boilers. Some biomass is converted to alcohol and used as automobile fuel. Solar collectors, which are
often seen on rooftops, are used for space heating, hot water, and to heat swimming pools. All renewable energy
sources, however, can be used to generate electricity. Among the renewable sources powering electricity generation,
hydropower provides by far the largest contribution to United States energy supplies. In 1993, hydroelectric
generation yielded about 269,098 gigawatthours (GWh) of electricity, 9 percent of all electricity generated
in the country. (A watthour is a unit of electrical energy equal to 1 watt of power steadily supplied to or
taken from an electric circuit for 1 hour. A gigawatthour equals a billion watthours.) Other renewable
sources--wood, waste, geothermal, wind, and solar--were responsible for about 69,000 GWh, representing
about 2 percent of total generation. Nearly 85 percent of this electricity was generated by independent
power producers and sold to electric utilities; the remaining 15 percent was generated by the utilities
themselves.
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Energy from the Sun
The sun is expected to radiate energy at a fairly constant rate for a few billion years.
The electromagnetic waves from the sun can be converted to other forms of energy, such as heat and electricity,
which can be utilized by people. In order for solar energy to be used extensively, certain major problems must
be dealt with. The sun does not shine steadily: when it is shining, it is not always at the same intensity;
and some of the rays are bent or reflected by water droplets and dust particles in the atmosphere. The sun's
rays have to fall on a relatively large area in order for enough usable energy to be collected. Where high
temperatures are required, a "concentrating collector" can be used to focus the rays that fall on a large
area onto a much smaller area. The major economic applications of solar energy at present are for heating
residences and other buildings. Solar energy can also be converted into usable electricity either by means
of a photovoltaic cell (based on the element silicon) or by using solar radiation to heat a fluid which, in
turn, drives a turbine connected to a conventional electric generator. In 1993, solar energy was used to
produce about 780 gigawatthours of electricity.
Energy from Wind
The wind has been used as a source of energy for centuries.
From 1880 to 1930, over 6 million windmills generated electric power in the western United States. The rising
cost of fossil fuels, coupled with technological advances in windmill design, has made wind an attractive
alternative energy source in the last decade. The western Great Plains and the New England and Pacific
coastlines offer the most sustained usable wind velocities.
Energy from Wood and Waste
Wood and waste used by electric utilities for
producing electricity include wood chips, sawdust, garbage, chemically inert gas, bagasse (plant refuse),
and sewerage plant gas. Wood once supplied up to 90 percent of the energy needs of our country. In recent times,
the demand for wood rose and fell with the price of fossil fuels. In 1993, wood and waste were used to generate
over 50,000 gigawatthours of electricity.
Geothermal Energy
Geothermal energy is heat generated by natural processes beneath the
earth's surface. It is recovered as steam and hot water. The steam is harnessed to run generators. Most of the
potential for using geothermal energy in the United States is in California, other far western States, and the
Gulf Coast States. By far, the largest geothermal facilities now in operation are at the Geysers in northern
California.
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Written by: Gianfranco Vidali
