Environmental Engineering Reference
In-Depth Information
The reasons the United States has lagged behind in this area of renew-
able energy are primarily objections by those who live on the coast and
do not want their ocean views spoiled and, secondarily, the cost. Off-
shore turbines cost 8 to 12 cents per kilowatt-hour compared to 5 to 8
cents for onshore wind.
46
Energy from the Sun: It's Hot Out There
Most of the power generated by people originates from the sun. Millions
of years ago, sunlight nurtured life that became today's oil, gas, and coal.
It is the solar heating of the earth's atmosphere and oceans that fuels
wave power, wind farms, and the rainfall that permits hydroelectric
schemes. But using the sun's power directly to generate power is rare.
Solar cells account for less than 1 percent of the world's electricity
production, with Germany and Japan leading the way, and only one-
hundredth of 1 percent in the United States. But annual global produc-
tion of photovoltaic cells has risen exponentially from about 250
megawatts in 2000 to 7,000 megawatts in 2008, largely because of
growth in Europe, particularly in Spain and Germany. Rapid growth is
likely to continue.
Solar energy, like geothermal energy, is inexhaustible, but it has
proven diffi cult to turn enough of this energy into electricity for its cost
to be competitive with other energy sources. At present, it is 30 cents
per kilowatt-hour, but it is expected to drop dramatically soon because
of China's entry into the production market.
47
The record conversion
effi ciency for a solar array is 31.25 percent, set in January 2008 in New
Mexico.
48
The previous record was 29.4 percent, set fourteen years
earlier. Solar cells in the laboratory achieved 42.8 percent in 2007, break-
ing the previous record of 40.7 percent set in 2006. Much higher effi cien-
cies from arrays of solar panels are required for solar electricity to be
commercially competitive with either other alternative energy sources or
fossil fuels, which are below 10 cents per kilowatt-hour. Only in places
unconnected to an electrical grid, such as rural Africa and rural Asia,
are solar cells commercially viable today.
Although sunny California currently has two-thirds of the nation's
grid-connected photovoltaic installations, the largest solar power plant
in the United States is located on Nellis Air Force Base in Nevada. It is
a collection of 72,000 solar panels built on 140 acres, including part
of an old landfi ll. The plant, a public-private venture that took six
months to build, cost $100 million and generates about a quarter of
