Page 306 - Handbook of Energy Engineering Calculations

price to conventionally fired stations using coal, oil, or gas. Traditional power
companies worry about a greenhouse gas cap on carbon dioxide and other
pollutants. They also worry about a future requirement to produce “clean”
power.
Solar energy is about three times more expensive than wind power. And

solar energy is also about three times more costly than natural gas. When
compared with power generated from coal, solar energy is about six times
more expensive.

Current statistics for electric-generation costs on a kWh basis state that
most coal-generated electricity costs about 4 cents per kWh. Natural-gas-
generated electricity costs about 6 cents per kWh to produce. Solar-energy-
produced electricity costs about 24 cents per kWh to produce. While these
numbers were valid at the time of this writing, they can change markedly,

depending on local conditions, fuel costs, and advances in the manufacture of
solar-energy devices. At the time of this writing, solar energy is producing
about 1 percent of the electric power in the United States. By comparison,

fossil-fuel-fired generation produces about 70 percent of electric power at this
time.
Solar manufacturers are aiming at producing panels that cost about $1 per
watt generated. Eventually, solar manufacturers hope to compete with gas- or
oil-fired plants that produce electricity at 4 to 6 cents per kWh. To achieve

this goal, a number of different solar designs are being tested and evaluated.
Solar-energy cost savings come from scale—that is, the larger the solar
installation, the lower (usually) the cost of generating a kWh of electricity.

Thus, large-scale rooftop installations of photo-voltaic devices in California
are becoming popular. One utility expects to install 50 MW of capacity on
rooftops over a 5-year time span.
Other land-based solar systems include: (a) concave dishes that follow the
sun and deliver heat to a Stirling engine producing some 25 kW of electricity;

(b) tower systems, which receive the sun’s energy from mirrors, using the
heat to generate steam for a turbo-generator, or to heat liquid sodium or a
similar material that stores the heat for use at another time; (c) trough systems

using parabolic mirrors that deliver heat to a pipe containing a heat-transfer
medium that produces steam to power a turbo-generator. Much work is being
done to develop more efficient steam turbines that can operate at lower
pressures and lower steam temperatures. Combined-cycle solar and fossil-