Power Plant Engineering

2.15.3 WIND POWER SYSTEMS
You usually stand in an open space to enjoy the wind.
You know how wind originates. Moving air is wind. Since
the wind has velocity it has kinetic energy. This is the en-
ergy of the wind. We shall see how the kinetic energy of the
wind can be used to produce electricity. For that, we can use
windmills. Windmills are devices, which work on wind. How
the kinetic energy of the wind is made use of in windmills
shall be looked into. We shall examine the working of a wind-
mill. The important part of a windmill is a structure with
large leaves, fixed at the top of a high tower.
What will happen when wind blows on these leaves?
You may have seen paper fans available at festival places,
rotating when the wind blows. In a similar manner the speed
of leaves changes with the speed of the wind. What happens
if the rotation of the windmill is given to the rotor of a gen-
erator? Rotor also rotates. Then electricity is obtained from
the generator. What happens if the windmill is connected to
a water pump? As the leaves of the windmill rotate pump
works pumping out water.
Wind machines are just as efficient as coal plants. Wind plants convert 30 percent of the wind's
kinetic energy into electricity. A coal-fired power plant converts about 30-35 percent of the heat energy
in coal into electricity. It is the capacity factor of wind plants that puts them a step behind other power
plants. Capacity factor refers to the capability of a plant to produce energy. A plant with a 100 percent
capacity rating would run all day, every day at full power. There would be no down time for repairs or
refueling, an impossible dream for any plant. Wind plants have about a 25 percent capacity rating
because wind machines only run when the wind is blowing around nine mph or more. In comparison,
coal plants typically have a 75 percent capacity rating since they can run day or night, during any
season of the year.
One wind machine can produce 275-500 thousand kilowatt-hours (kWh) of electricity a year.
That is enough electricity for about 50 homes per year.
In this country, wind machines produce about three billion kWh of energy a year. Wind energy
provides 0.12% of the nation's electricity, a very small amount. Still, that is enough electricity to serve
Fig. 2.6. Windmill farm.

---

NON-CONVENTIONAL ENERGY RESOURCES AND UTILISATION
63
more than 300,000 households, as many as in a city the size of San Francisco or Washington, D.C.
California produces more electricity from the wind than any other state of USA. It produces 98 percent
of the electricity generated from the wind in the United States. Some 16,000 wind machines produce
more than one percent of California’s electricity. (This is about half as much electricity as is produced
by one nuclear power plant.) In the next 15 years, wind machines could produce five percent of Califor-
nia’s electricity. The United States is the world’s leading wind energy producer. The U.S. produces
about half of the world’s wind power. Other countries that have invested heavily in wind power re-
search are Denmark, Japan, Germany, Sweden, The Netherlands, United Kingdom, and Italy. The Ameri-
can Wind Energy Association (AWEA) estimates wind energy could produce more than 10 percent of
the nation’s electricity within the next 30 years.
So, wind energy may be an important alternative energy source in the future, but it will not be
the sole answer to our energy problems. We will still need other energy sources to meet our growing
demand for electricity.