Q-
1 What is a wind turbine and how does it work?
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A
wind energy system transforms the kinetic energy of the
wind into mechanical or electrical energy that can be harnessed
for practical use. Mechanical energy is most commonly used
for pumping water in rural or remote locations. Wind electric
turbines generate electricity for homes and businesses and
for sale to utilities. There are two basics designs of wind
electric turbines: vertical-axis, or” egg-beater’’
style, and horizontal axis machines. Horizontal-axis wind
turbines are most common today, constituting nearly all
of the “utility-scale” (100 kilowatts, KW, capacity
and larger) turbines in the global market. Turbine subsystem
includes: A rotor or blades, which convert the wind’s
energy into rotational shaft energy; A nacelle(enclosure)containing
a drive train, usually including a gearbox* and a generator;
A tower to support the rotor and drive train; and Electronic
equipment such as controls, electrical cables, ground support
equipment, and interconnection equipment.
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Q- 2 How many
turbines does it take to make one megawatt (MW)? |
Most
manufacturers of utility-scale turbines offer machines in
the 700-KW to 1.8-MW range. Ten 700-KW units would make
a 7-MW wind plant, while 10 1.65-MW machines would make
a 18-MW facility. In the future, machines of larger size
will be available, although they will probably be installed
offshore, where larger transportation and construction equipment
can be used. |
Q-
3 What is “capacity factor”?
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Capacity
factor is one element in measuring the productivity of a
wind turbine or any other power production facility .It
compares the plant’s actual production over a given
period of time with the amount of power the plant would
have produced if it had run at full capacity for the same
amount of time . A conventional utility power plant uses
fuel ,so it will normally run much of the time unless it
is idled by equipment problems or for maintenance .A capacity
factor of 40% to 80% is typical for conventional plant’s,
A wind plant is “fueled by the wind” which blows
steadily at times and not at all at other times . Most modern
utility-scale wind turbines operate with capacity factor
of 25% to 40% , although they may achieve higher capacity
factors during windy weeks or months . It is possible to
achieve much higher capacity factor by combining wind with
a storage technology such as pumped hydro or compressed-air
energy storage (CAES). It is important to note that while
capacity factor is almost entirely a matter of reliability
for a fueled power plant ,it is not for a wind plant,it
is matter of economical turbine design .With a very large
rotor and a very small generator ,a wind turbine would run
at full capacity whenever the wind blew and would have a
60- 80% capacity factor-but it would produce very little
electricity. The most electricity per dollar of investment
is gained by using a larger generator and accepting the
fact that the capacity factor will be lower as a result
. Wind turbines are fundamentally different from fueled
power plants in this respect . |
| Q-
4 What is “availability factor”?
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Availability
factor (or just “availability”) is the measurement
of the reliability of a wind turbine or other power plant
.It refers to the percentage of time that a plant is ready
to generate (that is, not out of service for maintenance
or repairs).Modern wind turbines have an availability of
more than 98%- higher than most other type of power plant.
After two decades of constant engineering refinement , today‘s
wind machine are highly reliable. |
| Q-
5 How much does wind energy cost? |
Over
the last 20 years, the cost of electricity from utility
-scale wind system has dropped by more than 80% . In early
1980s, when the first utility -scale turbines were installed
wind generated electricity cost as much as 30 cents per
kilowatt-hour .Now state-of-the-art wind power plants can
generate electricity for less than 5 cents /kwh in many
parts of the U.S., a price that is in a competitive range
with many conventional energy technologies . The National
Renewable Energy Laboratory (NREL) is working with the wind
industry to develop next generation of wind turbine technology
. The product from this program are expected to generate
electricity at prices competitive with natural gas turbines,
the least expensive conventional power source . |
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