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ENERGY
Energy, however may be converted or transferred to different forms: The kinetic energy
of moving air molecules may be converted to The vast majority of wind turbines
produce electricity, so we usually measure their performance in
terms of the amount of electrical
energy they are able to
convert from the kinetic energy of the wind. We usually measure
that energy in terms of kilowatt
hours (kWh) or megawatt
hours MWh during a certain period of time, e.g.an hour or a year. Energy is not measured in kilowatts, but in kilowatt hours (kWh). Mixing up the two units is a very common mistake, so you might want to read the next section on power to understand the difference. ENERGY UNITS 1 J (joule) = 1 Ws = 4.1868 cal Electrical
power is normally measured in watt (W), kilowatt (kW), megawatt
(MW), etc. Power is energy transfer per unit of time. Power may be measured at any point in time, whereas energy has to be measured during a certain period, e.g. a second, an hour, or a year. If a wind turbine has a rated power or nameplate
power of 600 kW, that tells
you that the wind turbine will produce 600 kilowatt hours (kWh)
of energy per hour of operation, when running at
its maximum performance (i.e. at high winds above, say, 15 metres
per second (m/s)). ENERGY MEASUREMENTS If a country like Pakistan, has,
say 1000 MW of wind power installed, that does not tell you how
much energy the turbines produce. Wind turbines will
usually be running, say, 75 per cent of the hours of the year, but
they will only be running at rated
power during a limited
number of hours of the year. In order to find out how much energy the wind turbines produce you have to know the distribution
of wind speeds for each turbine. In England, the average wind turbines
will return 2,300 hours of full load operation per year. To get
total energy production you multiply the 1000 MW of installed power with 2,300 hours of operation = 2,300,000 MWh = 2.3 TWh
of energy. (Or 2,300,000,000 kWh). In other areas, like Wales, Scotland,
or Western Ireland you are likely to have something like 3,000 hours
of full load operation or more. In Germany the figure is closer
to 2,000 hours of full load operation. The power of automobile engines are often rated in horsepower (HP) rather than kilowatt (kW). The word "horsepower" may give you an intuitive idea that power defines how much "muscle" a generator or motor has, whereas energy tells you how much "work" a generator or motor performs during a certain period of time.
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All Rights Reserved. |
Physicists define the word
energy as the amount of work a physical system is capable of performing.
Energy, according to the definition of physicists, can neither be
created nor consumed or destroyed.
rotational energy by the rotor of a wind turbine, which in turn
may be converted to electrical energy by the wind turbine generator.
With each conversion of energy, part of the energy from the source
is converted into heat energy.