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Energy generation
Windmills
Windmills have been used for a very long time to harness the energy
of wind. A windmill has vanes that turn in the wind and, by connecting
them to a central axle, the force of the wind can be transmitted to
a variety of devices. Early windmills were used to turn a grinding wheel
over a stationary stone to grind flour. The Southern Cross windmill
can be used to lift water from an underground supply, or to turn a generator
to transform the rotational kinetic energy to electrical energy. Aerodynamically
designed windmills are used now in wind farms to generate electricity
for the mains supply.
Waterwheels
Wherever there is flowing water there is energy. Mills were often
built over a waterway to capture the movement energy of flowing water,
and convert it to rotational kinetic energy driving stone wheels to
grind flour. The energy from waterwheels was also used to drive other
machinery, or to move objects.
Hydroelectricity
The gravitational potential energy of water stored in high dams
is converted into kinetic energy as the water is funneled through pipes
to drive turbines and electrical generators in hydroelectric power stations
to produce electrical potential energy.
 Fossil
fuels
Coal, oil or gas are burned in thermal power stations to heat and boil
water. The water turns to steam under great pressure and it is this
steam that drives turbines that generate electricity
for the mains supply. Any of the fossil fuels can be used to convert
water to steam, the appropriate one being dependent on supply. Here
the chemical potential energy stored in the fossil fuel is released,
transferred to the water as thermal energy turning the water into steam.
The steam then transfers its energy to kinetic energy in the turbine
and finally electrical potential energy in the generator.
Nuclear energy
Another way of heating water to convert it to steam is by nuclear power.
Here the nuclear potential energy stored in radioactive elements is
converted to thermal energy and from then on the transfer is as for
fossil fuels - water to steam to turbine to electricity.
Solar energy
Energy from the Sun can be used directly by exposing black tubes containing
water to the Sun's energetic rays. The water is heated as the Sun's
energy is transferred to the water. Another way of using the Sun's energy
is through photovoltaic cells, where the energy is converted directly
to electrical potential energy. This is a valuable source of electrical
energy in remote districts, or on vehicles such as solar powered cars.
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