Around 90% of South Africa’s energy currently comes from coal. It is the most
cost-effective and abundant source we have available, with our coal-fired power
stations using over 90 million tons per annum.
Coal, oil, gas and nuclear fuels are used to heat water in reactors and convert
it into steam at high temperatures and pressures. Releasing the hot steam (between
500°C and 535°C) then turns a large magnetic turbine, generating electricity.
In South Africa, hydropower is critical in the “storage” of electricity.
Essentially, water is stored behind a dam wall and is released to drive huge turbines,
which are connected to generators. Using excess power, water can be pumped back
into the reservoirs, to be released in times of emergency.
The force of wind is the most promising renewable energy source. The windmills’
blades are designed to capture the wind as efficiently as possible. These are connected
to generators where electricity is then generated.
The earth is an inexhaustible reservoir of natural heat. In a few places (Iceland,
Italy, New Zealand and Kenya) underground springs are hot enough to produce steam
near the surface of the Earth and this may be worth tapping for electricity generation.
Solar cells, which convert sunlight directly into electricity, are a clean and free
source of power. However, due to high installation costs and the large scale of
panels needed to produce useful amounts of energy, Eskom only supplies solar energy
to fulfil household needs.
Gravity from the sun and moon raises and lowers the sea twice a day, and gives tides
of up to 8 metres. Electricity can be generated through a barrage (a special dam
built across an estuary) which lets the rising tide build up a body of water, then
releases the water through its turbines.
Floating generators capture energy from waves. These generators use the up and down
motion of the waves to force compressed air through bladed turbines. As the air
flows either up or down, it spins the turbines, creating energy.
A coil, energised by direct current to produce a magnetic field, is mounted on a
revolving rotor. Wrapped around this rotor is another series of coils that captures
the rotating magnetic field and generates the electrical charge.
In transformers, alternating current is led through a primary coil of wire, which
produces an alternating magnetic field in the ring-shaped core of soft iron. This
in turn creates a voltage in a secondary coil, from which the output current can