How the SnowyÕs Hydro-electric Power
Stations work.
After water from rain and snowmelt has been collected in the
SchemeÕs lakes and reservoirs, specially constructed tunnels and pressure
pipelines carry it to power stations at a lower level, where it flows through
turbines and drives electric generators.
Each generator is mounted on a vertical shaft above the
turbine. The water flows through a series of power stations, tunnels and
reservoirs before reaching an irrigation storage that regulates its return to
the river system.
The amount of electricity able to be generated depends
primarily on the distance the water falls (head) and the volume of water (flow)
regulated through the turbine.
The type of turbine used is determined by whether the water falls
from a high, medium or low head. Snowy power stations use Francis turbines,
generally suited to medium heads.
Francis turbines have guide vanes and runners with fixed
blades. These guide vanes control the volume of water required to drive the
turbine and thereby determine the amount of electrical power produced.
How Hydro-electricity is generated.
In its simplest form, rotating a magnet inside a wire coil
generates electricity. In a power station, this process is enhanced: the magnet
is an electro-magnet (or rotor) spinning inside the fixed coils (or stator) of
the generator. Water is used to drive the turbine, which operates the
generator. Transformers boost generated voltage to a level that can be
economically transmitted over long distances by transmission lines to the towns
and cities of southeast mainland Australia.
The Advantages of Hydro-electricity.
Electricity produced by water has several advantages over
electricity generated through conventional thermal power stations. Water is a
naturally renewable source. Each season the snowmelt from the peaks of the
Snowy Mountains is captured in the reservoirs providing a continual supply of
water.
Generation of hydro-electricity does not pollute the
atmosphere and produces no greenhouse gases. Hydro-electric generation is
virtually instant and can respond quickly to sudden demands of power. It takes
less than 90 seconds for the reliable power generated through the Snowy Scheme
to become available, compared with several hours to start up with traditional
coal-powered stations.