What is Hydro Power?

Hydro electricity is produced by utilising the energy produced when a mass of water falls from a high level to a lower level, is held in a dam and then allowed to flow through a turbine and generator to produce electricity. The height from which the water falls and the speed at which the water flows determines the amount of energy that is produced.

There are four basic systems available to generate hydro electricity:

• Hydro Schemes using low-level Diversion Weirs (Run of River Schemes)
• Hydro Schemes using High Dams

• Hydro Schemes using Low Dams (sometimes called Weirs); and

• Retro-fit Hydro Schemes

Run of the River Schemes

Run of the River Schemes use whatever water is currently flowing in the river, as they don't store any significant amounts of water. These Schemes usually involve a low level diversion weir or a stream bed intake and are usually located on swift flowing streams.

A low level diversion weir increases the river water level enough that a structure for intake can be located next to the river. The intake is made up of a trash screen and a submerged opening with an intake gate.

The alternative is a streambed intake where no weir is required. The water drops through a screened inlet duct to flush with the bottom of the riverbed. One process that is required is the flushing out of debris, as rocks and gravel will enter the streambed intake.

Water from the intake is usually carried downhill through a pipe (called a penstock) to a power station set up downstream of the intake at as low a level as possible to gain maximum head on the turbine.

High Dams

In order to provide sufficient head for the turbine, a large dam may be constructed to store water. These water storage systems enable the power station to generate at times of peak power demand and allow the water level to rise again during off peak times. Schemes using large dams are best suited to larger, gently graded rivers.

Low Dams

Sometimes called weirs, large rivers with high flow rates use low height dams and large low head turbines to construct viable hydro schemes. These are costly and are often only viable if the weir is required for water management or irrigation as well as hydro power.

Retro-fit Hydro Schemes

Hydro turbines can be used in place of a regulating valve that usually wastes energy in normal operation for some water supply or sewage schemes. These retro-fit installations can be very cost-effective as the water intake and penstock pipework is already in place.

For further information on Hydro power or any of the other renewable sources of energy visit www.seda.nsw.gov.au.