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What is it?
Hydroelectric energy is water energy. Moving water contains an enormous store of natural energy, whether the water is part of a running river or waves on the ocean. Think of the destructive force of a river breaking its banks and causing floods or of tall waves breaking on shallow coastlines with devastating results.
Water energy can be harnessed and converted to electricity. The generation of hydroelectric power does not produce greenhouse emissions. It's a renewable energy resource because water is constantly replenished through the earth's hydrological cycle. All a hydroelectric system needs is a permanent source of running water, like a creek or river. Unlike solar or wind energy, it can produce power continuously, 24 hours a day.
How powerful is it?
Wave power
The World Energy Council estimates that wave power could produce two terawatts of energy each year. This is twice the world's current electricity production and is equivalent to the energy produced by 2000 large oil, gas, coal and nuclear power stations.
The renewable energy within the world's oceans, if it could all be harnessed, would satisfy the present world demand for energy more than 5000 times over.
River power
10% of NSW electricity is produced by the Snowy Mountains Hydro Electric Scheme, a hydroelectricity project that harnesses the energy of a free-flowing river. Unfortunately, large scale hydro projects like the Snowy Mountains and Tasmanian hydroelectric schemes have drowned some ecosystems and starved others of water. The Snowy River currently gets less than 1% of its natural water flow and the river is dying.
Small-scale hydro systems can produce plenty of electricity without disturbing surrounding ecosystems. These hydro systems are classified as small, mini or micro, depending on how much electricity they produce. Small hydro systems can be built to capture the river's energy, without diverting too much water away from its natural flow and without flooding upstream environments or altering water use patterns downstream.
How does it work?
Hydro power harnesses the energy produced when a body of water falls from a higher to a lower level. As the water falls, it flows through a turbine and generator to produce electricity. The greater the height and the faster the water flows, the more electricity is produced.
The potential energy in tidal changes and waves can be harnessed using this technology. Water held in dams and weirs can also be used. Small hydro plants can use the natural free flow of river water to generate electricity for homes.
Problems
Building large-scale hydro power plants can be polluting and damaging to surrounding ecosystems. Changing water supply can also have a detrimental effect on human communities, agriculture and ecosystems further downstream.
Hydro projects can also be unreliable during prolonged droughts and dry seasons when rivers dry up or reduce in volume.
Hydro energy in Australia
Hydro power plants already contribute power to electricity grids in Australia.
In NSW there are four hydro projects. The Snowy Mountains Hydro Electric Scheme is the best known and is one of the world's most complex water supply/hydro electricity projects. It consists of seven power stations and a flowing river, with an overall capacity of 3756 megawatts (MW). It saves 5.5 million tonnes of carbon dioxide annually and supplies 10% of NSW energy. But in the process it has flooded a number of towns like Jindabyne and Adaminaby and has come close to destroying the ecosystem of the Snowy River.
