Hydro

Turning rain and gravity into electricity!

The water cycle is an amazing energy system involving the sun, clouds, rain and gravity. The rain water captured in dams can be used to make electricity when it is released into irrigation or the river system.

This is how the water cycle works.

When the sun shines it warms the water in the sea and on the ground.
Water evaporates and rises into the sky.
As the evaporated water rises, it cools and forms into clouds.
When the air cannot hold anymore water, the droplets fall as rain, hail or snow.
Gravity then carries the water down hills along rivers and streams and as underground water to the sea.
When the sun shines, the water cycle starts again.

We rely on this natural process to distribute water for plant and animal life across the planet.

People have diverted or blocked waterways to form dams for a long time. They also used the power of running water to turn machines using water wheels.

In the late 1880’s, people discovered that the power of falling or running water could be used to turn dynamos and make electricity.

In Australia, the streetlights in Launceston, Tasmania were first powered by generators turned by the flow of the South Esk River in 1895.

Since then, many large dams have been built across the world to control floods, hold water for irrigation and supply electricity. This includes the colossal Hoover Dam on the Colorado River in North America (zoom in with Google Earth for a view of the dam) and the giant Three Gorges Dam on the Yangtze River in China which will hold five times the water volume of the Hoover Dam when completed.

Another famous hydroelectric project is Australia’s Snowy Mountains Scheme in New South Wales. Built between 1949 and 1974, the scheme diverts mega litres of water for irrigation west to the Murray and Murrumbidgee river systems and produces hydro electricity using water from 16 major dams, seven power stations, 145 km of tunnels and 80 km of canals³.

How hydro works

The water stored in the dam is released through pipes that run through turbines that turn generating dynamos.

Hydro generator

The force of the water is very strong, so large and powerful generators can be used.

With a network of dams, the falling water can be used to produce electricity a number of times during its descent.

Because the flow of water can be quickly and easily adjusted, the generation of hydro electricity can be quickly increased or decreased as demand requires.

Snowy Hydro currently provides over 70 per cent⁴ of all renewable energy that is available to the eastern mainland grid of Australia, as well as providing fast response power to light up the morning and evening rush hours of Sydney, Brisbane, Canberra, Melbourne and Adelaide.

Energy buzz word

Peak load is an important concept in energy supply. It means the highest amount of electricity needed at one time. If there is not enough supply to meet peak load then there will be black-outs in some areas. Hydro electricity helps meet peak load because the power supply can easily be increased or decreased to meet demand.

Tides and waves – energy that is hard to tame

Waves are energy moving in water – they can be very powerful, just ask any surfer! But finding a practical way to turn wave energy into power has proved tricky. There have been many ideas about harnessing wave power – these mostly involve using the movement of waves to turn generators.

Tides are another source of energy in water. Everyday, the pull of the moon and the sun’s gravity move the oceans back and forth. There have been many ideas proposed, but few have resulted in commercial production of power.

But like all renewable energy sources, the search is on for new and creative ways to turn energy into power we can use.

Hydro pros and cons

Hydro electricity has served Australia well. Extensive networks of dams and power stations, especially in New South Wales and Tasmania have provided abundant, renewable electricity for many decades. However, as the most arid continent in the world, Australia has few options left for new large-scale hydro-electric generation.

	For	Against
	Clean (no greenhouse gas emissions after set-up)	Large set up costs
	Renewable	Concern about impact of dams on environments and river flows
	Dams enable irrigation and flood control	Vulnerable to variations in rainfall
	Hydro power output is flexible and responsive to demand

Hydro energy investigation:

Investigation 1 (Basic level): Water, gravity and Isaac Newton

Discover other renewable sources: Wind energy, Biomass

³ http://www.snowyhydro.com.au/levelTwo.asp?pageID=289
⁴ http://www.snowyhydro.com.au/levelTwo.asp?pageID=66