Hydroelectric
Everywhere you go, water is on the move. The force of water running down even a moderately sized river can exceed several million horsepower. The same force of water can, over time, erode mountains and gouge canyons, so it was only natural that man would one day harness this power to generate electricity.
What is hydro-electricity?
Electricity generated by damming rivers is called hydro-electricity. It is the most widely used form of renewable energy. Worldwide hydropower plants provide over a billion people with electricity and supplies over 24 per cent of the world’s total electricity.
Hydroelectric plants are operated on this simple concept: water flowing through a dam turns a turbine which in turn spins a generator. The volume of water plus the difference in height between the water’s source and the water’s outflow is what determines the energy extracted from the water. This difference in height is called the head. The amount of potential energy in water is proportional to the head. To increase the head, water for a turbine may be run through a long pipe called a penstock.
By moving water between reservoirs of different elevations, pumped storage hydroelectricity produces power to meet high peak demands. During periods of low electrical demand, water is pumped back into the higher reservoir. When there is higher demand, water is released back into the lower reservoir after passing through a turbine.
The power of the ocean’s tides will one day be harnessed for electricity. If the power of a river is strong, just think how mighty the tides are!
Domestic small hydro units
Small hydro units are becoming more commercially viable. For the person who wants to live off the grid, many kits are now becoming available. Such schemes have been popular in China now, which has over fifty per cent of the world’s small hydro capacity.
Some will argue that altering a river’s path is not a desirable thing as it may be prone to flooding and migratory fish cannot get past the dam. Also, a dam does alter the ecology of an area. As a source of clean power however, hydroelectricity’s many benefits often outweigh the negatives.
Further reading:
http://www.sciencelearn.org.nz/contexts/future_fuels/looking_closer/hydro_power
http://en.wikipedia.org/wiki/Hydroelectricity
http://www.howstuffworks.com/hydropower-plant.htm
