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 in the ocean. Think of the destructive force of a river breaking its banks and causing floods or of tall waves breaking on a shallow coastlines, and you can visualize the amount of power involved.
This energy can be harnessed and converted to electricity, and the
generation of hydroelectric power does not produce greenhouse gas
emissions. It is also 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.
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
2,000 large oil, gas, coal and nuclear power stations. The total
renewable energy within the world's oceans, if it could all be
harnessed, would satisfy the present world demand for energy more than
5,000 times over. But until now, harnessing wave power was only a
theoretical possibility. In fact, the technology is still under
development, and it's too early to estimate how soon it will
significantly contribute to the global energy picture.
River power
In 2003, 16 percent of the world's electricity was produced by
hydropower plants. Hydropower harnesses the energy of
water going from a higher to a lower level (i.e. water running
downstream). The greater the drop in elevation, the faster the
water flows, and the more electricity that can be produced.
Unfortunately, the dams that go with large scale hydropower can drown
ecosystems. Water needs of downstream communities, farmers and
ecosystems should also be taken into account. Plus, hydro
projects can be unreliable during prolonged droughts and dry seasons
when rivers dry up or reduce in volume.
However, small-scale hydro systems can produce plenty of electricity
without needing the large dams. Classified as "small", "mini" or
"micro" depending on how much electricity they produce, small hydro
systems capture the river's energy without diverting too much water
away from its natural flow.
Small-scale hydropower is an environmentally benign energy source with
large growth potential, but it won't reach this potential unless we
give it a chance. See the
Take Action page for how you can be
part of the solution to climate change.
Further info:
For a detailed overview of the issue related to dams check out the report by the
World Commission on Dams.