Hydroelectric Energy, as the name implies it has something to do with the water and generation of electricity. Concept is simple. Water flowing in a river and down a waterfall carries potential to do work, this potential can be harnessed.

Large examples are dams where a large bodies of water are held and the water that is permitted to go through runs through a tunnel that has generator turbines which are spun as the water flows through generating electricity. This form of energy is pretty reliable, since the water will almost always be flowing unless a drought occurs or the source of water stops supplying water.

There are dangers with generation of this sort of energy since for example if a dam was to break, it can cause massive flooding. History has shown that there is a potential for disaster if careful considerations are not taken into account with deployment of this type of energy generating systems see Shimantan Dam, China 1975.

Currently, it is the most widespread source of renewable energy. It amounts to about 88% of the world's energy from renewable sources, and about 20% of the total energy supply of the world. China is the leader in using hydroelectric energy. They also have the Three Gorges Dam, the world's single largest hydroelectric power plant.



China is the world's leader in hydorelectric power followed by Canada, Brazil, and the United States. Here is a graph that ranks all nations that utilize hydroelectric power.
external image hydrobycountry.gif

I thought it would be useful to add a visual aid on how hydroelectric power works, so here it is:

external image hydroplant-animate.gif

Pumped storage: Reusing water for peak electricity demand

Demand for electricity is not "flat" and constant. Demand goes up and down during the day, and overnight there is less need for electricity in homes, businesses, and other facilities. For example, here in Atlanta, Georgia at 5:00 PM on a hot August weekend day, you can bet there is a huge demand for electricity to run millions of air conditioners! But, 12 hours later at 5:00 AM .... not so much. Hydroelectric plants are more efficient at providing for peak power demands during short periods than are fossil-fuel and nuclear power plants, and one way of doing that is by using "pumped storage", which reuses the same water more than once.
Pumped storage is a method of keeping water in reserve for peak period power demands by pumping water that has already flowed through the turbines back up a storage pool above the powerplant at a time when customer demand for energy is low, such as during the middle of the night. The water is then allowed to flow back through the turbine-generators at times when demand is high and a heavy load is placed on the system.
The reservoir acts much like a battery, storing power in the form of water when demands are low and producing maximum power during daily and seasonal peak periods. An advantage of pumped storage is that hydroelectric generating units are able to start up quickly and make rapid adjustments in output. They operate efficiently when used for one hour or several hours. Because pumped storage reservoirs are relatively small, construction costs are generally low compared with conventional hydropower facilities.

PROS:
  • Dams can store rain water or water directly from the river itself. Then, in case of a Drought, the dam will still have a relatively constant supply of water.
  • Producing Power.
  • Controls flooding & provides recreational activities such as boating fishing and swimming, if the lake is not being used for drinking water (Dam Society).
  • Simple design makes for inexpensive repairs and maintenance costs (Dam Society).
  • Produce inexpensive (after completion) and clean power.
  • Renewable energy source, because the water is not destroyed by passing through the dam.
  • If needed, dams can be shut down instantly, where thermal plants take hours, and nuclear plants can take days! (Dam Society).
  • Very few breakdowns.
CONS:
  • Hydroelectric power production require flooding of entire valleys and scenic areas.
  • Disrupts natural seasonal changes in he river, and ecosystems can be destroyed.
  • Ends flooding that help to clean out the silt in rivers, causing them to clog (Energy Laboratory).
  • The silt that usually flows down to the Beaches and Estuaries is block by the dam.
  • Studies show that the plant decay caused downstream of major dams produces as many greenhouse gasses as more conventional methods of producing electricity.
  • Dams are expensive to build, and due to drought may become useless, or produce much less power than originally planned.
  • A dam being build in Quebec will end up flooding an area as large as Switzerland (Energy Laboratory).
  • Dams can break in a massive flash flood.