Hydroelectric Energy
Hydroelectric energy simply means producing electrical energy from water energy. Water is a heavy substance and as we watch a white-water river or, better yet, observe the Niagara Falls we are left in no doubt as to the tremendous forces unleashed by cascading water.
Producing electricity is usually a matter of rotating a dynamo. Water passing over the blades of a turbine wheel is one method of doing this. In order to accomplish this a dam is usually constructed to block the flow of a river and to build up a reservoir of water for the turbines. The water is then piped from the bottom of the dam where its great steady pressure spins the turbines at a constant speed. The turbines are attached to a dynamo that then generates electrical energy.
Occasionally, a nation is lucky enough to have natural lakes high up in mountainous areas. Boring holes in the rock walls containing the lake and allowing the freed water to pour over turbines obviously achieves the same ends so long as there is a supply of water sufficient to replenish the lake. In certain cases even this is not essential. In a pumped storage plant there are two reservoirs, one at a higher elevation than the other. When electrical energy is required, water pours out of the upper reservoir or lake into the lower one, passing over the turbine blades on the way. Clearly, if this goes on for too long the upper lake will empty and the lower lake will flood. But at periods of low energy demand, such as weekends or at night, the process is reversed. The water in the lower lake is pumped back up into the upper lake to get ready for the next peak demand period.
The advantages of a hydroelectric energy plant are obvious. It is using a renewable energy source, it produces no air pollution and, once built, is comparatively cheap to run since it needs no fuel. In addition it can provide a new lake with recreational uses and promote new aquatic and bird life. There are, however, some negative aspects to hydroelectric energy plants. The plants can restrict the flow of the water below the dams altering the fish and animal life. The dams do block upwardly migrating fish such as salmon. On occasions large fish kills have resulted from salmon overcrowding the waters below dams as they try to move farther upstream. Also fish can be sucked from the upper reservoirs into the turbines and be killed.
Most of these disadvantages can be overcome with care and planning. Fish ladders can be constructed to allow passage of migrating fish and filters can be placed over the entrances to the turbines. Environmental damage during the construction phase can also be minimized with forethought.
Mountainous countries with heavy rainfall, such as Norway and Canada, rely extensively on hydroelectric energy production. Hydroelectric production accounts for approximately 20% of worldwide energy requirements. The United States relies less on this mode of production with about 10% of its energy requirements being produced this way.
This is the complete article, containing 508 words
(approx. 2 pages at 300 words per page).
