The first question is, "How can we use water to create
electricity?" There are four main ways in which we use water to create
electricity. The first way is by harnessing the power of moving water
in large rivers. By building a dam in a selected area, you can create
a large reservoir of water with a great deal of pressure. Holes in
the side of the dam lead to turbines, which spin as a controlled amount
of water exits the dam. (Back
to the Generating of Electricity)
The second way we use water to create electricity is by the changing of tides. Tidal power plants are producing electricity for their nearby consumers in France, Canada, Japan and many other countries. Tidal power plants work on the power of changing tides. The first step in the construction of a tidal power plant is in finding a bay with a large difference between it's low and high tides. Engineers then design a dam to put across the outer end of the bay. When high tide comes to the area, huge quantities of water come rushing into the bay. The gates in the dam will shut when the water level has reached it's maximum height. At low tide, the water in the bay is trapped higher than the ocean water. Holes in the bottom of the dam let the water rush past turbines and then back into the ocean. When the next high tide comes around, the whole process begins over again. (Back to the Generating of Electricity)
The third way we can create hydroelectricity is by harnessing the power of waves. Large flotation devices can be placed in an area noted for regular wave action. These flotation devices are attached to a crankshaft underneath the water's surface. As the flotation devices move up and down, they cause the crankshaft to spin. This crankshaft is attached to a generator which produces electricity. Although there are many inventions which also use the power of waves, this method tends to be the most popular.
Last, and currently least, is our fourth way of creating hydroelectricity. This method works by taking advantage of thermal differences in ocean water. Although they are still in the experimental stages, Ocean Thermal Energy Conversion (OTEC) systems seem to have made a promising start. Due to the smaller differences in water temperatures compared to steam-based systems, estimates say that OTEC plants will require approximately 5,000 cubic feet per second of ocean water in order to provide enough energy for 200,000 people. Though this may seem like an incredible amount of water, it averages out to be 1.5 cubic feet per minute for one person.
Most electric power producing systems have a downside, and these are no exceptions. River-based hydroelectric dams have been known to upset the natural wildlife in their region. In times of drought, these dams will hold back the smaller amount of water coming down the river, compounding problems downstream. Tidal-based hydroelectric plants can cause widespread wildlife problems, as the regular intervals between high and low tides become disrupted. Cases have also been reported where harbors near tidal power plants completely dry up during low tide because there is an even lower amount of ocean water in the area. This can leave boats stranded on land until high tide comes in again.
Our last two hydroelectric plants have more mechanical parts, so they will require more upkeep than the first two, while at the same time producing less electricity. Our final problem is in the transportation of hydroelectricity. Hydroelectricity provides a good energy source for areas near large bodies of water, but many places are too far away to make the transportion of hydroelectricity cost effective.
Well, we got that over with. Now for the good news: Hydroelectric power plants produce no pollution; the smaller amounts of required labor and the fact that the water is free lead to a much lower electric bill; hydroelectricity can be produced 24 hours-a-day, and most important is hydroelectriciy's large amount of room for expansion. Estimates say that our planet's hydroelectric capability is greater than our entire oil supply. Hydroelectric power has a great demand and a very bright future.
My references for this web page were:
Energy: The New Look, Margaret O. Hyde, McGraw Hill 1981, New York
Wind and Water Power, Philip A. Sauvain, Schoolhouse Press 1988, Lexington, MA