Today, most of the world’s electricity-generating infrastructure involves generators which are turned by turbines. This technology has been in use for the past 120 years, and throughout its history, the two main means to turn turbines have been steam and moving water.

Steam is, of course, generated by boiling water, which is boiled using the combustion of a fuel. Today, those two main fuel sources are coal and nuclear (though there is a growing number of biomass combustion facilities coming on line). Unlike steam-powered turbines, hydroelectric facilities use no fossil fuels. They involve the use of either hydroelectric dams on rivers or tidal facilities on ocean coastlines.

Hydroelectric Dams

Hydroelectric dams are constructed on large rivers with a high volume of water. Electricity is generated in a hydroelectric dam when water is forced by gravity through a narrow tube, called a penstock. This moving water flows downward and through the blades of the turbine, turning it. Hydroelectric dams provide a constant source of uninterrupted power, so long as the river doesn’t dry up.

The major drawback of a hydroelectric dam is the environmental damage it can potentially cause. In some cases, so much water is diverted that it affects the entire river ecosystem downstream. If the river happens to be a salmon run, as is the case with the Columbia River, it prevents the salmon from being able to jump upstream to their spawning beds. This problem can be solved, in part, by installing a fish ladder. But in a few cases, entire ecological regions are destroyed to create enough water power for a hydroelectric dam. If a power company decides it wants to build a hydro dam but the rivers in the company’s region are not powerful enough, they have been known to divert rivers into one another to create enough water power, destroying animal habitat and traditional hunting grounds for indigenous people.

Tidal Power

Hydropower can also be generated from ocean tides. The movement of the tides (water flowing in and out of the coastal region) is powerful enough to turn turbines. It is also a regular and predictable source of power generation. This technology has been used to generate power in France since the 1960s. Tidal power facilities do not have the same potential environmental consequences as hydroelectric dams. The major drawback of this type of power generation, though, is that although it is regular and predictable, power can only be generated at certain times of the day. Because of this drawback, tidal power has had limited application worldwide.

Sources:

Wikipedia, the free encyclopedia (articles on Hydroelectricity and Manitoba Hydro)