Hydroelectric Energy Systems - An Intro to Hydroelectric Power

Hydroelectricity is less widely available as an alternative energy source than solar power and wind power; the sun and wind are ubiquitous, but hydro systems rely on the availability of moving water. However, people who have streams or other flowing systems running through their property might find that hydroelectricity is a viable energy source. A home-level hydro system costs about 12 cents per kilowatt hour; a large-scale hydro system costs from 11 to 16 cents per kilowatt hour.

Premise

Hydro power works on the same principle as wind power: a "reverse motor" uses electromagnetism to create an electrical current. (See 'wind' heading for a more detailed explanation.) Hydro systems rely on the push of moving water to propel their turbines, so the amount of electricity produced is dependent on the rate at which the water flows. A small stream, then, may not create enough electricity to be worth the cost and effort of starting up a hydro system.

Methods

Hydro systems commonly rely on dams. When a dam is built, water on the upstream side pools and is then released downstream at a controlled rate. This controlled flow of water from the upstream to the downstream side propels the turbines.

Another method of harnessing water power is to divert water from the main stream and use the smaller diversion to work the turbine. This only works on bigger water systems, since smaller systems won't have enough water to create such a diversion.

Ecological Effects

Although hydro electricity is clean, it involves a tradeoff between producing clean power and changing the local ecology. Water systems are either lentic (still) or lotic (flowing). The ecological balance of a lentic system is going to be much different than that of a lotic system; the temperature, light, oxygenation and velocity of water flow in one system will favor some species, while other circumstances will lead different species to thrive. Each species has a very specific niche in which it is adapted to live, and changing the local environment makes some niches disappear while others take their place.

A dam changes a lotic system to a lentic system. The species that lived there previously won't survive because their niches are gone; other species will take their place. This is a relatively minor phenomenon when it happens on a small scale, as in the damming of a stream. Dams, after all, occur in nature. On large-scale dams, however, such as the Hoover Dam, the ecological results can be dramatic.

Dams also affect a water system's natural flooding cycle. Although flooding can be the source of tremendous damage, it is a natural process that helps the land to replenish itself through the deposit of new silt and nutrients.

There are tools that seek to decrease the ecological effects of dams. Fish ladders, for example, are designed to allow spawning fish to swim upstream. However, some changes to the local ecology are inevitable.

It is up to the individual to decide which side of the tradeoff weighs more heavily to him or her- whether it is better to use power from the utility grid and contribute to the greenhouse gases polluting the atmosphere, or to use a hydroelectric system and change the balance of the local ecology.