A New Era in Home-Owner Hydro

Article Tools

Image Gallery

Print

E-mail

Comments

RSS

Recall that 400 watts will power a house. To generate that we'd need approximately: 100 gallons a minute falling 50 feet. Or 50 gallons a minute falling 100 feet. Or 25 gallons falling 200 feet. Or 16 gallons-a mere quart each second!-falling 310 feet.

The implication is clear. A rill, tiny brook, step-across creek, mountain spring, irrigation ditch—with enough head behind it—trickle of water from any of these can produce a torrent of power.

As head drops below 50 feet, power production diminishes and the economics of small hydro systems become increasingly tenuous. Nonetheless, if you've got a small pond a mere 25 feet above from which you can divert 100 gallons a minute, you can still generate 200 watts. Combine that with efficient lightbulbs and appliances, and you've got energy independence.

Surveying a Site

Okay, you've got a possible hydropower site. How do you assess its potential?

Two people can survey most sites in a day or less. You'll need a notebook, pencil, stopwatch, tape measure, bucket, shovel, and plastic tarp. Wear tennis shoes. Your feet will get wet.

Head first. Although a topographic map or handheld altimeter will provide a rough idea, more precise measurement requires some sort of level. In open terrain, use a builder's level or transit, four-foot carpenter's level, or cigarshaped sight level.

If you know what a transit is, you probably know how to use one. To use a carpenter's level or sight level, cut a staff of known height a few inches shorter than you are tall. Start at the proposed turbine location. Put the level on the staff and center its bubble. Then sight along it as your assistant climbs the hill. When his or her feet are level with your eye, have them stop. Bring the level up to that point and continue in this fashion uphill. At the intake, total your results.

In brushy terrain, use a water level—a 50-foot length of tubing attached to a plastic container—that can be snaked around trees, rocks, and other obstacles. Water levels are accurate and easy to use. They can be bought for $30 or cobbled up for $10.

A third method—perhaps simplest of all—exploits the fact that every foot of head equals 0.43 pounds per square inch (psi) of water pressure. Screw two or more hoses together, carry them to the intake and fill with water. Attach a pressure gauge to one end and carry it downhill. Note the pressure. Bring the other end to that spot (keep the hose full!) and repeat. At the bottom, divide your psi readings by.43. That's your head. Keep track of hose lengths, too, and you'll know how long your penstock needs to be.

RSS | Comments | E-mail | Print