A PROFITABLE PRIVATE MICROHYDROELECTRIC PLANT

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Of course, few companies are paying as much for power as they're charging for it. (After all, the utilities have such additional expenses as supplying the lines, customer service, billing, etc.) But PURPA has made it possible for small producers to receive at least some payment for the electricity they're capable of generating. And with buy-back rates (the price paid by utilities to small-scale power producers) running between 2¢ and 10¢ per kilowatt-hour (KWH) across the country, microhydropower is capable of becoming a paying proposition.

LAUREL CREEK HYDROELECTRIC

Perhaps the best way to understand the potential of microhydropower is to examine a successful example. Several of MOTHER's staff members have been keeping an eye on one such project since its beginnings, and recently paid a visit to the finished site to see it in full production.

The Laurel Creek microhydropower installation was started back in 1980, when a group of individuals—working under the auspices of the Blue Ridge Group Sierra Club and Appalachian State University (both of which have their headquarters in Boone, North Carolina), and cosponsored by the Blue Ridge Electrical Membership Corporation (BREMCO)—got a $21,416 Department of Energy Appropriate Technology grant to study the microhydropower potential in Watauga County, North Carolina and build a demonstration site.

Laurel Creek, the waterway they chose, is a cascading mountain stream in the western part of the county. The group erected a tiny (two-foot-high) dam, which diverts water into a penstock . . . and from that point, 1,640 feet of 8"-diameter plastic sewer pipe stretches down the mountainside next to the creek, for a total drop of 178 feet.

The crew had several good reasons for deciding not to build a more typical tall dam. First and foremost, they were able to avoid the primary disadvantage—in the environmentally oriented minds of the developers—of large hydropower installations: the need for flooding the land behind the dam. Second, from a practical standpoint, the diversion and pipe arrangement allow much more drop (or "head", in hydro terminology). Third, getting permission for their project—which required only a verbal OK from local wildlife agencies—was less complicated than it would have been if construction of a larger installation had been planned. And finally, the expense—even though the pipe alone cost more than $5,300—was a small fraction of the investment that's necessary to build a big dam.

Of course, before any work was done, the rate of water flow in Laurel Creek was measured on a regular basis and its profile compared with that of other streams in the area (as gauged by the U.S. Geological Survey). Once all the data were analyzed, Dr. Harvard Ayers (the program director) and builders Andy Feimster and Bob Powell decided to take no more than 2.5 cubic feet per second (CFS) of water—or 1,125 gallons per minute—from the creek. That amount equals about one-third the mean flow in the stream . . . and will leave sufficient water for aquatic life, while allowing the plant to operate about 90% of the time. (Should a severe drought occur, a partial or complete shutdown of the system would be required in order to maintain flow in the creek.)

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