Greenfield, N.H. — Along the northwestern ridge of Crotched Mountain is a ''farm'' that has nothing to do with raising vegetables, fruit, grain, or livestock. What it does produce is energy, about 1.5 million kilowatt-hours each year - or enough to supply the electrical needs of about 200 New England homes.
Its planners call it a ''wind farm,'' an enterprise that consists of 20 steel and fiberglass windmills that harvest their energy crop from the blustery mountaintop weather.
What they yield is bought by the state utility, New Hampshire Public Service, which then channels it into home and business electrical use.
Although the wind farm required the cooperation of several sources when it went into action last spring, it is largely the creation of two Burlington, Mass., engineers who founded a firm called US Windpower Inc. in 1974. Since then Stanley Charren and Russell Wolfe have been working toward their vision of a day when wind power can contribute to a significant portion of the nation's energy needs.
''The Crotched Mountain wind farm is basically a small testing ground for us to refine the system and put it to use on a much larger scale,'' says Mr. Wolfe.
''It's a chance for us to deal with such questions as location, the development of more efficient windmills, and finding sponsorship and private investment.''
This last concern is no small matter as the windmill system cost $1.2 million to construct and required a fairly level undeveloped site that received a good share of wind. After the totally private funds and the site were acquired approval from the town of Greenfield had to be won before construction could begin.
Although a few townspeople objected to the appearance of the whirling steel giants protruding on the pristine mountain skyline, the overwhelming majority voted to rezone the land for its new use.
''The citizens realized that the product of this operation was necessary if the electric age was to survive,'' said Paul Brooks, a Greenfield selectman who has been one of the project's most enthusiastic supporters.
''The operation as such would not contaminate the atmosphere and there would be no hazardous byproducts to dispose of,'' he declared.
The windmills at the Crotched Mountain site are larger and more technologically sophisticated versions of the type that have supplied the individual energy needs of farms and ranches for decades.
Mounted on 60-foot steel tripods, the windmills are propelled by three fiberglass blades that cut a swath of air about 40 feet in diameter. Although they operate independently of one another, each has a control system that allows it and the others to be monitored by a single computer.
The windmills spring into operation whenever the wind blows between 10 and 45 miles an hour, turning out of the wind at speeds above that to reduce wear and tear. They are at their peak efficiency of 600 kilowatt-hours when the wind is blowing at about 25 miles an hour.
Although there are few things as unpredictable as New England weather, the windmills can generally be expected to whip through the air about one-third of the time. The projected figure of 1.5 million kilowatt-hours a year is based on the site's average wind velocity of 15 miles an hour.
What has made the wind farm a feasible project for investors is that the New Hampshire Public Service Company is a ready customer for whatever it yields. The utility is buying the power at 7.7 cents a kilowatt-hour, a relatively expensive rate that Congress has allowed renewable energy suppliers to charge. In addition , investors can take advantage of the special tax credits that Congress also has enacted to benefit such suppliers.
Currently, US Windpower is constructing 100 windmills at Altamont Pass, near Livermore, Calif., a project that is expected to include 600 of the machines at completion. As in New Hampshire, the energy will be sold to the local utility company, in this case Pacific Gas & Electric.
''We are also looking at other sites in the West, including one in Hawaii,'' says Mr. Wolfe.
''The chief problem we are running into is that wind energy requires a lot of open land, a factor that makes it difficult to start a large project in the East where such land is scarce. And not only do windmills require an open, windy site , but they need to be fairly level as well.
''We hope to come up with a windmill soon that doesn't require so much space.''
When all 600 windmills are up at the Altamont Pass site, Mr. Wolfe says, the wind farm will occupy about a thousand acres. But because the land has been leased from ranchers who can still let their cattle graze around the steel towers, not much of the land's original use has been lost.
Both Wolfe and Charren hope to see the day when thousands of US ranchers and farmers lease part of their land to wind-farm operations as a new kind of cash crop.
It is, they insist, a crop with the potential of eliminating US dependence on foreign oil.