Catch the wind
Co-op's giant windmills work with Mother Nature to provide power
By Steve Thompson
USDA Rural Development
ind is free. So is the sun. So why aren't these free, non-polluting sources of energy ® in greater use as sources of electric power? Although cost and other considerations still limit the applicability of solar and wind power, utility cooperatives are using them more and more to fill power needs in important niche markets.
Harnessing the wind
Wind has been used as a power source for thousands of years. Perhaps its first use was powering ships and boats. Later, before the use of steam power, wind was used to power grain mills, oil presses, irrigation and drainage pumps in areas such as Holland, where climate or geography prevented the use of water power.
Even today, across many remote areas of the United States, wind-powered pumps draw water from wells to fill livestock watering troughs. These fairly primitive wind turbines, little changed from 100 years ago, are symbolic of American agriculture, particularly in the prairie states where wind is abundant. Across much of the Great Plains, the annual average wind speed is about 13.4 miles per hour the point at which electrical power generation is considered economically feasible.
However, as a baseline (reliable) power source, wind has major drawbacks. First, it's fickle it doesn't always blow, and it sometimes blows when you don't need it. Just as important, areas with sufficient wind are often far from the potential market for the energy they can produce, and far from available transmission lines. For these and other reasons including a cost premium the use of wind to produce electricity is not widespread in the United States, either among electric cooperatives or other power utilities. Despite these obstacles, wind power is on the rise.
Basin Electric Power Cooperative, a large power generation co-op head-quartered in Bismarck, N.D., thought that wind power could serve as a supplemental source of "green" power for its operations. After looking at the costs and available incentives, the co-op calculated that with available new technology and the right location wind generation would not be as cheap as conventionally produced power, but would be "the most competitive of the renewable technologies," says Ron Rebenitsch, an engineer at Basin.
"We have an advantage in this respect over many other co-ops," Rebenitsch says, "because our unique status as a not-for-profit, but taxable, cooperative allows us to take advantage of the 1.7-cent kilowatt-hour tax credit available for wind energy. There are similar incentives offered to untaxed nonprofits, but they are renewed yearly, and there's always the chance that they won't be available in the future. You can't take that to the bank."
Stepping up to the plate
To help launch the wind project, one of Basin's largest members, East River Electric Cooperative, with members in South Dakota and western Minnesota, stepped up to the plate. It offered to take on the liability for the extra costs of one wind turbine.
"A general survey we took a few years ago indicated quite a bit of interest in green power among our members," says Scott Parsley, assistant general manager for member services at East River. "So in early 2000, we took another survey specifically to find out if enough of them would be willing to pay a premium for wind-generated power. We got an over-whelming [positive] response."
As the initial sponsoring member, East River put out a request for proposals and got eight responses from wind turbine vendors. Fortunately, the vendor with the best proposal was able to offer a project in a location that was able to obtain power transmission approval.
"The problem is that power transmission infrastructure is not being milt right now," says Rebenitsch. Current federal requirements make it risky for power firms to build transmission lines, because others have the right to apply to use unused capacity. If the builder is counting on that unused capacity for future needs, this can put a serious crimp in the business plan.
"Transmission approval is difficult to find nowadays, and not being able to guarantee it could stop most projects," Rebenitsch says.
The Prairie Winds Project, as it was named, found an excellent location in South Dakota, reasonably close to transmission lines and with an average wind velocity of more than 16 miles per hour. With the proposed equipment, the site promised to generate electricity at full capacity 32 percent of the time. "That's the best performance anyone's been able to achieve so far in the United States," says Parsley.
USDA provides financing
Financing for the $2.9 million cost of two turbines, and connecting lines to a power substation, was provided by USDA Rural Development's Rural Utilities Service (RUS). "We're glad to be a part of Prairie Winds," says RUS Administrator Hilda Legg. "It's a good example of how green technology can work for the individual members of power cooperatives." Legg says RUS encourages utility cooperatives looking to exploit wind and other green sources of power to apply for financial assistance.
Land was leased for the project, with royalties for the landowner that are expected to be in the range of $2,000 to $3,000 per turbine each year a welcome income supplement. Two turbines were installed: one is dedicated to production for East River, the other's output is available to a number of other Basin member distribution co-ops.
The wind turbines are built by Nordex, a Danish company with a reputation for quality and reliability. The turbines are immense the biggest available when they were built late last year. Their rotors measure 60 meters in diameter or almost 200 feet and they are mounted on tubular towers 200 feet tall. Each can produce 1.3 megawatts of power. They are twice as big as any other commercially produced wind turbines, which presented a problem for Rebenitsch.
Nordex projected a useful life span for the turbines of 20 years, based on the records of smaller models. But with no actual experience to back up that projection, Rebenitsch decided conservatism was the better part of valor. He initially set depreciation at 15 years, and all cost calculations were based on that assumption.
Basin Electric projected power generation costs at 5.5 to 6 cents per kilo-watt hour. After subtracting the tax credit and market-rate revenue, they were left with a shortfall. Part of the problem is that the area enjoys the lowest-cost power in the nation. Firm, or baseline, power is available for only 3 cents per kilowatt hour. Non-firm power, available intermittently, was estimated at about 1.8 cents. That amount, plus the 1.7 cent tax credit, gave the co-op 3.5 cents per kilowatt hour, leaving a deficit of 2.5 cents, or (adding a safe cushion) 3 cents.
The result is a $3 dollar premium for a 100-kilowatt-hour block of power These are marketed as sponsorships: each household pays $3 monthly. In return, 100 kilowatt-hours of their power consumption for the month is generated by wind.
Blades the size of jet wings
The groundbreaking for the turbine installations took place last Sept. 7, and
both turbines were dedicated less than two months later. The construction went quickly because, except for the foundations, the parts, including the towers, were prefabricated. Says Parsley, "It would have taken less time than that, except that the wind slowed things down." On some days, high winds made it unsafe to operate the huge cranes lifting the tower sections, generator assembly, and fiberglass turbine blades each the length of a Boeing 747 wing into place.
The turbines are far more sophisticated than the typical prairie water pump. The mechanicals, including the generator and transmission, are hidden in a sleek fiberglass housing, which pivots on the top of a giant steel tube making up the tower. Unlike the old prairie "windmills," they do not use a weathervane like tail to turn them into the wind. Instead, hydraulics turn the turbine assembly, obeying a computer using information from a small wind vane mounted on top of the housing.
The same computer also takes constant note of the current wind speed, from an anemometer mounted next to the wind vane. It adjusts the angle of attack of the rotor blades for efficiency and to keep the speed of rotation within safe limits. If rotational speed goes higher than 19.2 rpm, centrifugally operated airbrakes automatically deploy from the ends of the rotor blades. Should they malfunction or prove insufficient to slow the rotor in high winds, a large disk brake mounted on the generator shaft can smoothly bring the turbine to a halt.
The turbines are remotely monitored using telemetry that transmits wind speed, temperature, hydraulic pressures, rotational speed, and other important data, allowing their operators to keep constant tabs on them without being on site. They are built to survive wind speeds of up to 145 miles per hour with the rotor stationary. The windmills begin producing electricity at 6 miles per hour and reach their peak output at 33.5 mph.
While it's too early to declare total success for the project, both Parsley and Rebenitsch are optimistic. So far the turbines have performed at, or above, expectations. "It's been an exciting project, and a lot of fun," Parsley says. "One thing I enjoy is people's reactions when they first see the turbines. Often they don't realize the size of these things until they see them in person."
Meanwhile, wind technology is marching on. Nordex is now taking orders for a monster wind generator with twice the power output of each of the Prairie Winds turbines. Its rotor diameter will be half again as big: 300 feet.
Other wind turbine manufacturers are offering similar products. Increases in economies of scale and other developments in this rapidly advancing field promise that costs will continue to decline, albeit gradually. Add the enthusiasm of many power customers and the Bush administration's policy of encouraging the use of renewable energy sources, and it seems that wind turbines may be an increasingly common sight in much of America.
