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A primer on wind energy  

The wind power proposal for Kibby Mountain and the existing facility at Mars Hill indicate that entrepreneurs are interested in the Maine wind resource. Much is made of the success achieved by Denmark.

Denmark’s flat topography and location between the North and Baltic Seas provide an excellent wind resource. The Danish population is less than 2 percent of that of the United States, but Denmark’s population density (the number of people per square mile) is four times greater. The greater the population density, the easier it is to the supply that population with energy. Denmark can rely on strong energy exchange capacity with its neighbors Norway, Sweden and Germany. Denmark is a very special case; wind energy is a very attractive option.

In the United States, the leading contenders for renewable energy are hydro and biomass. Each contributes about 3 percent of our total energy. Wind contributes about 0.1 percent.

Total U.S. consumption of electric energy is 4,000 billion kilowatt-hours per year; about 0.4 percent of total electricity is produced by wind turbines. The Energy Information Administration reports a U.S. wind generation capacity of 10 billion watts and an annual production of 14.9 billion kilowatt-hours. If those 10 billion watts of capacity operated 24-7, then 87.6 billion kilowatt-hours of annual electricity could be generated. The ratio of 14.9 to 87.6 is 17 percent. The 17 percent is called the “capacity factor” and reflects data on many inefficient machines in poor locations. U.S. history of wind power is not encouraging. But that may be about to change.

The Kibby Mountain Project under consideration by the Land Use Regulation Commission proposes 44 units with a “design” wind speed of 33 miles per hour. At that wind speed, each unit will produce three megawatts (MW) of electric power. At a wind speed of, say, 40 miles per hour, the control system will shift the pitch of the propeller to decrease the propeller efficiency. The input to the generator must not exceed three MW or the generator will overheat. As the wind speed approaches 56 mph, the automatic controls will adjust the pitch of the propeller to reduce the efficiency to about one percent – with the generator still producing three MW. At 56 miles per hour, the blades of the propeller will shift to a “no output” configuration; the wind disc and generator will brake to a stop.

If the engineers had chosen a lower “design” wind velocity, and installed a generator of less than three megawatts, that generator would produce its full capacity more hours per year. The capacity factor would increase, but the kWh per year generated would decrease.

The Mars Hill wind farm contains 28 units rated at 1.5 megawatts each. Based on April, May and June 2007 data, they have a capacity factor of 34 percent. The Mars Hill units reflect significant improvement in wind power technology. (For existing wind machines, the national average capacity factor is only 17 percent.) If the three months of available data were projected to annual performance, the Mars Hill output would be about 0.124 billion kilowatt-hours. Maine uses about 12 billion kWh, New England about 130 billion and nation-wide about 4,000 billion. Along with the now operating Mars Hill and the proposed Kibby Mountain, two other proposals are in the offing: Stetson Mountain and Black Nubble. If all of these wind farms are constructed, wind energy would supply about one percent of New England’s electricity.

As consumers, we pay the full market price for wind-generated electricity plus the value of renewable energy credits mandated by the Legislature. As federal taxpayers, we donate another two cents per kWh, and support the fast depreciation (tax savings) allowed wind installation entrepreneurs. Mars Hill’s units produce 1 percent of Maine’s electricity and 0.01 percent of New England’s. The Kibby Mountain proposal of 44 three-MW units is projected to produce about .37 billion kWh per year. The number of kilowatt-hours supplied by the wind is very small. The combined output from Mars Hill and Kibby Mountain would be about 5 percent of Maine’s or .5 percent of the total New England grid.

The real cost of wind energy, if broken out on our electric bill, would be a shock. But the fraction of the bill represented by wind energy would be small; we would find little change in the total cost of electricity. Public policy people should understand that a 10 percent wind contribution to the New England grid is a long shot indeed. A 10 percent New England wind program would require the construction of 20 Kibby Mountains and 20 Mars Hills.

By Richard C. Hill

Richard C. Hill of Old Town, now retired, taught engineering at the University of Maine in Orono.

The Ellsworth American

8 November 2007

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

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