By Kean W. Stimm
The Sierra Club is to be commended for encouraging the transition to renewable energies such as wind and sun since few people are aware of possible impending crises as we deplete our fossil fuels. Natural gas cost is up 50 percent this year and may go up more as the true cost of fracking takes hold. Oil is down to $50 a barrel below USA costs of $70 a barrel and big increases are suggested.
Bob Ciesielski’s Another Voice article Dec. 1 clearly defines what many dislike about three-blade windmills. The manufacturer, Vestas, of Denmark, specifies a windmill rating for Apex Clean Energy at 4.2 megawatts (4,200 kilowatts) or 197 megawatts for 47 windmills (if only it were true).
The 4,200 kilowatts is based on a wind velocity of 30+ MPH using 100 percent of the air mass delivered to the face of the windmill. However, the three slender blades occupy only about 4 percent of the span area and 96 percent of the wind energy passes between the blades and is unused. Thus the proper rating is 4 percent of 4,200 kilowatts or 168 KW.
This manufacturer’s implied power output suggests that the wind blows at 30+ MPH continuously whereas it actually blows at that velocity less than 6 percent of the time. The average wind in the United States is about 12 MPH, with a calculated 27 kilowatts output for these windmills since there is far less energy at lower wind speeds. The difference between actual average output and the manufacturer’s stated 4,200 KW rating is enormous, which means the project is incredibly overvalued.
The three-blade windmill is still the best we have for converting wind energy to electrical power but it’s just too inefficient. That’s unfortunate with almost 400,000 three-blade windmills across the world. If this 47-windmill farm put out the power they suggest, they would not need one cent of federal grants, subsidies or tax abatements.
The 4,200 kilowatt rating is equivalent to a 5,600 horsepower locomotive with enough power to pull a heavy freight train over a big mountain. The windmill torque, at 12 RPM and 5,600 HP, would quickly snap off the slender fiberglass blades.
Recently there have been significant breakthroughs in the efficiency of solar panels and small wind turbines. These technologies are advancing rapidly based on confirmed science. Expect them to be more efficient, smaller and less expensive than three-blade windmills.
Wind and solar farms where all generators have the same input are replaced by strategically placed turbines and solar panels where each “sees” different input that’s averaged, preventing huge undulations of power to the grid. Apex should wait as the USA’s investment is dependent on continuing government support.
Kean W. Stimm is CEO and chief scientist for Kean Wind Turbines Inc. of Amherst.