Current available information suggests that bats, for example, are more subject to deleterious or deadly interactions with wind turbines on evenings when wind speeds are lowest. On the other hand, a rotor speed of only 3.3 RPMs instead of current rotor speeds of 17-23 RPMs might (or might not) result in a lessening of deadly effects on bats and other wildlife.- Frank

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"A novel turbine design uses two rotors of equal diameter, one each at opposite ends of a nacelle, to capture wind at greater capacity factors than conventional designs can do, say developer Airgenesis LLC (airgenesiswind.com). The developer says the rotors, offset from each other by 60°, will be turning at low speeds of 2.5 to 3.3 rpm, and are capable of producing 51 kW in wind speeds of about 5 mph. With a maximum of 3.3 rpm, it minimizes the possibility of harming wildlife. The low speeds also minimize the danger of ice throws. “All the high rpm speeds are inside the turbine,” explains company spokesman Clayton Troxell. At a wind speed of 15 mph, the design will be producing over 1 MW with a maximum possible output of 10.7 MW at 32 mph."

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