Improvements in technology have reduced the unit cost of wind-electric power systems by almost an order of magnitude since 1981, and installed wind power capacity is growing rapidly world-wide. Paradoxically, the use of wind-powered pumpingsystems, formerly the major application of wind power, is declining and little progress has been made towards the direct application of wind power to drive other mechanical loads such as aerators and compressors for heat pumps, despite huge potentialmarkets in areas remote from electricity grids. A major reason for this failure to apply improved wind turbine technology to non-electrical loads is low system efficiency resulting from poor torque matching between the wind turbine rotor and the load.Methods of improving system efficiency are reviewed, including load-disengaging devices to permit easy starting and a simple mechanical control system for a variable ratio drive which would ensure that any wind turbine driving any load will operate nearpeak efficiency over the full operating range from cut-in to governing. The latter system could improve average system efficiency by a factor of 3 to 8 and has the further advantage that it can provide starting torque and can actuate overspeed control for Darrieus vertical axis wind turbines and low-solidity horizontal axis wind turbines.
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