Nationwide Assessment of Potential Output from Wind-Powered Generators

Abstract

A method of computing power output from wind-powered generators has been developed and applied to estimate potential power output at various sites across the continental United States. The method assumes a wind-powered generator system which can be characterized by a cut-in speed V0, a rated speed V1 and a cut-out speed V2. The generator output power is assumed to be constant at the rated power Pr between V1 and V2 and to vary parabolically from zero at V0 to Pr at V1. The wind distributions at various sites have been found to vary according to a Weibull distribution between realistic values of V0 and V1. Values of the Weibull distribution parameters at approximately 135 sites across the United States have been evaluated. These results have been projected to a constant height of 30.5 m (100 ft) and 61 m (200 ft) using data determined from observed Weibull parameter height variations at several meteorological tower sites across the country. A contour map is presented for generator capacity factor values (fraction of rated power output actually realizable). The capacity factor values were computed, using the above method, for wind-powered generator systems having cut-in speed V0 = 3.6 m s?1(8 mph), and rated speed V1 = 8.0 m s?1 (18 mph), the characteristics of NASA's 100 kW Plumbrook unit, and V0 = 6.7 m s?1 (15 mph), V1 = 13.4 m s?1 (30 mph), hypothetical values for a 1 MW class unit. Results of the evaluation indicate that at a height of 61 m in the central United States and in certain portions of the New England coast over 60% of rated output power can be achieved on an annual average basis, i.e., an average of ≥60 kW from the Plumbrook 100 kW generator. In these same areas the 1 MW system would have over 20% capacity factors, i.e., an average of ≥200 kW from the 1 MW system.