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- Author or Editor: W. R. Hargraves x
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Abstract
The Weibull function is discussed for representation of the wind speed frequency distribution. Methods are presented for estimating the two Weibull parameters (scale factor c and shape factor k) from simple wind statistics. Comparison is made with a recently proposed method based on the “square-root-normal” distribution with mean wind speed and fastest mile data as input statistics. The Weibull distribution is shown to give smaller root-mean-square errors than the square-root-normal distribution when fitting actual distributions of observed wind speed. Another advantage of the Weibull distribution is the available methodology for projecting to another height the observed Weibull distribution parameters at anemometer height.
Abstract
The Weibull function is discussed for representation of the wind speed frequency distribution. Methods are presented for estimating the two Weibull parameters (scale factor c and shape factor k) from simple wind statistics. Comparison is made with a recently proposed method based on the “square-root-normal” distribution with mean wind speed and fastest mile data as input statistics. The Weibull distribution is shown to give smaller root-mean-square errors than the square-root-normal distribution when fitting actual distributions of observed wind speed. Another advantage of the Weibull distribution is the available methodology for projecting to another height the observed Weibull distribution parameters at anemometer height.
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 V 0, a rated speed V 1 and a cut-out speed V 2. The generator output power is assumed to be constant at the rated power Pr between V 1 and V 2 and to vary parabolically from zero at V 0 to Pr at V 1. The wind distributions at various sites have been found to vary according to a Weibull distribution between realistic values of V 0 and V 1. 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 V 0 = 3.6 m s−1(8 mph), and rated speed V 1 = 8.0 m s−1 (18 mph), the characteristics of NASA's 100 kW Plumbrook unit, and V 0 = 6.7 m s−1 (15 mph), V 1 = 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.
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 V 0, a rated speed V 1 and a cut-out speed V 2. The generator output power is assumed to be constant at the rated power Pr between V 1 and V 2 and to vary parabolically from zero at V 0 to Pr at V 1. The wind distributions at various sites have been found to vary according to a Weibull distribution between realistic values of V 0 and V 1. 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 V 0 = 3.6 m s−1(8 mph), and rated speed V 1 = 8.0 m s−1 (18 mph), the characteristics of NASA's 100 kW Plumbrook unit, and V 0 = 6.7 m s−1 (15 mph), V 1 = 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.
