Calculating the capacity credit of wind power
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The value of wind power as firm capacity in an electricity grid without storage is investigated, primarily by means of a numerical probabilistic model. The magnitude of wind power capacity credit is usually found to be greater than 40 percent of the capacity credit of a typical conventional unit with the same average power output. For very small values of wind power penetration into the grid, the two measures of capacity credit utilised are each approximately equal to the average wind power, while for large penetrations the measures approach different constant values. The behaviour at both limits is in good agreement with the results of an analytic probabilistic model. The results are also compared with those from an hour by hour computer simulation.
It is found that wind power capacity credit is very sensitive to the penetration of wind power into the grid, to the unit sizes of the conventional plant in the grid and to the start up speed of the aerogenerators. The credit is moderately sensitive to the replacement of the load distribution by a Gaussian distribution, to the forced outage rate of conventional plant, to the wind speed distribution and to the magnitude of the loss of load probability in the absence of wind power plant. The credit is found to be insensitive to the rated speed of the aero generators (given the same average wind power output).