Site Specific Optimization of Rotor/Generator Sizing of Wind Turbines

Abstract

Economics, including all incentives, is the primary factor that drives the development of wind farms. Optimizing the wind turbine generator size-to-rotor size design based on an economic figure of merit shows that maximum wind turbine capacity factor does not yield the best economics for a given wind resource. A large rotor on a small generator will have a high capacity factor but a low annual output of electrical energy. For the same capital investment a different configuration would produce more electricity making the project more economically sound. This study varied rotor-to-generator size at a fixed capital cost and used a modified blade element momentum model to predict annual electrical energy production for each design at a given wind resource. Optimal design was the design that resulted in the highest annual electrical energy production. This was done at a series of fixed costs and a series of wind resources defined by the Weibull distribution parameters. The results indicated the following: At larger turbine sizes, (higher capital cost per turbine), the economics shifted toward a larger generator and smaller rotor (relatively). This exact relationship is dependent on the wind resource. At large turbine sizes, greater flexibility is shown in optimum generator sizing vs. rotor sizing. Having multiple generator size options for the same rotor size allows developers to more closely match and capitalize on the characteristics of their wind resource. The end result of the research is a set of diagrams developers can use to select the best turbine based on economics for their wind resource. This provides an additional tool they can use to make their projects more cost effective.