Adjoint Optimization of Wind Farm Layouts for Systems Engineering Analysis

Wind is an important renewable energy resource, but in order for it to be competitive with other energy sources, wind farm layouts must be optimized to reduce the levelized cost of energy (LCOE). This requires an analysis that integrates high-fidelity flow models with physical turbine and cost models. We present a new flow model and turbine optimization tool, WindSE, that optimizes wind turbine locations and axial induction factors as part of the National Renewable Energy Laboratory’s open source wind energy systems engineering software tool WISDEM. WindSE enables gradient-based layout optimization by solving the discrete adjoint equations corresponding to the forward flow model. This provides a computationally efficient way to calculate gradients used in the optimization process. We discuss the development of WindSE and provide optimization results based on simulations of single and multiple inflow directions. In the case of strongly directional wind roses the optimal layouts take advantage of flow curvature and speedup effects that are not generated by standard industry linear flow models. When optimizing with respect to a uniform wind rose, local speedup effects are found to be less beneficial and the optimal layouts instead reduce wake losses by maximizing spacing. Sensitivity to wind direction bin sizes and weights is demonstrated with a full layout and axial induction factor optimization using a wind rose from an offshore wind farm.