Optimization of Wind Farm Layout taking Load Constraints into Account

Abstract

Optimization of a wind farm layout is of utmost importance due its economical aspect. The primary aim of optimizing layout is to increase the overall energy production. The higher energy production creates more revenue from wind farm during its operational life time. Wind turbines situated within wind farms are subjected to wake losses due to numbers of factors one of such factor is wind disturbance from the wind turbines installed in front. Therefore, the wind turbines will produce less output as compared to front wind turbines facing winds in free stream. Thus, to have an economically feasible performance, it is necessary to optimize wind farm layout in terms of both maximum energy and load constraints for life time of wind turbines. The turbines in the large wind farm causing increased turbulence that increases the fatigue damage levels, and the increased loads must be analysed. The thesis is devoted to the optimization of wind farm layout to maximize the energy production, and verifying the significance of wake loss effects with respect to optimal placement of wind turbines within wind farm. Thesis is divided into two followings parts: In the first part, in the WFDs approach, the WindSim software for CFD simulations is used to calculate flow fields at various heights over the planned layout to set number of turbines as per IEC 61400-1 standard. Then, the resulting layout from WindSim is fed into the Wind Assessment Tool (WAT) to check if the chosen position of turbines verifies the IEC compliance criteria for effective turbulence. Next, the Park layout is used as in Park Optimizer tool to verify the project constraints, such as exclusion of areas where it is not possible to set up turbines, layout is optimized by calculating the energy production, etc. The Park optimization is based on the following factors: i) minimum distance between turbines, ii) to check the effective turbulence if it’s not violating IEC criteria, and iii) minimizing wake deficits. In the benchmarking of software tools, Wind Farm Designs (WFDs) optimization approach is used to maximize the annual energy production (AEP) by optimizing the turbine positions and comparing it with OpenWind (OW) software tool. OpenWind tool is used significantly for the layout optimization. The difference between both WFDs and Openwind optimization results compared based on gross and net annual energy production, and array efficiency from the park layout. Based on the results, it was found that the WFDs estimated lower net energy and array ii | P a g e efficiency as compared to OpenWind optimizer for the entire wind farm layout, differs same for both -1 %. However, the gross energy is estimated almost similar by both the tools, but WFDs optimizer estimated slightly lower. In the second part of thesis, an analytical approach is used to check the sensitivity of wake losses at distances that are IEC compliant for simple cases between two turbines. Jensen wake model is used for the wake loss analysis due its high degree of accuracy. Frandsen model is used to satisfy effective turbulence criteria. The energy production of downwind turbines decreases from 2 to 20% due to the lower wind speeds as they are located behind upwind turbines, resulting in decreasing the wind farm overall energy production. Higher wake loss also increases the effective turbulence that leads to reduction in overall energy production within wind farm.