Partial Repowering Analysis of a Commercial-Scale Wind Farm by Turbine Hub Height Variation to Mitigate Upstream Wind Farms Wake Interference /

Abstract

Repowering enhances the power generation capacity and service life of wind farms. In this study, a partial repowering strategy has been analyzed for a large commercial-scale wind farm in Jhimpir, Pakistan. The wind farm is highly influenced by upstream farms wake interference. Wind speed and power deficit of individual turbines were evaluated using the mesoscale Weather Research and Forecasting (WRF) model coupled with Wind Farm Parameterization scheme. The test case wind farm is experiencing a 15% reduction in wind speed and 35% decline in power production due to the presence of upstream farms. The wind speed and power results from the WRF model were also validated by comparison with the observed data. Wind turbines with the highest power deficit were identified and their hub heights were varied to mitigate the wake interaction. Wind shear profiles and power output of modified turbines were evaluated at the new hub height of 61.5m and 100m separately and compared with the existing hub height of 80m. A power reduction of up to 12% was observed in the 61.5m hub height case, while an increase of up to 13.6% was seen in the 100m hub height case compared to the existing layout. A mean increase of 4.9% was observed in the total power generation of the modified wind farm which can lead to a significant increase in annual energy production. This research work lays out the foundation for repowering of old wind farms in Pakistan and around the world, as it presents the use of mesoscale model as a fast and reliable tool for technical assessment of old wind farms.