Study of Building Effects on Small HAWTs Performance in Building - Obstructed Wind Flow Area by using a CFD k-ε Turbulence Model Validated with Site Measurement

Abstract

 The power performance of small wind turbines (SWTs) in a building-obstructed wind-flow area faces significant challenges such as highly turbulent wind flow, low wind speed, etc., that can affect the wind power utilization. Therefore, it is necessary to ascertain the power performance in such areas before installing SWTs by using processes that are simple, reliable, and economical to reduce the invested cost and time. Using computational fluid dynamics (CFD) techniques is one such process. In this study, three rotational 5-kW horizontal-axis wind turbines (HAWTs), WT1, WT2 and WT3 which are located in the Defense Energy Training Center (DETC) in Rayong Province, Thailand, are studied to explore the influence of the wind-flow on them. The objective of this study is to investigate the effectiveness of the HAWTs’ power performance as the wind flows across the obstructive buildings in the DETC from two directions, namely the north-east (NE) and the south-west (SW), by using a CFD k-ε turbulence model and to validate the model with the data measured on the site with free spinning rotor condition as the wind flows from the SW. From the results of the CFD simulation, which were compared with the results from the WT0 (a wind turbine without obstruction, at an incoming wind speed of 4.5 m/s), it was found  that as the wind flowed from the NE, the free spinning rotating of WT1–WT3 increased by 39.12%, 26.47%, and 28.53% respectively. As wind flowed from the SW, the free spinning rotating of WT1 and WT2 increased by 7.73%, and 5.68%, respectively, while, the free spinning rotating of WT3 decreased by 7.50%. Hence, when the wind flows from different directions, the free spinning rotating of the WT1–WT3 from the NE are higher than the wind flowed from the SW by 31.39%, 20.79%, and 36.03%, respectively. From the results of the site measurement as the wind flows from the SW, it is observed that at an incoming wind speed of 4.5 m/s, the free spinning rotating of  WT1 > WT3 > WT2, while from the CFD analysis, the free spinning rotating of WT1 > WT2 > WT3. Consequently, this study investigated that the wind flow in such area causes both increased and decreased power performance of the SWTs.