Development and application of an improved blade element momentum method model on horizontal axis wind turbines

Development of wind energy is gaining a great interest nowadays with over 25% annual growth in any configurations and sizes. Designing a wind turbine with improved performance remains the ultimate research and development goal. Therefore, understanding the influence of the different wind turbine key parameters, e.g., tip speed ratio (TSR), twist and pitch angles, number of blades, and airfoil chord distribution, is critical. In this work, an improved blade element model (BEM) is developed by correcting the code with tip loss, Buhl empirical correction, skewed wake, and rotational effect. These corrections are necessary to extend the application of the method to the turbulent wake regime for the horizontal axis wind turbine (HAWT) configuration. Results from the developed code are compared with the NREL measured data of the two-bladed Unsteady Aerodynamics Experiment (UAE) phase-VI turbine. They indicate an improved trend with the incorporation of these corrections. The performance of the three-bladed 3.5-kW HAWT was tested and found to follow closely the experimental trend. As the mismatch between these low fidelity analyses (BEM) and the experimental work persists, the undertaken analysis demonstrates its limitation, and it emphasizes the role of high fidelity wind tunnel and flow simulations. BEM analysis, however, shows that designing blades with proper twist and pitch angles, and targeting suitable TSR could lead to substantial gain (over 10%) in the performance.