Effect of Flow Inclination on Wind Turbine Performance

Abstract

This work examines the effect of flow inclination on the performance of a stand-alone wind turbine and of wind turbines operating in the wakes of upstream turbines. The experimental portion of this work, which includes performance and flowfield measurements, is conducted in the ETH dynamically-scaled wind turbine test facility, with a wind turbine model that can be inclined relative to the incoming flow. The performance of the wind turbine is measured with an in-line torquemeter, and a 5-hole steady-state probe is used to detail the inflow and wake flow of the turbine. Measurements show that over a range of tip-speed ratios of 4–7.5, the power coefficient of a wind turbine with an incoming flow of 15 deg inclination decreases on average by 7% relative to the power coefficient of a wind turbine with a noninclined incoming flow. Flowfield measurements show that the wake of a turbine with an inclined incoming flow is deflected; the deflection angle is approximately 6 deg for an incoming flow with 15 deg inclination. The measured wake profiles are used as inflow profiles for a blade element momentum code in order to quantify the impact of flow inclination on the performance of downstream wind turbines. In comparison to the case without inclination in the incoming flow, the combined power output of two aligned turbines with incoming inclined flow decreases by 1%, showing that flow inclination in complex terrain does not significantly reduce the energy production.

An investigation of in‐field blockage effects in closely spaced lateral wind farm configurations

“…The effects of the wind inclination angle due to terrain effects on wind farm performance were evaluated by Tsalicoglou et al using two rotors in a tow tank. 4 The downstream separation varied from 3D to 6.5D, and the flow inclination angle was 15 ı . The study demonstrated that the downstream rotor in axial flow generated 45% less power than the upstream rotor but that the power loss was reduced in inclined flow because of deflection of the wake from the upstream rotor.…”

Identification of wind turbine testing practices and investigation of the performance benefits of closely-spaced lateral wind farm configurations

“…The dow nstream separation varied from 3D to 6.5D and the flow inclination angle of 15° was achieved by tilting the rotors in the w ater channel. The study dem onstrated th a t a dow nstream rotor in axial flow generates 45% less power th an the upstream rotor, b u t th a t the drop in power was less significant in inclined flow due to the deflection of the wake by the upstream rotor [67].…”

“…T he study did produce uncharacteristically large power losses at the dow nstream rotor, however, which were 85% a t a dow nstream distance of 3D and were still 65% 10D dow nstream [42]. the effects of the wind inclination angle due to terrain effects on w ind farm performance using two rotors [67], T he experim ental setup was designed to mimic inclined wake effects th a t occurred between two, longitudinally-aligned but vertically-separated wind turbines installed on a hill. The dow nstream separation varied from 3D to 6.5D and the flow inclination angle of 15° was achieved by tilting the rotors in the w ater channel.…”

Wind energy potential above a high-rise building influenced by neighboring buildings: An experimental investigation

“…With this regard, there is an opposing behavior between Horizontal Axis Wind Turbines (HAWT) and Vertical Axis Wind Turbines (VAWT) [6] in terms of energy harvesting. While the HAWT's performance shows a decrease with increasing skew angle (for example, the power coefficient with an incoming flow of 15° inclination decreases on average by 7% [10]), recent works on Darrieus VAWT ( [6,11]) showed an increase in performance with regard to the skewed flow (the power coefficient with an incoming flow of 15° inclination increases by 20% [6]). In particular, this increase is observed for the attended angles in urban environment of 0°-30° [6].…”