Abstract
The effect of separation distance between turbines on overall cluster performance were simulated using computational fluid dynamics software and we found that at a distance equivalent to two rotors, there was an improvement of +8.06% in the average performance of the cluster compared to a single, isolated turbine. A very small improvement in performance was noted at the equivalent distance of 12 rotor diameters. The performances of three individual turbines in pyramid- and inverted pyramid-shaped vertical axis wind turbine clustered farm configurations with varying oblique angles at a fixed spacing of two equivalent rotor diameters were also investigated. The design experiment involves the simulation of test cases with oblique angles from 15° to 165° at an interval of 15° and the turbines were allowed to rotate through 18 full rotations. The results show that the left and right turbines increase in performance as the angle with respect to the streamline axis increases, with the exception of the 165° angle. The center turbine, meanwhile, attained its maximum performance at a 45° oblique angle. The maximum cluster performance was found to be in the configuration where the turbines were oriented in a line (i.e., side by side) and perpendicular to the free-stream wind velocity, exhibiting an overall performance improvement of 9.78% compared to the isolated turbine. Other array configurations show improvements ranging from 6.58% to 9.57% compared to the isolated turbine, except in the extreme cases of 15° and 165°, where a decrease in the cluster performance was noted due to blockage induced by the left and right turbines, and the center turbines, respectively.
Highlights
The spacing of individual turbines in a clustered farm affects the overall performance of the system due to the impact of changing local wind velocities brought about by the influence of the wind turbines’ proximity to each other, including funneling and turbine wakes
In the study of Tang et al conducted in a wind tunnel set-up, there was a notable decrease in the performance of both the upstream and downstream turbines in two horizontal axis wind turbine (HAWT) arranged in tandem, in comparison to the performance of a single, isolated turbine simulated in the same wind tunnel [4]
The performance of shows each turbine cluster arrangewere compared to resulting the Cp of coefficients the isolated of turbine
Summary
The spacing of individual turbines in a clustered farm affects the overall performance of the system due to the impact of changing local wind velocities brought about by the influence of the wind turbines’ proximity to each other, including funneling and turbine wakes. Wake production is detrimental to the overall performance of clustered horizontal axis wind turbine (HAWT) farms, with some research finding a more than 10% loss in performance at spacing equivalent to six to ten turbine diameters in the downwind direction and a three to five turbine diameter separation in the crosswind direction [1,2,3]. When deployed in clusters with insufficient turbine spacing, HAWTs tend to reduce the overall cluster performance due to reduced wind speed received by the downwind turbines. Recent studies show that wake recoveries behind vertical axis wind turbines (VAWTs) are achieved in a spacing of as few as four to six equivalent turbine diameters compared to HAWTs’ 15 to 20 equivalent diameter distance [5,6]. VAWTs’ rapid wake recovery characteristics allow a more compact wind turbine arrangement, resulting in higher power density per unit area
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