Measurements of the wake characteristics of co- and counter-rotating twin H-rotor vertical axis wind turbines

• Published in: Energy (Oxford) Vol. 131; pp. 13 - 26
• Main Authors: Lam, H.F., Peng, H.Y.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 15.07.2017; Elsevier BV
• Subjects: Aerodynamics; Array configuration; Co-rotating; Counter-rotating; Energy efficiency; Packing; Packing density; Studies; Turbines; Turbulence; Turbulence intensity; Twin VAWTs; Velocity; Vertical axis wind turbines; Wake aerodynamics; Wind farms; Wind power; Wind power generation; Wind tunnel; Wind turbines; Counter-rotating; Array configuration; Co-rotating; Wind tunnel; Twin VAWTs; Wake aerodynamics
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2017.05.015

Increasing the efficiency of individual vertical-axis wind turbines (VAWTs) has been the subject of much research. However, wind farms that comprise individual VAWTs are not necessarily the most efficient configuration in accordance with VAWTs’ signature wake pattern. This study aims to identify efficient array configurations and thereby increase the packing density and power output by grouping individual VAWTs as a unit. Systematic measurements of wake aerodynamics of co-rotating and counter-rotating (forward- and backward-rotating) twin VAWTs were taken in a wind tunnel. The wake was measured both along the blade mid-span plane up to 10 turbine diameters (10D) and along the vertical plane. The wake of co-rotating twin VAWTs showed great asymmetry, similar to that of a single VAWT. Interestingly, the wake of counter-rotating twin VAWTs demonstrated elegant symmetric patterns. Two pairs of stationary counter-rotating vortices were found to evolve in the wake. The turbulence intensity downstream was observed to experience drastic changes and slow recovery compared with its velocity counterpart. Finally, two types of array units are proposed for applications in wind farms in accordance with the measurements. •Measurements of the wake aerodynamics of co- and counter-rotating twin VAWTs.•Discussions on the wake asymmetry and symmetry of three twin turbine systems.•Discover stationary counter-rotating vortices in wakes of counter-rotating VAWTs.•Twin and triangular array units are proposed in accordance with the measurements.•Applications of twin and triangular array units in wind farms are assessed.