An Experimental Investigation on the Performance of Vertical Axis Wind Turbine in Steady Wind

Abstract

An experimental study was carried out into the performance of a wind tunnel scale vertical axis wind turbine (VAWT) under steady wind conditions. Wind speed tested was 7m/s, giving a Reynolds number of around 75,000. The power coefficient (CP) of the VAWT over a wide range of λ reveals a negative trough from λ = 1 up to λ = 3 with the lowest CP of -0.11 at λ = 2.4. Beyond λ = 3 CP rises to a maximum of 0.21 at λ* =4.0 after which it falls close to zero at λ = 5. This CP profile is typical of the scale of the VAWT tested where a negative trough is present mostly due to high zero-lift drag that hampers the ability of the rotor to generate positive torque at low λ and self-start. The negative trough is observed to slowly diminish as wind speeds, and consequently, Reynolds number increases.