Flow field and performance of a vertical-axis wind turbine on model buildings

Abstract

The placement of a scaled-down Savonius (drag) vertical-axis wind turbine on model buildings is analysed experimentally by the use of turbine performance and flow field measurements in a wind tunnel. The set-up consists of two surface mounted cubes aligned in the flow direction. The turbine is tested at six different streamwise positions – three on each cube. Velocity field measurements are performed with particle image velocimetry along the centreline of the cubes with and without the turbine. The performance at each position is evaluated based on measurements of the produced torque and the rotational speed of the turbine. It is demonstrated that the common practice of estimating wind resources based on the urban flow field without the turbine present is insufficient. The turbine has a substantial influence on the flow field and thus also on the available power. The performance is found to be optimal in the front and centre of the first building with a significant drop-off to the back. This trend is reversed for the downstream building. Holistically, for more generic geometries and varying wind directions, the results suggest the central position on a building is a good compromise.

Influence of incoming turbulence and shear on the flow field and performance of a lab-scale roof-mounted vertical axis wind turbine

“…It consists of two semi circles with a diameter d T of 0:4h and a blade height h T of 0:3h with an overlap of 0:05h between the blades to decrease the starting torque. 49 The same turbine has been used in Jooss et al 18 The size ratio between turbine and building represents a typical VAWT installation for one to three storey-houses and buildings. 18 To evaluate the turbine performance at the different positions, the converted power, P c , is measured as described in Jooss et al 18 For this, the turbine is connected to a brushed DC motor (12G88 Athlonix) functioning as a generator.…”

“…49 The same turbine has been used in Jooss et al 18 The size ratio between turbine and building represents a typical VAWT installation for one to three storey-houses and buildings. 18 To evaluate the turbine performance at the different positions, the converted power, P c , is measured as described in Jooss et al 18 For this, the turbine is connected to a brushed DC motor (12G88 Athlonix) functioning as a generator. The rotational velocity of the turbine X T is tracked with a reflective object sensor (OPB705WZ).…”

“…Experimental studies are needed to complement the simulations 2 such as by Al-Quraan et al, 15 Sarkic Glumac et al, 16 and Vita et al 17 Furthermore, it has been demonstrated that the interaction of a wind turbine with the flow in such an environment is complex and not easily predictable. 18 It extends beyond blockage effects documented for wind turbines generally, 19 as well as in complex terrain, such as hills. 20 Thus, a wind turbine is included in the present study.…”

“…Buildings are often modeled as surface mounted cubes in experimental and numerical studies. 3,14,18,41,42 This approach is also used in the present study with two-surface mounted cubes placed in line with each other in the flow direction with a distance of two cube heights (h) in between. The flow on this configuration has been studied by Martinuzzi and Havel 43,44 and Jooss et al 18 for low turbulence intensities and uniform inflows.…”

“…3,14,18,41,42 This approach is also used in the present study with two-surface mounted cubes placed in line with each other in the flow direction with a distance of two cube heights (h) in between. The flow on this configuration has been studied by Martinuzzi and Havel 43,44 and Jooss et al 18 for low turbulence intensities and uniform inflows. To account for the above described complexity that is presented by an urban flow field, in the present study, the turbulence intensity and vertical shear are varied in the inflow.…”