The integration of Diffuser Augmented Wind Turbines (DAWT) into the built environment
MetadataShow full item record
The Diffuser Augmented Wind Turbine (DAWT) combines a diffuser and a Horizontal Axis Wind Turbine (HAWT). This set-up was designed with the intention to accelerate upstream wind speeds to the wind turbine rotor using a diffuser thereby generating more power at a given upstream wind speed. The purpose of this research was to investigate the DAWT in terms of optimising performance through diffuser design and testing the effect of building integration on performance. Numerical studies were used to evaluate performance parameters: turbine disk loading, pressure coefficients, tip speed ratio and power coefficient. Augmentation factors quantified the improvement in wind turbine performance when applied with a diffuser using measured wind speeds and pressures. The first study observed the drop in performance between a free stream and roof-mounted DAWT. Following this, two ‘shrouds’ were compared where the diffuser outperformed the concentrator with an augmentation factor of 2.94 versus 1.87 respectively. Numerical studies then focussed on diffuser design by testing eight aerofoil cross-sectional profiles and applying design area (At/Ae) and length-to-diameter (L/D) ratios. The ‘Optimum DAWT’ design was identified as the A5 (FX60 PR281 At/Ae 0.25 L/D 2.5) model. The augmentation factor was an average of 1.42 and 7.43 based on the ratio of wind speeds. A study then tested the roof-mounted A5 model in four Atmospheric Boundary Layer’s (ABL) each representing the wind speed profile of a different urban terrain. The change in ABL was found to have little influence on augmentation. The Optimum DAWT restored wind speeds otherwise lost at the rotor due to building presence. Higher wind speeds and a favourable pressure drop across the roof-mounted rotor in the direction of wind flow were better controlled and distributed with the diffuser. From experimental testing of the Optimum DAWT it was found that wind speeds to the test rotor increased by 136% from 1.02m/s to 2.41m/s. The augmentation ratio was 8.32 based on the ratio of wind speeds. The Optimum DAWT exhibited better responsive behaviour than the test bare wind turbine in terms of matching the expected output power profile and a smaller response time for output power in relation to changing in wind speeds.