A Method for Estimating the Potential Power Available to Building Mounted Wind Turbines within Turbulent Urban Air Flows

Small-scale wind energy applications have shown great promise in terms of their potential contribution to transitions to low carbon economies. However, the energy generation potential of such turbines within built environments has not yet been fully utilised due to the complexity of turbulent urban winds, and the challenges this creates in developing effective scoping tools for viability assessments. Effective scoping tools for turbine systems across sites within built environments require an estimation of power generated by the turbine under turbulent conditions, in addition to more commonly applied assessments based on mean wind speeds. A new methodology is therefore presented here for predicting the power generated by a turbine system operating within an urban wind resource. It was developed by employing high temporal resolution wind measurements from eight potential turbine sites within urban/suburban environments as inputs to a vertical axis wind turbine 2-D double multiple streamtube model. A relationship between turbulence intensity and the unsteady performance coefficient obtained from the turbine model was demonstrated. Hence, an analytical methodology for estimating the unsteady power coefficient at a potential turbine site is proposed. This analytical methodology was combined with an excess energy estimation model to develop a turbine power estimation (TPE) model which is used in predicting the turbine power within urban canopies. Finally, the effect of turbine control response times on the unsteady power coefficient and the turbine power estimation model was assessed. Estimates of turbine performance based on the present methodology allow a more comprehensive assessment of potential urban wind projects.