Design considerations for a small ducted wind turbine

While ducted wind turbines (DWTs) have not yet enjoyed commercial success, theory has shown their potential and suggests a need to identify and explore key drivers of the design space for DWTs. A governing optimization metric of cost/annual energy production (AEP) was examined and a key cost driver for DWT of turbine thrust identified. A review of generalized actuator disc theory indicated that increasing the axial induction of the duct increases the power/thrust ratio and reduces the cost/AEP. It was shown that the particular selection of the rotor power coefficient, C-P,C- Rotor or the total power coefficient C-P,C- Rotor, as a design parameter, changes the nature of the AEP optimization, either maximizing AEP with C-P,C- Rotor or optimizing C-P/C-T and minimizing turbine size with C-P,C- Total. Increasing the blade number to raise C-P and lower tip speed ratio optimizes rotor torque as well for generator matching. Iterative interaction between the wind resource, generator specifications, and design elements to minimize cost/AEP is introduced. The relationship between turbine maximum power output and AEP was explored and it was observed that increasing generator size raises AEP/rotor diameter.