The above graph shows the effect on CP of increasing the size of the rotor hub while keeping the tip radius constant. It can be seen that the maximum value of CP decreases but occurs at roughly the same inflow velocity. However, it can also be seen that increasing the hub radius from 10% of the tip radius to 20%, 30% and even 40% results in a disproportionately small reduction in power coefficient. Increasing hub radius from 10 to 40% of the tip radius results in only around a 10% drop in power extraction and increasing hub radius from 10 to 20% of the tip radius results in almost no variation. This may eliminate the requirement for compact or complex miniaturised generator, reducing capital costs.
