Electricity in the Air: Using Roof-Mounted Wind Turbines to Partially Recharge EV Batteries and Extend EV Range

Drivers of electric vehicles (EVs) are currently limited to driving ranges of a few hundred miles before recharging is required. In this study, we consider the use of roof-mounted vertical axis wind turbines (VAWTs) as a means of possibly extending EV range. We conducted field tests to experimentally measure the drag force, F_D, produced by the roof-mounted VAWT, as well as the power generated by the VAWT, P_T, as functions of vehicle speed, v. Our VAWT power data is well described by Betz's law: P_T = Av^3. The power loss due to drag has the same speed-dependence: P_D = F_D * v = Dv^3. We report on a variety of VAWTs, which we tested in the hopes of finding a case for which A > D, as this would allow partial recharging of EV batteries while in transit, thereby increasing driving range.