This work aims at developing a new cooling fan for vehicle engine. This fan can operate as a cooling fan at low vehicle speed. At high vehicle speed, however, the fan is rarely used as a cooling fan. Therefore the fan can be used as a wind turbine, which generates electric power. In the previous report we had confirmed the effect of S-Shaped blade profile on the wind turbine efficiency by CFD analysis and the experiments. The present paper reports the improvement of wind turbine efficiency by adopting high solidity for the rotor. The tip portion of the low solidity rotor works as the cooling fan even in the wind turbine operation. However, high solidity rotor can work as the wind turbine at the whole portion. Therefore high solidity increases the wind turbine efficiency and can regenerate more electric power than the original rotor.