In coastal areas with a shortage of fresh drinking water, but enough wind, the combination of wind energy and reverse osmosis (RO) may provide a sustainable way to produce drinking water. Especially in remote areas the combination is also cost effective. At the moment there arc already systems that use windmills in combination with RO installations. But in these systems the wind energy is first transferred to electricity, electricity is stored and used to drive a high-pressure pump. Our system uses a direct mechanical drive of the RO pump by a windmill and storage of clear water covers periods of low wind speed. No electricity is required and the system can be used in remote areas. A commercial windmill, normally used for irrigation Purposes, is connected to the RO-piston pump. The installation has a mechanical dry-run protection, low speed and high-speed limitation. The energy recovery system is not only to recover the energy from the concentrate flow, but also to control the water recovery (10-25%).