Abstract: An embodiment for generating energy from a fluid flow is proposed. A corresponding energy generation system includes energy conversion means, sail means switchable between an active condition for being carried away from the energy conversion means by the fluid flow and a passive condition for minimizing said carrying away, connection means for connecting the sail means to the energy conversion means, the energy conversion means generating said energy when the sail means in the active condition is carried away, return means for returning the sail means in the passive condition towards the energy conversion means, and switching means for switching the sail means to the passive condition and to the active condition in response to a maximum distance and to a minimum distance thereof, respectively, from the energy conversion means.