A fluid power-generating system operatively disposed between a first support and a second support, the system characterized by an absence of a centrally disposed rotor member, and including a machine capable of acting as a motor and as a generator, the machine coupled to the first support; a flexible wing(s) having an arcuate shape, a distal end coupled to the machine and a proximal end coupled to the second support, for catching and passing a flowing fluid; a tensioned balancing system coupled to the supports for stabilizing operation of the power-generating system; and a rigid strut(s) disposed between each flexible wing and the balancing system for supporting each flexible wing.