Consistent kinetic energy is harvested from wind and from flowing water in streams, rivers and tidal flows using a translating large sail, foil or wing which is permitted to translate in one direction, followed by translating in the opposite direction while pushing or pulling a cable, rod, or tether which in turn turns a pulley, wheel or other device from which traditional sources of power can be generated. The pulley wheel can be used to generate electricity, create hydrogen from water by electrolysis, compress air for transmission or storage, charge batteries, or perform work such as pumping water, heating water, moving objects, etc.