Methods, systems, and techniques for harnessing wind energy use a tethered airfoil and a digital hydraulic pump and motor, which may optionally be a combined pump/motor. During a traction phase, a wind powered airfoil is allowed to extend a tether and a portion of the wind energy harnessed through extension of the tether is stored prior to distributing the wind energy to an electrical service. During a retraction phase, the wind energy that is stored during the traction phase is used to retract the tether. The digital hydraulic pump and motor are mechanically coupled to the tether.

Methods, systems, and techniques for harnessing wind energy use a tethered airfoil and a digital hydraulic pump and motor, which may optionally be a combined pump/motor. During a traction phase, a wind powered airfoil is allowed to extend a tether and a portion of the wind energy harnessed through extension of the tether is stored prior to distributing the wind energy to an electrical service. During a retraction phase, the wind energy that is stored during the traction phase is used to retract the tether. The digital hydraulic pump and motor are mechanically coupled to the tether.

A motor (10) to be driven by a pressurized fluid includes a manifold (16) with an arcuate surface (20) defining a valve opening (22) surrounded by a sealing surface. A cylinder (26) has an aperture (30) cooperating with the arcuate surface (20). The cylinder (26) is pivotally mounted so as to be pivotable between a neutral state in which the aperture faces the sealing surface, an inlet state in which the aperture (30) is in fluid connection with the valve opening (22), and an exhaust in which the aperture (30) is in fluid connection with a drainage volume. A piston (34), deployed in the cylinder (26), is driven to extend by pressure within the cylinder. The piston is linked to a crank (36) so that rotation of a crankshaft (38) causes a cyclic motion of the piston (34) and cylinder (26) from the inlet state for an extension power stroke of the piston (34), through the neutral state and to the exhaust state for a return motion of the piston (34). The pivot axis of the cylinder, preferably implemented using a pivot axle (32), is located between the crankshaft axis and the arcuate surface (20).