Abstract: A windmill energy system for extracting energy from available wind power comprising a windmill in combination with a compressor pump in an essentially closed loop system with the compressor pump including a tubular upper section having a cylindrical bore forming a piston chamber in which a piston is reciprocated and a lower section having a control chamber, a crankshaft assembly located in the control chamber for reciprocating the piston, a first and second passageway in the lower section, conduit means for interconnecting the first and second passageways with the piston chamber and a heat exchange medium and means rotatably mounted to the crankshaft assembly for opening the first passageway while closing the second and vice versa during consecutive discharge and suction strokes.