An energy conserving highly efficient hydraulically energized cooling tower fan system is provided having a rotary fan and hydraulic motor for operation thereof located at elevation within the upper portion of a cooling tower. An axial piston, variable displacement, pressure compensation hydraulic pump and its electric motor, together with a hydraulic fluid reservoir, hydraulic fluid filters and coolers arranged in closed loop assembly are located remotely from the hydraulic motor and fan assembly such as at ground level, to facilitate ease of maintenance and to minimized fire hazard and electrical hazard within the cooling tower itself. The rotational speed of the cooling tower fan is within a predetermined infinitely variable range and is controlled responsive to the temperature sensed in the cool water basin of the cooling tower by a temperature sensor and controller which controls the velocity of fluid output from the hydraulic pump. The hydraulic pump system is also equipped to reverse the characteristics of flow to the hydraulic motor to thereby reverse the operational rotation of the fan according to the temperature of water sensed within the water tower system.