A solar powered pump that maximizes available energy usage under variable insolation conditions is disclosed. It also permits the integration of parameters such as minimum flow control, set point operation, etc., without the use of additional sensors, thereby reducing the overall cost of the system. It comprises a solar array or other intermittent power source, a motor drive system that provides the power to an electric motor through a variable output power module and a flow loop comprising a pump coupled to the motor, valves and one or more sensors for flow control. The variable output power module uses data from at least one of the sensors to maximize power utilization by maximizing the flow rate in the fluid circuit/loop.