Owen Edgerton, Steve Drouilhet
Sustainable Power Systems LLC, United States
Keywords: wind power, solar, water pumping, renewableIn May 2013, Sustainable Power Systems LLC recently commissioned its first 100% renewable commercial scale wind-powered water pumping system at Hawi, Hawaii. The system is powered primarily by a Northern Power Systems 100 kW wind turbine. A deep well submersible pump is driven by a variable frequency drive that is controlled such that the electric load follows the electrical output of the wind turbine. Because the wind turbine is designed to be connected to the utility grid, it was necessary to create a micro-grid with well-regulated voltage and frequency that would allow the turbine to operate. A bidirectional inverter, combined with an advanced lithium battery is used for this purpose. The inverter controls frequency and voltage, while the battery charges or discharges as necessary to make up any short term imbalance between the renewable generation and the load. The pump load set point is biased as necessary to maintain the battery state of charge is an appropriate operating range. A small solar array and battery is used to maintain continuity of control power when there is no wind energy available. This system is the first of its kind in the world.