Submitted to: Windpower
Publication Type: Proceedings
Publication Acceptance Date: March 26, 1995
Publication Date: N/A
Interpretive Summary: Many farmers and ranchers rely on aging mechanical windmills (some of them 50 to 60 years old) to pump water for their livestock. The maintenance cost on these windmills is rising every year, and replacing these windmills with wind-electric water pumping systems is becoming more attractive to farmers and ranchers. Research on wind-electric water pumping systems has been conducted at the USDA-ARS Conservation and Production Research Laboratory in Bushland, Texas, for the past eight years. In this paper, the pump controller performance was evaluated on three different size wind turbines. The wind turbines tested varied in rated power from 1 kW to 10 kW at a wind speed of about 12 m/s. Since no inverter is used in the pumping system, capacitance is added in the pump controller to improve the power factor. Additional capacitance was shown to improve the water pumping performance at high wind speeds for all three wind turbines. Downtime which was caused by inadequate pump controller performance on two of the wind turbines was also discussed. The manufacturer of these two wind turbines is designing a new controller for a new wind turbine, so this paper should help that manufacturer's new controller design. Good pump controller performance resulted in no downtime on the other wind turbine, but damage to the alternator or motor is possible unless some modifications are made to the controller. At the end of the paper, a new wind turbine pump controller is discussed which is being designed at the USDA-ARS.
Technical Abstract: Pump controllers for wind-electric water pumping systems were tested on several different size wind turbines at the USDA - Agricultural Research Service, Bushland, TX. All the wind turbines tested used permanent magnet alternators which generated 230 volt, 3-phase, AC electricity. The wind turbines tested varied in rated power from 1 kW to 10 kW at a wind speed of fabout 12 m/s. The submersible motors and pumps tested varied from 0.38 kW to 5.6 kW. The pump controllers tested ranged from simple (on/off at certain frequency) to moderately sophisticated (low/high cut-in/cut-out frequency selection with thermal protection for submersible motor). No inverters are used on any of the pumping systems in order to reduce the cost and increase the efficiency of the pumping systems. An inverter is not necessary for off-the-shelf AC motors and pumps if the voltage to frequency ratio is maintained between 3 and 4. A voltage to frequency ratio of 3 to 4 was obtained on all the pump controllers tested from the cut-in wind speed to a 13 m/s wind speed by adding the proper capacitance on all three phases. Capacitance was varied on all of the pump controllers tested and it was discovered that optimal capacitance for maximum water pumping performance varied with wind speed. Problems which occurred during the testing (no water pumping when sufficient winds were available, inability to stop the wind turbine in high winds, blade failures, burned up motors) which could have been prevented with a modification of the controller are also discussed in the paper.