Submitted to: National Solar Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/16/2003
Publication Date: 7/21/2003
Citation: Vick, B.D., Neal, B., Clark, R.N., Holman, A. Water Pumping With AC Motors and Thin-Film Solar Panels. CD-ROM. Solar 2003. Interpretive Summary: A common dilemma for most farmers and ranchers is determining the best way of pumping water from an underground well at a remote location where no utility electricity is available. In these remote locations, the most economical way of pumping water from a well for livestock watering or domestic purposes is usually with a wind or solar powered water pumping system. One way of converting solar energy into electricity is with thin-film solar panels. Two different types of thin-film solar panels (cadmium-telluride and amorphous-silicon) were tested on a water pumping system at the USDA - Agricultural Research Service laboratory near Bushland, TX. It was found that there was a 50% decrease in the amount of water pumped over a 3.5-year period due to degradation of the cadmium-telluride panels. Amorphous-silicon panels have only been tested about a year and a half, but so far the panel degradation hasn't been as rapid as with the cadmium-telluride panels. A controller was needed for these solar water pumping systems in order to convert the DC electricity output from the solar panels to the AC electricity needed to run the AC submersible motors. A 1998 model controller was found to be more user-friendly than the one installed in 1995. The controller installed in 2002 resulted in a 60% increase in water pumped when single-phase AC motors were used. Presently this solar water pumping system consists of: twenty-five 43 Watt amorphous-silicon thin-film solar panels, a ¾ horsepower 3-phase 230 Volt submersible motor, a 12 stage 4-inch centrifugal pump, and a 2002 controller. This solar water pumping system will pump enough water from a 140 foot well in the Texas Panhandle to satisfy the water requirements of 164 cattle at a total cost of about $8000 (including wiring, pipe, and solar panel mounting structure).
Technical Abstract: Water pumping system performance was measured for two different types of thin-film PV panels. The controllers used during the testing converted DC from the solar panels to single or 3-phase AC depending on submersible motor type. It was found that on similar solar irradiance days, a 3-phase AC system with cadmium-telluride panels would pump 80% more water than a single-phase system. However, a 3-phase system with amorphous-silicon panels pumped only 20% more water than a single-phase system due to an improved model controller that was more efficient in single-phase mode. The cadmium-telluride panels were observed to degrade significantly in performance with time. Over 3.5 years the flow rate was observed to decrease by 50%. The 3-phase PV water pumping system with amorphous-silicon panels can pump enough water from a 42 m (138 ft) well to water 164 cattle in the Texas Panhandle.