Submitted to: National Solar Conference
Publication Type: Proceedings
Publication Acceptance Date: 6/10/2007
Publication Date: 8/8/2007
Citation: Vick, B.D., Clark, R.N. 2007. Comparison of solar powered water pumping systems which use diaphragm pumps. In: Proceedings of the 36th American Solar Energy Society Annual Conference, July 7-12, 2007, Cleveland, Ohio. 2007 CDROM.
Interpretive Summary: While the significant price increase in gasoline at the pump is a hot topic in today’s headlines, a looming much more serious problem for the semi-arid and arid areas of the world is a projected severe water shortage in the next few decades. Most people in the Great Plains and Southwest United States know the importance of water since their existence is dependent on the declining underground water aquifers. At the USDA-ARS Conservation and Production Research Laboratory near Bushland, Texas, we have been conducting research on the most efficient way of pumping water from the Ogallala Aquifer for different applications (water for domestic use, livestock watering, and irrigation) using wind or solar energy. In this paper, four different stand-alone water pumping systems were tested which used a specific type of pump (diaphragm) and were powered by solar energy at one or two power ratings (100 and/or 160 Watts). The maximum amount of water pumped by these systems ranged from 950 gallons per day (gpd) at a well depth of 100 ft to 425 gpd at a well depth of 230 ft. Also, some of the diaphragm pumps tested in this study showed pump efficiencies approaching 50% whereas only a 40% pump efficiency was demonstrated in previous PV powered diaphragm pump testing. While we had shown in previous research that the solar PV diaphragm pump was the most economical alternative for ranchers and farmers with about 30 beef cattle to water with a well depth of 100 ft, this research has shown that solar photovoltaic (PV) diaphragm pumps can water the same amount of beef cattle (30) at a 230 ft well and 75 cattle can be watered at the 100 ft well depth – both these improvements require using additional solar energy (160 instead of 100 Watts). This research also indicates that if more water is needed or a deeper depth required, the pump dealers and well drillers should recommend a different type pump (like helical or centrifugal) with higher solar PV rating.
Technical Abstract: Four solar photovoltaic (PV) powered diaphragm pumps were tested at different simulated pumping depths at the USDA-ARS Conservation and Production Research Laboratory near Bushland, Texas. Two of the pumps were designed for intermediate pumping depths (30 to 70 meters), and the other two pumps were designed for moderate flow rates (9 to 15 liters/min). Using the solar resource of Bushland, Texas and the ARS Laboratory PV panel angle procedure, the estimated average daily water volume of the diaphragm pump systems tested varied from 1300 to 3650 liters/day at a 30 meter pumping depth and 750 to 1650 liters/day at a 70 meter pumping depth. The maximum pump efficiencies of the diaphragm pumps tested varied from 25 to 48%. The graphs depicted in this paper should help a PV pump installer determine which diaphragm pump should be selected or whether another type pump is needed.