Things that Work! The PV Powered Econosub Pump by Solarjack by Jonathan Hill Deep-well water pumping has always been the Achilles heel of the photovoltaic industry. Until now, we usually advised folks to use a generator and a standard a.c. submersible pump. But with the ECONOSUB SDS series pumps, all that has changed. The ECONOSUB is a positive displacement, diaphragm-type, submersible pump. It operates on one or two standard size PV panels or a 12 or 24 volt battery bank. With flow rates of up to 2 GPM and lifts up to 230 feet, the ECONOSUB revolutionizes solar pumping. Requiring no batteries or lubrication, if used with a pressure switch and a battery, it can be used as a home pressure system. Test results show 8,000 hours on the diaphragm with no noticeable wear. The pump is constructed of marine quality bronze and stainless steel. Although it will operate directly from a 12 volt photovoltaic array of as little as 35 watts, the ECONOSUB reaches its maximum output with 2 ARCO Solar M75, 47 watt PV modules (or the equivalent) connected in series. When used in an array-direct configuration, a linear current booster is suggested. I prefer the Sun Selector LCB 3-4-8/T, as it can be adjusted to various PV modules. It also performs well when connected to a 12 or 24 volt battery bank. No LCB is required in when a battery is used. For maximum output, a 24 volt system (or two series PV modules) is recommended. Here's the kind of performance that you can expect from this unit: With one 47 watt module at open discharge, it delivers 60 gallons per hour. At 225 foot head, the pump delivers 19 GPH. With two 47 watt modules at open discharge, you can get 120 GPH, and at 225 feet, 33 GPH. With a 24 volt battery bank, it will deliver 55 GPH at 225 feet. At 100 feet, it produces 81 GPH on either 2 module array-direct or 24 volt battery operation. Our preliminary testing has shown these figures to be just about right. Another unique feature of this pump is its small size and weight. It is the only pump I've seen that will fit down a four-inch diameter well casing. At a weight of only 14 pounds, installation is quick and easy, even for the first-time user. In addition to providing water for the PV-powered household, the ECONOSUB works well as a backup for a standard submersible pump used with utility power or a generator. Because of its modest size, it can be installed above the AC pump, with room to spare alongside for the pipe and wire from the lower pump. All that is required here is a small battery bank and a small automatic charger, which keeps the batteries at a constant state of full charge, should the power ever fail. Needless to say, this allows future conversion to PV-power with a minimum of hassle. In closing, I feel that the ECONOSUB is just about the best (and most affordable) pump of its type currently on the market. At under $800 (less than $1,500 including two 47 watt modules and an LCB), it's a value that's hard to beat. I only wish that they made a larger unit for those of us with lawns! For the last nine years, Jonathan Hill has been the proprietor of Integral Energy Systems, a full-line dealer in Nevada City, CA. You can reach him at (916) 265-8441.