![]() The desired flow rate is at least 2.7 gpm.ĥ0 ft of vertical rise is (50 ft)(0.433 psi/ft) = 22 psiĨ00 ft of 3/4 inch black poly pipe with 2.7 gpm has a pipe friction pressure drop of 0.81 psi per hundred ft, or 7 psi for 800 ft. The pump has to overcome 1) 50 ft of vertical rise, 2) pipe friction in 800 ft of 3/4 inch pipe, and 3) provide enough pressure at the greenhouse end to make a soaker hose work. Should be able to provide much more than this even allowing for charging efficiency and some cloudy days, so it seems fine.ĭoes the pump have sufficient pressure capability? The optimistic ratings on PV panels, battery charging efficiency of about 80%, and limits of simple charge controllers will result in less than this, and cloudy days must be considered.īut, we only need about 48 watt-hours on a typical day, and the PV On a sunny day, the 30 watt PV panel should be able to provide about (6 hours)(30 watts) = 180 watt-hours a day. Since the actual energy use on an average day is less than 1/5th of this, the battery should have plenty of margin for cloudy days or occasional longer pumping periods. ![]() If the battery discharge is limited to 20% of its full capacity for long life, then the allowable discharge is (115 amp-hrs)(12 volts)(0.2 discharge) = 276 watt-hours per day. In watt-hours, this is (4 amp-hrs)(12 Volts) = 48 watt-hours per day. ![]() This is (8 amp)(0.5 hrs) = 4 amp-hrs a day Pump is 800 ft from the greenhouse - connected with 3/4 inch black poly pipe.Įnergy use: effective run time is half an hour a day with a draw of 8 amps from the 12 VDC battery. Lets go through the sizing for Stan's situation - you can adjust the numbers for your situation as needed.įlow: About 1 hour every other day at about 2.7 gpm (about 160 gallons per pumping session). This works well because the run time for the pump is not very long and can be handled by the battery, and the PV panel has all day to recharge the battery. Instead of direct PV drive, Stan incorporates a deep cycle 12 volt battery to drive the pump, and then uses a small (30 watt) PV panel to charge the battery over the course of the day. The pump draws about 8 amps, so, to drive it directly with PV panels would have required at least 100 watts of PV array, and perhaps a linear current booster for startup. Stan's solution was to use a relatively inexpensive 12 VDC Shurflo pump that is intended for spraying and RV applications. So, this would have been an expensive solution for the relatively low flow required. Using one of the submersible well pumps that are made to run directly from solar PV panels is a nice solution, but the pumps are expensive and they require quite a bit of PV panel area to drive. Using a conventional AC powered pump would have meant running a lot of wire, and the 800ft distance would have meant a larger than normal wire gage to keep the voltage drop from being excessive. The flow requirement was relatively small at about 3 gpm for for an hour and half a day about 3 times a week. Stan was faced with a difficult garden watering problem in which he had to get water from a spring to a greenhouse that was located several hundred feet away and 50 ft uphill from the spring. make sure your wire is at least as big as the amperage of the motor.A Simple and Inexpensive High Lift Solar Pumping Setup the wire should be sized according to that amperage. that is how much power it will draw from the battery. it will say how many amps somewhere on the package. To elaborate, a pump uses a certain amount of amperage (amps). If you have a 24V pump, use a 24V battery. If you have a 12V pump, use a 12V battery. Be careful, you have to match the battery voltage and the pump voltage. It's determined by the power requirements of the pump, not the voltage of the battery or anything else. The fuse and switching is there for safety, not to prevent the pump from draining the battery all at once. It won't drain all the power from your battery and damage the pump. ![]() when you connect a motor (or any load) to a battery, it will only draw the amount of power that it requires. I guess my question was what prevents all the juice from the battery going into the water pumps all at once and ruining the pump? Is the pump designed to only draw a certain amount of power? Is that amount of power determined by the voltage of the battery? If I were to use a 24 volt battery, would twice as much water come out? Sorry, but I still have a little bit to learn about the basics.I think this will answer your question.
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