First let me give you a little background. I'm developing a self-sufficient homestead in the foothills of the California Sierra. Our homestead land is on a south-facing ridge at about 5000 feet. Right now our cabin is powered by a meager 400 watt system charging Trojan T105s and powering a 1000 watt Xantrex inverter. It's OK for lights, TV, and occasional power tools. We have extensive garden space and about 110 orchard trees in the ground right now, that must be watered weekly. Our 400 foot deep well has a 1.5hp 240VAC Grunfos pump powered solely by generator power. The static water level of the well is at -100 feet, with the pump down at -380 feet.
We'll be retiring in the not distant future and I'm in the design phase for a more substantial system that can power the whole cabin and the well pump. I'm looking at this Renogy kit as the heart of the new system.
I'm at a crossroads now, debating whether or not I can successfully power the AC well pump on solar, or if I should install the smaller 2700W system and keep using the generator. Let's assume I build the system with four 3panel strings of Renogy's 300Watt panels. I'd wire them such that each string of three produces 900 watts at 112.5 volts, going into a Midnight solar charge controller. This will charge a bank of 8 L-16 Trojan batteries, wired in series for a 48V battery bank. Perhaps I'll utilize Magnum's 4400 watt 120/240V inverter.
Assuming these panels are putting out 80% of rated output at local noon, that would give me about 2800-2900 watts of instantaneous power to start the well pump. I think the starting amps of this pump is ~11.6 amps at 240VAC which works out to be 2785 watts. So, if the inverter actually puts out that much power at 240V, I could start the well pump without even drawing any power from the batteries. Is that realistic to think that way? Right now I'm assuming that the rest of the cabin would be satisfied with about 4000-5000 watt-hours per day to power the rest of 21st century living, like a regular refrigerator, satelite connection, TV, and lights.
I'm going to need about 3000 gallons of water per week, and my pump output is about 275-300 gallons per hour, so that means about 10-11 hours of pumping per week. I have 5000 gallon storage tanks at the top of the hill. I normally pump once a week all day long, fill the tank, then let if fall back by gravity to supply water on demand. I'm assuming I can only pump water for ~3 hours per day, when the panels are producing at least 1100-1200 watts. I'm thinking that if I delay turning on the pump till noon, the morning sun will top off the batteries by noon. By my calculation, the panels might be producing at least 1200 watts till about 2:00-2:30 in the afternoon.
I'm playing with ideas on how to improve afternoon solar production. Using the sizing program, a Midnight 200 can only handle 4 strings of three 300W Renogy panels. BTW, Renogy is local, so I can buy their panels cheaper because I can pick them up without shipping charges. One idea is to add additional panel strings in directions other than due south. Let's say I took 6 strings of 3 panels, two facing southeast, two facing due south, and two facing southwest. At 9am the southwestern panels would be in the shade, with more or less zero production. The southeast panels would be at full output (~1440 watts from 6-300watt panels) while the south-facing strings might be at about 1/4 output (maybe 360 watts). That level of output should stay about the same as the sun swings over from east to west. By the time the southwest panels start recieving light, the southeastern panels should start shading. I'm assuming that only 4 strings will be producing significant power at any given time.
By my math, I'd be producing about 1800 watts more evenly from about 9am to 3pm as the sun switches from one string to another. Does an idea like this work in the real world? Don't want to destroy an expensive controller with too much experimentation. The down side of this stratege is the panels won't reach the same highest peak if they were all producing max power at noon, which would be ~2800-2900 watts, so about a kw of power will need to come off the batteries to top off the panels when starting the well pump. Assume that the greatest water needs coinside with maximal insolation rates, in midsummer
Will this work in the real world?
Thanks for reading through this!
We'll be retiring in the not distant future and I'm in the design phase for a more substantial system that can power the whole cabin and the well pump. I'm looking at this Renogy kit as the heart of the new system.
I'm at a crossroads now, debating whether or not I can successfully power the AC well pump on solar, or if I should install the smaller 2700W system and keep using the generator. Let's assume I build the system with four 3panel strings of Renogy's 300Watt panels. I'd wire them such that each string of three produces 900 watts at 112.5 volts, going into a Midnight solar charge controller. This will charge a bank of 8 L-16 Trojan batteries, wired in series for a 48V battery bank. Perhaps I'll utilize Magnum's 4400 watt 120/240V inverter.
Assuming these panels are putting out 80% of rated output at local noon, that would give me about 2800-2900 watts of instantaneous power to start the well pump. I think the starting amps of this pump is ~11.6 amps at 240VAC which works out to be 2785 watts. So, if the inverter actually puts out that much power at 240V, I could start the well pump without even drawing any power from the batteries. Is that realistic to think that way? Right now I'm assuming that the rest of the cabin would be satisfied with about 4000-5000 watt-hours per day to power the rest of 21st century living, like a regular refrigerator, satelite connection, TV, and lights.
I'm going to need about 3000 gallons of water per week, and my pump output is about 275-300 gallons per hour, so that means about 10-11 hours of pumping per week. I have 5000 gallon storage tanks at the top of the hill. I normally pump once a week all day long, fill the tank, then let if fall back by gravity to supply water on demand. I'm assuming I can only pump water for ~3 hours per day, when the panels are producing at least 1100-1200 watts. I'm thinking that if I delay turning on the pump till noon, the morning sun will top off the batteries by noon. By my calculation, the panels might be producing at least 1200 watts till about 2:00-2:30 in the afternoon.
I'm playing with ideas on how to improve afternoon solar production. Using the sizing program, a Midnight 200 can only handle 4 strings of three 300W Renogy panels. BTW, Renogy is local, so I can buy their panels cheaper because I can pick them up without shipping charges. One idea is to add additional panel strings in directions other than due south. Let's say I took 6 strings of 3 panels, two facing southeast, two facing due south, and two facing southwest. At 9am the southwestern panels would be in the shade, with more or less zero production. The southeast panels would be at full output (~1440 watts from 6-300watt panels) while the south-facing strings might be at about 1/4 output (maybe 360 watts). That level of output should stay about the same as the sun swings over from east to west. By the time the southwest panels start recieving light, the southeastern panels should start shading. I'm assuming that only 4 strings will be producing significant power at any given time.
By my math, I'd be producing about 1800 watts more evenly from about 9am to 3pm as the sun switches from one string to another. Does an idea like this work in the real world? Don't want to destroy an expensive controller with too much experimentation. The down side of this stratege is the panels won't reach the same highest peak if they were all producing max power at noon, which would be ~2800-2900 watts, so about a kw of power will need to come off the batteries to top off the panels when starting the well pump. Assume that the greatest water needs coinside with maximal insolation rates, in midsummer
Will this work in the real world?
Thanks for reading through this!
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