Skip to comments.Need help with solar power
Posted on 03/21/2014 6:38:18 AM PDT by Shaun_MD
hey fellow freepers, I need some advice.
I'm trying to set up a small solar panel system in case the grid goes down. I know I won't be able to power the whole house, but I want to be able to run a 750 watt deep well pump, a couple of 40 watt lights, a ceiling fan or box fan, cb base station and maybe a small freezer/refrigerator. I've got a 12v 100 watt solar panel, a 2000w 12v pure sine wave inverter and a 200 amp hour agm battery. Plus a 30 amp charge controller.
Will this be enough? I'm mainly concerned with making my battery last as long as possible and not kill it with undercharging/overcharging since these suckers are expensive.
I'd like to hear your thoughts and suggestions! Thanks
You should be. Solar is not a dependable power source in times of an emergency. Batter energy storage large enough to run pumps are either very expensive, or greatly undersized.
You really need to look at a fueled generator. You can use the solar/battery and size the battery and wiring large enough to run the pump, but you are going to need a generator to charge up that battery, unless you are only looking for a very short time frame for back up. Hours, not days.
FWIW, my guitar player just bought for his home about $4,000 worth of solar panels mail order from some company in California (he is an electrician that actually specializes in solar installations). 280 watt panels for $.61 a watt. I forgot the name of the company, but I’m planning on doing the same in the next few weeks. I want to run EVERYTHING off it if necessary. I may even augment with wind power (we can get serious wind here at night because we live on a plateau).
Part of my reason for posting is to bookmark this page, since I can’t really answer your question. Yet.
If you cannot run your pump, refrigerator, and fans and also recharge your battery bank, well, you can guess what quickly happens.
You might want to look into a combination of solar and wind.
The cost on a power windmill gives about a 50% ROI over the life of the windmill. I have actually seen the costs, run the figures.
Battery storage is your biggest cost.
If you have the space, add a cistern for your well with filters, fill the cistern using the pump during the day. That takes the load off the batteries in the night hours as well as keeping the overall pressure up, and giving adequate reserves in case of power failures. You don’t want to be relying on batteries to drive a well pump. These are power hogs.
I have a generator but I’m concerned about being able to get fuel in a crisis scenario
I would concentrate on the devices first. Try to go all DC to reduce conversion loss. A high efficiency DC freezer, ice could be used in a high efficiency ice chest for refigerator. Leds instead of 40 watt bulbs, etc.
Your observations are very correct. This type of installation is very location specific.
In the desert southwest it is more reliable.
I noted his comment about pure sign wave inverter. That does not mean 60 cycle. DC to AC inverters are not generally efficient at low frequency. Most such inverters operate at several thousand cycles per second and even those are 50% or less efficient.
I could be wrong,not being that much of an electrical technician.....but you have a 12V. 100 watt input,need a fair amount of output,plus some power loss through that inverter. Doesn’t seem to add up to me for anything other than very short term usage. Then there’s the consideration of whether or not you can depend on the sunshine.
The cost on a power windmill gives about a 50% ROI over the life of the windmill.
Solar+Wind+Gas or Diesel or NatGas/LPG generator.
Because some times the sun don't shine and the wind don't blow...
You can make a fairly nice windmill system cheap and use the same batteries as the Solar system.
I’ve tried to go DC where possible. I’ve been looking at 12v submersible pumps for a deep well.
12v 100 watt panel will give about 8 amps if my math is correct. So if I have a 200 amp hour battery, not going over 5% of the charge would be about 10 amps, correct?
I have a generator but Im concerned about being able to get fuel in a crisis scenario
I know it would not be practical, but my mind just wandered into an idea regarding storing kinetic energy from solar cells. Imagine some huge concrete blocks or rocks attached to a chain connected to a drive at the top of a tree that drives a generator. During the day, the solar powered motor cranks them up to the very top. Then, at night, as you use power, they drop, spinning the generator, supplying power kinda like the weights of a cookoo clock.
SI have a generator but Im concerned about being able to get fuel in a crisis scenario
I suppose you wouldn’t get all that much power out of such a thing though, unless you had a tree a couple miles high.
It also sounds kinda rube goldbergish...
Add up all your ac watts and divide by 120. That is your ac load in amps.
Say you have a TV that consumes 1.5 amps of AC current and you are running it off your batteries through an inverter.
In order to power that TV, you are actually using 15 Amps of DC current (1.5 Amps (AC) x 10 = 15 Amps (DC)) (The 10 comes from the relationship of battery voltage 12, to ac line voltage 120).
Therefore, if you plan to watch TV 3 hours a day, then you will consume 45 Amp Hours total (15 Amps (DC) x 3 hours = 45 Amp Hours) .
You need more, but you have to figure out how much the pump and frig are going to run over time, etc.
A 200 ah battery will supply approx. 1 amp ac for 20 hours max. (or 20 amps ac for 1 hour).
I know someone in sunny california who has an entire roof of panels and a large bank of batteries who is almost entirely off the grid. Very expensive, but he used tax credits and such at the time to put it in.
Like our ancestors, you need to plan how to live without electricity altogether. Use a hand pump or a wind mill for the water. Candles to replace the lights. Hand fans for the ceiling fan. No refrigerated foods. Maybe use the solar panel just for the radio or else just forget it.
Yeah, I’m all over LED’s for all lighting. Heck, those solar powered yard lights stay on all night in our yard, even during the winter. I was really surprised.
You can power a cb and lights with what you have. No way you can do the rest.
Theres a way to turn an alternator into a windmill generator. I haven’t done it but there are guides online. You can attach it to a bike as well for momentary power during low wind situations.
lol I’m too old and fat to get on a bike for too long :D
A 2000 watt invertor might not be able to start the 750watt pump motor. The motor will draw a lot more than 750w for a second at start-up. The invertor circuit breaker might click off on you.
I’d get a portable gas generator to run the pump for short intervals.
I’d plan on 12v peltier coolers instead of a small fridge.
I’d get a few more solar panels.
I’d get a few cheap Chinese charge controllers from ebay as backups. You can get a 30amp for like 25 dollars.
I’d downsize the 40w lights to 17watt florescents or even better LED lights.
Get at least one backup invertor.
Get a couple more deep-cycle marine type batteries at
Wal-Mart ... I got mine there and they were cheap at less than 100$
Small system Solar is good for powering small fans, low watt lights, CB radios and such...not so great for microwave ovens, fridges, air conditioners, pump mortors.
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