How much solar/battery is needed

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JOhnH

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I bought the lot next door. I plan to knock the house down and combine the two lots. The only thing I plan to keep from the house is the 2 hp irrigation pump. Rather than jury-rigging some sort of extension cord or conduit from my house I'd rather set up a solar panel and battery combination.

Assuming I want to run this pump for about 3 hours, twice a week (6 hours per week), how many solar panels and how many batteries would I need? What type of batteries are recommended?

I would be charging the battery(s) for about 3 days, then running it for about 3 hours. I get good direct Florida sunshine.
 
Amps times volts times running hours running give you necessary watt hours to store. Same calculation with charging hours tells you how many panels.
If you use lead acid batteries, go with at least double the amp hour (watt hours divided by voltage) capacity so they last longer (even deep cycle).

I would dig a trench and run some wires from the house.
 
Maybe check out farm supply stores
Farmers and ranchers around here all use solar powered water pumps at decent prices ... mind you they just fill large water troughs which may not work if you use pressure sprinkler
 
JOhnH said:
I bought the lot next door. I plan to knock the house down and combine the two lots. The only thing I plan to keep from the house is the 2 hp irrigation pump. Rather than jury-rigging some sort of extension cord or conduit from my house I'd rather set up a solar panel and battery combination.

Assuming I want to run this pump for about 3 hours, twice a week (6 hours per week), how many solar panels and how many batteries would I need? What type of batteries are recommended?

I would be charging the battery(s) for about 3 days, then running it for about 3 hours. I get good direct Florida sunshine.
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Why battery. If the sun ain’t out, it’s probably raining. There’s your irrigation. Or not, I dunno Florida weather. I also don’t know much about Solar panels.
 
Yeah, I agree, skip the battery. Make sure the solar panels aren’t shaded, easy peasy. If you want to limit it running, are you going to turn it on manually or have some sort of sensor/switch?
 
2hp = 1.5kWatt, so figure 1.5-3kW panel if you forgo the battery. If you add in a battery, then it'll need to be in the 4.5kW-hr to 9kW-hr range but the math adjusts the panel requirement downward by a factor of 6/solar-hrs per week.

EDIT: Note that I simplified the math quite a bit. There are number of factors to consider, like if you are running the pump while the solar panels are still contributing electricity, which battery technology you choose and whether you'll run them down past 20%, etc.
 
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luvflyin said:
Why battery. If the sun ain’t out, it’s probably raining. There’s your irrigation. Or not, I dunno Florida weather. I also don’t know much about Solar panels.
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Sprinklers run from about 4 am to 7am. They will be on a timer with a rain sensor. Running an irrigation system while the sun is shining wastes half the water through evaporation and the ever present daytime breezes. So it needs a battery for the timer and the pre-dawn running.
 
JOhnH said:
Sprinklers run from about 4 am to 7am. They will be on a timer with a rain sensor. Running an irrigation system while the sun is shining wastes half the water through evaporation and the ever present daytime breezes. So it needs a battery for the timer and the pre-dawn running.
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Gotcha. Just curious, what’re you growing? I met a guy once who grew palm trees. He made some big buckos doing it.
 
luvflyin said:
Gotcha. Just curious, what’re you growing? I met a guy once who grew palm trees. He made some big buckos doing it.
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It's just a residential yard. I'm expanding my lot from 1/2 acre to 1 acre.
I have removed about 50 percent of the St. Augustine grass (high water use) from my yard and replaced it with islands full of native plants (low water use).
The lot I have purchased is almost all St. Augustine grass that needs watering, at least until I start removing it and replacing it with native plants. It will still need occasional irrigation, but not frequent. In fact, I just realized I might get away with using long hoses and manually placed sprinklers. That is very rare in Florida, but I used to do that all the time when I lived up north.
 
I would run an electrical line over to the pump.

I have used solar panels on a boat for several years. Quick search on the internet told me 2hp motor draws 24 amps at 120V AC. Since the solar panels I know put out DC power you need to multiply the amp draw by 10 that equals 240 amps at 12V. Plus a motor draws around 3 times the normal usage at startup. You would need to buy allot of solar panels plus an inverter and batteries to cover the start surge. I do not know of any commonly found inverters that would cover that start surge.
 
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JOhnH said:
It's just a residential yard. I'm expanding my lot from 1/2 acre to 1 acre.
I have removed about 50 percent of the St. Augustine grass (high water use) from my yard and replaced it with islands full of native plants (low water use).
The lot I have purchased is almost all St. Augustine grass that needs watering, at least until I start removing it and replacing it with native plants. It will still need occasional irrigation, but not frequent. In fact, I just realized I might get away with using long hoses and manually placed sprinklers. That is very rare in Florida, but I used to do that all the time when I lived up north.
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We have a place in Santa Barbara. Years ago, because of the water situation, we went dry. No more watering anything, just turned it over to Mother Nature. We were surprised to find just how much stuff thrived.
 
luvflyin said:
We have a place in Santa Barbara. Years ago, because of the water situation, we went dry. No more watering anything, just turned it over to Mother Nature. We were surprised to find just how much stuff thrived.
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We may be doing that. Since we don't live in a community with an HOA, we can do pretty much as we like. Once we get rid of most of the St. Augustine we shouldn't need much water. Native plants can withstand pretty severe weather and need no fertilizer or pesticides. That is a big reason we bought this lot. It is full of invasive vegetation that we are going to get rid of. But temporarily, in order to keep it from looking like the Addams' Family lawn, we will need to do some irrigation.

edit: And we do live in Florida. So a portable solar /battery solution may come in handy during hurricanes.
 
Does the house that is there have electrical service? Would it be worth it to keep that service for the pump (and the giant garage\shop you'll want to build on the lot eventually)?
 
ColoPilot said:
Does the house that is there have electrical service? Would it be worth it to keep that service for the pump (and the giant garage\shop you'll want to build on the lot eventually)?
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Your are reading my mind.

Yes, it does currently have electrical service, and I do imagine having a giant shop/garage on the lot. But at the moment, that is not in the plans. But the plans are very fluid at this point.

The house is a mess. Leslie and I really want to tear it down and start with a clean slate. She has already approved of me building a big shed/workshop of some sort. But I am sure she will balk when she sees what I have in mind.

It might take a while for us to swallow this financial hit before we can proceed with the next step.
 
Keep the service intact if possible. My power utility wanted crazy money to hook it back up after I tore a house down and rebuilt in the same place. And that was with me trenching and buying the cable and bringing it to the pole for them. Looked into solar for my livestock and it wasn't worth it for me. For that small of a lot, trench it.
 
luvflyin said:
We have a place in Santa Barbara. Years ago, because of the water situation, we went dry. No more watering anything, just turned it over to Mother Nature. We were surprised to find just how much stuff thrived.
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.

I just realized that this summer .... we went thru a rare severe drought and all the lawn grass in all the homes went completely brown ... looked dead to me for over 2 months.

In my small front yard I would irrigate it and keep it green ... took a lot of water but I figured cheaper than paying for a new lawn next year.

Then we finally got 3 days of rain and cool cloudy weather for a while .... and to my surprise all the neighborhood lawns revived and some are even greener than mine now.

.
 
I sell solar setups for off grid for a living

go to your local equipment rental place and rent a ditch witch and wire in from your house

the cost for a setup to reliably power that pump is going to be expensive. Not to count the ongoing cost for battery replacement. (AGM will last 2-3 years)

The startup amps on a 240v pump are generally very high. Requiring you to over design your battery bank.

We sell systems into the oil and gas industry. With panels operating metering valves which also have a high starting amp load. We compete against diesel powered generation for this application, and usually diesel wins out.

Dig the trench. Even if the cost is the same as installing a solar system, the ongoing costs will eat any savings you get. Due to shipping costs and lead prices, we’ve raised our prices of batteries 35-40% in the last six months and will be increasing again before the end of the year.

on another note, why not just have your existing sprinkler system tie into the new one? Yes, big cost for that, but then it’s controlled at a single location through your own system.
 
cowtowner said:
I sell solar setups for off grid for a living

go to your local equipment rental place and rent a ditch witch and wire in from your house

the cost for a setup to reliably power that pump is going to be expensive. Not to count the ongoing cost for battery replacement. (AGM will last 2-3 years)

The startup amps on a 240v pump are generally very high. Requiring you to over design your battery bank.

We sell systems into the oil and gas industry. With panels operating metering valves which also have a high starting amp load. We compete against diesel powered generation for this application, and usually diesel wins out.

Dig the trench. Even if the cost is the same as installing a solar system, the ongoing costs will eat any savings you get. Due to shipping costs and lead prices, we’ve raised our prices of batteries 35-40% in the last six months and will be increasing again before the end of the year.

on another note, why not just have your existing sprinkler system tie into the new one? Yes, big cost for that, but then it’s controlled at a single location through your own system.
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Both excellent suggestions. We will probably try to do the second one since we need to do a major overhaul of the irrigation system on our current lot anyway. Since we removed so much turf grass and replaced it with native plants, many of our sprinklers are aimed at the wrong place. So we just don't run some of the zones very often, but that does leave some other areas under-watered.
 
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