24 V system 4 water well?

bmetbmet Solar Expert Posts: 630 ✭✭
Curious to know if there are previous threads covering pro/con of 24 volt systems? My ultimate goal is to make our water well self-sufficient in times of emergency. I know there is no such thing as a free lunch, would need to determine the support of an A/C well pump(220V A/C, 2.5 HP)

Pumps don't run all the time, but could solar bear the instant loading required for well pumps to operate?

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,205 admin
    Re: 24 V system 4 water well?

    Anything can be done--Is is practical? Only you can an$wer that que$tion for yourself.

    A XW 6048 (6kW continuous, 12 kW surge) with a > 600 AH (1,200 AH?) 48 volt battery bank may support such a pump. The XW does Grid/Off Grid/Grid Tie with Solar panels/backup generator support.

    If the pump has a soft start (or look at using a VFD--Variable Frequency Drive to provide a soft start/power limiting function) can help.

    If you could use a smaller second well / pump and/or convert your current well to a smaller pump--would probably be a better long term solution...

    Otherwise, how much water storage do you have? The other (perhaps more practical solution) would be to design/build a smaller solar power system to supply a minimal amount of solar power (fridge/freezer, few lights, pump to pressurize home water system--put the Inverter/AC charger/battery bank/backup genset in first--Add solar panels/grid tie operation later as funds permit) and use a good sized genset to power the 2.5 HP well pump a couple times a week to refill a cistern.

    -Bill

    Just to give you an idea of what kind of current you are talking about (12/24/48 volt battery bank).... A 12,000 Watt surge (how long to start your pump, 5 seconds?), 42 volt low battery cutoff, 80% inverter efficiency, 1.25x NEC safety factor for wiring/fuses:
    • 12,000 watts * 1/42 volts * 1/0.80 eff * 1.25 NEC factor = 446 amps @ 48 volt circuit
    • ~892 amps for a 24 volt battery bank
    • ~1,784 amps for a 12 volt battery bank
    Pretty much any design approaching a 200 amp circuit is already requiring some series copper/breakers/switches/battery banks...
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 24 V system 4 water well?
    bmet wrote: »
    Curious to know if there are previous threads covering pro/con of 24 volt systems? My ultimate goal is to make our water well self-sufficient in times of emergency. I know there is no such thing as a free lunch, would need to determine the support of an A/C well pump(220V A/C, 2.5 HP)

    Pumps don't run all the time, but could solar bear the instant loading required for well pumps to operate?

    Yup. Starting "standard" 2.5 HP deep well pump is a bear, all right! Depending on the actual unit and the install (depth, piping) it could overwhelm even a Xantrex XW 6048.

    For off-grid water pumping, it usually makes sense to re-evaluate the pump set-up first rather than trying to power the existing unit from solar. This is because the usual practice when you have grid power available is to install a "whonking great" pump that will definitely do the job, even if it is 4x what is actually needed. With solar, you need to take a minimalist approach.

    If you have grid, why do you want solar? It won't save you any money, you know. :cry:
  • mike95490mike95490 Solar Expert Posts: 9,461 ✭✭✭✭✭
    Re: 24 V system 4 water well?

    To begin, we need to know your water system specs:
    daily usage
    Storage capacity
    lift from pump to tank (feet)
    is it a pressure tank, or gravity feed

    2.5HP is too much to try for solar, that's about 5,000W of power. Unless you are rich
    bmet wrote: »
    Pumps don't run all the time, but could solar bear the instant loading required for well pumps to operate?

    That's starting surge, and the batteries and inverter have to be able to handle it.

    Maybe your solar pump will need to be .5GPM for 6 hours, would that be enough water for you ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • bmetbmet Solar Expert Posts: 630 ✭✭
    Re: 24 V system 4 water well?

    I have been asked to give an opinion about emergency usage, strictly for home. We have both pressure tanks and a 2500 gallon cystern. The rational is sort of doomsdayish, we can do without alot, but we can't do without water.

    If a realistic estimate could be used to educate, then the sort of suggestions offered could become the basis for conversion. I've no doubt the pump is overkill for a single home, but the well used to be part of a commercial property. I've sought advice from trusted friends, but none of us have solar experience. And the costs are more than just the solar contribution. It is expensive to extract the old pump and replace it with new.

    Some components of our current well would-be removed. For example, in an emergency we would take water straight from the pumphouse, eliminating need for a booster to the house. The amount of time the pump would run would also be reduced, with drastic conservation.
  • bmetbmet Solar Expert Posts: 630 ✭✭
    Re: 24 V system 4 water well?

    I do not have good answers for these, but will start documenting what I can. The whole justification comes from very conservative senior citizens who see the world becoming hard, and they want to explore possibility of continued water access in face of disasters, natural or otherwise. They think there will come a time when a portable geneator will be useless without petrol to power it. They believe they may have to buy bullets for their guns. They grow most of their own veggies, and they see laws changing that will make it harder to live independently. They want to know if solar water well is possible. Thanks for your responses.
  • mike95490mike95490 Solar Expert Posts: 9,461 ✭✭✭✭✭
    Re: 24 V system 4 water well?

    still need to have you figure out this:
    To begin, we need to know your water system specs:
    daily usage
    Storage capacity
    lift from pump to tank (feet)
    is it a pressure tank, or gravity feed
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 32,205 admin
    Re: 24 V system 4 water well?

    And batteries will last 3-10 years or so... There are the grundfos and other pumps that will run directly from solar panels (pump into a cistern). But even then, how long do well pumps last (3-10 years themselves?--I am not on a well, so I have no idea).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 24 V system 4 water well?
    BB. wrote: »
    And batteries will last 3-10 years or so... There are the grundfos and other pumps that will run directly from solar panels (pump into a cistern). But even then, how long do well pumps last (3-10 years themselves?--I am not on a well, so I have no idea).

    -Bill

    Hugely variable, Bill. Depends on the particular pump, how hard/often it works, and the quality of the water it pumps. Oh, also the "quality" of the power it's fed (yes; a little 'dig' at MSW inverters! :p )
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