Retreat Center water supply

System
System Posts: 2,511 admin
Hello,

I want to switch our water supply to solar pumping. I have been puzzling over the best way to it for some time now. It's time to turn to the pros.
The scene:
Remote Southern Baja retreat center. No Grid in sight.
There are around 35 people using approximately 1700 gallons a day.
Organic garden and landscaping uses about 2500 gallons.
We have a 1250 gallon holding tank. It takes about 25 minutes to fill the tank with the gas pump we are currently using. It's noisy and if someone forgets to turn it on in the evening, the people that get up early don't have water for a shower.
Most of the water is used between 8am and 2pm when the garden is watered. If the tank is full at 5pm then we normally have enough water to last until next morning.
There is 60 feet of head from the bottom of the 18 foot well to the top of the water tank. Our water pressure is provided by gravity.

The most straight forward solution is the a Grundfos 25 SQF-6, 600 watts of panels, and 2 horribly expensive Grundfos control boxes. Approx $5500 +more for mounting the panels.
I don't like this route for a few reasons. I don't have a secure place for the panels. The nearest rooftop is 150 feet away. Pole mounting equipment is expensive. Next I have to buy 2 different control boxes. One for the float switch and another to be able to connect a generator for backup. Lastly I worry that we will be using the generator to often because our tank is to small to last the night if we aren't completely topped up at 5 or 6pm.

I would prefer to upgrade our existing PV system that we use for power and figure out some way to get the electricity over to an appropriate pump. A distance of 150 feet. Right now I have excess PV. I am planning to balance the system with a battery upgrade next month. I could still use the Grundfos 25 SQF-6 but feed it AC. But I have a feeling Grundfos may make something cheaper if I want to do it that way. I'm not sure how much PV/Battery I would have to add to my system to power a 1hp (guessing) pump.

My current system is 1.7KW of panels, Flexmax80 and C60 charge controllers, Xantrex Prosine 2000 watt inverter/charger 12V, Mini DC box for breakers, 8 Golf cart batteries wired to 12 volt soon to be upgraded to 8 L16 size batteries.

I know the 12V battery is a bit of a limitation. We have had to build our system slowly for financial reasons. Last year I added more panels and better charge controller. This year batteries. Next year I want to upgrade the inverter so we can switch over to 24 volt.

Any ideas for moving lots of water in a reliable quiet way?

Thanks.
Jon

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Retreat Center water supply

    The problem with battery based PV system is that batteries are around 80% efficient. The Inverter is around 85% efficient--so 0.8*0.85=0.68 or you have already lost ~32% of your power so you can offset your power usage (more solar panels, possibly another charge controller, etc.). Plus the added cost of wear and tear on your battery bank from the pump loads.

    If this added cost is worth it to you (and it very well maybe)--then replacing the gas driven pump with an efficient (but probably lower horse power) pump is possible.

    You probably do not need a 50 gallon per minute pump (like your current gas pump).
    • 1,700 + 2,500 = 4,500 gallons per day
    Assume 12 hour a day pumping (do most of your pumping in daylight--then you don't have the battery losses):
    • 4,200 gallons per day * 1/12 hours a day pumping * 1hr/60 min = 6 gpm
    So, assuming your minimum needs are 6 gpm, 60' of head, and some margin for error--that is around 0.17 HP. Taking some more guesses (50% efficient pump) and such--call it 1/3rd HP and 250 watts.
    • 250 watts * 12 hours = 3,000 Watt*Hours per day...
    Assuming somewhere around 5 hours of day of sun (don't know your area), 0.52 derating for all Solar PV/Controller/battery/Inverter losses:
    • 3,000 Watt*Hours * 1/0.52 eff * 1/5 hours of sun = 1,200 watts of solar panels to run AC pump from off-grid solar system...
    So--you would almost need to double your existing system--I would guess...

    If this looks at all reasonable--then your next step is to work with somebody that knows a heck of a lot more about water pumping than I to size the most efficient AC pump for your well system based on your daily (and future) needs.

    A small pump keeps the peak power requirements down... But an efficient pump will keep the total power needs low--it will be a balancing act to find a pump that will meet your needs and be efficient. (in well submersible? avoid jet pump as inefficient, etc.).

    A larger pump that does most of it pumping during daylight (such as 12 gpm for 6 hours per day) may be easier on the battery bank (less cycling as you are using power directly from the panels during the day)...

    What are your thoughts?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • blackswan555
    blackswan555 Solar Expert Posts: 246 ✭✭
    Re: Retreat Center water supply

    A couple of thoughts,
    Conservation, That seem a lot of water usage, 50 gal`s a day each person! can you do anything there to start, it is costing you to move it about, How do you irrigate ? drip to base of plant seems about the most efficient, can you turn the water pressure down a little ?, fit smaller shower heads? put a Rock in the WC cistern?

    PV > AC pumping, as mentioned it is not cheep with all the losses involved, One way to save a little if your load is not too time sensitive, Try to run it during "good sun" hours, That way you will save the bat in > out losses,

    Tim
  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    Re: Retreat Center water supply
    Organic garden and landscaping uses about 2500 gallos
    What about water conservation by putting in a gray water system on your showers and filtering this.
    water and using it for irrigation?
  • Chuck46
    Chuck46 Solar Expert Posts: 95
    Re: Retreat Center water supply

    Hello, these folks have a boat of information on this suject. I guess its alright to post this?

    http://www.oksolar.com/pumps/solarjack.html

    If not i beg forgiveness now.
    Chuck
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: Retreat Center water supply

    I went through a similar decision process and came to the conclusion that it's more efficient to have a single PV system than different ones for different loads. That way, when you're not pumping you can still use the PV to charge your bats - and the other way around too.

    A cost effective route for AC pumping is to use a 3phase pump and a variable frequency drive to convert single phase to 3 phase. The benefit of this combination are:
    - More reliable 3 phase motor
    - 3 phase pumps can be cheaper than similar single phase units
    - There's no in-rush current so you don't have to supersize your inverter

    Then you can spend more on expanding your existing PV panel.
    Your water storage is definitely too small, any chance of expanding it? This will let you effectively use it as a battery in the way that Tim is suggesting. Pump more when the sun's out and then you'll have spare PV for battery charging on bad sun days.
  • PhilS
    PhilS Solar Expert Posts: 370 ✭✭✭
    Re: Retreat Center water supply
    ravemind wrote: »
    The most straight forward solution is the a Grundfos 25 SQF-6, 600 watts of panels, and 2 horribly expensive Grundfos control boxes. Approx $5500 +more for mounting the panels.

    Wouldn't you only need one control box? I installed a smaller Grundfos pump last year and only use one CU200 control box. I can power it from any of my inverters or the generator by just moving the plug that is wired to supply its power.

    (Having worked extensively with electric and electronics since the mid-sixties, I still find this pump totally amazing in that it can take AC or DC and from 30V to 240V.)

    Phil
  • blackswan555
    blackswan555 Solar Expert Posts: 246 ✭✭
    Re: Retreat Center water supply

    I second Stephan`s point about a VFD if you can use one, the other benefit being they are speed (pressure/flow) variable and nearly linear in consumption vs speed,
    I use one on a 3 ph swimming pool site that has a large infinity effect pool, need`s a big pump to create waterfall but about a 1/4 of the flow for every day sanitation, Owner has a party switch, pump uses 5 amps to run daily, 19a to "party"
    Tim
  • audredger
    audredger Solar Expert Posts: 272 ✭✭
    Re: Retreat Center water supply

    Water conservation should be the first order of the day! 48 gals per person per day is too much!
    More storage! Two days worth of storage at the min.
    I would go with a pv direct pump. Have you looked at sun pumps?
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: Retreat Center water supply

    PV direct pumping might be more efficient at converting sunlight into litres/second but in a mixed system where you need both electricity and water pumping it will waste power in the long run. PV direct is fine if you have a large storage reservoir and your water needs are such that it doesn't matter too much when you do the pumping.

    But in a system where you need PV for electricity and PV for pumping, having 2 separate systems means that you can't share surplus power. So consider the following scenarios:
    - The water tank is empty and needs filling up right now, but there's very little sun and the PV system for the pumping can't fill it fast enough. But the batteries for the elec generation system are fully charged so the PV for that system is doing nothing and can't be used for water pumping.
    - The water storage tank is full, so the PV system for the pump is doing nothing. But everyone has turned on their hairdryers so the batteries are taking a beating and the PV system for the batteries can't charge them fast enough.... so all that PV installed just for pumping is standing around doing nothing.

    It would be more efficient and give you more flexibility if you had one large PV system because you can then decide how to prioritise the loads between battery charging and water pumping.
  • System2
    System2 Posts: 6,290 admin
    Re: Retreat Center water supply

    Hi Guys,

    Thanks for all the good information. I'm still going through it all at looking more closely at the options. I'm going to spend some time getting a more precise idea of how much water and power we are currently using.

    I will look for more steps we can take towards conservation. We use a drip system in the garden, but I will try to get an expert in to see if it is being used efficiently. We have put in a lot of new Palm trees and they need a lot of water until they tap in to the water table (only 5-12 feet.) We are going to look for more ways to keep the soil from losing moisture so quickly when we water them. Moving and filtering the gray water

    After I put in my new batteries (I'm now considering going to 2100 AH), I think I will have a considerable amount of excess PV. Even with my woefully undersized battery bank being nearly depleted/recharged everyday, I am still having 3 or more hours a days with my 1.6kw of panels doing nothing.

    We use a lot of electricity in the evenings from 6pm to 9:45pm. If my Xantrex is to be believed, about 800 watts per hour for those 3.45 hours. 35 CFLs, and a fully electrified band. If I can slow down the drain on my batteries from 6pm-9:30pm. I think it will make a big difference to what I have available for pumping water.

    The Grundfos pump can move 5000 to 7000 gallons in a 6 hour period of sun with 600 watts of panels. Would it be able to move the same amount of water with 600 watts of AC?
    It seems like using my main system to power it is do-able with adding 400 more watts of panel. I'm thinking I should have plenty in the batteries to pump a little later in the evening and start a little earlier in the morning. Can I use a timer to keep it from topping up the tank at night?

    I like the idea of having a VFD for the pump. I had been wondering what type of device would be necessary for variable speed of a pump. Now I know. I'm not really sure where I can find help sizing/pricing one here in Mexico.....
    I wonder if Grundfos has a product for controlling the speed of their pumps?

    Thanks
    Jon
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Retreat Center water supply

    I believe the Grundfos will MPPT (Maximum Power Point Tracking) on attached solar panels--and the pump speed (and output flow) is based simply on how much power is available (sun, angle, weather, etc.).

    If you feed XXX volts/Amps of battery backed power--the pump will simply speed up to meet the available power (with in its capabilities).

    The big difference in efficiency between a direct attached solar array and a battery+inverter is that the battery+inverter cost you:
    • ~0.80 batt eff * 0.85 = 0.68 overall efficiency...
    So, you end with an extra 32% losses to use your battery backed central system (and he extra cycling on battery, etc.).

    It is a close call as to what is best for you--a central system or two separate systems (one off grid; the other dedicated panels to the pump). I do like the central system (one power collection point) as opposed to independent systems where one may have extra power and the other is deficient.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Retreat Center water supply
    ravemind wrote: »
    We use a lot of electricity in the evenings from 6pm to 9:45pm. If my Xantrex is to be believed, about 800 watts per hour for those 3.45 hours. 35 CFLs, and a fully electrified band. If I can slow down the drain on my batteries from 6pm-9:30pm. I think it will make a big difference to what I have available for pumping water.

    It ain't sexy, but it's what you need. Something in the 2000W class inverter generator powering a battery charger (is one in your inverter?) With a fixed evening load, it's just killing your system. 4 hours at vari-throttle may only be 1/2 gallon of gas. It would really save your system, and could be used as great example of "Hybrid" power.
    Also usable on the cloudy days.
    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 ,

  • System2
    System2 Posts: 6,290 admin
    Re: Retreat Center water supply

    I have been using a Honda eu2000i for for a few years as my auxiliary power. It works really well with the charger built into the Xantrex Prosine Inverter.


    My big concern is if I plug the Grundfos unit in to AC it will just take as much as it can (1400 watts?) and start pumping at 30 gallons a minute. I really want to slow it down. The Grundfos SQFlex pumps run on single phase AC. What type of equipment would I use to limits the power that it can take? Would it be the same type of VFD that a controls a 3 phase pump? A giant dimmer switch?


    I tried calling a few installers in the US, but they really didn't know anything other than the standard installations configurations in the literature.

    Jon
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Retreat Center water supply
    ravemind wrote: »
    My big concern is if I plug the Grundfos unit in to AC it will just take as much as it can (1400 watts?) and start pumping at 30 gallons a minute. I really want to slow it down. The Grundfos SQFlex pumps run on single phase AC. What type of equipment would I use to limits the power that it can take? Would it be the same type of VFD that a controls a 3 phase pump? A giant dimmer switch?

    http://www.genproenergy.com/sq_flex_brochure.pdf does not state if you can throttle it back, if running on AC. You could always get a DC power supply that matches what you desire, and power the supply from the AC.
    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 ,

  • bluetick
    bluetick Registered Users Posts: 19
    Re: Retreat Center water supply

    Crazy as it sounds, looking at the wind patterns for Baja, it looks like you get steady winds for most locations. How is the wind in your area? If stable, sink another well and use an aeromotor, use your current well setup for backup. Their not sexy but they work day and night.

    http://www.aermotorwindmill.com/Sales/CommonQuestions.asp