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  • What size solar for well pump?

    I have a Grundfos 5SQ-180 that is sitting 250' down a 260' well that has a static water level of 30' (so lots of water sitting down that hole). The replenish rate of the well is only about 2 gpm, but I just pump it to the surface into water storage containers (55 gallon food grade barrels) for now.

    For the last year since I have had the well drilled, my little Honda EU2000i has worked admirably (on gas, won't run the pump on propane though), but I really want to get a solar system set up to run the pump.

    I know the Grundfos is a 1/2 hp motor and the pump pulls about 12amps @ 115v.

    With this in mind, I believe i need a 1500 watt inverter (and I can only seem to find modified sine wave inverters below 2000 watts), but what size battery bank would I need to run the pump for say an hour before I was at 50% DOD?

    And how many watts in solar panels would I need if my winter peak sun hours is 1.5? I know I'll also need a charge controller....but am I missing anything else?

    Would a system like this function when it was 10 degrees Fahrenheit out?

    Thanks

  • #2
    Based on your specification:

    Panel wattage = 2000 watts
    Charge Controller = MPPT 80 amps
    24 Volt Battery Capacity = 300 AH AGM type
    Inverter = 3000 Watt True Sine Wave
    MSEE, PE

    Comment


    • #3
      Wow, at the US Dept of Energy avg of $8 - $10 per watt, that comes to about $18,000 just to run my well pump. I'm just shocked that it would cost that much.

      If I bought a 1000 gallon propane tank + 800 gallons of propane to fill it = $6500 (roughly)
      6Kw propane generator + installation = $3500 (roughly)

      So about $10,000 total.

      I would only need to run the pump about an hour a day (at 4 gallons of water per minute). The generator consumes .85 gal/hour at 50% load, so if I only used it for the well, I could run that well pump for over 20 years for a little more than half of what it would cost to run it on solar (assuming the batteries lasted 20 years, which I don' think they would).

      After everything I have been finding out about solar power, at least for the area I am in (NE Washington state), I don't ever see a break even point (much less getting ahead). This is depressing.

      Comment


      • #4
        NE Washington is one of the better locations for sun! NW Washington doesn't get enough sun for much of anything but you are better off - if a bit colder

        The cost may be more like 5$ per DC watt

        Look at solar hot water heating or air heating if you want a solar project with better efficiency/return.
        sigpic

        Comment


        • #5
          It's not quite that bad
          Panels about 3500
          Racking (roof mount flush) 600
          Charge controller about 600
          Batteries 800?
          Inverter about 1000
          Total about 6500.00
          Fuel costs 0

          Now for the generator
          About 10K installed
          .85 gallons of propane per day x365 = 310gallons per year.
          Propane here is about $3.00 per gallon so $950 per year in fuel costs.
          figure 6-7 oil changes per yer in there at ?
          With oil changes figured at $20 each and not counting other breakdowns in the generator let's look at life cycle costs over 20 years.
          Total install and operating over 20 years $31,400

          Solar 6500
          If you buy good batteries you should be able to get 5 years out of them.
          So over 20 years $3200
          Inverter and charge controller will probably die and need to be replaced.

          Solar initial investment 6500
          Less 30% federal credit 1950
          Net solar cost 4550
          Battery replacement 4x 800 = 3200
          Inverter and charge controller replacement 1600
          Total install and operating over 20 years. $9350

          The numbers are based on a diy install using UL listed components.
          Last edited by Naptown; 01-23-2012, 03:57 PM.
          Rich
          WWW.solarsaves.net

          NABCEP certified Technical Sales Professional

          http://www.solarpaneltalk.com/showth...Battery-Design

          http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

          www.gaisma.com

          Comment


          • #6
            Originally posted by Naptown View Post
            It's not quite that bad
            ...
            Now for the generator
            About 10K installed
            .85 gallons of propane per day x365 = 310gallons per year.
            Propane here is about $3.00 per gallon so $950 per year in fuel costs.
            figure 6-7 oil changes per yer in there at ?
            With oil changes figured at $20 each and not counting other breakdowns in the generator let's look at life cycle costs over 20 years.
            Total install and operating over 20 years $31,400
            ...
            I see where you are going with this, but it's not quite that bad with the propane genny either. Propane is only $2.20/gallon here and the maintenance interval on the genny is 500 hours. So the cost for the generator is probably closer to $20K. But that is still double what you came up with for solar costs.

            I'm kind of thinking out loud here...but our house is 300' from the well. How far could I run a line that was pushing 110-120v before the loss was impractical or the size of the cable too expensive to justify?

            Comment


            • #7
              Maybe...

              A Wood Gassifier? They ran trucks with them back in the early '40. Scrounge wood from the forest floor, It's still renewable and doesen't put any more CO2 into the atmosphere than if it were left to rot on it's own,...just does it faster.

              Though, I would investagate why that honda won't do the job on propane first. There might be a cheap fix, or at least cheaper than all that money your talking about. Just some thoughts that popped into my head, bounced around a bit, so I had to let them out. Good luck.
              Charlie

              Comment


              • #8
                Originally posted by Decidion View Post
                I see where you are going with this, but it's not quite that bad with the propane genny either. Propane is only $2.20/gallon here and the maintenance interval on the genny is 500 hours. So the cost for the generator is probably closer to $20K. But that is still double what you came up with for solar costs.

                I'm kind of thinking out loud here...but our house is 300' from the well. How far could I run a line that was pushing 110-120v before the loss was impractical or the size of the cable too expensive to justify?
                300' is 300' whether it is the generator or PV. Voltage drop is a function of draw in amps and distance. To reduce voltage drop you would move the generator or the PV closer to the well or increase the wire size to accomodate.
                Rich
                WWW.solarsaves.net

                NABCEP certified Technical Sales Professional

                http://www.solarpaneltalk.com/showth...Battery-Design

                http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

                www.gaisma.com

                Comment


                • #9
                  You'd probably be better off to replace your existing pump with a Grundfos SQF series pump, and get the Grundfos CU-200 control box. Then you could run the pump on grid AC, sine wave AC locally produced, or directly off DC from solar arrays.

                  Since you are pumping into storage now, this is the idea pump to run directly off solar...skipping the conversion to AC, batteries and all that. You simply put a couple hundred watts ( depends on head, and flow you want ), and when the sun shines, the water flows.

                  They also make a generator interface to make it easy to connect a generator to the pump if solar isn't enough to run it ( like extended clouds ). If the generator runs out of fuel, the interface auto switches back to solar.

                  Comment


                  • #10
                    Propane is a less dense fuel than gasoline, I think it's almost 20% less.

                    Your startup surge that the inverter needs to supply, is going to be at least 5x the running power

                    My 1/2 hp pump, running, pulls 1,000w from the inverter (according to the inverters meter)) so that's at least a 5,000w starting surge.

                    I run 240VAC to my pump, 400', over #6 alum wire. Same as #8 copper.

                    240V AC 1/2 hp pump is the same watts as 120VAC, but half the amps.

                    Voltage drop calc in my .sig will help you a lot, figuring distance, amps and wire gauge.

                    Don't forget the wire splice to the underwater cable in the well, you have about 250' of likely #10 wire, unless you are lucky and they installed #8 down the well.

                    If you set the pump to only run while the sun is shining, a 600W array could keep batteries charged (making half the power you need) so you can downsize a lot. If you want to pump every day, rain or shine, and night, that's going to cost you.
                    spreadsheet based voltage drop calculator:
                    http://www.solar-guppy.com/download/...calculator.zip
                    http://www.solarpaneltalk.com/showth...oss-calculator

                    http://www.mike-burgess.org/PVinfo_2.html

                    solar: http://tinyurl.com/LMR-Solar
                    gen: http://tinyurl.com/LMR-Lister ,
                    battery lugs http://tinyurl.com/LMR-BigLug
                    Setting up batteries http://tinyurl.com/LMR-NiFe

                    gear :
                    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

                    Comment


                    • #11
                      Originally posted by Decidion View Post
                      Wow, at the US Dept of Energy avg of $8 - $10 per watt, that comes to about $18,000 just to run my well pump. I'm just shocked that it would cost that much.
                      Well you are comparing Apple to Oranges, and the info you read is old.

                      DOE is quoting a grid tied system (Apples), you want a Off-Grid Battery system (oranges). $8 - $10 watt sis 3 to 5 year old information for a grid tied system. Today $5 to $7/watt. Again you want a Battery Off-Grid System, not grid tied so forget all that jazz, it does not apply.

                      Battery systems are priced per Kwh not watts. For a grid tied system in your area will cost you roughly $4000/Kwh. So by your statement of a 1440 watt pump run 1 hour = 1.44 Kwh/day. That will cost you around $6,000, plus a generator and misc equipment.

                      Don't even try to figure break even point , because it is not possible with a battery system It will cost you at least 10 times more for electricity the rest of your life. Of that $6000 is $1600 battery that needs replace about every 5 years.
                      MSEE, PE

                      Comment


                      • #12
                        Lots of good input here I'll have to digest. I am thinking I am going to have to start out small and then just deal with only being able to fill our topside tanks on sunny days. This at least gets me started down the solar path, otherwise I might never get there.

                        Thanks for the feedback!

                        Comment


                        • #13
                          Originally posted by Decidion View Post
                          Wow, at the US Dept of Energy avg of $8 - $10 per watt, that comes to about $18,000 just to run my well pump. I'm just shocked that it would cost that much.

                          If I bought a 1000 gallon propane tank + 800 gallons of propane to fill it = $6500 (roughly)
                          6Kw propane generator + installation = $3500 (roughly)

                          So about $10,000 total.

                          I would only need to run the pump about an hour a day (at 4 gallons of water per minute). The generator consumes .85 gal/hour at 50% load, so if I only used it for the well, I could run that well pump for over 20 years for a little more than half of what it would cost to run it on solar (assuming the batteries lasted 20 years, which I don' think they would).

                          After everything I have been finding out about solar power, at least for the area I am in (NE Washington state), I don't ever see a break even point (much less getting ahead). This is depressing.
                          That's why your better off replacing you pump with one that can be run solar direct. A solar slow pump that only pumps 1/2 to 2 gallons per minute but spends all day pumping into your storage. The tanks servive as your storage so no need for batteries. Cost would most likelybe in the $2k to $5k range

                          Hear are some examples

                          http://www.builditsolar.com/Projects...terpumping.htm

                          This is a really nice DIY system

                          http://www.otherpower.com/otherpower_waterpumping.html

                          Comment


                          • #14
                            115 volt well pump

                            Hi . I have been reading tour threads about water well pumping. I am in the same predicament. I live off grid in north Idaho, My well is 240' deep my pump is at 140' I pump the water into a 275 gal water tank. I use a 6000 watt generator to run the pump. I would like to put a pressure tank in and run it on solar power. I build my own panels at 18v 63w 3.5a right now I have 10 panels witch runs my house. My well pump is 120v it draws 24a on start up for 1sec than 10a while running. I have 63psi at tank, with a pressure tank it would run about 3 minutes,what size of array would I need.

                            Comment


                            • #15
                              Originally posted by Bigbirdd View Post
                              ....I have 63psi at tank, with a pressure tank it would run about 3 minutes,what size of array would I need.
                              Huge. You would need a 48V system, to have enough amps avaibable to feed the inverter DC, as the motor starts (surge reuirement.)

                              You need to consider an elevated tank, that will provide gravity pressure all night long, till the sun is up again to run the pump.

                              Or look into an 12 v RV pump that will take ground level water from your storage tank, and pressureise your system.


                              120V @ 24A starting, a 48V battery has to supply about 3000 watts to the inverter, @ 48V that's 62 amps
                              spreadsheet based voltage drop calculator:
                              http://www.solar-guppy.com/download/...calculator.zip
                              http://www.solarpaneltalk.com/showth...oss-calculator

                              http://www.mike-burgess.org/PVinfo_2.html

                              solar: http://tinyurl.com/LMR-Solar
                              gen: http://tinyurl.com/LMR-Lister ,
                              battery lugs http://tinyurl.com/LMR-BigLug
                              Setting up batteries http://tinyurl.com/LMR-NiFe

                              gear :
                              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

                              Comment

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