Off Grid Organic Farmer and Water Pumping Questions

Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
A big issue with our home is water-in and water-out.

Our well pump is 220VAC 7amp [though I understand that it peaks at 15amp when starting]. Then our leech field is 100 yards away and slightly up-hill. So we have to pump water out also. Once from the septic tank, and again at a septic transfer station. These are both smaller 110VAC chunky pumps that I think are only rated at 1amp.

Water in and water out, is the bulk of our electricity consumption.

We have 4000watts of panels now, and are saving up for another purchase of 4000watts of panels. I was told by a local installer that if I go with a 24v system, then I can get an invertor that has a 220VAC output capable of running our well pump.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,063 admin
    Re: Can I Use Solar for 220 volt AC Well Pump?

    When you talk about 4,000-8,000 watt solar arrays, you are speaking of pretty large systems. I would probably suggest a 48 volt system. That will save you money on Charge Controllers and wiring/wiring issues.

    For example, a 4,000 watt array will require a minimum controller (MPPT type) rating of:
    • 4,000 watts * 1/14.5 volts battery charging * 0.77 panel+controller deratings = 212 amps @ 12 volt bank
    • 4,000 watts * 1/29.0 volts battery charging * 0.77 panel+controller deratings = 106 amps @ 24 volt bank
    • 4,000 watts * 1/58.0 volts battery charging * 0.77 panel+controller deratings = 53 amps @ 48 volt bank

    So--the same 12/24/48 volt rated MPPT charge controller can handle a 4x larger array vs 12 volts.

    There are now a few different inverters out there now that "natively" produce 120/240 VAC 60 Hz split phase power (typical North American home type power).

    Magnum (24 and 48 volt models)
    Outback Radian
    Xantrex XW

    If you are currently using MSW (modified square wave) Inverters, I would highly suggest using TSW (true sine wave) Inverters (which will cost more than MSW type):

    All About Inverters
    Choosing an inverter for water pumping

    Have you looked at conservation for your installation/home/business? 4-8kW array systems are pretty large--Typically I would expect a system that large would be support Air Conditioning and/or other heavy power usage (like water pumping). There are some pretty nice options out there these days (Mini-Split A/C, very efficient water pumps/systems with low surge current and lower peak current) out there that could help save on your power system costs.

    There are also water pumps that run directly from solar panels. If you can pump during daylight hours directly to the field and/or a water storage cistern/pond--Your "solar power" system costs can be 1/4 that of a similar capability solar panel + battery bank + inverter power system.

    Also--Have you looked at larger AH battery banks (keep the number of strings of batteries down)--A 48 volt battery bank will also help with this too (4x the voltage means 1/4 the current/AH rating battery bank).

    Battery FAQ
    www.batteryfaq.org

    Before you spend any more money--You want to understand/measure your loads and do some paper designs. I am a big believer in "balanced" system design and conservation of energy because it will save you money in the long therm (smaller system, lower capital costs, lower maintenance costs, less "problems").

    The load requirements will define the battery bank size. Battery bank size and daily loads (and amount of sun for your area) will define your overall solar PV array/backup genset size. And the maximum wattage (loads and solar array) will define the battery bank/inverter/system battery bus voltage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
    Re: Can I Use Solar for 220 volt AC Well Pump?

    I am a farmer, our monthly consumption ranges from 500kwh to 900kwh. When speaking to a local installer, he said we need a 6000watt system.

    Some people we know look at this as "shift loads from electric to propane or kerosene", so you can go with a smaller PV system. But in our view that just means that instead of paying one Electric Utility bill, then you'd be paying a different set of bills [plus hauling propane or kerosene].

    We live in an area where Municipal Utility service goes down regularly. Never does a month go by without at least one outage. It may be an hour, it may be 4 days. We hate how unreliable our electric company is. We want reliable power and we want to stop paying for our utilities. This is our seventh year on this property, and our electric service is not getting any better.

    We do not have A/C. We heat using wood. We maintain a row of 55-gallon drums filled with water for our livestock, because on a daily basis, we can not rely on having power to run our well.

    I have looked at systems that pump water directly from PV. Low flow into a tank/cistern. Problem is that we see -20F. A cistern must be greater than 5foot below grade, or else heated to keep it from freezing and ripping it's seams.

    Thank you.

    I apologize if my post sounds like a rant. :)
  • BB.BB. Super Moderators, Administrators Posts: 31,063 admin
    Re: Can I Use Solar for 220 volt AC Well Pump?

    I moved this to your own thread so you can lead the discussion along the lines you need--and not confuse with the original poster (if they ever return).

    Are you somewhere around Bangor Maine? Would like to look up how much sun you have in your region.

    You are not using a lot of grid power. 1,000 kWH per month is considered "average".

    At this point, it would be helpful to know how much water (Gallons per day, depth of well, etc.) to figure out if you are pumping "efficiently".

    Just a warning--typically full off grid solar costs around $1-$2 per kWH hour--or 5-10x the cost of grid power. So spending money on conservation can be a big help.

    What do you do for heating (electric, heat pump, natural gas, wood, etc.)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Eric LEric L Solar Expert Posts: 262 ✭✭
    Re: Can I Use Solar for 220 volt AC Well Pump?
    Our well pump is 220VAC 7amp [though I understand that it peaks at 15amp when starting]

    Given your needs should definitely move to a 48 volt system like BB suggests, if possible. I have a similar 220v well pump on a 48 volt, 4KW battery-based pv system, and the start up surge from the pump causes a noticeable voltage drop. With a 12 or even 24 volt system I think it would be really hard to make sure enough current was supplied to the inverter for a pump like this, especially when other things are drawing power. You could do it perhaps, but you'd spend a lot of money on the massive DC wiring you'd need.
  • Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
    Re: Can I Use Solar for 220 volt AC Well Pump?
    BB. wrote: »
    I moved this to your own thread so you can lead the discussion along the lines you need--and not confuse with the original poster (if they ever return).

    Yes, thank you. I apologize for having taken over the other thread :)


    ... Are you somewhere around Bangor Maine? Would like to look up how much sun you have in your region.

    I am North of Bangor. 'Sun' is 4.2 ?


    ... You are not using a lot of grid power. 1,000 kWH per month is considered "average".

    Hmm, then is the installer correct in saying I need a 6Kw system?

    btw, the installer is 2 hours South of me, in a tourist region [Moosehead lake]. He is the closest installer I could find to go speak with face-to-face. I am not hiring him. I think that being in a tourist area he focuses on folks building $5Million homes. Too rich for my blood.

    We have no desire to 'grid-tie' or net-meter, we just want reliable electricity. :)

    We have two neighbors who are off-grid using 12vdc systems, their homes are 12vdc wired. They were built decades ago, with old-tech. We thought about it, but do not want to shift to 12vdc appliances [or the heavy wiring].


    ... At this point, it would be helpful to know how much water (Gallons per day, depth of well, etc.) to figure out if you are pumping "efficiently".

    200' well casing, water is typically at 68'.

    I have no idea of how much water we honestly use. Loads of laundry, watering raised beds, etc, it all changes from day-to-day.

    We have looked at shallow sand-point wells with handpumps. I know I hit water at 4', though it is pretty murky. But I suspect the gpm would be low, I would pump it 'dry' quickly [unless I buried a drum-cistern].


    ... Just a warning--typically full off grid solar costs around $1-$2 per kWH hour--or 5-10x the cost of grid power. So spending money on conservation can be a big help.

    Yes, I hear you. :)

    I am retired, my Dw wants to retire, but we need to rid some of these monthly bills, to drop our Cost-Of-Living, before she can retire. By getting off-grid, we get rid of the Utility bill, which puts her a step closer to retiring. I hope that makes sense :)


    ... What do you do for heating (electric, heat pump, natural gas, wood, etc.)?

    A homemade Woodstove. [Vogelzang two-barrel with 50' of copper tubing in the upper drum to heat water]

    It is in the center of our living room, with a ceiling fan directly over it [so the heat is pushed out really nice]. The woodstove also heats water, which circs through a thermal-bank, and through radiant flooring. Heated floors are nice and they allow the house to technically be cooler while being comfortable.

    We also have a good deal of South-facing picture windows [triple-pane, argon this, low-E that] that give us a good deal of solar gain.

    The house is insulated to R-60.
  • Eric LEric L Solar Expert Posts: 262 ✭✭
    Re: Can I Use Solar for 220 volt AC Well Pump?
    btw, the installer is 2 hours South of me, in a tourist region [Moosehead lake]. He is the closest installer I could find to go speak with face-to-face. I am not hiring him. I think that being in a tourist area he focuses on folks building $5Million homes. Too rich for my blood.

    We have no desire to 'grid-tie' or net-meter, we just want reliable electricity. :)

    JMO, but you can probably do it yourself and save a lot of money in the process. There is an initial learning curve of course, but as long as you don't jump into things and start buying equipment without knowing exactly what you need, it's really not that complicated.

    You may need to have the system inspected at some point (by your home's insurance company, e.g.), so if you DIY it you'll have to consider whether you need to learn to build it to code.

    Besides saving money, it will probably be more reliable if you do it all yourself since you will understand how everything works and not be dependent upon an installer to come out when something malfunctions.
  • Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
    Re: Can I Use Solar for 220 volt AC Well Pump?
    Eric L wrote: »
    ... You may need to have the system inspected at some point (by your home's insurance company, e.g.), so if you DIY it you'll have to consider whether you need to learn to build it to code.

    Besides saving money, it will probably be more reliable if you do it all yourself since you will understand how everything works and not be dependent upon an installer to come out when something malfunctions.

    The only time inspections are required is for grid-tie net-metering.

    I have evergreen panels. They had an odd wiring connection on them that I am not familiar with. Each panel has two pig-tails. So it appears that they all snap together neatly. However I thought that each component needs to have a fuse to connect to any other component.

    Do I need fuses between panels?

    Or simply before the power from the panels connects to any other component?
  • BB.BB. Super Moderators, Administrators Posts: 31,063 admin
    Re: Can I Use Solar for 220 volt AC Well Pump?

    Not a problem with moving posts--That is what Moderators are here for (and the free cookies--never forget the free cookies ;)).

    Regarding solar array sizing... PV Watts has a station in Caribou Main. I will pull the data for two setups... One fixed array tilted from horizontal to your latitude and a second using 2 axis tracking (if you have lots of snow--Tilting to near vertical can help a lot--keeps the snow off and gets refections from the snow fields):

    First the fixed array:
    Month    Solar Radiation (kWh/m 2/day)
    1      3.36     
    2      4.34     
    3      5.23     
    4      5.75     
    5      4.99     
    6      5.09     
    7      5.15     
    8      4.99     
    9      4.26     
    10      3.45     
    11      2.38     
    12      2.73     
    Year      4.31
    

    And second with a two axis tracking array:
    Month    Solar Radiation (kWh/m 2/day)
    1      4.08     
    2      5.30     
    3      6.48     
    4      7.64     
    5      7.13     
    6      7.66     
    7      7.10     
    8      6.74     
    9      5.43     
    10      4.11     
    11      2.73     
    12      3.29     
    Year      5.64
    

    The winter 2-axis tracker does not help that much (20-40% more of a little amount is still a little amount). But if you are using a lot of power in summer (water pumping, etc.) then it is possible a tracker will help a lot (trackers are not cheap and buying more fixed panels may be cheaper than a tracker, and trackers require their own maintenance. One person here with lots of off grid experience really likes trackers with battery banks--Many more hours per day charging can help extend battery life significantly).

    Any way--This gets us back to knowing your loads... Do we match 500 kWH per month in the summer, or 1,000 kWH per month in the winter?

    Just to give you an idea--Say 750 kWH per month for 9 months of the year with a fixed array. That would be 3.45 Hours of sun per day (noontime equivalent sun power per sqft/meter) at 52% end to end system efficiency (yes--about 1/2 of the solar panel's marketing numbers are "lost" in the process to give you AC power from your inverter):
    • 750,000 WH per month * 1/30 days per month = 25,000 WH per day (25kWH per day)
    • 25,000 WH per day * 1/0.52 system eff * 1/3.45 hours of sun per day (October) = 13,935 Watt solar array

    And if you wanted a battery bank with two days of storage (1-3 days recommended, 2 day is a nice value) and 50% maximum discharge (for long life), a 48 volt battery bank would be:
    • 25,000 WH per day * 2 days no sun * 1/0.50 max discharge * 1/0.85 inverter eff * 1/48 volt battery bank = 2,451 AH @ 48 volts

    There are other calculations to make--But that gives you a very rough back of the envelope idea of what you are asking about.

    Regarding water pumping--If you are not growing in a green house--Then you would only need "a lot" of water storage during non freezing weather (I would guess). Use a smaller tank or several pressure tanks to store water in the home/heated/insulated shed for domestic use during winter.

    Anyway--just some ideas and rough guidelines--It really does get back to accurately knowing your needs.

    To be honest, if you have grid power, then off grid systems will (in my humble opinion) never save you money and would be a "bad investment". There are other options for folks that have unreliable AC grid power (AC battery charger, smaller battery bank, backup genset) that would get your through a few weeks of power failure for much less money (yes--this is a solar forum and I am telling you Grid/Backup Genset as a possible solution for your needs--We are all very practical and most of us are "cheap" :p and don't want you to waste your money).

    I know that you said that you don't want Grid Tied (Hybrid Grid Tied/Off Grid systems are another option)--But if your utility supports a "reasonable" net metering plan or other subsidies for solar--Grid Tied is one of the few alternative power electrical systems that can actually save money and provide some inflation protection for your power bills.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
    Re: Can I Use Solar for 220 volt AC Well Pump?

    http://www.wholesalesolar.com/StartHere/OFFGRID/OFFGRIDCalculator.html#sunhoursmap

    This was the site I had gone to for how many hours / day of sun light. They said 4.2
  • BB.BB. Super Moderators, Administrators Posts: 31,063 admin
    Re: Can I Use Solar for 220 volt AC Well Pump?

    4.2 is the average over a year. The chart I used gives the data month by month. And you can change tilt and if it does not point south... Ectc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
    Re: Can I Use Solar for 220 volt AC Well Pump?

    The mounts I am making allow for incremental changes in tilt, while always facing South.
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