PV and generator combo system for powering 1 HP motor for 12 hrs a day

slurry bowl
slurry bowl Registered Users Posts: 34 ✭✭
in Off Grid Solar & Battery Systems #1
Hello forum.

My first post and not my last, what a great resource.

I am assessing the feasibility of running a single phase 1 HP motor off solar and a propane generator or other similar generator.

The motor runs at 4.9 amps at 230 volts. With a starting inrush current of 22 amps, kVA code K.

I realize this is ALOT of power and not the ideal situation for a off-grid system.

Can anyone recommend a motor starter for battery systems that could utilize the generator for starting and utilize the generator to maintain 12 hr performance?

Connecting to the grid is not an option here and replacing the motor with a DC 12V motor is an option but would use 80-100 amps. UGH....

Any input appreciated. THANKS
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
    Re: PV and generator combo system for powering 1 HP motor for 12 hrs a day

    It sounds like you may be setting up a pumping system... Is there any way you can pump just during daylight hours (~9-15) and if you need water outside those times use an elevated tank/pond or even a smaller pressure booting pump?

    More or less, if you can limit your heavy pumping to daylight hours, you can cut your solar power installation costs to 1/4, and avoid having to replace a very expensive battery bank every 3-8 years or so (and avoid battery maintenance).

    Just to give you some ideas--Here are some threads about driving larger 3 phase pumps from VFDs (variable frequency drives) with direct connect solar panels:
    BB. wrote: »
    Some discussions about VFD (Variable Frequency Drives)... Basically a variable frequency inverter with (typically) three phase output. Used to soft start motors (handy for 3 phase well pumps, or pumps with well head starting capacitor) and can also turn an AC motor into a variable speed motor (very handy for pumping applications).

    WELL PUMP and Inverter QUESTION
    Wind/solar for large scale pumping etc (out of my depth!)
    could use knowledge - using Gould jet pump - transfering from 230vAC to ? DC (new link/thread 10/27/2012)
    Help required to design off grid system (information on possibilities to connect "standard VFDs direct to solar panels) (new link 1/13/2013)

    If you really need 12 hours of pumping--You should also research pumps... The 3 phase pumps and PM motor pumps (permanent magnet pumps that use a version of VFD--These are not DC brush motors) can be much more efficient than a simple capacitor start 1 HP single phase motor.

    In the end, conservation should be your first goal. Do not over size the pump, do not pump to higher water pressure than needed). In-well/submersible pumps are more efficient than ground level "jet pumps". Pumps designed for positive inlet pressure (no lift) are more efficient than pumps that can draw/lift water).

    Of course these efficient pumps cost more money (in well pumps are also more difficult to service)--But, in the end, you will save more money in conservation vs throwing money at a larger off grid/solar installation (for a permanent installation).

    For seasonal/short term installations (summer cabin, construction site), it is many times, more cost efficient, just to throw a diesel/gasoline/propane generator or pump at the solution. Solar is never "cheap". Solar usually only makes sense for 9+ month operation and many years of use.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • slurry bowl
    slurry bowl Registered Users Posts: 34 ✭✭
    #3
    Re: PV and generator combo system for powering 1 HP motor for 12 hrs a day

    Thanks Bill,

    I am not trying to pump water. My other thread in the water pump sub-forum is for a small art project. This motor is driving a pump jack, for oil.

    I can change the pump, but it needs to meet the reqs. and it seems to reduce the voltage would make for VERY large wiring and expensive components.

    I need a way to start this motor and subsidize the solar with a generator. Maybe no battery is the way to go. Run the generator and allow direct PV to help it when available and maybe allow the generator to shut off occasionally.

    thanks
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #4
    Re: PV and generator combo system for powering 1 HP motor for 12 hrs a day

    I agree - use a 3 phase motor and a VFD to eliminate the start-up current issue. 12 hours/day will put a lot of hours on a generator. Look for low RPM. Solar can be made to work.

    I am available for custom hardware/firmware development

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #5
    Re: PV and generator combo system for powering 1 HP motor for 12 hrs a day

    Take a look at some of these Google searches on our forum:

    https://www.google.com/search?q=pump+jack+site%3Asolar-electric.com

    Jensen Pumpjack motor/prime mover
    Power consumption by electric pumpjack
    500' Jack pump with solar options?
    SunPumps Solar Powered Water Pumps

    I think most of the above are for water--But the questions/issues are the same.

    Of course, you have the option of running raw oil into a diesel (if that is still legal). Some those water guys cannot do (yet:p).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • slurry bowl
    slurry bowl Registered Users Posts: 34 ✭✭
    #6
    Re: PV and generator combo system for powering 1 HP motor for 12 hrs a day

    Ok, thanks for all the input.

    It is now my understanding that if I wanted to only run the pump when the sun is out, I would ideally use a 3 phase motor with a VFD. Can anyone recommend a solar VFD/Inverter that could run a 1 hp pump using direct PV?

    THANKS
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