Running a pump on direct solar

Texas Wellman
Texas Wellman Solar Expert Posts: 153 ✭✭
in Solar Water Pumping #1
I have a 12-V pump that I would like to run on a 100 W 12V panel.

The pump is a very small 12V pump (rated for 4.5 amps)

Panel Specs:

Electrical Specifications
Optimum Operating Voltage (Vmp): 18.9V
Optimum Operating Current (Imp): 5.29 A
Open - Circuit Voltage (Voc): 22.5 V
Short- Circuit Current (Isc): 5.75 A
Maximum Power at STC: 100 W
Operating Module Temperature: -40°C to + 90°C
Maximum System Voltage: 600 V DC (UL) / 1000 V DC (IEC)
Maximum Series Fuse Rating: 15A
STC: Irradiance 1000 W/m2, module temperature 25°C, AM=1.5;

Since my panel is 12V but the "12V" panel really outputs about 17V do I need something to interface between the panel and pump or do you think it will blow the pump? All of my other set-ups require a controller between the panels and pump but it outputs PWM power. This will be direct solar. I do not need any batteries as I only want the pump to run when there is enough sun.

Thanks
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Running a pump on direct solar

    Not really. Panels are current sources and they basically will allow the Voltage to go to any level.
    A 12 Volt pump is usually designed to run on an RV system so up to 15 Volts on the input would not be unrealistic either. Between the two variables it should work okay, if you can get enough sun on the panel to develop the required current. At worst it will run between 'dead battery mode' and 'fully charging alternator mode'.
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #3
    Re: Running a pump on direct solar

    You may want a solar booster controller for the pump so less than ideal conditions the pump will still start
    http://www.altestore.com/store/Solar-Water-Pumps/Linear-Current-Boosters-For-Pumps/Solar-Converters-10A-1224V-Linear-Current-Boost-for-Solar-Pumps/p1354/

    There are a ton of different ones.
    http://www.altestore.com/store/Solar-Water-Pumps/Linear-Current-Boosters-For-Pumps/c581/

    No experience with any of them BTW.
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #4
    Re: Running a pump on direct solar

    Your voltage can go too high and many of these pumps run close to their heat limits under continuous operation anyway. Do something to reduce the voltage, preferably to less than 12V (for less heat and longer life). I run direct from panels at 60% of rated voltage.

    I am available for custom hardware/firmware development

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Running a pump on direct solar
    jonr wrote: »
    Your voltage can go too high and many of these pumps run close to their heat limits under continuous operation anyway. Do something to reduce the voltage, preferably to less than 12V (for less heat and longer life). I run direct from panels at 60% of rated voltage.

    No, it can't.

    Pump is a resistive load. Connect to panel and it will hold the Voltage to Vmp or less.
    Panels are not a Voltage source like a battery is.
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #6
    Re: Running a pump on direct solar

    > Pump is a resistive load.

    Nope, a pump motor isn't a resistive load and will draw much less current when the pressure it is pumping is low. Drawing little current from panels causes the voltage to rise above Vmp towards Voc.

    I am available for custom hardware/firmware development

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Running a pump on direct solar
    jonr wrote: »
    > Pump is a resistive load.

    Nope, a pump motor isn't a resistive load and will draw much less current when the pressure it is pumping is low. Drawing little current from panels causes the voltage to rise above Vmp towards Voc.

    It does not take much resistance to drop panel Voltage below Voc. Practically any load will do it. As far as the PV is concerned the pump is a resistive load. You will not see Voc from the panel even at minimum pressure.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #8
    Re: Running a pump on direct solar

    Ron, the suggestion below is the best way to do this if you want long hours of pumping, do you? The panel to pump direct will probably work but weather, time of year, and shorter run hours may be issues. Good Luck! Let me know if you come up with a reasonable surface equivalent of an SQ!
    solar_dave wrote: »
    You may want a solar booster controller for the pump so less than ideal conditions the pump will still start
    http://www.altestore.com/store/Solar-Water-Pumps/Linear-Current-Boosters-For-Pumps/Solar-Converters-10A-1224V-Linear-Current-Boost-for-Solar-Pumps/p1354/

    There are a ton of different ones.
    http://www.altestore.com/store/Solar-Water-Pumps/Linear-Current-Boosters-For-Pumps/c581/

    No experience with any of them BTW.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: Running a pump on direct solar
    Dave Angelini wrote: »
    Ron, the suggestion below is the best way to do this if you want long hours of pumping, do you? The panel to pump direct will probably work but weather, time of year, and shorter run hours may be issues. Good Luck! Let me know if you come up with a reasonable surface equivalent of an SQ!

    Yep. There have been people around here who thought it would be great to run their Shurflo directly from a solar panel. All of them put in batteries and controllers because of the marked inconvenience of having the pump run only when there was sun rather than when they wanted water.

    For the reassurance of Texas Wellman I have just tried this experiment with a working Shurflo 12 Volt pump that pulls 7 Amps and has a measured resistance of 1.6 Ohms. The panel Voc of 19.9 (old panel) dropped immediately the pump was connected. I did not try different angles to see how high I could get the V to rise, but it is extremely doubtful it would exceed pump maximum unless the panel is way too much power for the pump - or you're in Canada mid-Winter where the cold can push Vmp up to nearly 2X the pump nominal.

    Looks like the old 'Coot was right again. No surprise there, really.
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #10
    Re: Running a pump on direct solar

    Since I will be pumping into an open livestock trough I really have no need to store energy. This is more or less an experiment, just trying out some new things.
    Dave Angelini wrote: »
    Ron, the suggestion below is the best way to do this if you want long hours of pumping, do you? The panel to pump direct will probably work but weather, time of year, and shorter run hours may be issues. Good Luck! Let me know if you come up with a reasonable surface equivalent of an SQ!
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #11
    Re: Running a pump on direct solar
    Texas Wellman wrote: »
    Since I will be pumping into an open livestock trough I really have no need to store energy. This is more or less an experiment, just trying out some new things.

    Because you have a largish tank for storage, this sounds like a perfect application for direct solar.
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #12
    Re: Running a pump on direct solar

    Got the panels ordered and should be able to report in a week or two. Kinda excited to see how this works, a little bit different set-up for me and will solve a common problem that I have in this particular part of the country.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #13
    Re: Running a pump on direct solar

    It does and even without the linear current booster you suggested it may be good enough. If he does choose to use the electronics it will give him more hours and should run the pump better in poor solar weather. It never hurts to have more water, this year has been a bummer for many of the folks up here in the mountains with wells. Rainwater was 1/3 normal and snowpack was even worse. He told me he was using a bilge pump. The one on my old sail boat would shut off when the water was low without a float switch.
    solar_dave wrote: »
    Because you have a largish tank for storage, this sounds like a perfect application for direct solar.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #14
    Re: Running a pump on direct solar

    TWM, if the first part works for you, you might look into a 'virtual tracking ' array ie 2 or 3 smaller panels to give longer hours of pumping... especially in Texas. you'd just have to play with it to get the right amperage for that pump to handle...
     
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #15
    Re: Running a pump on direct solar
    westbranch wrote: »
    TWM, if the first part works for you, you might look into a 'virtual tracking ' array ie 2 or 3 smaller panels to give longer hours of pumping... especially in Texas. you'd just have to play with it to get the right amperage for that pump to handle...

    The linear current booster will also give more hours per day of pumping. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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