Water catchment circulation and pump to storage

SystemSystem Posts: 2,511 admin
Greetings from a new member. I was seeking advice to size a simple system for water catchment that might have 2 functions. I would like advice on a 12V collector and pump matchup that would circulate water in my catchment container to keep mosquitos suppressed with water movement. I would hopefully like to be able to manually valve this same pump to lift the water from the main catchment to a higher storage barrel for gravity feed to drip irrigation. I prefer not to have a battery or controls to keep cost down. As long as the pump runs when it is sunny and could pump about a 10ft. differential height, I'd be happy. I understand I would be limited in filling the higher container to when conditions are appropriate. Freezing won't be an issue as I won't need it to work in colder weather.

Thanks, Ray


  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: Water catchment circulation and pump to storage

    Assuming you are from around Indianapolis, You will get around 5+ hours of full sun per day for 6 months of the year (mosquito season?).

    Do you need to disturb the water only for 6-8 hours per day, or 24 hours per day?

    Second, how much water do you need to pump per day (both to mix the water surface, and to pump to the elevated tank)?

    Would a small pump like a sump pump for a boat be good enough (last a couple seasons), or does this need to have higher quality pump that will last years?

    Will this need to be a submerged pump (more expensive, more likely to leak and fail) or something outside the pond (needs to be protected from water/rain/etc.).

    Would you consider two pumps... One in the pond for circulation, a second for the elevated tank.

    I agree with your ideas to keep it simple (no batteries, no chargers, more efficient use of solar power)--But you will be limited to pumping while the sun shines.

    Lastly, if this is located withing several hundred feet of utility power--You might just bite the bullet and bury a power cable to the pond/irrigation system. Solar power is expensive and solar pumps may not last as long (built for efficiency and many are positive displacement pumps--May need maintenance with new valves/diaphragms every few years). Sometimes, a good old reliable 120 VAC centrifugal pump running on $0.10-$0.20 per kWH grid power is the best way to go.

    Some pumps available from our host NAWS (Northern Arizona Wind & Sun).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Water catchment circulation and pump to storage

    Bill: Thanks for the quick reply. I live in Louisville so the figures for Indy are probably close. I just went to a house on a Solar Tour today and got the idea (and excited). There was a DHW system that used glycol for the heating loop with a small in line circulating pump powered directly by a collector (maybe 2 sq. feet?) with no controls, logic being that the glycol only needs to circulate when the sun is shining.

    I believe periodic disturbance of the water would be sufficient to prevent the larvae from hatching. This could be a rain event, I would be depending on the pump to disturb the water during times between rain (longer and longer it seems).

    I could get electric to the pump, however I am developing an "sustainable urban homestead" which gets a lot of visitors. In addition to gardening, animal husbandry, composting, and water catchment, I think some sort of practical solar display would be informative.

    I will have a 250 gallon tote with the bottom about 3 feet off the ground which I would plumb to circulate, as well as another 250 gallon tote set maybe 5 feet higher for additional storage and to feed the garden by gravity. I specifically don't want a submersible pump.
    I would lean more towards a higher quality pump, especially if it was serviceable.
    I'm not sure if I understand how the 12v DC would perform as it went from cloudy to sunny. Would the pump run slowly and then speed up as the sunlight increased? Is this period of slow speed damaging to the motor?

    What would my choices be in a pump between $100 and $200 that would lift water this high (volume not critical)? What size collector would be needed to drive this pump?

    Thanks, Ray
  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: Water catchment circulation and pump to storage


    The more expensive solar pumps use a linear current booster circuit... Basically, it electronically matches the IV characteristics of the solar panels (Current source) with the requirements of the motor (the lower the input voltage, the more current a motor needs to start and run).

    You can also purchase linear current boosters directly:

    7 amp Linear Current Booster/Pump Driver $91.00
    wind-sun_2125_28793947 Used to control and power a DC motor from a solar panel. The unit prevents stalling of the motor under less than full sun condition.
    So, basically as the sun sets (or clouds move in) the output voltage of the solar panels stays around Vmp but the current falls (1/2 the sun is 1/2 the current).

    So, your 12 volt pump that ran on 5 amps just fine at noon time, now is facing a panel that can output (just examples) 17 volts at 1 amp...

    Well, 1 amp will not even turn the pump motor (and the panel will probably be pulled down to just a few volts... The LCB will instead, run the panel at around 17 volts and 1 amp = 17 watts; and output perhaps 5 volts at 3.4 amps... The pump will not be running at full speed, but it will still be turning and pumping water for your (depending on a lot of other factors).

    Assume that you want 3-7 amps at 12 volts--Roughly:
    • 7 amps * 12 volts = 84 watt panel.
    You will get around 1-3.5 GPM for 10-40 PSI with a positive displacement diaphragm pump. And it will run most of the day while the sun it hitting the panel.

    Is this over kill or under kill for you---I don't know.

    If your pressures are low, then I probably would look at a centrifugal pump (fewer parts to wear out).

    As you look through all of these options--you are going to find DC motors with brushes and those without (electronic commutation of some form). For a pump that is running hours a day and for months/years on end--You do not want brushed motors--they will only last a few months before they need new brushes.

    There are lots of options out there--Just need to do a lot of reading to find out what you will work for you (in your price range).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Water catchment circulation and pump to storage

    Back to the project. I'm now looking at the Shurflo 2088 and using the http://store.solar-electric.com/7amplincurbo.html

    What panel would be best suited for this combo?

    On the pump: 12V or 24V? I note different levels on the pump. The more expensive ones are sealed but what's the difference between the others?

    Thanks, Ray
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