Running small aquaponic system on solar

SystemSystem Posts: 2,511 admin

I've been round and round on the internet trying to figure out how to switch my aquaculture system to solar, and I'm pretty confused about 12 volt water pump applications. But rather than ask questions perhaps I should explain my application first and let you folks draw your own conclusions as to how my application can be tackled?

I have a small 1,000 gallon aquaponic system stocked with Tilapia. It's a continuous recirculating system which means water has to constantly be flowing from tank to tank in order to maintain natural water circulation (oxygenation) for the fish. The minimum flow rate must be 500 gallons per hour.

The tanks are located in a greenhouse that currently runs off a 60 amp sub panel divided into 4 / 15 amp circuits.


  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Running small aquaponic system on solar

    duplicating your inquiry is not going to get you a faster answer so the other one was deleted as they were identical.
    i'm assuming you have a hefty 115vac pump currently. if you were to replace that one with one like it you wouldn't care of the specs excepting that it will push the needed gallons per hour. this may be done with a dc pump that can handle the same gallons per hour or go with an inverter to keep the same ac pumps going. being watts is watts then having 10 times less voltage means 10 times more current plus losses. to go on a 24hr a day basis you need to add up that power and this gives the total watt hours you need in a day. for a solar setup to provide this power you need more power to overcome losses. now this must do this 365 days a year and the amount of sunshine varies per season and per day and in addition to its intensity by location. that means a higher amount of power must be available to overcome all of these other factors.
    look over what has been placed in the forum as there's much information here. do not have the attitude of just hurry up and do it as you must learn some aspects of this before diving into it. questions may arrise from you later and the forum will still be here for them.
    if possible you could just use an inverter/charger with battery(s) as a backups to your system too. this works reguardless of if you use photovoltaic panels(pvs) to charge the battery(s) or not. this makes it possible to downsize the system in size, requirements, and costs using it as a backups. how long you need it to be able to run the pump determines the size battery bank you'll want. there are differences in batteries too to be considered. i think you landed in the right place, but you'll need to arm yourself with enough knowledge to know what you want and need as we don't like to tell you what you want. we could make some recommendations or say of differences on some products, but only as examples of what we think you may want and need as the decision is yours ultimately.
  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: Running small aquaponic system on solar


    The decision between AC and DC pumps--at first guess, you would probably be best to stay with properly sized AC pumps. 1) because you already have them and don't need to spend more money up front that you need, and 2) getting reliable DC pumps (especially around water) is sometimes a gamble.

    There are other interesting alternatives for variable speed pumps... For example, some in-well pumps are 3 phase AC units in the hole, and come up to a controller that takes AC (DC input may be available too), and puts out varying frequency and amplitude 3 phase to the pump--the motor acts somewhat like a DC motor (variable speed and good efficiency) but has the reliability of 3 phase motors (no starter circuits, switches, commutator, or electronics).

    Now, back to the AC... You really need to give people an idea where you are (country, major city or something)... If you are in the US, some states offer rebates for solar/green projects, and many more have instructed their electric utilities to allow net metering (were sometimes you consume power, sometimes you generate power--and at the end of 1 month or 1 year, the net bill or credit is calculated and paid).

    Net metering, if available to you--is a great thing. For example, in California, PG&E acts like a giant AC battery for me that averages my power in/out over one year for about $5.00 per month (minimum charge). You still get a monthly statement, but you can run a debit or credit at any point in the year.

    In terms of efficiency, a Grid Tied solar system with net metering is the most efficient (both in terms of cost and solar panel to load efficiency). Batteries cost money, have to be replaced every 6-15 years or so, consume about 4-15% of your generated power, require both a solar charger and DC to AC inverter (more costs and efficiency losses) and will probably need a back-up generator for cloudy weather.

    Prices for panels are high right now (may change in a year or two and go down). Electronics keep getting less expensive, and in general, better at what they do.

    First suggestion, find out your current electric usage (by month, or season and for 1 year), look at conservation measures (always cheaper to first conserve, then go solar for what is left), give your location/weather conditions (mostly sunny, or lots of clouds/wind in certain seasons), if utility allows Grid Tied systems, and if you are willing to spend, roughly $15-$30,000 for 400 kWhrs per month (1 year average) for your electricity (say roughly $0.17-$0.25 per equivalent kWhr--battery systems will cost somewhat more than pure Grid Tie).

    Solar is not cheap. Battery backed solar is more expensive. Grid Tie with emergency generator backup is probably the most cost effective (as a starting point for costing a system). Battery systems are needed for off-grid applications (or where power is too expensive to bring lines in).

    Questions, Answers?

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Running small aquaponic system on solar

    You might try looking into commercial bilge pumps. The Shurflo Commercial Bilge 1500 is a 12 V pump rated for 1,500 GPH and continuous duty (I have to admit that I’m a bit leery of the latter claim).

    Assuming a 12 V x 6 A spec but an average charger- or battery voltage of 12.7 V, that would be an 81 W load, or 1,944 Wh/day. Assuming 67% effective system efficiency and the equivalent of 4 hours/day of full Sun, you’d need a PV array rated at 725 W STC.

    Check here for alternate solutions.

    Designing the system based on Winter insolation (fewer hours of full Sun/day) should leave you some extra power in the Summer (longer days, more insolation) to operate a DC cooling fan. You may be able to find out more about your location’s seasonal insolation from this reference site.

    Good Luck!
    Jim / crewzer
  • System2System2 Posts: 6,290 admin
    Re: Running small aquaponic system on solar
    niel wrote:
    duplicating your inquiry is not going to get you a faster answer so the other one was deleted as they were identical.

    Thank You, I didn't know how to delete the post and figured the water pump discussion was more appropriate place.

    My greenhouse is tied into a 60 amp sub that is connected to the main service panel of our home.

    So isolating the Kwh for the greenhouse, maybe impossible? I averaged our annual Kwh for the home AND greenhouse and it was 1,900 per day.

    I live in Northern California, PG&E has rebates and I considered net metering before, but the system quoted me was $17K after the rebate, and for us right now that's too much.

    Sounds like net metering is going to be the direction I go ultimately, just where to start and how much? I don't want to finance a system. I just wanted to get my greenhouse off the PG&E bill.

    Thank you so far for your responses I'll do some more homework in the next day or two and come back with more Q's
  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: Running small aquaponic system on solar

    Depending on the power requirements... A kill-a-watt meter for $25-$35 is a great investment to measure 120 VAC items that plug into a standard outlet.

    You can get a pretty cheap AC current clamp/meter and measure your total current x voltage use and figure a rough power usage--if the loads are constant it is simply kWhr / Month = Volts * Current * 24hrs/day * 30 days/month

    For example you measure 10 [email protected] vac total (both legs if 240 single phase, running 120 vac loads):

    kWhr/Month = 120 VAC * 10 amps * 24h/d * 30 d/m = 864,000 watts/month or = 864 kWhrs per month

    If you loads are cyclical (lights, pumps on/off) with random cycles, a totalizing watt hour meter is best.

    Another way that I have done this is to get an old utility meter and wire it into your green-house mains and just read the dials like the meter reader does. Or, you can kill the power to your home (fridge/freezer during the day or night) for a few hours and read your own utility meter before and after to get an idea of the kWhrs/hour you are currently used.

    I am not sure about the 1,900 per day... if that is 1.9 kWhrs per day--that is very low (60 kWhrs / month or something like $6 per month). If that is 1,900 kWhrs per day--that is huge (60,000 kWhrs per month or $6,000 to $18,000 per month).

    A $17,000 system (after rebates, installed?) is probably somewhere around a 2kW to 3kW peak system, which for me (a 3kW peak system) generates an average of 400 kWhrs per month--or around $45 monthly electric bill (I typically use 200-300 kWhrs per month with gas appliances and an electric space heater because I currently have "power to burn" in the winter with net metering--no AC for now). If you have better sun and/or site conditions than me (mine are OK, but not perfect), you might get another 20%+/- more power than I do per year...

    So far, my system has worked great. I have about $200 credit after 10 months of E-7 Time of Use metering (great for solar systems where you generate more energy than you use from noon-6p, Mon-Fri). Here is the PG&E tariffs link (E1 is standard residential, E7 is one of the more common TOU metering for residential--$277 fee for E7 meter, and a minimum 1 year contract). Of course, after 1 year, I will lose any credits and start from zero again.

    If the green house and fish farm is a business, then a separate meter will allow you to deduct business expenses.... Also, PG&E may give you another baseline amount (~300 kWhr per month for my area) which will help keep costs down (first 300 kWhrs is ~$0.11 per kWhr, after 1,200 per month it is ~$0.30 per kWhr).

    If you are above base line rates, you don't need to get the entire bill to zero kWhrs/month or per year, but just get it down one or two baseline usage tiers will actually save you money right from the get go (if, for example you are above 1,200 kWhrs per month and paying ~$0.30 per kWhr over 1,200 kWhrs).

    And there are further tax breaks for business investments and, specifically, solar business investments too that can even reduce the after tax price even more.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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