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Low Energy Aquaponics
  • I started a thread over at BYAP (Backyard Aquaponics) to get some input on how we could develop a low energy aquaponics system that could be powered by solar.  Here's the link:

    The idea is a system with a max requirement of 10 watts.  The solar component for a 10 watt system can be had for under $400 USD. Of course, if we can get the power down even further, that's fine, too.

    To meet this goal, the going idea is a constant flood, constant height (zero/low head) recirculating system. We're looking to turn over the FT (fish tank) volume every hour at least, and stock at appropriate rates (maybe up to 25kg/m3).

    The response has been awesome, and currently, the talk is about using airlifts or powerheads for circulation.  Folks are running tests, and a member has achieved 1200 lph with 5 watts on an airlift, making that suitable for a 1,000L (IBC) system.

    Just to be clear, that's a $300 USD solar system for a 1,000L FT and 1,000 GB (grow bed) in a constant height, constant flood configuration running 5 watts.

    So, I want to get as many ideas as possible, so what are the thoughts over here?  How would YOU do a 10 watt system, and how can we stretch the limits of the box to make this work?

    If this sounds foreign to you, follow that link and start learning about aquaponics. This is kinda advanced AP discussion, but I think most folks can get the concepts with a bit of reading.  It seems like to reduce energy in recirculating aquaponics systems, you have to reduce the head to almost zero.  By doing that, you require the minimum amount of power to pump the maximum amount of water (not necessarily the most efficient way, just the most practical). So, we're looking for ways to reduce that head, and reduce the pump sizes.  So far, 10 watts seems easy to meet, 5 watts is possible, and I think we could even trim it to 3 watts, if we really try.
  • 6 Comments sorted by
  • Vote Up0Vote Down
    February 2012
    Low energy aquaponics is great idea. However your cost estimate of $400 is way too high. I can buy 4.6 watt solar cells with tabs for $2.25USD, I can also get 15 and 30 watt aquarium pumps for around $20USD. Add in a 75 watt 12 volt inverter from Walmart, for $20USD, a battery, wire, one could assemble a system for $150 quite easy that would work 24/7 and have excess solar capacity as redundancy against cloudy days...
  • Sounds like it's time to update the wiki...
  • well, the cost estimate was buying the parts off the shelf.  I am not building a solar panel (been there, done that), as I like 25 year warranties.

    That $400 includes components that have been proven to last a long time.  With aquaponics, you need reliability.  That $20 inverter from wal mart won't last 6 months. You cannot afford to have a component fail, cause all of the fish will die within hours.

    To run 5 watts continuous, you need at least 30 watts in solar, and I wouldn't go less than a 90 amp-hour battery. But, of course, I welcome you to build a system, build your components, and tell us how it works out!

    While I think you can put together a 30 watt system for less than $400, I go with that price just as a conservative estimate.
  • Vote Up0Vote Down
    February 2012
    You do realize that low-head aquaponics means a tradeoff between high energy efficiency, and efficient use of what may be valuable greenhouse (or other) horizontal space, right?  Instead of stacking growbeds above the fish tanks (which might even be partially buried), one would need to give up growbed space for a fish tank, and the surface area of your growbeds is directly tied to the main output of the aquaponics, so you then limit from the start, how much your yield can be...

    Granted, there will be some who have more space or real estate than energy, but I suspect that most who would really be trying to raise enough food to feed their families will need that space for growing food more than they will need the energy savings, because just going to a higher power pump can produce so much more food per square foot of space used...

    At what point is the "low energy consumption" becoming less practical & more bragging rights???

  • high energy = high start-up cost.  solar systems cost around $10/watt installed.  If you have a system running on 60 watts (normal for 1,000L FT), that's an extra $3000 in system cost for a production of 25kgm3 of live fish (less than a square meter), and roughly 6 square meters of vegetable production. If you go low energy, you're looking at a solar cost of $400, and really, you've added 1 square meter of space at most (1/6th the cost of greenhouse).

    Greenhouse space is usually under $10/square meter, so the cost is definitely saved with lower energy. Fish tanks don't take up much space. You are still looking at a very productive area.  Most larger aquaponics systems don't stack vertically, anyway.

    Everyone in my area (developing world), which is a semi-arid environment, has a lot more space than electricity and money.
  • here's another option for low-energy fish farming - Greenwater Aquaculture:

    Here's a snapshot for a 10 watt solar powered system:

    4000L Fish tank
    200-400L clarifier (basic baffles for solids removal)
    500 lph pump (or less) - easy with airlift
    5-10 watts of aeration
    stocking rate of 13kg/m3 (total biomass 52kg, yearly production 100-150kg)

    Cost (including solar system) - around $600 for up to 150kg of fish/yr

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