Backyard Aquaponics
A place to discuss aquaponics

I'm designing a system at the moment that I want to be as productive as possible, while using minimal power. I’d like some inputs and suggestions on a few points.

It will consist of 4, 2m x 1m plastic growbeds that will be 500L each filled with gravel. The 2000L plastic fish tank will be buried to allow for gravity return drains from the growbeds, but the fish tank will be buried only a minimal amount to keep the pumping head as low as possible..

It will use PV cells and batteries for power storage, and will be set on a timer so that it only goes on once or twice during the night. Now this is the point where I’m trying to weigh up the pros and cons of different methods. I would think that the most efficient method for power consumption would be a small wattage pump running continuously with the growbeds using auto siphons to flood and drain. However, this method has the disadvantage of not being as effective for solids removal because of the small pump. The other option is to use a larger pump capable of pumping some solids, and cycle it with only reasonably short run times, ie 10-15 minutes an hour, using standpipes to flood and drain the beds..

Would the current inrush from starting the pump reasonably often be too much consumption to make the system efficient?

Is it cost effective to use 12/24V pumps, or cheaper and almost as efficient to use a small inverter and 240V?

Anyone have any thoughts or suggestions?

As far as I have seen, EB, DC pumps are much more efficient, but cost more to begin with.
I might side more with a pump continuously run, but sized for the amount of water turnover you require.

I'm afraid I don't have any sources for you right now, I may be able to dig up some later.

A DC motor typically does not have much of an inrush and I'm told that DC pumps are more efficient -- typically because they are run on finite systems where efficiency is a concern. But usually they are more expensive for the same performance.

Inverters can be remarkably efficient. If you use a battery the size of a car battery, the inrush shouldn't be a big problem -- for the battery at least -- if the inverter can start it, the battery will be able to hold up its end of the bargain (Car starters pull 200 - 400 amps for short periods)

My preference would be a variable speed drive. I have a bit of experience that I can share if you're interested. Basically, any Variable speed drive (also known as AC drives, VFD's -- for variable frequency drive...) can operate off of single-phase power or DC -- even if they are designed for three-phase input -- with some deration and caveats. To run a commercial 240VFD on DC, you'd need 300V DC to supply to the buss.

The beauty of VFD's is that they can ramp up a motor as slowly as you wish (and ramp down, run faster, slower, reverse, etc) and monitor amps, volts, speed, and other parameters. And they can be purchased fairly inexpensively compared to 12V inverters.

Another thought for you, EB,

Travis is using a multistage airlift pump. Reportedly he's operating at about 4 watts. It seems to me that with a DC air pump and a geyser pump, you could get good solids removal and efficient water pumping. The beauty of the geyser pump is that no matter how slowly your air pump runs -- the surge of water will be the same -- just spaced out more. It might work out pretty well considering that you'd need more flood cycles during the day (when your PV's would be putting out peak power)

now that I like..
ems -- so could you have micro hydro turbines under the returm water to generate some power?

ata.org.au has a simple DC controller for DC motors running directly from a solar panel, or with battery. The most important thing is to impedance match the motor to the source.

I would just use a microcontroller and PWM and a DC motor rather than VFD and a 3phase motor. (3phase motors are great in high power applications, but we're talking low energy to begin with, so low power is almost implied) You'll probably need some kind of microcontroller to make decisions about run cycles anyway. PIC or basic stamp are obvious starting points (I use PICs, my friend uses basic stamps - they're almost the same thing and use microwatts of power).

The best motor to use in this situation is solid state commutated permanent magnet brushless motors - the sort used in computer fans for example. Perhaps you can connect up such a scheme.



Probably more efficient to just minimise the fall in the system to minmise the energy per litre. But, an interesting idea that just occured to me is to use a single, large pipe with a good axial flow pump and simply 'slosh' the water back and forth between fish and food by reversing the motor direction. Using locked-antiphase type control you could possibly recover a useful amount of energy.

The axial flow pump could even be a computer fan with suitable potting! (though they aren't generally reversible)

(probably not a good idea for a number of other reasons)

edit: continuously flooded looks much simpler and energetically smaller.

Mmmmm, just reading about the geyser pumps now... I'm hoping that most compnents with be fairly simple off the shell items, pumps etc, I don't want to be mucking around too much with bits and pieces..

EB, from my adventure into the geyser pump world:
-Highly effective at solids removal and I feel are a great potential for aquaculture.
-Starting cost of around $200 (Canadian)
-Give it a go with making one if you like, but my conclusion is that the designer has not revealed the true nature of the geyser, despite what various websites claim (I have spoken with him)...you must have read into the topic created here on it....
-requires a decent amount of submergence


hope this gives you more to go on with the geyser pump

EB, with all the talk of continuous flood/flow designs recently, I had some thoughts that may apply to this:

Picture your growbeds only half-2/3 full of gravel, with the level of the water in the fishtank being at around the same height as the top of the gravel. Then on top of the gravel and filling the growbed you could place coarse coco coir for the plants to root into. If the water was continually pumped through the gravel underneath, it could just sufficiently wet the coir, while providing biofiltration surface in the gravel. Without entirely flooding the coir, roots would have adequate access to oxygen, and a simple low energy pump, operating at a very low head(a few inches?) could keep things moving. An airlift may give good results here as lift is low. Added aeration for the fish may be needed, but other than that, I would think it would have a very low power consumption.

Hi EB

So you required minimal power consumption and outlay cost

On my new system I plan it to use minimal energy and have a low running costs..and use a solar system for backup.

I selected the Laguna PowerJet Max-Flow 6000 pump (AUD 234) with gives a max. flow rate of 5900 L per hour. Max head at 3.5 metres all for 80 watts. Approx annual running costs of $96.00 (running continuous) with 6mm solid removal.

This pump should be easy for an inverter to handle.

EB- some thoughts on Solar powered systems.
(My house is totally solar powered and so will my aquaponics setup be.)
It will probably never be economically reasonable to run any system on solar power as the total setup costs are still about $10 per installed watt.
I estimate that to run the 240V pump I will probably buy from Murray will likely use about 800whours per day. To do this I have 160watts of solar panels and a huge battery bank with an inverter- These items were not purchased for the aquaponics system but were in the shed and I decided to use what was basically going to waste.
My decision to go 240Volts vs 12Volts re pump was a bit biased-I already had the bits and the only big 12Volt bilge pumps available in Australia seem to be Rule pumps and my experience with that brand has not been good - I use a small 380litre/hr pump in an outdoor pond powered via a 20w solar panel with a maximiser and although it works well the pumps only last from 3 to 9 months. They only cost $30 each but it is still a pain to have to replace them all the time.

I know of 2 such systems already. The key is to start by using as little energy as possible. Think solar garden lights (or even better example - solar garden pond pumps), not arrays, inverters and batteries.

Axial flow pumps are much more efficient for large volumes. All seriously large high flow/low head pumping systems use axial flow. Impellor based designs are more suited to low flow/high head. I think a computer fan could probably be fashioned into a low power pump to drive a 90mm pvc pipe with some care, but you'll only get a few cm of head.

Could you draw up and post such a pump njh... I'm intrigued....and I have a tub full of fans sitting there doing nothing....

raimiuso-did make a proto of the geyser last month,

must be working ok, but had at hand only a small aquarium burbler,

not strong enough.

Will make a PS for a small 12v compressor to see what happens.

Could be of use as a vacuum cleaner.

OK, thanks SS... That looks like a fun project...