Low Energy Aquaponics - LEAP

[GaryD]

Hi Abe,

the drag would affect the return flow to the tank, causing the Fish tank to drop, and effectively increase the head required to pump. I think a solids filter should be considered, but I'm not sure sand would be the best solution. Maybe a swirl filter or something where we can maintain a high rate of flow.

My problem is that I'm still unclear as to exactly how you visualise your system......and how it works.

Can you talk me through the water flow path in your system.....and what you expect will happen at each stage.

By way of a general caution, if you run the proposed system right on its upper (or lower energy) limits, you may well kill fish the first time anything goes remotely wrong.

Because I remove solids and have copious quantities of air in my systems, I can run for longer periods of time (whenever the poop hits the fan) than those who do not. This is what I'm talking about when I refer to a system having resilience.

Gary

[velacreations]

ok, say we have a 1000L FT (IBC or whatever). It has a pipe from the bottom of the FT, going up to the top of the water (and using an airlift or powerhead), going through the side of the FT, and dumping below the water level of the 1000L GB. At the other side of the FB, there is your standard media guard and standpipe, that drains through the bottom of the GB, and returns to the FT. That return line goes through the side of the FT, then goes up, to end right below the top of the water. This pipe might also have an airlift/power head in it, too.

If we were to use a solids filter, then it goes between the FT and the GB. The whole idea is to try and keep the water level constant throughout the system.

[velacreations]

lol well I always plan for the worst case, never failed me once. If I do that the fish are living in the best case...

Anyway, the solution to your 10watt problem is reducing the water volume in the sytem. Reduce that to the minimum required for the fish and apply much smaller volumes for the plants.

I suggest you look for a media that has capacity to retain moisture for the plants eg: soil...

Have your fish system running on air as a fish system. That is very simple

Split off some air to lift water to a point above your plants.

Have it gravity drip feed pots, containers with soil or expaned clay or what ever you like really.

Have the pots in shallow, long trays.

The shallow trays slope one direction towards a common channel or pipe that goes back to your fish tank.

Then you only need to move 5% to 10% of the fish tank volume through your plants per day.

My point was that I don't see many systems running at the numbers you propose, and they are doing fine. I think it is worthwhile to consider the worst case scenario, and have a plan for it, but not necessarily build the system for the worst case.

At the current 10 watts, we should be able to handle a 1500L AP system, maybe even bigger. I think 1500L of GB should be able to grow a decent amount of plants, and 1500L FT should be able to give us around 35kg of fish.

I don't see the reasoning on reducing the water volume. Would that be able to produce more fish for the 10 watts? If I'm running air for the fish anyways, I might as well be circulating the water, too.

[ande]

Iff LowEnergy is the goal(LEAP) it's imperial to look at the flow thruout the hole system (RAS)

This is a good doc / pdf on the matter when you design the LEAP RAS

http://www.tesisenred.net/bitstream/...pdf?sequence=1


The title of the thesis in the pdf
HYDRODYNAMIC CHARACTERISATION OF AQUACULTURE TANKS AND DESIGN CRITERIA FOR IMPROVING SELF-CLEANING PROPERTIES

Type of pump is only one of many things you have to consider.

the airlift in the thread you linked to is a good diy alternative there is some good ways to solve the airdelivery Qs on koiphen forum amongst other

cheers

[ande]

Here is one nice diy layout http://www.koiphen.com/forums/showth...ift-Components
And a discussion on yet another forum here http://www.koiquest.co.uk/forum/view...php?f=3&t=8923

Iff you skim thru the differente Koi forums (a lot) you will se the same persons involved in the discussions across the differente forums/boards and many good diy variations are thorougly described and documented.

Also you'l find many of the persons involved in axialpump discusions, Low Energy is the main motivation for their involvement, but also initial cost, service/maitnance on pump, And safety(avoid electric instalations in water) wich is a real potential hazard with any traditional pump.

cheers

[Earthan Group]

My point was that I don't see many systems running at the numbers you propose, and they are doing fine. I think it is worthwhile to consider the worst case scenario, and have a plan for it, but not necessarily build the system for the worst case.

Are you growing tilapia in this set up?....

What is the point of considering, planing and then not building it for worst case? Aim for once per hour turn over you will be just fine. Metabolically, you will need to comprimise on the amount of fish you can grow but you will do fine.

I see efficiency as getting the most out of the input. If I have 1500 litres of fish tank I want to be able to grow 1500 litres worth of fish not 500 litres worth. Working that out is very simple metabolism, not partial gas pressures, friction losses, turbulant/laminar flows etc....

At the current 10 watts, we should be able to handle a 1500L AP system, maybe even bigger. I think 1500L of GB should be able to grow a decent amount of plants, and 1500L FT should be able to give us around 35kg of fish.

Not entirely sure what you mean by "give us around 35kg of fish". Is that 35kg per year or is that the amount of fish the system will be holding at a give point in time?

Permit me to give you an example:

Let's say the 35kg is how much you want to grow out in the year. I will also say your feed rates and feed conversion will be low. These are only some of the comprimises I talked about in the post you read on my site.

Your standing stock in that senario will be around 11kg/m3 (11kg of fish per 1000 litres of water). I do not see that as being very efficient at all, more like an aquarium. The oxygen demand will be as low as 110grams per day or around 140 watts...

That is close to your target yes?

Let's go the other way and assume your 35kg is the standing stock (24kg/m3). This will give you a production of around 110kg per year. Looks a little better for sure. In that senario your oxygen demand will be around 350grams per day or around 460 watts.

A little over your target...

I don't see the reasoning on reducing the water volume. Would that be able to produce more fish for the 10 watts? If I'm running air for the fish anyways, I might as well be circulating the water, too.

In the suggestion I made, the fish system is running on the air and nearly all of the air supplied is to run the fish system. Meaning you will get more production out of the fish system. Metabolism is the key here, without it you will have poor growth in both parts.

Only part of the water and air is used (10% max) to circulate around the plant system. The plants dont care if you have 450 litres of water in your 1500 litre grow bed as long as they are getting their required amount of water every day. The flow rate make not one iota of difference to them, but it will to the fish...

Fishtank - solids - bio - fishtank all on the same water level = next to no head 90% air to move the water.

Fishtank - plants - fish tank = head is the height of the trough 10% of the air to move the water.

[velacreations]

What is the point of considering, planing and then not building it for worst case? Aim for once per hour turn over you will be just fine. Metabolically, you will need to comprimise on the amount of fish you can grow but you will do fine.

Yeah, we are planning on the FT turning over every hour. That's 1200lph on less than 10 watts (currently down to 5 watts). The point about worst case, is that for the majority of the time (80%), you do not require the maximum flow. So, why not build for the average, but set up a contingency for worst case. It seems wasteful to build a system that runs at a level that is only required for one week a year.

Our target stocking rate is 25kg/m3. That being said, I don't know how things will be run yet, whether it will be a seasonal system or continual harvest. I expect it will be a seasonal system, like most AP systems in this size. So, yes, when they are fingerlings, it will not hold 25kg/m3, but our plants won't be at a level to filter that, either.

I am confused with this:

In that senario your oxygen demand will be around 350grams per day or around 460 watts.

Where did you get those figures? Is there a standard 02 demand from watts? Surely, that must depend on your aeration method. For example, if I had a giant tank above my FT, and I let the tank poor into the FT constantly, I will be getting aeration for zero watts.

Fishtank - solids - bio - fishtank all on the same water level = next to no head 90% air to move the water.

Fishtank - plants - fish tank = head is the height of the trough 10% of the air to move the water.

I am still confused by this. Are you just suggesting that we only use 10% of the air to move the water? In both cases you are using the same amount of air/energy. In the second system, you are just pumping air into the fish tank, where the first system has that air going into moving the water. But I expect the results to be the same, you still have to pump 100% of the air, you might as well have it doing useful work (filtering your water).

Most aquariums are run like your example, but those stocking rates are several times lower than the standard I'm seeing in AP (25kg/m3). What am I missing?

[Earthan Group]

What am I missing?

The fish system is a fish system with filtration...................................................
The water is circulated at zero head with air lift through the fish tank and filtration. I have built quite a few of these.

You take some of that water and exchange it through the plants..........................
Using some of the air to move a small amount of the water (5 or 10%) from the fish tank to cycle through the plants and the water is returned to the fish tank by gravity.

Just a suggestion, take or leave it...

[ande]

Hi again VC/All
I cut/past this from page 5 in this doc./pdf www.ecw.org/ecwresults/205-1.pdf

Air Lift Pumps
Recirculation aquaculture is energy intensive because water must move continuously through the system to remove
wastes and replace oxygen. The standard method of moving water is the use of a centrifugal pump. An alternative
pumping system is the airlift pump, which uses the buoyancy produced by entrained air bubbles to lift water. Studies
by Reinemann (1987), Turk et al (1991), and others indicate that use of the airlift pump is substantially more energy
efficient for moving water under low-head conditions than centrifugal pumps. The economic benefits of the airlift
pump are further increased when the electrical requirements for aeration, carbon dioxide removal, and foam
fractionation are considered. The airlift pump does all of these simultaneously, whereas separate component systems
are required when standard pumps are used. Energy usage for a combination pumping and aeration are
approximately one-third the cost of a conventional pumping system (Reinemann et al., 1987).
The airlift pump has other important benefits to the aquaculturist. Capital costs are significantly less than that for
standard electrical (i.e., centrifugal) pumps. The simplicity in its design—there are no moving parts—means that
maintenance costs are also low.
Despite the fact that the existing body of research indicates that the airlift pump is under most instances the preferred
system for recirculation aquaculture, the aquaculture industry is generally biased against investment in culture
systems employing the airlift pump. The reasons for this are lack of awareness of its inherent advantages, lack of
available systems that employ the airlift pump, and performance deficiencies in instances where they are used. The
simplicity in its design—made mostly from PVC pipe—makes it less profitable to market relative to standard
electrical pumps. Most of the major supply catalogs for the aquaculture industry do not market airlift pumps.
Furthermore, companies that sell package aquaculture systems typically use electrical pumps. The majority of
recirculation aquaculture systems are not designed to take advantage of the efficiencies of the airlift pump.

IMO airlift pumps is sort of a natural choise in AP
"the eco friendly aproach towards agri/aqua culture"
It does have it's limitations so it's not aplicable in all setups but in a new build I would design the RAS so it that airlift pump fits.

cheers

[ande]

VC
You could try to pm AndyW at Koiphen about a smaller zize axialpump he might build you one? I see you are discussing his pump at BYAP
Here http://www.koiphen.com/forums/showth...light=aquatech

cheers