Aquaponics - Thinking low energy

Just for a laugh, I thought I'd run the low energy aquaponics question through the invention engine yet again.

Yet again, it spat out something surprising.

So far we've seen it cough up a zero head system, and then try to raise and lower a grow bed by pumping air under it, then releasing it. We've seen some kind of wacky stepped air lift, and a device that dumps air from a small pump all at once to make it pretend to be a big pump, but only for a brief moment. That way, we might send a big lump of air acting as a piston to carry water up a pipe. (I think I might have missed one) That last one I think has some potential, and might also apply to this next one. But this most recent one is most interesting, and it's this...

If you put air into a media filled grow bed that's also full of water, the air should displace water. If the grow bed is attached to a fish tank so that the water can breath in and out depending on the amount of air flow, we should see something a bit like a zero head flood and drain system, running on a few second burst from a decent sized air pump, once every 20 minutes or so.

You would need to turn the air on and off so the grow bed breathed in and out and changed the tide.

Easily enough done.

With a big air pump only running for a few seconds every 20 minutes or so, we might see a turnover of fish tank water comparable with a standard system.

So we put a stack of air stones into a grow bed under the gravel.

We flood the grow bed constantly, and connect it to a fish tank so water can move freely between the two.

Each time the air is turned on for a few seconds, water is displace by the air, and the water level of the grow bed rises.

The water then overflows into the fish tank.

The air stops, and the water fish tank water flows back until the two are back to the same level.

Repeat as required to turn over the fish tank water every hour.

Maybe.

Aquaponics - New air lift design

If you pump air down into a submerged tube, when the bubbles rise to the surface, by virtue of the fact that they take up some space, they change the average density of the water in the tube.

The result is that the new, lower density water floats, and you get water sticking up above the surrounding water.

In short, you get a pump.

This is nothing new, and even if all you do is stick some bubbles at the bottom of an aquarium and let them rise to the surface, you are seeing what has become to be known as an air lift.

Through the introduction of air into water, the bubbles cause a vertical current.

If you stick those bubbles in a tube, you create something of a pump.

An air lift in an aquarium is mainly used to create current and keep the top surface of the water moving. This top surface is exposed to the oxygen in the air, and the exposed water gains dissolved oxygen, or DO,  essential for the ongoing good times, and life, of the fish in your aquarium, or aquaponics system.

I don't have an air pump, because I run so much water through my pump, that it's not necessary. I do run a powerhead, which is a lot like a little outboard motor, that achieves the same thing, and in my case is totally unnecessary because, as mentioned, I pump so much water with my over sized pump.

An air lift, and a powerhead both move large amounts of water for a small amount of energy. My 5000L pump was 150 watts, my 5000L powerhead is only 13 watts.

The difference is the pump could lift water 5m, and the powerhead cant really lift water at all. All it can do is stir it.

An air lift can lift water, but it's a bit limited in how high it can lift it. It would be nice if an air lift could lift air to a greater height, because then we could create a really low energy aquaponics system in a conventional (grow bed above fish tank) arrangement, and still get the desired flow.

To this end, I drew this.

Normally a picture might paint a thousand words, but this is a picture of particular poor quality, so I'll need to add a few to make it paint up to around 150.

Picture a pipe with some chambers, all sealed and air tight, so whatever pressure is in there, stays in there.

If the air lift were to deliver it's water to a chamber, the water and air would separate.

If the air was then bled off from the chamber, and re-introduced under the collected, chambered water, it might be reused to create a second or third (etc) air lift.

This might mean we could lift air higher than with a normal air lift.

I have no idea if it would work, because I haven't been able to rope anyone I know who runs air in their system into trying it yet.

If I cant get anyone to test the idea, I'll have to buy an air pump.

Either way, I'll let you know if it turns out to be interesting.



120 things in 20 years, bringing you the vaguest suggestion of science in the hope that someone else will do the actual tests and see if my aquaponic, new air lift design actually works.

Aquaponics - Absurdly low energy system

I've had an idea.

It's been a while.

I keep running the problem of a low energy system through what I like to call the invention engine, and it keeps telling me to lower the difference in height between the fish tank and the grow bed. Eventually it told me to make them at the same level, and use a powerhead to just stir water from the fish tank to the grow bed.

But when I run it with the new system design, it says to drop the grow bed even lower.

Into the negative.

Which doesn't make a lot of sense until you think about moving the grow bed back up again to drain it.

When I ran that through the invention engine, it came up with floating the grow bed in and out of the fish tank.

By pumping air under it.

An air pump is inexpensive to run, and I know it's already capable of the pressure required to get air to the bottom of a tank, because a lot of people use them in exactly that way.

The thing I dont know, is if it's capable of shifting enough volume to raise the bed often enough. It will definitely raise the bed, but if it takes too long, then it's not going to be worth it. I'm guessing I'd need to raise and lower the bed at least twice per hour. Dropping it back down should be easy to make quick, so as a target to aim for, I think I'll look at raising the grow bed within half an hour. 

So if I put a grow bed on another, inverted growbed, I can fill the bottom (upside down) one slowly with a small air pump, and effectively, float the grow bed up and down rather than shift the water up and down.

As the grow bed lowers into the water, it displaces water, causing the fish tank water level to rise, and thus contribute to submerging the media to the desired level. The reverse would occur when the air was trapped and the grow bed rises. It would displace less water, so the fish tank level would drop, resulting in a quicker low tide.

The air pump can be even smaller than I first thought, because there's really no need for all that pumping to the bottom of the tank, so no need for all that pressure. That combined with the way all that stuff in the previous paragraph should work, might mean it will be an absurdly low energy use aquaponics system.

I haven't worked out the down bit, but that wont prove difficult at all. I really enjoy inventing things where the force I'm trying to overcome is used to do the overcoming, so in this case I'd like to make use of the pressure build up to release itself, but even if I cant work something out, I can always use electronics to make a valve open at the top of the cycle, dumping the air, and dropping the grow bed back down.

I might even be able to use the rush of air to do something productive.

Cooling perhaps... who knows.

It might even be possible to use the incoming water from an existing system to get a free lift, by using it to force some bubbles under a new air powered grow bed.

Or to fill the grow bed, raise it, and then distribute the water to another grow bed, creating a kind of pump.

It might also need a few guides to keep it from wearing where the grow bed would inevitably touch the fish tank.

I have a really spooky feeling I've had this idea before, and this may just be a side effect of my current lifestyle (that being sleeping in a post-op haze) or could just be because I have had the idea before. Or it could even be confirmation of the sneaking suspicion, that whenever I have an idea, what I'm really doing is simply remembering having had the idea in the future, at some point after that.

This means all the invention engine does is jogs the memory I'm yet to have had...

yet

Either way it will work.

All it would need is a grow bed media that weighs less than the water the air displaces, and it will work.

And some buckets...

I'll need some buckets.

I'll make one tomorrow.

Buckets, and media...

I'll need some media.

Sleep now.


120 Things in 20 years, For all your absurdly low energy aquaponics systems and pre-think.