Backyard Aquaponics
A place to discuss aquaponics

I dont agree. In my experience "wet feet" is all about root oxygen uptake ability and can be resolved/worked around with high dissolved oxygen levels in the water. Hence why i said aerate your fish tanks.


stuart, i know you disagree with me just to disagree but i dont see how 4 pumps or 6 pumps can consume less power than 1 pump of the same size. And i am not even going into the fact that power requirements at zero head height could likely be less than the power requirements for each head height of the original design.

bcotton

Why does the 1 pump need to be bigger than the 4 or 6 pumps? The multiple pumps are not speeding up anything, they are working independent of each other. The net speed of the water flow around the system is not improved by many.

I think in most cases this is correct it is about getting enough oxygen to the plant roots but I wouldn't rule out the possibility that there are plants that don't like their "feet wet" so to speak. Carrots being a good candiate


I don't understand what you are saying here. I'm pretty sure I wrote that the one pump would consume less energy than 4 or 6 because it would be possible to get a larger pump with a greater efficiency than the smaller pumps.

Whether the power requirements would be less at 0 head would depend on a number of factors. Principally what pump was being employed to provide circulation. Many pumps use more electricity at low heads and their maximum draw is at 0 head. If using one of those pumps then a lower head system could indeed use more power than a higher head system.

One pump to do the same amount of work needs to be bigger because it is one pump doing all the work that would otherwise be spread over many.

It depends on what you mean by bigger though.

In Terry's original four bed design the pumps are pumping for about 15 minutes each hr lifting the water about 0.5m (according to Terry). The same work could be done by one pump if the beds were terraced. The flow would be the same but the pump would need to be "bigger" to pump to a head of 2m (4x0.5m) in order to do the same amount of "work".

All this though assumes that your trying to compare apples with apples or at least apples with oranges painted green to look like apples.

You could reduce the number of pumps and not increase the size of the pumps by reducing the number of beds. More work would be done by each pump because it would be running for longer but the total amount of work done would remain the same.

For BC

Terry's problem is that his FT's are 1m high which gives him the penalty of 1/2m because the GB's would be too high.
It is possible to cascade with one pump running continuously but then I would be accused of painting fruit.

I did overlook that the float switch pumps would not be constantly running, but i dont see how that changes much. you still need to turn over you fish tanks Y amount of times per X amount of unit time. This requirement shouldnt change because the pump is running 10 minutes an hour or 60 minutes an hour.

Maybe the multiple sump pumps would need to be bigger than one pump?

Also i will let the engineer tell me.
1) Does a pump draw more power when it is turned on? turned off?
2) Does starting and stopping a pump cause increase wear and perhaps lower life expectancy to a constant running pump?

I wasnt suggesting a cascading design. I do like cascading designs and think they have very good qualities. I was suggesting a constant height design with small head height caused only due to grow bed / tank water level inequality.

This has been debated. Gungala believes (because he has measured the draw) that single phase pond pumps don't draw more on starting. For three phase they do in a big way. As to more or less wear and tear it depends on the pump. Some pumps can run continuously for years without maintenance. Others can not.



I wasn't suggesting you were but it had been raised before in relation to one pump drawing less power than multiple pumps. In this thread there are at least three maybe now four configurations being discussed. Some of the answers are appropriate to some of them but not others. Very confusing.

All,

Pump selection in any application is about selecting the right pump for the job being asked of it.

The other thing is, in most situations, well designed pumps rated close to what you want to do, will have enough fudge factor built in to not cause issues.

If we take a pumping load that has a stable delivery rate and a defined static head then pump selection is a very simple affair. You would just select the pump that will deliver the flow rate into your designated head and if things like reliability, format and packaging are equal then choose the pump that will get the job done for the least energy used. Simple really.

Where it gets more complex is, when head heights and flows rates vary. A single pump in this situation may be required to run for considerable periods outside of its design parameters. As a pump is asked to perform further from its design parameters it might use much more power or might begin to cavitate or stall. One thing is certain the closer a pump is to perfect efficiency for the chosen task the faster efficiency drops away as you move further from the designed flow and head parameters.

For this reason two or more pumps may be appropriate.

Another idea,

I have been thinking, today as a matter of fact amongst all this pump talk, that it may be possible to have a constant flow through all the tanks and growbeds in the system and to superimpose over the top of this constant flow a flood and drain filling and lowering of the growbed water levels.

If you run the system on a number of pumps running constantly to turn over the water in the tanks hourly then these pumps need not be turned off. The water being circulated will just trickle along the bottom of the growbeds into the pump wells and onto the next node.

Over the top of this constant low level circulation you could superimpose a body of water controlled by float switches that circulates as a tide for the flood and drain effect drawing air into the substrates of the growbeds.

I haven't thought much about the implications of this idea so I'm just spewing it into the aether and it may come to nothing, but who knows. It would certainly be an aid to water oxygenation and tank retention times if it's possible. I was looking to address the tank water retention times with the Baki showers, so this idea may address that issue.

Hi all!

Terry, before I comment, a few questions:

- Does your commercial approach also use IBCs as FTs? (as suggested in the other thread...)
- Are you looking to IBCs for GBs as well or would these be of other construction?
- If IBC-GBs - do you plan to cut them in 1/2 to increase BG-surface?
- What is your priority - fish or plants?
[IF you insist in going IBC-FTs for commercial, then I assume it is fish....]

Cheers,

thjakits

Hi everyone,

A very interesting diversion from the 'usual' methodology of AP. It took some time but once I had read up to here I think I am onboard in terms of understanding and support. I think it will work, and like you are arguing telonline, the biggest benefits of this method will come when it is utilised on the massive scale.

However, a few possible problems come to mind and I would like to know how you think they would be addressed.

I think it is a certainty that you will have to incorporate some form of speed control vs time between when a pump is triggered and when it approaches the end of it's pumping cycle. Either this, or some kind of holding system (single or multiple sumps or stalled emptying of growbeds) in association with timed stop and start of the pumps so as to initiate a tide which can then propagate through the system.

I say this because under constant working conditions it is likely that the rates of flow through the media in the growbeds and small differences in pumps, head highly etc may create a situation where flow through the whole system evens out and you lose the 'tide' effect and end up with a constant flow situation.

This may be remedied by maintaining an absolute minimum water level so that there is not enough water in the system to allow it to balance, but in the massive scenario this would be difficult at times as there is rain to contend with.

A system may need to be incorporated to pump water out to maintain low water levels, and therefore the 'tides', during wet periods. Obvious ways to minimise the demands of this system would be to cover the system (unlikely on the massive scale) or the system is lifted above potential flood heights or significant bunds are built.

This will undoubtedly dilute your nutrient pool and potentially create nutrient rich waste water unless it is stored for later replenishment of the system.




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Another approach I forgot to mention may be to overspec the pumps utilised so that they provide a massive surge to the next growbed and empty their void quickly. This would likely create a number of smaller 'tides through the system, however I can't help but think that flow would inevitably even out throughout the system...

So again, I come back to maintaining a maximum amount of system water as the most likely solution...


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