Backyard Aquaponics
A place to discuss aquaponics

One slight point although we are getting away from the topic
The input energy from a PDP air blower (piston) appears to be variable with the load placed on the outlet. Or in simple terms the deeper the air outlet the greater the wattage used.
Tested on a SIP oiless pump using a variable release valve to simulate load. (not a very good test as I did not connect a pressure gague to the outlet, also its pretty old). It appears that the energy is expended as heat ie the compression of the air above normal air pressure, which I expected.
If I get a chance I will test a diaphram air pump.
This is not an argument Frank merely an observation , I do not currently use airlifts or bubblers.

Yes Myles it was just a statement re the depth as I was a little concerned over the possible variations other than lift capabilities.

Now isn't that a bit silly and "the easy way out", Mylesau (I prefer first names in a friendly discussion)?
After me going through the pains of demonstrating that the probably most used pumping system in AP and in aquaculture is horribly inefficient for both pumping and aeration (the -mainly saltwater- aquarium world has given up airlift pumps some time ago),
your reaction sounds to me like you are thinking I have created a problem for you and now are telling me: "you created it, now go and solve it".
I have not created this problem, merely pointed out it's existence.
Shouldn't we ALL go looking for solutions ???
I believe that to be better in spirit with this forum: warn people of existing wrong assumptions, then help each other to find solutions.

And I have not limited myself to exposing the misconception, I have also already taken the next step:
I mentioned the existence of propeller pumps which seem more suited for low head/high volume pumping than either centrifugal or airlift pumps.
I pointed to a very interesting link:
http://www.advancedaquarist.com/issues/ ... review.htm
from which I quote (but you should read it completely):
"... The pattern of deflection of the PE-1 is similar to the Gemini in some respects. The strips furthest from the pump deflect the most and deflect towards the pump. One difference is that the strips closest to the pump are deflecting more with the PE-1 than the Gemini. What is interesting is that the Gemini is rated at 960 gph while the PE-1 is rated at 170 gph. A pump rated at less than 20% the flow of the Gemini appears to be generating as much turbulent flow as the Gemini. The PE-2 in the bottom frame generates the greatest flow nearly flattening the test strips on the opposite side of the tank.

The strong flow of the PE-2 inadvertently demonstrated another difference between a powerhead and the prop. In the first few tests I used insufficiently weighted strips and the flow was sufficiently great enough to push all of the test strips to the right side of the tank. A powerhead like the Gemini would have drawn the strips into the impeller of the pump. Any hobbyist who has had anemones, snails, or other invertebrates drawn into powerheads knows the effect. Instead of drawing the strips into the propeller, the propeller appeared to create a zone around the rear of the prop that kept the strips away. While the final version of the mounting bracket includes a shield to keep animals away from the spinning propeller, the danger seems to less than it might first appear.(To test this I have been running both modified bilge pumps as well as the Little Giant based devices in my main display tank between tests. No animal has approached or been drawn into the propeller.) ... ".

Rest assured I will keep looking for alternatives.
But I could use a little help here.

friendly greetings

frank

Firstly... I'll admit to having only skimmed most of this thread.... but I'm confused Frank...

You constantly reference and quote articles regarding "propellor" pumps.... that seem to be information primarily related to generating wave motion in reef tanks.... and their efficiencies relative to 12v bilge pumps....

I seem to be missing the point... (1) what relation does this have to the use of airpumps... (2) what application do they have to AP systems and pumping requirments...

Rest assured I will go back through the thread tonite.... but I'm confused.... seems to be an esoteric argument about apples and oranges.... and not even the same orchard

Rupe

Quick summary

Burton asked a question re lift from airlift pumps (think this was sorted)
Frank pointed out that airlifts are inefficient
Myles is using an airlift to move water bottom to top of FT (mix water and aerate) and reckons he gets a better flow for his 35W than a centrifugal (at zero head).
Slight disagreement at this point
Frank reckons that for this purpose propellor pumps are more efficient.
All AP related no drama's

Ok.... not sure exactly what sort of airlift was being envisaged or discussed... or for what purpose....

But they use a very simple "airlift" at Natfish in their recirc research tank... to move solids from the bottom of the tank... to the swirl filter....

Consists of a 25mm pipe... with an airstone inserted in the bottom of the pipe... that lifts the water and solids up to the swirl filter....


About as cheap as you could possible get.... and obviously efficient...

Delivers more than enough lift to raise the solids... and create enough flow for the "swirl" seperator... (right pipe - the left is the return)



Can't for the life of me see how a "propellor" pump could be any more efficient or cheaper to run..... and obviously the "head" and "flow rate" are just fine

I also think Frank is talking about "Axial flow propellor pump'.
And yep ,, at low heads they are very efficient.

A 3 phase powered Axial flow propellor pump at low head / high flow is basically unbeatable in terms of efficiency.


Myles will probably conter with " but the air-lift NOT only mooves water but also oxygenates.
Well true ,, but the inneficiency is so great that you could use say 30% of the allotted power for the axial propeller and another 30% for a seperate aerator and still be a long way in front.

AHHH I have got links to proove all this ..... UMMM on my broken lap-top It didn't appreciate me giving it a drink of beer

Probably agree with Frank and Chappo on this one

Thanks Sleepe, for the summary
and thanks Chappo, for the support
propeller pumps seem to suit ALL heads needed in AP and aquaponics better than any other pump encountered so far.
I could do with some of the links you lost to back this up... pity
Rupert,

all sorts of airlift pumps, and all purposes fall under the discussion as far as I'm concerned.
Airlift pumps are absolutely UNefficient at ALL tasks.
With the only possible exception of protein removal.
For ALL other purposes there are alternatives which I already have described.
take your example: raising solids... and create enough flow for the "swirl" seperator
your conclusion that in this case an airlift pump is:

is based (I'm sorry to say) only on perception, not on knowledge.
Perception is frequently fooling us all.
you can hardly call energy efficiency of less than 5% "obviously efficient".
I notice that the head in the pictures is over 30 cm. This is very high for an airlift pump.
I would be VERY surprised if this airlift pump would have an energy efficiency of even 1 %.
Most probably much less.
Though the actual airlift part of the system may be simple and cheap, you forget to take into account the price (and energy consumption) of the blower, which is the error I most often have encountered in almost all papers read on the subject.
One solution to removing solids without an airlift pump was also already described by me: a siphon will do the same.
So will a motor with the shaft and propeller inserted in the central vertical tube (but that might disintegrate the solids).
So will a central drain.
All of these are just as simple and could be cheap and most certainly are more energy efficient.

And for the exception of protein removal, this can probably be solved with a venturi air injector.

Now how important is all this?
Based on the actual consumer price of kW in Belgium (somewhere around 0.2 €/kW day tariff), a 60 W centrifugal pump will consume two to three times it's investment value per year (24/7 operation), so improving the energy efficiency of your pump gives a return on investment of between 4 and 6 months.
Or else: a propeller pump may cost more than double (but shouldn't): still the price difference is recuperated in the first year.

Greetings

frank

Frank ,, links are only temporarily in holding pattern ,, lap top not entirely dead , just screen has very little back-lighting.
I'll see if I can squint out my links in the favourites:)

Frank, it's just Myles.

It's far from silly! I am constantly looking for more efficient methods and equipment to achieve what I am currently achieving.

Just to be clear, I think airlift pumps are a poor choice for pumping to anything but very small heads, unless there is a particular reason to have a maintenance free, no foul, low/no risk of damaging to what flows, pump.

However at small heads, I believe they are a good choice with many benefits. I have experimental evidence that they outperform a typical centrifugal pump - this is a fact, like it or not.

Issues I have with your arguments Frank are mainly to do with your application of 'science'.

Using your method/argument of determining pump efficiency and using it as a measure of a pumps worth, I would be significantly better off to using my centrifugal pump with a 1 meter head pipe dumping water back into the pool.

Without the head pipe, efficiency is around 0.2% with a flow of 3,000lph.

With the 1 meter head pipe, efficiency is around 15% with a flow of 1,900lph (based on manufacturer stated flow for this head).

Do you now see why I find your application of 'science' to be faulty in relation to practical efficiency!

I also find your argument about the lack of airlift pump performance data being a reason to doubt their practical use, when all details you provide relating to propeller pumps to be equally lacking, to be a weak argument.

I have previously stated that I believe a propeller pump would be the best choice for this application if it wasn't for the fouling issue that I would no doubt encounter:

I have looked into propeller pumps in the paste - you may find the following useful.

If you go to the following yahoo group:
Yahoo Swimming-ponds

You will find two possibly useful links - unfortunately you will have to sign in to Yahoo. The ReNew Magazine article, where Dave Keenan discusses the use of a propeller (axial) pump in recirculating water at very low head (I won't say zero), and the Propellor Pump link which shows how Dave made one using a Rule Bilge pump. I have seriously considered this as an option, but these pumps do not last long, and having the propeller, I feel, will not suit my application...

In my opinion Airlift pumps have their place, I've tried to show this which is what you originally asked for?


Not at all, I would just like some actual supporting evidence, which I don't believe you've provided. Simply saying that a pump has poor efficiency based on power in to power out ratios is of little value without showing comparative details of other pumps with better efficiency.


I did read it, but found it very lacking in any actual measured detail. Were are the efficiency values


Perhaps the links I provided are of some help...if you can't access them (don't want to join) I could possibly email them to you.

One question I would raise about propeller pumps in relation to some AP uses - What effect does increasing head have on their performance? I would imagine that slippage would be a major issue and their performance would suffer as head increased?

This is a very enlightening read Frank and Myles

I think the main advantage of an air lift pump is - no moving parts in the water. This advantage can outwiegh the efficiency issues.

I reckon in the photo that rupe posted, a standard pump (or even a propellor pump) would get blocked extremely quickly, the blades or vanes would get covered in crap, and its efficiency would probably be reduced to a point somewhat below that of an airlift pump.

I like the discussion.

+1 without regular maintenance a propellor pump would somewhat be less efficient with blades and vanes crap collecting. Not sure if below that of an airlift pump.

I'm certainly no expert in these matters... far from it.... but I think I understand Frank's point in terms of "efficiency" as a pure measure of a singular pump in comparison to another...

The pic I posted has air delivered as part of a general supply throughout the research facility... and I have no idea of the actual "efficiency" of the blower that does so...

It's obviously efficient in as much as it delivers sufficient air to provides for the needs of the facility... and as such has economies of scale...

In terms of simplicity and "effectiveness" in acheiving the desired goals in the tank pictured... and in other areas.... it meets the desired goals....

And in general terms for AP... I think as such it has its place...

As Frank says... in AP a venturi siphon.... ala Chift Pist.... is also effective....

And that's probably where we've become diverged to some extent... many, including myself are probably arguing from the standpoint of "effectiveness"... rather than the point of technical "effectiveness"....

As such Frank is probably correct..... in real world terms..... I guess we often make trade offs.... especially in small AP systems... i.e ... we may wear the extra cost vs pure efficiency... for the sake of simplicity and/or availability....

And in some ways I think that was Myles point..... OK... it may not be technically "efficient"... but what are the options.... and relevant costs and availability....

Should read....

"are probably arguing from the standpoint of "effectiveness"... rather than the point of technical "efficiency"...." ...

If we reduce 'efficiency' to 100 % reliability ,, i'd vote on my mother-in-law working , hands on with a bucket:)

We should be talking REAL world ,, not fantasy.
Real world says ,, the axial
propeller pumps is efficeient,,, the air-lift is not.

What if's ,, but If's are mere conjecture ,, facts are facts.

I'm not going to argue against air-lift being a reliable and low cost alternative ,, I use it on one of my Lakes,,,,but efficient it is not.