Mollison's Trompe - alternative energy

I was watching a lecture of Bill Mollison and he went off on a very interesting tangent about Trompes. I have never heard of such a thing, at first it seemed a little bit like a perpetual motion machine, too good to be true. But after looking around a little bit, it seems there might be some possibility that this is a viable thing. Anyone heard of this, can speak to the viability of it as an alternative energy source? Anyone know how tall it needs to be to create a decent amount of pressure?




Details:

A trompe is basically an elevated funnel connected to a long pipe that water is poured through, the funnel has air ports that pull air into the water. The air and water flows down the pipe and into a tank with the input port and exit port at the bottom on opposite sides. The water fills the tank because the water is flowing in faster than it can exit (the exit port connects to a pipe that rises above the top of the tank). As the water fills the chamber, the air rises to the top of the tank and displaces the water down. As this happens the air pocket builds in pressure. At the top of the tank a air valve can be open and closed to gain access to the pressurized air. The pressurized air then can be used to drive air powered tools, spin a turbine for electricity and when released, the preasure difference cools the air as a sustainable Air Conditioning function.

It seems to me that you would need energy to pump the water into the funnel, creating a net negative. If you have flowing water on elevation change it seems like it could work...but there are lots of technologies to draw energy from this situation.

Interesting idea, just my two cents

IIRC, there is a mine in France that has been using one of these for about 100 years. I did a bit of research when I first heard that lecture from Mollison as well.

They seem to be well suited to areas that have a significant height differential and a water source at the higher elevation. How the water gets up there in the first place is, of course, very important in terms of overall yield. If you end up using a ton of energy to push the water uphill, you will probably end up net negative in energy capture. If you use an existing stream, windmill pump, ram pump, etc you will probably end up net positive.

This Mother Earth News article has some good detail as well as the Wikipedia page. No moving parts, relies on no computers, makes no noise, and doesn't pollute the environment. Seems like a pretty good deal but I would suspect that you are going to get much more energy output per dollar if you had a small scale hydroelectric system.

Yes I would use this in a situation where I could get the height of the water to be above where I need it. I wouldn't plan to pump it up there. I know the big industrial sized ones are very tall, one in Canada is 351 feet tall. But what about small scale use? Would 20 feet work or 10? I wish I could figure out an equation to punch in the height and see the output of PSI from the valve.

Just thought of something. In rain barrels for every foot of elevation you have, you get 0.4 psi. I wonder if this would be a constant that might help calculate the height of the tower and the resulting pressure in terms of psi.

That would probably depend on how many venturi drains you have plugged into the side of the pipe.

The wikipedia page talks about a Pulser Pump which works off the same principle. Here is a video of a small pulser pump which I found the link to on this page (which has a details and theory page with equations that you can use).

Here is a video of a guy using a trompe for cleaning mine waste water by increasing the dissolved oxygen.


I think an over-looked application is actually refrigeration, preservation of food, and energy storage. Air conditioning is a good secondary use after first being used for refrigeration. Also air conditioning (cooling) can be done with cooling tubes buried underground in conjunction with solar towers, but it's hard to find an alternative for active refrigeration (freezing) to preserve food year-round. Root cellars work, but not in Louisiana where I am. Bill Mollison said in the video that a property of compressed air as an energy storage medium is that the energy doesn't degrade over time and can be distributed without losing power unlike electricity. I can imagine large banks of low-pressure air tanks for storage and networks of piping throughout a community for distribution.

Joel Francis wrote:Here is a video of a guy using a trompe for cleaning mine waste water by increasing the dissolved oxygen.

I think an over-looked application is actually refrigeration, preservation of food, and energy storage. Air conditioning is a good secondary use after first being used for refrigeration. Also air conditioning (cooling) can be done with cooling tubes buried underground in conjunction with solar towers, but it's hard to find an alternative for active refrigeration (freezing) to preserve food year-round. Root cellars work, but not in Louisiana where I am. Bill Mollison said in the video that a property of compressed air as an energy storage medium is that the energy doesn't degrade over time and can be distributed without losing power unlike electricity. I can imagine large banks of low-pressure air tanks for storage and networks of piping throughout a community for distribution.

There are losses in distribution, related to friction as the air passes through the pipes.
There is a short pamphlet circa 1897 by a Mr. Taylor who was the fellow behind the big Canadian trompe project that discusses the issues of distribution a bit.

I just wanted to clarify, because I just watched Mollison's lecture. He was talking about diverting water from a stream or river, so no need to haul water up to an elevation. He even mentioned that the outbound water has more dissolved air than when it was received, so it was good for wild fish.

I could not verify all of his claims. In particular it seems like it could power something like a car, but significantly less horsepower and maximum speed than what we think of as a car. For example, the technology might not be able to scale to replace a pick up truck that could haul horses and gravel. But you could use it to go grocery shopping and perhaps 70 kph.

https://www.youtube.com/watch?v=SScpJMsCm9c

Sounds like you need a handful of the right conditions for this to work. A stream that runs year round a place to put the hardware and a decent elevation drop. Just read a story about an entire mine in Canada that was run almost entirely off of a large trompe.

That or you consider it a seasonal form of energy, when you have running water.

You don't need an elevation drop, if I'm understanding the physics. You could just bury the equipment. You just need the elevation drop from the input to where the tank is that is collecting bubbles.

The greater the difference between the inlet and outlet the better potential for flow. if the inlet and outlet were at the same height, no water would move through the system.

I recently built a small scale trompe, here are the specs:

Closed system using a bucket of water being pumped to the top of the inlet and then returning to the bucket. Im doing this only to test out the dynamics of it, this will be used on a natural water way.

3/4 inch inlet with one straw for air introduction, this is about 8 feet tall
transition to 1 1/2 transfer pipe then to a vertical 3" air entrapment with 1/4 air compression gauge and valve. The air chamber is about 2 feet tall.
The outlet part of the transfer pipe then goes to 1 ". The outlet pipe is about 5 feet tall. I experimented with a one way valve to try and create back pressure. Youtube Mr. Teslonians Trompe Hammer for the gist of this.


No matter what I do I cannot seem to generate more than 1 PSI and of course once the pressure is releases the water level comes up and spills out of the top. I want to test this on actual falling water because I think it has to do with the volume of water going into the inlet pipe, it doesn't seem to be enough since im pumping through a 1/2 tube into a 3/4 inlet pipe.


If anyone has any further ideas/thoughts I would appreciate it and I can post more details if desired. I tried to contact Mr. Telonian but I can't find his contact info anywhere, he would certainly know the answer.

Unfortunately I don't know of a point of reference - this volume of water falling this distance can produce X amount of pressure.

However, I feel like there are a few components you could try modifying.

Could you try reducing the size of your reservoir where the air gathers at the bottom? The air will still want to collect, but if it's forced into a small space, it may compress further.

Similarly, could you try to introduce more air on your inbound? For example, attach a funnel shape with many straws instead of just one?

Have you seen Mr. Teslonian's video?

https://www.youtube.com/watch?v=xv1lQA-tnwo

BTW this is great of you to share your project! Much appreciated.

Thanks Katherine, the larger air introduction was my next step and I just bought some parts to reduce the air chamber. Its all welded now so I have to cut and splice Those are great ideas and I will post my results. For those of you that are way smarter than me I need to be able to take whatever air comes out of there and then do a secondary compression but I can't seem to find any resources on manual compression in DIY context. Get gaskets etc to hold that much pressure may not be available on a smalls scale.

Oh and I have seen that video from Mr. Teslonian, he and Mollison both inspired me to do it. I want to experiment with small scale refrigeration and pond aeration all off grid. Stay tuned, and keep the comments/criticism coming!

This is certainly not my area of expertise either. But it seems like some of these finer points are critical, because there's a lot of physics going on. Things to check in your system:

Do you have one-way values in place to prevent backflow (Mr. Teslonian mentions several key places where he put them)?
Is your input both a wider pipe and at least a few feet higher (sounds like 3 feet may be sufficient) than your output?

There was a great suggestion about optional ideas you could do with straws to help create a swirling affect when the water flows down, which will add more air bubbles: put the straws slightly offset from each other. So for example if you had 6 straws, inside the inbound tube, have the base of the straws be at different heights, maybe each one 1" apart from each other inside of the pipe. You could use a simple spacer to help hold them in place - think maybe a tin can lid with holes.

This is the first time I've run into this guy on youtube. It's very inspiring to see his stuff put together. As a side note, it looks like he has some serious welding skills. If you truly do succeed, be careful to think through where your weakest point is in your system.

I need to put a secondary chamber with a one valve on it, and I think that might help with the actual compression storage but it wont address the initial low PSI. From what I understand from the research the inlet pipe has to be smaller than the outlet, can someone correct if Im wrong? I believe Mr. Teslonian stated that in his follow up video as well.

No. The opposite - input should be slightly larger than output. Mr Teslonian covered it in the video I linked. Then again he's combining two machines together. But it makes sense to me. You're trying to encourage water to swirl and input a large volume on the way in, but create to a small degree a bottleneck on the way out, forcing the pressure to increase.

Some patterns show inbound and outbound as similar or do not appear to be to scale. Others show a very significant difference between the two. A few more designs for reference if it's helpful to you:
http://charleshtaylor.blogspot.com/2009/02/hydraulic-air-compressor-brief-history.html

Well if that's the case then that is probably the main issue! Thanks Katherine, I'll keep at it.

Hey gang, just a quick update. I moved this system out to my pond and doubled up the pumps to put almost twice as much water down the intake. Ive reversed it so the larger opening is the intake and the exit is the smaller diameter. I let it run for 30 minutes and it still wont get any higher than 1 PSI. Im not sure if its just not enough volume of water (size of tubes) or something else. Very frustrating since this seems like it should be more simple. Any thoughts? Im happy to answer any questions or try things. Thanks.

Joel Francis wrote:Here is a video of a guy using a trompe for cleaning mine waste water by increasing the dissolved oxygen.

I think an over-looked application is actually refrigeration, preservation of food, and energy storage. Air conditioning is a good secondary use after first being used for refrigeration. Also air conditioning (cooling) can be done with cooling tubes buried underground in conjunction with solar towers, but it's hard to find an alternative for active refrigeration (freezing) to preserve food year-round. Root cellars work, but not in Louisiana where I am. Bill Mollison said in the video that a property of compressed air as an energy storage medium is that the energy doesn't degrade over time and can be distributed without losing power unlike electricity. I can imagine large banks of low-pressure air tanks for storage and networks of piping throughout a community for distribution.

There are solar freezer's and ice makers already designed & are being used that can be built with a minimal amount of knowledge. I have posted here before about them and yet no one seems to take an interest. I posted a PDF with explanations & diagrams. The problem of refrigeration has been solved. Do the research, I did. I won't mention it again.

This is not new. It was used in California gold mines to power machinery. I have used a bench grinder that was water powered & could not stop it from turning.

The draw back is: To create "useful" power the water has to be very high & most people are not going to be able to make anything that will work any kind of machinery. Just remember you have to be able to get the water "up there" before it is usable "down here".

Hi, I made the pulser pump. A pulser pump is a thrompe powering an airlift pump. I publicized it and it really only became accepted (even if very little used) when I asked other people to make their own models and post on youtube. This they did on 3 continents. There were 2 attempts at universities (based on what I did) to make and quantify trompes powering airlift. Both screwed up. I had no input to the first one (in Canada) and early input into the second one (England). The second one was the most disappointing because the guy used one trompe to power several airlift pipes (as I have done successfully) but he decided to leave out little taps that control the air speed to each airlift pipe. In this case, all the air goes into one airlift pipe and produces very low efficiency. If he had bothered to consult, I could have told him that his experimental setup had a huge error. Anyway, I will try to list some misconceptions and uses for trompes and And especially uses for mini trompes and mini airlift pumps.
First off, a psi is 27.7 inches of water. Your trompe has an inlet on top and an exit level of water where the water comes out. To get pressure in PSI you measure vertically down from the exit level to the top of the air chamber in inches and divide by 27.7 to get the psi. And that is it. You cannot increase that number. It is the best that you can do. I made a 3 psi trompe and it ran over 20 years. I hooked it up directly and indirectly to airlift pumps to send water from a stream to cattle and sheep in houses.
However, it is a big deal building a 3 psi trompe. My stream had 300 liters per minute of water falling half a meter at a little dam. Watts is gravity by kg per second by height in meters. S0 300/60 multiplied by 0.5 multiplied by 10 = 25 watts. That is all I had for power and that does not justify digging 15 ft deep. I found out in experiment that the trompe section was maximum 33% efficient at making compressed air at this depth. So you are down to 8 watts now! and then this air for powering airlift has a max efficiency of about 33% too and this brings it down again (you always combine efficiencies in a chain) so now we are at less than 3 useful watts!
HOWEVER, at one stage my pulser pump video was the most popular airlift pump video on youtube and it helped spawn "mini airlift pumps for horticulture and hydoponics" Airlift pumping is interesting because the physics as applied to small tubes is completely different than the physics of big airlift pumps. I learned this with my pulser pump but it was very very hard to spread the knowledge. Essentially, small tube airlift works best with "plug flow" to pump water while large scale in big pipes uses the lower density (and higher column height) of bubbly water to pump water. The physics is completely different. So I have worked on testing for things that only need 1 or 2 psi. So bottom line, you can easily pump water 6 ft high with 1 psi of pressure. And you can use one trompe to power several airlift pumps. This is very useful because cycling water around planters or compost tea massively speeds up chemical and biochemical reactions. I now live in a city and I use mini air pumps powered by electricity to run the "pneumatic grid" that moves water in my greenhouse, in my planters and running a compost tea brewery. It is always less than 1 psi. and has ran about 6 airlift tubes in different locations on about 7 liters per minute of air. I will put a youtube video of the pulser pump. but note that I have many videos about mini airlift and mini trompes too. Brian White

There was a mine that used this to create compressed air for work in the mine.
The water was pumped down a 8 inch pipe that went to the bottom of the mine.
The pipe had numerous small pipes inserted at a 60 degree angle
This allowed air into the water.
A heavy concrete tank at the bottom allowed air out.
The pressure of the air equaled the water pressure.
Water is .404 psi.
So 40 psi at 100 ft
80 psi at 200
1000 ft is 400 psi.

I believe I read about this in whole earth review

We need a little realism when doing trompes. Lots of mines used them in the past, they were used to build alpine tunnels. (Powering the air tools) but these days, nobody is going to dig a hundred ft deep hole for a trompe. or a 20 ft hole or a 40 ft hole. People have to think mostly low pressure trompes or they are not going to happen. I use low pressure air (1 psi) for lots of stuff round my garden. It is very easy to make a 1 or 2 psi trompe but after that, it gets seriously hard. If you want higher psi, why not a small gravitational vortex running a compressor instead? Technically easier than the trompe.

Tom Robertson wrote:There was a mine that used this to create compressed air for work in the mine.
The water was pumped down a 8 inch pipe that went to the bottom of the mine.
The pipe had numerous small pipes inserted at a 60 degree angle
This allowed air into the water.
A heavy concrete tank at the bottom allowed air out.
The pressure of the air equaled the water pressure.
Water is .404 psi.
So 40 psi at 100 ft
80 psi at 200
1000 ft is 400 psi.

I believe I read about this in whole earth review

With electricity, it becomes an inefficient tech.
But I can see it for back to the land movement
Any micro hydro instalation can be modified slightly to produce air pressure.
Just add air intraining
Put a tank next to the generator......

Micro hydro is an inefficient tech. Its payback period is never. A 3 ft deep trompe in a 25 watt stream can pump water around greenhouses to keep things watered even though it is only producing 1 psi. There is pretty much no other way to use the water from a 300 liter per minute stream falling half a meter to generate useful power. I made a 2.5 meter deep trompe that pumped 11 to 15 liters per minute of air down to 3 psi. meaning that a i meter trompe would be making about 35 liters per minute of compressed air at 1 psi. 1 liter per minute will easily run a mini airlift pump, meaning that you could run 35 airlift pumps from that one trompe. If you "modify" a micro hydro system to entrain air you also make it more inefficient at producing electricity and lengthen the payback period to beyond never.

Tom Robertson wrote:With electricity, it becomes an inefficient tech.
But I can see it for back to the land movement
Any micro hydro instalation can be modified slightly to produce air pressure.
Just add air intraining
Put a tank next to the generator......

Micro to me is small installations
100 ft head from 4 inch pipe.
Imagine adding air entraing.
The plastic could not handle it but a concrete 'tank' could.
I think a heavy duty tank would let the air escape the water but the water should still have its energy
I no longer have access to the family farm so I can't experiment any more with free flowing water.

I'm all for old tech finding new uses.
A epa engineer is using the air to oxidize heavy metals.

Hers one guy using the water hammer effect for increased air pressure

Here's the engineer with some history too.

No. The water does NOT still have its energy. The energy has been used to compress air, and has been used in turbulence and the usable head is reduced by the height of the air column en-trained. My working trompes predated the epa engineers trompes by a couple of decades and were published in an Irish magazine in about 1989 and in and English mag around 1995
Mr telsonian's tromp hammer is also uses energy as the pressure wave goes back up the pipe and compresses air at each stroke. That repeated high compression of bubbles is a recipe for high nitrogen in the exit water. (Fish can get "the bends" and die). If you really want to use a water ram to compress air, you are better off putting something on the ram itself to compress air at each stroke. They have a "snufter" so this should be relatively straightforward to redesign. But a ram cannot operate properly in a couple of ft of head. And areas with a couple of ft of head (with massive flow) abound. A couple of ft of head and massive flow cannot be used by a water ram.
http://nxtwave.tripod.com/gaiatech/pulser/detailed.htm

Tom Robertson wrote:Micro to me is small installations
100 ft head from 4 inch pipe.
Imagine adding air entraing.
The plastic could not handle it but a concrete 'tank' could.
I think a heavy duty tank would let the air escape the water but the water should still have its energy
I no longer have access to the family farm so I can't experiment any more with free flowing water.

I'm all for old tech finding new uses.
A epa engineer is using the air to oxidize heavy metals.

I bow to your greater knowledge.
I'm just an interested amateur
I like how something is in the back of my head can come back 30 years later and still be useful.

Brian Whites design is interesting and relevant to this discussion thread. In fact I am still surprised.

I am really surprised at the dearth of info on pumps on Permies. Aside from getting water with your property, how to move it seems to be the next big thing that we deal with in design. Not everyone will be so fortunate as to have a site on a slope from top to bottom with enough 'head' to make a RAM pump work. So what's left? Grid driven electric? Fuel driven electric? Solar driven electric? Hand power? Gravity?

What I have discovered is that a RAM pump is pretty cool, but takes at least 18 inches of head pressure to run, And then, very slowly. This means that a storage tank or basin will be required in addition to 'head' Or you will need to use a water wheel of some sort. In Boise there is a lifting wheel design on display that was used years ago before electricity. Nothing else?

Windmills, manual or electric? This means storage too.

Screws, Siphon, Sprials...the Rife River Pump (no successful copies by DIY yet. No testimony by Permies on these either! Still storage issue.

I guess this is one of those places where electricity driven pumps is the most AT?

Thoughts?

I'm not sure there is a way out of the storage issue. Ponds, I guess. There is another alternative "pump" that I think has super potential for low head sites. I would bet that a gravitational vortex could be made in a rain barrel at a little dam and attached directly to a water pump or to a cam to make low pressure air. (I think probably up to 5 or 10 PSI but that is a bit of a guess) Gravitational vortex is something that is very simple yet nobody tries it. Everyone loves ram pumps, and they have great efficiency but they are strictly for medium head / low volume power sources. The available sources for energy (world wide) are mostly medium to low head and high volume). I made a mini gravitational vortex to demonstrate its unusual behavior a few years back. One beautiful thing is that if you remove the power draw, the vortex gets higher. (It stores some energy within the chamber). If people made them and tried to use them to pump water and to compress air on the 300 to 600 liters per minute and half to one meter head range, we could have some data and new ideas. I find the gravitational vortex very interesting. (the solar panel stuff is probably not so relevant in the video).

Ty Morrison wrote:Brian Whites design is interesting and relevant to this discussion thread. In fact I am still surprised.

I am really surprised at the dearth of info on pumps on Permies. Aside from getting water with your property, how to move it seems to be the next big thing that we deal with in design. Not everyone will be so fortunate as to have a site on a slope from top to bottom with enough 'head' to make a RAM pump work. So what's left? Grid driven electric? Fuel driven electric? Solar driven electric? Hand power? Gravity?

What I have discovered is that a RAM pump is pretty cool, but takes at least 18 inches of head pressure to run, And then, very slowly. This means that a storage tank or basin will be required in addition to 'head' Or you will need to use a water wheel of some sort. In Boise there is a lifting wheel design on display that was used years ago before electricity. Nothing else?

Windmills, manual or electric? This means storage too.

Screws, Siphon, Sprials...the Rife River Pump (no successful copies by DIY yet. No testimony by Permies on these either! Still storage issue.

I guess this is one of those places where electricity driven pumps is the most AT?

Thoughts?