Harness Hydro Power with a Trompe

Don’t run to the hardware store and by a new compressor, this trick will teach you how to compress your own air using water pressure.

| July/August 1977

  • 046-078-01-harness-hydro
    This diagram shows the inner workings of a trompe and "blow-off" pipe.
    ILLUSTRATION: MOTHER EARTH NEWS STAFF

  • 046-078-01-harness-hydro

The trompe. Its use dates back to the beginning of the Iron Age, and yet — like many good ideas involving the manufacture of power — the trompe concept has been all but forgotten in the recent stampede to mine, refine, and consume readily exploitable supplies of fossil fuels.

For the homesteader or farmer with a small waterfall or a good-sized stream on his property, the trompe is a natural. It offers a virtually inexhaustible supply of free compressed air ... cool, dry air that can be used to operate a forge, drive machinery, or aircondition a house or barn in hot weather.

What exactly is a trompe? Very simply, a trompe (sometimes spelled trombe) is a device that uses the energy of falling water to pressurize air. This pressurization is achieved by means of a standpipe or shaft down which a column of water is allowed to fall. As it drops, the water draws air through small inclined orifices (see the accompanying diagram) and carries it to a submerged plenum or reservoir, where the air separates from the water and is held under pressure. (The water — meanwhile — continues to flow to an exit pipe, the end of which is high enough to balance the pressure in the reservoir.) The pressurized air can then be drawn off through a tuyere — or escape nozzle — to be used as needed.

Many large-scale trompes — or hydraulic air compression plants — were built at the turn of the century to supply mines with fresh air. One of the biggest of these — and probably the last one still in use — is the Ragged Chutes plant on the Montreal River near the town of Cobalt, in northern Ontario's silver mining country.



At Ragged Chutes, water falls down a shaft 351 feet deep and nine feet across to generate the compressed air that supplies the area's mines. The Ontario Hydro Electric Commission engineers who operate the plant are said to view the giant trompe with some disdain, since — except for a simple water-flow control — it has no moving parts, relies on no computers, makes no noise, and doesn't pollute the environment. So far, however, the mining companies have successfully resisted attempts to have the plant replaced with something more "modern."

One remarkable feature of trompes (the Ragged Chutes plant included) is that the air that comes out of the system is actually cooler and drier than the air that goes in. The air comes out cooler because the cold water flowing through the trompe absorbs the heat that's usually generated by the compression of air. It comes out drier because the atmospheric moisture held in the air bubbles that flow through the system condenses — so to speak — on the bubbles' walls (since those walls are, after all, colder than the air they're surrounding). The result: Compressed air that's the same temperature as the cool water it just left and drier than it was when it entered the trompe. Free air conditioning!

GBCAPS
5/21/2019 6:26:41 AM

GBCAPS: 5/21/19 GOOD morning. I have a business plan for Trompe power that needs seed money and investors. "seedventures8/22/2018 2:35:41 PM interested in funding this technology...........anyone need financing?" If you see this sir, lets figure out how to talk through some ideas. My basic plan is to convert an existing coal plant into biomass powered station in a clean green and sustainable way while actively cleaning up the existing site and ash ponds.


wowwnc
3/24/2019 11:03:44 PM

differentconstructionco, I'm looking at a piece of land (to purchase) that is north facing (so no solar probably) but has a tiny amount of water cascading downhill and an old abandoned gravity spring water system. They both fall probably 100 feet (not sure, but it is a hike to get up to the old spring reservoir & the majority of the land is fairly steep mountainside in western NC). I'm retired, on disability, & not handy, but would really like to pursue getting this system on the property. Do you know anyone in or near Western NC that could create one? My goal is to be completely off-grid, but I need AC to control mold, power for medical equipment, etc. (don't know if this could power that). Have you created any of these for yourself?


differentconstructionco
3/18/2019 10:22:27 AM

Hi everyone, I realize that you probably won't be checking to see if your questions have been answered anymore. But I can answer them, or at least point you into the right direction. Green Taiwan - small scale trompes are only able to produce a very small amount of pressure. Typically between 1-3 psi. This is great for aerating fish ponds or something of that ilk,but certainly cannot be used to produce electricity. In order to produce enough compressed air for power generation, you need a massive trompe (think 100-300 feet of fall). norrisarchitecture - There are plenty of old books (pre-1900s) whose copyright has expired and can be found in PDF form online. But a good rule of thumb is that for each foot of fall, you get 0.5psi. The temperature of the air is cooled to the temperature of the surrounding water. seedventures - There are companies pursuing this technology. One is company out of Canada and they advertise it mostly to mines. Additionally, there have, in the past, been commercial sized trompes. I suggest a search for the Ragged Chutes Compressed Air Plant.







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