Russell Seitz, the Harvard physicist who contacted me last year to explain and promote his 'microbubbles' scheme to reduce evaporation (see my post) recently emailed me with an updated version of his explanatory PPT (in PDF version), Microbubbles, Water Conservation and Climate Change:
He also sent along a paper, Bright Water: Hydrosols, Water Conservation, and Climate Change, that I had posted earlier and will repost here:
There has been some concern over the amount of energy that would be required to produce all the microbubbles. Seitz speculates that a trompe could do the trick.
He says:
Simple, cheap and reliable ,trompes and ram pumps can operate without electric motors using low head hydropower. Some have no moving parts, and can readily provide the four atmospheres / 60 psi of air pressure needed to supersaturate water with dissolved air for dissloved gas microbubble generation, This can locally eliminate the need for the motor driven mechanical pumping stages employed in aquaculture and oil field microbubble generators.Only a meter or two of hydraulic head is required for a ram pump to generate 60 psi , and some very large trompes have been constructed. The still operational one in Cobalt, Ontario, continuously provided 5,000 m3/ minute of free compressed air for mine ventilation and jackhammer operation for over 80 years. Such a device, and its compressed air distribution system ,could continuously brighten a 100 km stretch of river without any external energy input.
Trompes are very simple devices. As can be seeen in this diagram of the Ragged Chutes [click to enlarge] facility in Ontario, a vertical pipe or shaft goes down to a separation chamber, a pipe coming away from that chamber allows the water to exit at a lower level, and another pipe coming from the chamber allows the compressed air to exit as needed.Water rushing down the vertical pipe falls through a constriction. The constriction produces a lower pressure because of the venturi effect, allowing air to be sucked into the flow . The air forms bubbles in the pipe which as they are swept downward are pressurized in proportion to the hydraulic hea provided by the height of the column of water in the pipe. In the horizontal flow section at the bottom, the compressed air rises to the top of the separation chamber. The separation chamber has a compressed-air takeoff pipe, and the compressed air can be used as a power source.The energy of the falling water entrains the air into the water, but that is not the energy that pressurizes the air, as is often incorrectly claimed. That energy is solely a derivative of the hydraulic head. The system can be arranged as an inverted siphon for use in relatively flat terrain.[Click on figure to enlarge.]
Pretty nifty.
Seitz says funding for a pilot project is being sought. It would be great to see a demonstration. A few of my ecologist friends wonder about the effects on aquatic organisms.
But it's geoengineering, you say.
"If geoenginering is defined as purposeful human activity that significantly alters the state of the Earth, we became geoengineers shortly after our species started using fire.” - Sir James Lovelock (courtesy R. Seitz)
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