by Emil Morhardt
Low-head hydro, in this case 2 meters, is not normally viewed as a good source of energy for electricity production, but a clever paper from the engineers at Lancaster University, in the UK, suggests using a shore-based siphon to generate air pressure (their field test rig is shown above). Although they didn’t try converting the air pressure to electricity, they certainly could if the economics were right, and it looks like they might be. As they point out, there are other alternatives to water turbines in current use, including Archimedes screws, hydro-venturis, and water wheels, all of which minimize harm to fish, but this approach might be even cheaper. The idea is to siphon water from above a small dam (weir) to below it, and entrap air into the water stream through a tube at the top of the siphon. The air gets compressed in the process and can be bled off for whatever use is handy; generating electricity with it might not be the best use since it will involve energy losses that might be avoided if the air were used directly, say to run some kind of pneumatic machine.
The engineers managed to capture 63% of the energy of the change in water elevation which seems pretty good to me. They also note that since there are no moving parts inside the siphon, it might make a good fish passage facility as well, something not true of any of the competing technologies.
Mardiani-Euers, E., 2014. An Alternative Approach in harvesting Low Head Hydropower using a Siphon System by converting Water Power into Air Pressure, Proceedings of the 3rd Applied Science for Technology Innovation, ASTECHNOVA 2014, Yogyakarta, Indonesia.