Several different types of water turbines can be used in micro hydro installations, selection depending on the head of water, the volume of flow, and such factors as availability of local maintenance and transport of equipment to the site. For mountainous regions where a waterfall of 50 meters or more may be available, a Pelton wheel can be used. For low head installations, Francis or propeller-type turbines are used. Very low head installations of only a few meters may use propeller-type turbines in a pit. The very smallest micro hydro installations may successfully use industrial centrifugal pumps, run in reverse as prime movers; while the efficiency may not be as high as a purpose-built runner, the relatively low cost makes the projects economically feasible.
In low-head installations, maintenance and mechanism costs often become important. A low-head system moves larger amounts of water, and is more likely to encounter surface debris. For this reason a Banki turbine, a pressurized self-cleaning crossflow waterwheel, is often preferred for low-head microhydropower systems. Though less efficient, its simpler structure is less expensive than other low-head turbines of the same capacity. Since the water flows in, then out of it, it cleans itself and is less prone to jam with debris.
Two low-head schemes in England, Settle Hydro and Torrs Hydro use a reverse Archimedes' screw which is another debris-tolerant design. Other options include Gorlov[2], Francis and propeller turbines[3].
Another alternative is a large diameter, slow turning, permanent magnet, sloped open flow Kaplan turbine. A number of these have been installed at Trousy VLH, France
In low-head installations, maintenance and mechanism costs often become important. A low-head system moves larger amounts of water, and is more likely to encounter surface debris. For this reason a Banki turbine, a pressurized self-cleaning crossflow waterwheel, is often preferred for low-head microhydropower systems. Though less efficient, its simpler structure is less expensive than other low-head turbines of the same capacity. Since the water flows in, then out of it, it cleans itself and is less prone to jam with debris.
Two low-head schemes in England, Settle Hydro and Torrs Hydro use a reverse Archimedes' screw which is another debris-tolerant design. Other options include Gorlov[2], Francis and propeller turbines[3].
Another alternative is a large diameter, slow turning, permanent magnet, sloped open flow Kaplan turbine. A number of these have been installed at Trousy VLH, France
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