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"While trying to find a method for aerating water without energy input, Austrian engineer Franz Zotl\u00F6terer stumbled across the idea of a mini-power plant which is simple to construct and has a turbine efficiency of 80% but which is safe for fish due to"^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.treehugger.com/renewable-energy/gravitational-vortex-power-plant-is-safe-for-fish.html>