Miniature water flow energy harvester based on savonius-type microturbine: an experimental study

In this experimental study, a miniature turbine-based water flow energy harvester designed for the purpose of providing power to wireless sensors within water pipes is reported. The device comprises a Savonius-type turbine and a radial flux permanent magnet electromagnetic generator. The two are magnetically coupled so that, while the turbine is submerged in the water flow, the generator operates in air. The device is cylindrical with a diameter of 0.8 cm and a length of 7.2 cm and, when inserted through a hole in a pipe wall so that only the turbine protrudes into the flow, it presents a cross-sectional area to the flow of only 1.25 cm². Manufacturing was achieved through a blend of conventional machining methods, laser cutting, rapid prototyping, and the utilization of flexible printed circuit board technology for the generator stator. To ensure low friction and minimize cut in speed, ceramic ball bearings were employed. The prototype can function effectively at water velocities as low as 0.5 m s⁻¹, generating electrical power within the range of 125 µW–5.1 mW when subjected to flow speeds between 0.5 and 2 m s⁻¹. A maximum overall efficiency of 2.2% is achieved, when the water speed is 0.8 m s⁻¹. Performance curves derived from experimental testing of the turbine for a range of rotor designs, obtained on a water flow rig, are presented and discussed.

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