Experimental and numerical analysis of a backpressure Banki inline turbine for pressure regulation and energy production

Water distribution networks have become, in recent years, a major opportunity for the harvesting of renewable energy, which is otherwise dissipated though hydrovalves installed for discharge and pressure regulation. Mini and micro hydroturbines have the capability of providing the same functionality of hydrovalves, producing at the same time a relevant amount of electric power. In this paper a 10 kW prototype of a new compact in-line turbine, named Power Recovery System (PRS), has been designed, constructed and tested in the hydraulic laboratory of the University of Palermo. The proposed device is a Banki-type micro-turbine, with positive outflow pressure and a mobile regulating flap for hydraulic control of the characteristic curve. The device is aimed to control pressure or discharge inside a water transport or distribution network, while producing energy with good efficiency values, up to 76%. Using two pressure meters located immediately before and after the turbine, it is possible to control the net head with given discharge (passive mode) or to control discharge by regulating the net head (active mode). 3D numerical analysis and laboratory measurements provide a low variation of efficiency for different positions of the mobile flap, especially for low variations in discharge.