Selection, control and techno-economic feasibility of Pumps as Turbines in Water Distribution Networks

Water Distribution Networks (WDNs) are becoming an attractive area of application for small hydropower, which can contribute to the development of distributed energy generation from renewable sources. Indeed, WDNs experience considerable water leakages due to their age and water management authorities often divide the WDNs by inserting Pressure Reducing Valves (PRVs), which waste a potentially recoverable hydraulic head. The replacement of PRVs with Pump as Turbines (PaTs) can be considered as an economically feasible solution to achieve both an effective pressure control and a throttling energy recovery. The selection, installation and control strategy of a PaT in a WDN must consider the variability of the pressure and the flow rate demand. Starting from the evaluation of the available head and the water demand, in this work, we describe a methodology to select from pump catalogues the most suitable PaT and the best control criteria for a specific WDN. Then, knowing the pump geometry, it is possible to predict the characteristic curve of the pump operating as a turbine by using a 1-D performance prediction model. The WDN of a town in the Apulia region (Southern Italy) has been used as a case study. Finally, a techno-economic evaluation has been carried out by considering both economic and environmental benefits.