Urban water distribution systems (WDSs) exhibit significant energy potential that is currently dissipated in the form of excess pressure, either at brake-pressure tanks (BPTs) or pressure reduction valves (PRVs). Recent research focuses on the implementation of energy harvesting methods within WDSs in order to improve the energy efficiency of such systems. This paper provides a systematic review of the technologies developed for energy exploitation in WDSs, covering both their technical and economic aspects, while considering their reliability in providing water pressure regulation. Drawn from the existing literature and state of the art, a systematic analysis was carried out that specifies and categorizes the most essential parameters that impact the implementation of energy recovery turbines into WDSs. Different turbine types, design parameters, and performance properties, such as generation efficiency and pressure regulation precision, were considered. Finally, practical challenges and consequences emerging from the joint optimization of water and power systems are addressed.

Gravity flow water distribution systems (WDSs) are used to permit water flow from an input point of highest elevation (source) to the terminal points of a system (consumers). In such WDSs, typically, there is no need for external power to maintain the flow due to the typical high gradients that exist. However, those gradients cause high water velocity and pressure to some network areas that could potentially lead to pipes bursting. Currently, the only means to regulate pressure within allowable range are Pressure Reduction Valves (PRVs). They are installed at various locations, but they cannot utilize the existing hydropower potential in terms of electrical energy production. This paper provides a methodology for hydro-turbines dimensioning, so that they mimic PRV operation in terms of pressure regulation while producing power efficiently. This includes an algorithmic process within which the proper turbine design and performance prediction are initially determined, and then, via an interconnection between EPANET and MATLAB, the hydraulic behavior of their operation within the water network is modeled and simulated. The methodology has been tested with simulations of a typical urban WDS. The results indicate that the produced turbine geometries mimic PRV action at the respective locations with more than 1% accuracy during 70% of the time (2% maximum error), while producing electric energy with hydraulic efficiency over 60%.