Mass, Energy, and Cost Balances in Water Distribution Systems with PATs: The Trondheim Network Case Study

In water distribution systems, the substitution of regulating valves by pumps as turbines (PATs) is sustainable if the energy recovery balances the installation and maintenance costs, with a comparable and efficient reduction of the volume lost by leakage. Hence, the installation feasibility and regulation of a PAT require analysis of the introduced effects on the components of the energy, mass, and cost balances. In this paper these effects are explored by means of a case study, i.e., the water distribution system of Trondheim, Norway. Different hydraulic regulations of a PAT are analyzed to maximize the recovered energy, considering the daily variation of the system functioning conditions and the substitution of valves of different kinds, meaning a constant opening degree, a fixed value of pressure at a node of the system, and a control in time of the setting. A feasible solution for the Trondheim network is shown, consisting of the implementation of two twin PATs in parallel with a discontinuous functioning of one of them.