Fine tuning a PAT hydropower plant in a water supply network to improve system effectiveness

The installation of hydropower plants equipped with pumps as turbines (PATs) in water supply systems has been demonstrated to be suitable and advantageous in order to both reduce pressure and recover energy. However, certain technical difficulties have delayed the widespread adoption of this innovative approach. The design of a hydropower plant within a water network should address three main problems, i.e., (1) the scarcity of information about PAT behavior; (2) the large and stochastic variability in the working conditions that can influence the efficiency and the reliability of the plant; and (3) the need to guarantee the correct operation of the water supply system. This paper presents a new regulation procedure based on the maximization of an upgraded version of the plant effectiveness, which takes into account the plant efficiency, reliability, and sustainability. Four plant regulation schemes are presented. A stochastic model is used to simulate the fluctuations of the hydraulic characteristics, while the PAT behavior has been calculated with a recently developed model that revises the turbomachinery affinity equations. A case study demonstrates the application of the new procedure with reference to a pressure reducing station in southern Italy and a semiaxial PAT.