Energy Recovery Using Micro-Hydropower Technology in Water Supply Systems: The Case Study of the City of Fribourg

TLDR

Water supply systems are major man‑made infrastructures with untapped micro‑hydropower potential, yet quantifying this beyond pressure‑reducing valve replacement is challenging due to network complexity. This study proposes and applies a methodology to quantify hydropower potential from excess energy in a water supply network. The approach employs a novel five‑blade tubular propeller micro‑turbine, optimizes its placement to maximize 20‑year net present value, and includes an expedited cost‑energy estimation, tested on Fribourg’s system. The method captures 10 % of Fribourg’s energy potential, is economically attractive, confirms PRVs as viable sites, and underscores the need for sensitivity analysis of consumption.

Abstract

Water supply systems (WWSs) are one of the main manmade water infrastructures presenting potential for micro-hydropower. Within urban networks, local decentralized micro-hydropower plants (MHPs) may be inserted in the regional electricity grid or used for self-consumption at the local grid level. Nevertheless, such networks are complex and the quantification of the potential for micro-hydropower other than that achieved by replacing pressure reducing valves (PRVs) is difficult. In this work, a methodology to quantify the potential for hydropower based on the excess energy in a network is proposed and applied to a real case. A constructive solution is presented based on the use of a novel micro-turbine for energy conversion, the five blade tubular propeller (5BTP). The location of the MHP within the network is defined with an optimization algorithm that maximizes the net present value after 20 years of operation. These concepts are tested for the WSS in the city of Fribourg, Switzerland. The proposed solution captures 10% of the city’s energy potential and represents an economic interest. The results confirm the location of PRVs as potential sites for energy recovery and stress the need for careful sensitivity analysis of the consumption. Finally, an expedited method is derived to estimate the costs and energy that one 5BTP can produce in a given network.