Feasibility assessment of micro-hydropower for energy recovery in the water supply network of the city of Fribourg

In water supply systems there is potential for hydropower production at several scales, from small hydro to micro. The energy recovery within the urban water supply networks is a type of micro-hydro that may be useful for the control of excessive pressures. On the other hand, local decentralized production of electricity may have multiple uses, considering self-consumption at local grid level or storage. However, there is still a lack of technologies and specific solutions for such applications, since the flows are highly variable and the available heads are small and limited to service pressures. A scheme specially conceived for water supply networks making use of a micro turbine is proposed.Adequate positioning conditions are identified using a search algorithm which considers both the assessment of the energy production and sizing of the main equipment and works. Typical schemes are proposed where the installation of up to four turbines is possible within the same buried chamber created around an existing pipe. Preliminary results obtained for a network case study show that the implementation of the proposed energy recovery solution is feasible. The installation of a by-pass revealed to have a key role in the feasibility of each solution, demanding customized engineering judgment. Further testing of the search algorithm as well as a first in-situ implementation of the scheme may be foreseen in the near future.