**6. Conclusions**

A methodology has been presented in this paper to estimate the potential for hydropower in urban water supply networks based on an available energy concept. It is applied to the city of Fribourg, Switzerland and, for comparison, an optimization algorithm was used to estimate the actual energy production in the best locations of the network with a proposed micro-turbine, the 5BTP. The optimization maximizes the economic value of the installation, and combinations with one to four turbines were tested. It is concluded that one turbine can produce 60.5 MWh/year in this network, representing 10% of the available energy, and that four 5BTP turbines would extract 136.2 MWh/year, which is less than four times the production with one turbine. Locations where PRVs are already in place are attractive, especially if a civil infrastructure that can be adapted is already in place. The costs for civil construction were seen to have an important weight on the feasibility results. Sensitivity analysis of the demand should be considered to verify the impact of this in the energy production and in the behavior of the network. Finally, a method for an expedited assessment of the location and energy production with one turbine is proposed based on discharge data in the network and on typical design assumptions.

**Acknowledgments:** This research is supported by Ph.D. gran<sup>t</sup> ref. SFRH/BD/51931/2012 issued by FCT under the IST-EPFL Joint Ph.D. initiative. Sponsoring by the Swiss Competence Center for Energy and Research—Supply of Electricity (SCCER-SoE) under contract CTI.2013.0288 is also acknowledged. The authors thank the Industrial Services of Fribourg, Switzerland, for the data provided to support this work and Ribi SA for sharing their knowledgeable insight on the Fribourg water supply network.

**Author Contributions:** Irene Samora is a Ph.D. Student supervised by Helena M. Ramos and Anton J. Schleiss; Mário J. Franca and Pedro Manso contributed to the developed concepts; all authors contributed to the writing of the paper.

**Conflicts of Interest:** The authors declare no conflict of interest. The funding sponsors had no role in the design of the study; in the collection, analyses and interpretation of data; in the writing of the manuscript; and in the decision to publish the results.
