Hydropower recovery in water supply systems: Models and case study Mateus Ricardo Nogueira Vilanova a,⇑ , José Antônio Perrella Balestieri b a Univ Estadual Paulista, Faculdade de Engenharia de Guaratinguetá, Avenida Dr. Ariberto Pereira da Cunha, 333, Guaratinguetá, SP, Brazil b Univ Estadual Paulista, Faculdade de Engenharia de Guaratinguetá, Energy Department, Avenida Dr. Ariberto Pereira da Cunha, 333, Guaratinguetá, SP, Brazil article info Article history: Received 28 February 2014 Accepted 17 April 2014 Keywords: Energy efficiency Hydropower recovery Water utilities Sustainability abstract The energy efficiency of water supply systems can be increased through the recovery of hydraulic energy implicit to the volumes of water transported in various stages of the supply process, which can be con- verted into electricity through hydroelectric recovery systems. Such a process allows the use of a clean energy source that is usually neglected in water supplies, reducing its dependence on energy from the local network and the system’s operation costs. This article evaluates the possibilities and benefits of the use of water supply facilities, structures and equipment for hydraulic energy recovery, addressing several applicable hydroelectric models. A real case study was developed in Brazil to illustrate the technical, economic and environmental aspects of hydropower recovery in water supply systems. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Water and energy are two of the most important resources associated with the sustainability of cities and nations. According to Baños et al. [1], energy is a vital input for social and economic development; this statement is absolutely applicable to water resources, too. This importance in terms of sustainable develop- ment is even greater when considering the interactions between these resources (the so called water–energy nexus), taking into account that water is used in various energy generation processes (e.g. hydroelectric, thermoelectric and biomass production), while water treatment and distribution require large amounts of electric- ity, mainly for pumping. Hydropower recovery is a relevant energy efficiency measure that can be applied to water supply systems (WSSs), resulting in environmental, economic and social benefits. Hydroelectric power is a mature technology and currently the largest of the perpetual or so-called renewable energy resources (RESs) [2], and although the hydropower potential of WSSs is known for quite long time (with some cases being reported in literature, for example [3]), it is still little explored worldwide [4]. According to Yüksel [5], the capacity of small hydropower plants of being combined with other water infrastructure facilities will enable the dissemination of such tech- nology in developing countries, as improvements in their water supply systems are made. WSSs located in areas with high topographic gradients, or even those exploring high pressure groundwater sources, present large hydraulic heads in pipelines and distribution networks, that can be recovered through hydroelectric power generation. Besides that, WSSs that use free flow conduits (especially in form of channels) can generate hydroelectric power via hydrokinetic turbines or low head systems. Boreholes for water catchment in confined aqui- fers, in which the artesianism phenomenon occurs, also provide raw water with high energy potential. The energy recovery poten- tial of water supply systems is highly variable according to their characteristics and layouts [4]. Some works presents estimations of hydropower recovery potentials worldwide. Kucukali [6], for example, estimated that the hydropower potential of 45 municipal water supply dams in Turkey is of 173 GWh/year, while McNabola et al. [7] estimate the recovery potential of ten cases in Ireland varying from 2 to 115 kW of installed power. A method to quantify the energy efficiency potential of hydropower recovery systems applied to water supply utilities, based in efficiency indicators, was developed by Vilanova [8]. Besides recovering energy, hydraulic turbines can also act as pressure control devices in WSSs, instead of pressure reducing valves (PRVs), which is an important tool for reducing water losses due to leakage [9,10]. While PRVs reduce pressure by energy dissi- pation, hydraulic turbines can convert the pressure excess in the water network into useful electricity [10–13]. Considering that most of its components are available (originally dedicated to water supply), the deployment of small hydropower plants in WSSs presents a low implementation cost [14]. Besides that, hydropower recovery does not imply harmful effects on the water supply, if the hydraulic (pressure and flow) http://dx.doi.org/10.1016/j.enconman.2014.04.057 0196-8904/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +55 35 36220959, mobile: +55 35 91348406. E-mail addresses: mathidr@yahoo.com.br (M.R.N. Vilanova), perrella@feg.unesp. br (J.A.P. Balestieri). Energy Conversion and Management 84 (2014) 414–426 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman