To achieve maximum efficiency in water pressurized transport, it is necessary to perform a global analysis, whenever possible starting from the system’s conception. The first stage of the process is the network layout, the main topic of this paper. The optimum topology from an energy point of view (or eco-layout) is the one that, insofar as is feasible, allows equalizing the network’s pressure to the set pressure standards. Eco-layouts can be easily designed in new systems but are difficult to implement, mainly in the short term, in operating networks. Nevertheless, because no system is eternal, the required actions can be gradually implemented. Therefore, the main goal of this paper is to identify and discuss these guidelines and actions, some of which are apparently contradictory to current design criteria, whereas others endorse modern management trends. These strategies can be summarized in two points: (1) providing lower pressure to consumers saves energy, and (2) setting up smaller pressure zones in terms of the elevation steps between zones will enable water companies to supply water at lower pressure in hilly areas. In the end, networks with more-efficient layouts can achieve important energy savings.

Energy intensity, I_e (kWh/m³) is the most popular indicator when characterizing the energy requirements of the water cycle, due to its direct and easy interpretation. In pressurized water transport systems, when referred to an appropriate physical framework (such as a single water transport pipeline), it assesses the efficiency of the process. However, in complex urban water transport networks, I_e only provides a basic notion of the energy needs of the system. The aim of this paper is to define a standard physical framework for assessing the energy intensity in water transport and distribution systems. To that purpose, an analytic expression that estimates I_e is proposed, based on system data and its operating conditions. The results allow for a realistic approximation of the energy needs of water transport. This energy assessment is completed with two context indicators: energy origin (C₁) and topographic energy (θ_t), both essential when the energy efficiency of different systems is to be compared.

Pressurized Water Transport Systems (PWTSs) are responsible for a large percentage of the electricity consumption around the world, and current trends suggest that this proportion will continue to increase in the future. Controlling PWTS is therefore fundamental, including improving efficiency when necessary or compulsory. To achieve this, metrics to objectively assess the efficiency of the different losses and of the whole system are needed. These metrics, based on economic criteria, will be stricter if environmental costs are added to current water and energy costs. To assess different improvement strategies, some relative metrics, applied to both operational and structural losses, are considered. At the end, taking into account their relevance, these metrics are combined in a global energy score (IS), this being the main contribution of this paper. Finally, to focus on the concepts and methodology, a simple case study is presented.

The Infrastructure Value Index (IVI) is quickly becoming a standard as a valuable tool to quickly assess the state of urban water infrastructure. However, its simple nature (as a single met...

The layouts of most urban water systems are known. A head tank with an appropriate elevation is used to supply water through the network at a pressure equal (or higher) to that set by the relevant standards. Furthermore, equalization, fire and emergency storage are important benefits of tank use, as is the possibility of avoiding peak rate electricity fares. However, at the end of the last century, some tanks were reported to have a negative impact the quality of water, and recommendations were made to limit their volume and revise their geometry. Recently, alternative options have been considered. Equalization can be achieved with pumps with variable-frequency drivers, emergency situations can be avoided with electric oil generators and solar plants can be used to offset other generation types and reduce energy costs. Therefore, this article analyses the performance of tanks as an energy source, and tank and pump supply methods are directly compared; overall, direct supply through pumps is cheaper, more energy efficient and more environmentally convenient. Therefore, in the context of climate change, it seems reasonable to avoid water tanks as energy sources.