Nowadays, in the management of water distribution networks (WDNs), particular attention is paid to digital transition and the improvement of the energy efficiency of these systems. New technologies have been developed in the recent years and their implementation can be crucial to achieve a sustainable level of water networks, namely, in water and energy losses. In particular, Digital Twins (DT) represents a very innovative technology, which relies on the integration of virtual network models, optimization algorithms, real time data collection, and smart actuators information with Geographic Information System (GIS) data. This research defines a new methodology for an efficient application of DT expertise within water distribution networks. Assuming a DMA of a real water distribution network as a case study, it was demonstrated that a fast detection of leakage along with an optimal setting of pressure control valves by means of DT together with an optimization procedure can ensure up to 28% of water savings, contributing to significantly increase the efficiency of the whole system.

Water distribution network are energy-demanding systems affected by low efficiency. In such systems, the pressure is generally kept under control by regulation valves to reduce the waste of water due to the leakages. The employment of energy production devices may be an efficient strategy to both reduce waste of water and produce energy, whose feasibility basically depends on the amount of recoverable energy, though. In this study, the optimal location of both pumps as turbines (PATs) and pressure-reducing valves (PRVs) within a literature water distribution network is investigated to maximize the production of energy and water savings. A new mixed integer non-linear model has been developed and a global optimization solver has been employed to perform the optimization. According to the results, the new optimization ensures good solutions, in term of water and energy savings, when compared with other procedures in literature.

Water systems are usually considered low efficiency systems, due to the large amount of energy that is lost by water leakage and dissipated by pressure reducing valves to control the leakage itself. In water distribution networks, water is often pumped from the source to an elevated tank or reservoir and then supplied to the users. A large energy recovery can be realized by the installation of energy production devices (EPDs) to exploit the excess of pressure that would be dissipated by regulation valves. The feasibility of such a sustainable strategy depends on the potential of energy savings and the amount of energy embedded in water streams, assessed by means of efficiency measures. Alternatively, energy savings can be pursued if the water is directly pumped to the network, bypassing the elevated reservoir. This study focuses on the comparison of two solutions to supply a real network, assessed as a case study. The first solution consists of water pumping to a reservoir, located upstream of the network; the excess of energy is saved by the employment of a pump as turbine (PAT). The second scenario is characterized by a smaller pressure head since a direct variable speed pumping is performed, bypassing the reservoir. The comparison has been carried out in terms of required energy, assessed by means of a new energy index and two literature efficiency indices. Furthermore, differing design conditions have been analyzed by varying the pumping head of both the scenarios, corresponding to different distances and elevation of the water source.

The paper is focused on the optimal scheduling of a drainage pumping station, complying with variations in the pump rotational speed and a recurrent pattern for the inflow discharge. The paper is structured in several consecutive steps. In the first step, the experimental set-up is described and results of calibration tests on different pumping machines are presented to obtain equations linking significant variables (discharge, head, power, efficiency). Then, those equations are utilized to build a mixed-integer optimization model able to find the scheduling solution that minimizes required pumping energy. The model is solved with respect to a case study referred to a urban drainage system in Naples (Italy) and optimization results are analysed to provide insights on the algorithm computational performance and on the influence of pumping machine characteristics on the overall efficiency savings. With reference to the simulated scenarios, an average value of 32% energy can be saved with an optimized control. Its actual value depends on the hydraulic characteristics of the system.

The recovery of excess energy in water supply networks has been a topic of paramount importance in recent literature. In pressurized systems, a pump used in inverse mode (Pump As Turbine, PAT) demonstrated to be a very economical and reliable solution, compared to traditional energy production devices (EPDs). Due to the large variability of flow rate and head drop within water distribution networks, the operation of PATs could be performed by a series-parallel regulation system based on an electronic or a hydraulic principle. Despite the low cost of the PATs and of regulation and control systems, a great barrier to the diffusion of a small hydro power plant in water distribution is represented by the necessity of additional civil works to host the whole plant. Based on laboratory and numerical experiments, the present paper proposes a new low-cost technology, overcoming most of the limitations of the present technologies when low energy is available and high discharge variation occurs. The operating conditions of the plant are properly optimized with reference to the working conditions of a case study. Despite the laboratory prototype having exhibited a significantly low efficiency (i.e., 16%), due to the use of small centrifugal pumps suitable for the analyzed case study, in larger power plants relying on more efficient semi-axial submersed pumps, the energy conversion ratio can increase up to 40%. The results of this research could be useful for network managers and technicians interested in increasing the energy efficiency of the network and in recovering energy in the peripheral branches of the network were a large variability of small flow rates are present.

The installation of hydropower pressure reduction (HPPR) technology in water supply networks (WSN) has recently been encouraged to limit water losses through leakage. Traditionally, pressure reducing valves (PRVs) were positioned at strategic nodes in a water network and were operated continuously to dissipate excess energy and minimize pipe failure. The alternative adoption of low-cost and highly reliable HPPR technology—Pump As Turbine (PAT)—can recover energy to improve the sustainable management of water networks and increase the energy, economic, and environmental benefits derived from the provision of water resources. To encourage the exploitation of HPPR, indicators and metrics were developed and applied for a case study (olive crop production with an irrigation network in Andalusia, Spain). The case study incorporated (1) a number of WSN scenarios based on water supply conditions, location of the HPPR within the network, and pipe age; (2) the expected performance of the PAT in the market; and (3) the expected optimal performance of an HPPR design based on a variable operation strategy (VOS). Independent life cycle indicators and nexus metrics were created to enhance the evaluation of the performance of HPPR technology as part of the water-energy-food nexus. In this case study, the new metrics expressed the impact of HPPR technology on the water-energy food nexus in terms of climate change and in the context of olive production in an irrigation network. The methodology for assessing combined energy, economic, and environmental metrics (3EM) can be used to account for the value of HPPR deployment in any WSN. These metrics can inform local decision makers and national policy makers, by providing relative and/or absolute evidence on the environmental impacts of HPPR technology in the water sector.