Operational optimization: water losses vs. energy costs

Management efficiency of water distribution networks (WDNs) is of relevant interest for the water industry and operational optimization plays an important role. The energy to pump water is a significant element of operational costs and depends on electricity tariffs varying over time. As a result pumping optimization accounting for electricity costs and relevant boundary conditions of a WDN, e.g. demands, is of practical interest. When the electricity tariffs are lower, as for example in the night hours, optimization generally results in pumping more water during those hours, if the presence of tanks which are internal to the hydraulic system allows for water storage. Nevertheless, the pressure and, therefore, water leakage of the network greatly vary from night to daylight hours. Pressure and leakage generally increase in the night because of a lower level of demands and a greater level of pressures. Previous studies rarely account for this. This work investigates pumping optimization background leaks, i.e. the non-revenue water cost besides the energy cost. It is shown and discussed that the reduction of background leaks conflict with, and generally dominate, energy cost.