Development and application of a water circularity index to evaluate the water energy nexus in Italy

Most of the world today relies on the presence of electricity and its production is key for the life of billions of people. Even if the production is moving towards renewable sources, in 2022 more than 70% of the power plants still relied on water availability and about 60% of the power plants are based on thermodynamic cycles (Rankine cycle for coal plants, Brayton-Joule for gas turbines that can be part of a combined plant) and so they may need big amounts of water supply for two main purposes: as working fluid and for the cooling process. This means that the water supply is a crucial factor for electricity production and this may become an important issue in case of water scarcity, which is becoming a more probable scenario due to the climate change and the consequent variation of precipitations and accumulation of water, even in places where water was taken for granted until now. It needs to be considered also the increasing importance of the necessary switch from a linear economic model to a circular one, in order to better use and exploit the primary resources, such as the water, and decrease the waste production, such as wastewaters. It is under these assumptions that is necessary to evaluate the circularity of a process, in order to understand what the best practises are and where there is the possibility of improvement. To accomplish these results, a Water Circularity Index has been studied and developed: it considers the water intakes, discharges, and other factors that help to improve the so called Water Energy Nexus. This Index is then tested on part of the electricity production plants that provide the electric energy to the Italian grid, with the goal to take a picture of the situation and understand if and where there is space for improvement.