Paper Title
Thermodynamic Model of a Carnot Battery for the Exploitation of Waste Heat Energy

Abstract
The rapid increase in the installed capacity of RES power plants is leading to a significant overproduction of electricity in several European countries, for long periods. The conventional solutions to use the excess of renewable electricity produced by photovoltaic plants and, therefore, achieve the goal of the energy transition are energy storage by using electric batteries. A technology that would allow the recovery of excess electrical energy produced by photovoltaic systems and, at the same time, exploit the availability of waste heat are Carnot batteries (also called Pumped Thermal Energy Storage – PTES) which is particularly attractive, because for example they do not require a huge amount of critical materials, such as lithium-ion batteries. By using this technology, the thermal waste produced in energy-intensive companies should be reused to increase the energy efficiency of the storage plants. The issue of the exploitation of waste heat is regarded as very important in the European Industrial Countries. In this sense, the CE-HEAT project (Interreg Central Europe) of the European Union aims to improve the governance of energy efficiency by focusing on the field of waste heat use in the Central European space; waste heat exploitation is recognized as a major issue in the latest Energy Efficiency Directive (2012/27/EU). In general, the efficiency of Carnot batteries is poor but can increase if they are thermally integrated, reaching efficiencies close to the best mechanical energy storage technologies (Pumped Hydro Energy Storage – PHES). The paper, using data from the waste heat of the European project CE-HEAT and the excess electrical energy produced by photovoltaic systems in the Friuli Venezia Giulia region, aims to estimate the energy that can be recovered by producing a Carnot battery. Keywords - Carnot Battery, Waste Heat, Power-To-Power Efficiency, Organic Rankine Cycle, Pumped Thermal Energy Storage.