PRELIMINARY INVESTIGATION OF A COMBINED HEAT AND POWER REVERSIBLE-BRAYTON SYSTEM INTEGRATED WITH A RENEWABLE POWER SOURCE

Pumped Thermal Electricity Storage (PTES) technology is drawing increasing attention as a promising solution to limit the mismatch between the electric demand and the renewable production. In this context, a preliminary model of a reversible Brayton PTES is developed on a commercial software to finalize a comprehensive performance investigation. In the proposed arrangement, the system allows to store the surplus of electric renewable production, by converting it into heat, through an inverse cycle, and then to convert it back into electric energy when needed, through a direct cycle. A systematic analysis comparing two configurations (base and recuperated) of the reversible Brayton system is carried out to assess the performance of the system. Since thermal and electric energy flows are involved, PTES is particularly interesting when adopted to satisfy both thermal and electric demands, in a combined heat and power (CHP) system. To this aim, the system has been simulated when delivering both thermal and electric energy, in different partitioning. Results show that if 25 % of the stored heat is addressed to a thermal user the integrated system can be convenient in terms of saved primary energy, compared to conventional separate production. In case 70 % of the stored heat is delivered to a thermal user and 30 % reconverted into electricity, the maximum investment cost to have a return of the investment in 10 years is assessed to be between 2000 and 5000 €/kW, depending on the configuration.