Thermal-electric decoupling approach for a medium-size CHP system: electric storage vs thermal storage, economic comparison with different constraints

Abstract Cogeneration is a highly efficient process that decreases the energy supply costs, the primary energy consumption and reduces emissions at the same time. CHP devices are characterized by the constrained relationship between the electricity and heat production, which decreases their suitability with particular load conditions and, in some cases, limit the rated power output of the prime mover. The use of an energy storage system coupled with a CHP unit provides an interesting solution to the problem. With the recent improvements in the technical and economic performance of the electric storage systems, designers are facing a new option whose suitability is strictly dependent on the application context. The present analysis aims to estimate the main parameters driving the designers to option for an electric storage instead of a heated water tank coupled with a medium-size cogeneration system. Thermal and electric consumption profile in the Italian industrial context are considered in this study; CHP size is defined as a function of the considered load pattern, with the starting point being the satisfaction of the base load of the hypothesized system. The results are presented and analysed considering the economic performance, i.e. the plant running costs, the NPV and PBT, and general comments on the suitability of the each solution are provided.