The Contribution of Thermal Energy Storage to the Energy Efficiency of Combined Cooling, Heating and Power Systems

Abstract

Combined cooling, heating, and power (CCHP) is considered a promising technology. Because thermal demand varies strongly with time (and can even be discontinuous), the power generation in CCHP systems can be inefficient and significant heat can be wasted. This paper proposes incorporating thermal energy storage (TES) in CCHP systems (CCHP-TES). TES can balance heating, cooling, and power loads. Authors describe several mathematical models for CCHP system components – TES, heat-recovery devices, auxiliary heating and cooling devices – and for criteria used to evaluate system evaluation performance. Authors assess the impact of adding TES to CCHP systems by analyzing simulated performance of an office building in Beijing, China. The simulation models use heating and cooling load profiles for a whole year as well as for peak summer and winter days. Using the primary energy consumption ratio and energy-savings rate (ESR) as indicators of the different performances of the CCHP system with and without TES, authors found that the ESR of CCHP-TES compared with CCHP is 6.4% greater under winter operating conditions and 8.7% greater under summer operating conditions. Authors conclude that incorporating TES improves the energy efficiency of CCHP systems. Our research provides guidance for designing and retrofitting CCHP systems to benefit from TES.