Comparison of Thermal Performance of BCHP System with Latent Thermal Energy Storage in Different Locations

Abstract

Building cooling, heating and power (BCHP) is an integrated energy system to provide the three energy commodities, which is characterized by cascading utilization of primary energy and high energy efficiency. Latent thermal energy storage (LTES) is a promising technology to smoothen the fluctuating loads, and improve the system efficiency due to the isothermal property during phase change process and the high energy storage density. This paper aims at studying the influences of LTES location on BCHP system, in the upstream or downstream of waste heat recovery unit, with consideration of partial load performance of equipment. Firstly, a general model is presented for a typical BCHP system working in winter, consists of gas turbine (GT), absorption heat pump (AHP), and LTES unit. Based on the assumption of infinite number of transfer unit (NTU) of LTES, the comparison of the two designs is conducted in terms of primary energy consumption (PEC) and equipment capacity for an office in Beijing. Then, the influences of the limited heat transfer area of LTES are analyzed. The results show that the addition of LTES can significantly reduce the PEC and equipment capacity because it enables the GT work efficiently. In addition, the choice of the LTES in the downstream of AHP is preferred when assuming infinite NTU of LTES. However, when considering the limited heat transfer area, the heat transfer temperature difference makes the downstream choice less advantageous.