Off-design performances of gas turbine-based CCHP combined with solar and compressed air energy storage with organic Rankine cycle

Abstract

The conventional CCHP systems often operate at part load and cause power surplus under the operation mode of power following thermal load. In order to improve the energy efficiency of CCHP systems, a novel combined cooling, heating and power (CCHP) system combined with compressed air energy storage (CAES) was proposed. However, the output power of CAES was probably not high due to the low temperature of high-pressure air at air turbine inlet. In this paper, solar energy was introduced to heat the high-pressure air from air storage cavern. For the further energy utilization of the air turbine exhaust with relatively high temperature, an organic Rankine cycle (ORC) was proposed to recover the heat carried by air turbine exhaust. To obtain the off-design characteristics of the proposed system, the typical off-design models of gas turbine, compressor and air turbine were built through the performance equations of each component. The sensitivity analysis on S-CAES with ORC system was investigated to evaluate the effects of several key parameters on its performances. The results show that the energy efficiency and exergy efficiency of S-CAES with ORC system reach 98.30% and 68.94% respectively, in a whole round trip cycle. A case study of the proposed system in a typical hotel building with 180,000 m2 located in South China concludes that, compared with the conventional CCHP, the energy consumption can be reduced by 124.78 GJ, 33.82 GJ and 62.1 GJ and the average energy efficiency increased by 7.72%, 1.47% and 3.61% in summer, transition season and winter typical days, respectively.