Thermodynamic analysis of operating strategies for waste heat recovery of combined heating and power systems

Abstract

The multi-generation system often operates under off-design conditions due to the highly dynamic energy demand. Improving its off-design performance is crucial for energy conservation and emission reductions. To this end, this paper proposed a novel control strategy for the gas turbine cycle applied in combined heating and power (CHP) system, which effectively combines turbine inlet temperature control (TITC) and inlet air throttling control (IATC) methods, to improve system off-design performance and avoid discharging low-temperature gas. The hybrid control strategy can improve system efficiency by 3.70% on average over the traditional TITC method during the entire load range. Moreover, the maximum efficiency difference between these two methods reached 5.15% at the 30%-load factor conditions. To further showcase the effectiveness of the IAT-TITC method, the CHP system is integrated with an electric chiller and thermal refrigeration, respectively, forming four combined cooling, heating, and power (CCHP) system scenarios to supply the energy for a hotel building. Not only did the CCHP system scenarios with the IAT-TITC method show better performance, but also considering an electric chiller as an extra cooling supply machine can reduce primary energy consumption by 30.73%, 28.32%, and 11.56% in summer, transition season, and winter typical days, respectively, compared with separation system.