Thermodynamic, operational, and techno-economic analysis of the cascade heating system with a double-unit

Abstract

High back-pressure technology is an efficient way to recover waste heat and improve the energy utilization efficiency and heating capacity of cogeneration systems. In this study, a coal-fired cogeneration system with a double-unit (2 × 300 MW) was selected as the reference system and modeled in the EBSILON professional system. Then, a detailed comparative analysis of cogeneration systems with double-units was conducted from the perspective of thermodynamic, operational, and techno-economic analyses. The results show that with the high back pressure technology, the gross thermal and generation efficiencies of the novel system increased by 8.82% and 14.28%, respectively, while the standard coal consumption rate for generation was reduced by 43.47 g/kWh. Besides, the average energy quality coefficient of the novel system was reduced by 0.12. The temperatures of the exhaust steam, supplied and returned water changed the operational characteristics, including the maximum heating capacity and feasible operational region. Moreover, with the decrease in the maximum temperature rise ratio in the heating condenser, the feasible operational region of the novel system was reduced. The techno-economic analysis shows that under the given conditions, the net annual revenue of the novel system is 3.55 × 106 CNY/year, and the discounted payback period of the novel system is 10.55 years.