Comparative analysis on thermodynamic performance of combined heat and power system employing steam ejector as cascaded heat sink

Carbon neutrality is important for achieving sustainable development; in this regard, combining power generation and heat supply systems is a viable option. To solve the cascaded utilization of energy, a combined heat and power system employing steam ejector as cascaded heat sink (CHP-SECHS system) is employed in this study. An evaluation index is proposed to estimate the net profit in terms of the electricity price, heat price, fuel cost, and subsidy for peak-load regulation. Furthermore, performance evaluation models and a solution procedure are introduced to present the thermodynamic performance of the CHP-SECHS system. Simulation results show that the variations in exergy efficiency and net profit of the CHP system show opposite trends to those of heat consumption. Specifically, the heat consumption reaches its minimum value as the heat output of the extraction heating unit increases. In addition, the unchanged exhaust heat of the high back-pressure unit in the CHP-SECHS system causes a difference in heat consumption under the high-power output of the high back-pressure unit. Generally, both energy-based and exergy-based assessments indicate that the CHP-SECHS system offers better thermodynamic performance by employing cascaded extraction and exhaust heat, which is a viable option for applications combining heat and power requirements.