Off-design performance analysis of organic Rankine cycle using real operation data from a heat source plant

Highlights: • ORC systems driven by waste or residual heat from a combined cycle cogeneration plant were analyzed. • An off-design analysis model was developed and validated with commercial ORC data. • A procedure to predict the actual variation of ORC performance using the off-design model was set up. • The importance of using long-term operation data of the heat source plant was demonstrated. - Abstract: There has been increasing demand for cogeneration power plants, which provides high energy utilization. Research on upgrading power plant performance is also being actively pursued. The organic Rankine cycle (ORC) can operate with mid- and low-temperature heat sources and is suitable for enhancing performance of existing power plants. In this study, an off-design analysis model for the ORC was developed, which is driven by waste heat or residual heat from a combined cycle cogeneration plant. The applied heat sources are the exhaust gas from the heat recovery steam generator (Case 1) and waste heat from a heat storage unit (Case 2). Optimal design points of the ORC were selected based on the design heat source condition of each case. Then, the available ORC power output for each case was predicted using actual long-term plant operation data and a validated off-design analysis model. The ORC capacity of Case 2 was almost two times larger than that of Case 1. The predicted average electricity generation of both cases was less than the design output. The results of this paper reveal the importance of both the prediction of electricity generation using actual plant operation data and the need for optimal ORC system sizing.