Thermo-economic-environmental optimization design of dual-loop organic Rankine cycle under fluctuating heat source temperature. (1st February 2023)

• Record Type: Journal Article
• Authors: Xia, Xiaoxia; Liu, Zhipeng; Wang, Zhiqi; Sun, Tong; Zhang, Hualong; Zhang, Sifeng
• Is Part Of: Energy. Volume 264(2023)
• Publication Date: 2023-02-01
• Subjects: Dual-loop organic Rankine cycle -- Multi-objective optimization -- Temperature fluctuation -- Off-design performance; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2022.126144
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: Fluctuating heat source temperature leads to off-design operation of organic Rankine cycle systems, which is a challenge for its optimal design. For a dual-loop organic Rankine cycle, this study proposed a multi-objective optimization design framework, which integrates off-design optimization into design optimization to determine the optimal design point of the system under heat source temperature fluctuations. In the optimization design framework, we developed a multi-objective optimization model to maximize the exergy efficiency and annual CO2 emission reduction of the dual-loop organic Rankine cycle and minimize its payback period. Then, the effects of design heat source temperature T d, h on the lifetime performance of dual-loop organic Rankine cycle were investigated. To balance the conflict between different indexes, we proposed a comprehensive evaluation index based on the entropy method. The results show that the influence of actual heat source temperature on the performance of dual-loop organic Rankine cycle is greater than the T d, h . Compared with traditional research that ignore the off-design performance, the proposed design method can avoid 35.8% annual CO2 emission reduction overestimation and 58.7% payback period underestimation at T d, h of 573.1 K. In addition, the optimal T d, h is significantly influenced by the selected index. The optimal T d, h is 513.1 K for the dual-loop organic Rankine cycle to minimize its lifetime payback period. To maximize the comprehensive index, the optimal T d, h for the dual-loop organic Rankine cycle is 573.1 K, which is the temperature at 0.9 of the cumulative distribution curve of the heat source. The average exergy efficiency and annual CO2 emission reduction in the lifetime of the dual-loop organic Rankine cycle at the optimal T d, h of 573.1 K is 4.1% and 6.0% higher than that at the average T d, h of 529.1 K, respectively. Highlights: The optimal design framework of DORC system at fluctuating heat source is proposed. Thermo-economic-environmental performance is optimized in optimal design framework. A comprehensive performance index is proposed to evaluate the optimal design point. The optimum design temperature is at 0.9 of the cumulative distribution curve.