Abstract：[Objective] The existing freshwater scarcity and the energy crisis are severely limiting the economic restructuring and social development of the world. An integrated cogeneration system using 100% renewable energy resources and desalination can effectively solve the problem of freshwater scarcity and energy shortage. Desalination technologies such as multistage flash evaporation and reverse osmosis are important means of addressing freshwater scarcity problems. Furthermore, concentrating solar power technology enables renewable energy capture and utilization with lower costs and higher dispatchability. Concentrating solar power can generate electric and thermal energy that can be consumed in desalination operations. Therefore, the integration of the two helps to make the desalination industry environmentally sustainable. However, the existing integrated concentrating solar power-desalination systems have problems such as single-capacity structures and poor system flexibility. The design of cogeneration systems with a high flexiblity for the integration of renewable energy and desalination to meet the user's energy demands under complex weather conditions is a critical challenge in this field. [Methods] This paper proposes a water cogeneration system with integrated concentrating solar power-desalination, comprising a concentrating solar power unit, a heat storage unit, a multistage flash evaporation unit, a reverse osmosis unit, an electrothermal steam generator, and a water storage unit. Furthermore, a mathematical model with the minimization of the annual cost of the integrated system as the objective function is established as a mixed-integer nonlinear problem. Moreover, this paper proposes a flexibility index and a flexible design method applicable to the optimization of integrated hydrothermal power systems, implementing the definition, calculation, and optimization of the boundary constraints of the flexibility index. A two-layer algorithm for flexible design is developed, with the outer algorithm obtaining the system size and the inner algorithm optimizing the flexibility of the system. GAMS and MATLAB are used to obtain the optimal configuration and the minimum total annual cost of each system, as well as compare the results of the flexible design with those of the fixed-condition design to verify the effectiveness of the flexible design and analyze the advantages of the flexible design. [Results] The case study reveals that the flexible design results in a 10.7% reduction in the total annual costs and a considerable reduction in the system redundancy compared to the fixed-condition design. In addition, the flexible design reduces the consumption of coal by 166 617 t and reduces CO2 emissions by ~436 538 t compared to conventional thermal power generation every year. The fluctuation of the supply-demand ratio of water-heat-power is considerably suppressed, and the proportion of days with abnormal supply and demand of water-heat-power decreases from 91.11%, 98.19%, and 60.69% to 0%. These results verify the feasibility and effectiveness of the system model and algorithm proposed in this paper. [Conclusions] Results reveal that the cogeneration system designed in this paper is instructive for the conversion of seawater desalination from an energy-intensive industry to a zero-emissions industry and the adoption of renewable energy in various energy-intensive industries. This research contributes to the application of renewable energy cogeneration systems in a wider range of fields.
孙启超, 孙志伟, 伍联营, 周鑫. 基于柔性设计的光热电站-海水淡化集成系统优化[J]. 清华大学学报（自然科学版）, 2024, 64(3): 528-537.
SUN Qichao, SUN Zhiwei, WU Lianying, ZHOU Xin. Optimization of integrated concentrating solar power-desalination systems based on a flexible design. Journal of Tsinghua University(Science and Technology), 2024, 64(3): 528-537.
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2024, Vol. 64 
