Advanced heat source design method for thermochemical cycles based on pinch analysis

Abstract

The heat absorption processes of thermochemical water splitting cycles (TWSCs) are complex characterized by multiple temperatures, streams, and pinch points. Directly applying the traditional heat source design method may result in infeasible heat supply, complex calculation, and the risk of falling into local optimal solution. Therefore, this article proposes a heat source design method for TWSCs based on pinch analysis. Compared with the traditional method of obtaining local optimal solution by presetting the heat source parameters, this method directly obtains the global heating performance map by determining the feasible regions of the pinch points, revealing the transformation mechanisms of the heating performance and obtaining reliable global and local solutions, avoiding the empirical dependence on the initial value. The method is applied to the heat source design of the copper-chloride cycle. The results indicate that in the global optimal solution, the input temperature (T_hot) and output temperature (T_cold) of the heat source are 770.92°C and 61.28°C, with an input exergy of 240.76 kJ·mol^-1_H2, which is 5.89 % lower than that of the local optimal solution when T_hot is preset to 600–900°C. This method has a solid thermodynamic foundation and can obtain reliable optimal solutions by simple calculation, which can support the heat source design of TWSCs.