Performance analysis and optimization of solar thermochemical reactor by diluting catalyst with encapsulated phase change material

Solar thermochemical reactor, which can produce solar fuel at low cost, suffers discontinuous low-efficiency performance due to solar radiation fluctuation caused by cloud passage. To achieve highly efficient steady and dynamic performance of solar chemical reactor with less catalyst, in this study, catalytic activity is adjusted by diluting catalyst with encapsulated phase change material. At first, two-dimensional model of solar parabolic trough receiver reactors diluted with encapsulated phase change material is established and validated. Then, effect of catalytic activity on performance of reactor is discussed. Afterwards, one-dimensional model is derived from two-dimensional model to train Back Propagation neural network for quick and precise performance prediction of reactor. Finally, optimal catalytic distribution is obtained by genetic algorithm and Back Propagation neural network, and steady and unsteady performance of reactor between uniform and optimal catalytic distribution are compared. The results show that when catalytic activity decreases from 1.0 to 0.2, steady methanol conversion efficiency and production rate of H₂ are reduced by 8.4% and 9.9%, and reactor shows more stability under unsteady condition of solar radiation. One-dimensional model derived in present study is accurate enough and time-saving compared to two-dimensional model. And compared to reactor fully packed with catalyst, reactor with optimal catalytic distribution can achieve similar steady performance with 56% less of catalyst, but shows better stability under the fluctuation of solar radiation.