Solar thermochemical water splitting provides an efficient route for converting solar energy into renewable fuels. The operation of solar thermochemical reactor under real on-sun condition requires in-depth understanding of its dynamic behaivor under fluctuating direct normal irradiation (DNI). In this work, we developed a 2D axial-symmetric multi-physical model to assess the reactor’s dynamic behavior with three oxygen removing technologies electrochemical oxygen pump (EOP), sweep gas (SG), and vacuum pump (VP), under varying solar irradiations. To alleviate the negative effect of decreased DNI, two control strategies (CS) including varying operational conditions for oxygen removing technologies (CS1) and replacing the reduction step with the oxidation step (CS2) were conducted. We found that CS1 was only effective when DNI reduction was larger than 75 % over the whole reduction step (case 2). In general, CS2 can be implemented to alleviate the efficiency decrease for all DNI variations expect for the case 2 in this study. Especially, CS2 significantly increased the solar-to-fuel efficiency compared to the case without control strategy for the reduced DNI from 1000 W/m² to 500 W/m² during the whole reduction step. The reactor dynamic behavior in response to the daily DNI variations is also reported which shows that the efficiency profiles are highly in line with the DNI profile. This modeling work as well as proposed control strategies can be used to guide the design and control of solar thermochemical reactors under realistic conditions and hence for better assessing the performance of the reactor in practice.

太阳能热化学水分解提供了将太阳能转化为可再生燃料的有效途径。太阳能热化学反应堆在真实日照条件下的运行需要深入了解其在波动直接法向辐照（DNI）下的动态行为。在这项工作中，我们开发了一个二维轴对称多物理模型，以评估反应器在不同的太阳辐照下使用三种除氧技术电化学氧气泵 (EOP)、吹扫气 (SG) 和真空泵 (VP) 的动态行为. 为了减轻 DNI 降低的负面影响，进行了两种控制策略 (CS)，包括改变除氧技术 (CS1) 的操作条件和用氧化步骤 (CS2) 代替还原步骤。我们发现 CS1 仅在整个还原步骤中 DNI 减少量大于 75% 时才有效（案例 2）。一般来说，可以实施 CS2 来缓解本研究中案例 2 预期的所有 DNI 变化的效率下降。特别是，与没有控制策略的情况相比，CS2 显着提高了太阳能燃料效率，将 DNI 从 1000 W/m 降低在整个还原步骤中为²至 500 W/m ^{2 。}还报告了响应于每日 DNI 变化的反应堆动态行为，这表明效率曲线与 DNI 曲线高度一致。这种建模工作以及提出的控制策略可用于指导太阳能热化学反应器在现实条件下的设计和控制，从而更好地评估反应器在实践中的性能。