Volumetric solar carbon dioxide receiver designs with geometric parameters optimized in combination

Porous volumetric solar receivers with carbon dioxide as the working fluid can simultaneously harvest solar energy and utilize carbon dioxide. This means they hold promise for next-generation solar thermal power applications. The optimization of porous receivers has been performed in many works with their geometric parameters optimized using an exhaustive method. Such method are computationally intensive and their deduced design guidelines are not consistent. This work presents a distinct design method where geometric parameters (porosity, pore size, and length) are combined into three heat transfer parameters (volumetric convection coefficient, effective solid-phase thermal conductivity and optical thickness), so that they are optimized in combination. The optimization objective is the combination of a large volumetric convection coefficient, a large effective solid-phase thermal conductivity and an optimal optical thickness. The corresponding combination of parameters is a small pore size, a small length and a moderate porosity. Guided by this criterion, the best combination is 0.4 mm pore size, 4 mm length and 0.85 porosity, which result in a corresponding thermal efficiency of 71.5%. This combination is consistent with that from the exhaustive method and the optimization complexity for the developed method is reduced by two dimensions.