Reticulated porous volumetric solar receiver designs guided by normal absorptance and hemispherical volumetric emittance investigations

Abstract

Here, we designed volumetric receivers from the angle of their normal absorptance and hemispherical volumetric emittance. We showed that the optimal receiver with the reticulated porous structure to date should have 95% porosity, 0.4mm average pore diameter and 8mm length. This receiver has both high normal absorptance and low hemispherical volumetric emittance because these geometric parameters are designed to achieve the minimum optical thickness that is sufficient to achieve the largest possible normal absorptance. In addition, its high porosity and small pore size achievable using replication technique contribute to high specific surface area and resultant high volumetric convective heat transfer coefficient. Our results demonstrated that the thermal efficiency can be potentially further enhanced by integrating textures comparable to the wavelength within the millimeter-scale pores to tune radiation as well as convection properties.