Different effects on thermal conductivity of Ca-based thermochemical energy storage materials for a concentrated solar power plant

Abstract

Concentrated solar power plant with calcium looping (CSP-CaL) is a promising candidate to overcome the intermittency of solar energy owing to its numerous advantages, such as high energy density, low cost, and widespread availability. The reliable effective thermal conductivity of CaCO3 and CaO particles is crucial on designing reactors and gas–solid heat exchangers for a CSP-CaL plant. This paper investigates the different effects of pore structure, temperature and thermal expansion on effective thermal conductivities of CaCO3 and CaO particles using a reasonable mathematical model which combines the heat transfer and structural mechanics models. The results show that the pore structure has a negative effect on the effective thermal conductivities of both CaCO3 and CaO particles, especially for the large theoretical effective thermal conductivity of particles. In addition, the effective thermal conductivities of both CaCO3 and CaO particles at a low temperature is less than that with the same pore structure at a high temperature owing to their different thermos-physical properties at various temperature. This might lead to a more terrible heat transfer performance during heating process of energy charging process. Finally, the effective thermal conductivities of CaCO3 and CaO particles are also affected by thermal expansion arising from high temperature which can change the pore structure, and result in a 37.65 % and 52.69 % reduction in effective thermal conductivities of both CaCO3 and CaO particles, respectively, during heating process of energy charging process.