Concept and feasibility of solar indirect heating plant in batch-wise processing for thermochemical CO2 splitting via tubular furnace experiment and reacting heat transfer simulation

This paper examines feasibility of a solar indirect heating plant for CO₂ splitting with enhanced performance. The conceptual plant comprises a solar receiver, a reactor and a heat storage unit connected thermally with a heat transfer fluid. Such a configuration of the system enables a larger amount of metal oxide as reactive material than direct irradiation technology, and is suitably applicable to regenerating exhaust heat incurred by a temperature swing between two levels of reduction and oxidation temperatures. A ceria foam device is tested experimentally in an externally heated tube reactor, similar to the indirect heating plant. The experiment indicated that the externally heated reactor could produce a comparable volume of product gas to the direct irradiation method with various amounts of reactive material mass and the temperatures for reduction and oxidation. A numerical simulation was used to solve the one-dimensional unsteady process for solar heating and reduction. The simulation demonstrated that the solar to fuel efficiency for the proposed system increased with an increasing load of the material and could exceed that of the direct irradiation plant when recovering the exhaust heat.