Oxygen Crossover in Solid–Solid Heat Exchangers for Solar Water and Carbon Dioxide Splitting: A Thermodynamic Analysis

Abstract

In solar thermochemical redox cycles for H2O/CO2-splitting, a large portion of the overall energy demand of the system is associated with heating the redox material from the oxidation temperature to the reduction temperature. Hence, an important measure to improve the efficiency is recuperation of sensible heat stored in the redox material. A solid-solid heat exchanger can be subject to undesirable oxygen crossover, which decreases the oxygen uptake capacity of the redox material and consequently the system efficiency. We investigate the extent of this crossover in ceria based cycles, to identify, under which conditions a heat exchanger that allows oxygen crossover can improve the system efficiency. In a thermodynamic analysis we calculate the amount of transferred oxygen as a function of the heat exchanger efficiency and show the system efficiency of such a concept. A second law analysis is applied to the model to check the feasibility of calculated points of operation. For the investigated parameter set the heat exchanger design improves the system efficiency by a factor of up to 2.1.

Solar-driven thermochemical conversion of H2O and CO2 into sustainable fuels

“… 258 Solid–solid heat exchanger 1773.15K 1073.15K 10 −3 bar / / / / / Holzemer-Zerhusen et al. 259 Reactor train system for heat recovery 1773K 1073K 10Pa Ceria porous brick / Radiation ∼80% ∼30% Patankar et al. 251 Counter-rotating inert solid heat exchanger / / / Ceria porous medium Inert material cylinder solid Radiation >50% / Lapp et al.…”

Synergies between Direct Air Capture Technologies and Solar Thermochemical Cycles in the Production of Methanol

“…No limitation of number nor size of heat exchangers is set and therefore, the suggested solution is the most energetically efficient. Finally, solid-solid heat exchangers between reduced and oxidized ceria were assumed to have an efficiency of 50%, even though this equipment is still under development [55]. In Figure 4, the solid-solid heat exchangers are depicted with units E-102 and E-202.…”