The 6th Assessment of the IPCC underlined the need for urgent measures for carbon dioxide removal from the atmosphere, so as to meet the 1.5 °C goal by the end of this century. One option to achieve this is direct air capture (DAC) technologies. This work assesses the thermodynamic performances of different categories of DAC technologies, i.e., adsorption-based, absorption-based, ion exchange, and electrochemical. An exergy analysis is performed on the DAC processes in each category to identify hotspots for efficiency loss within the system. The results show that the consumption of materials is responsible for 5–40% of the exergy consumption of the most-developed DAC processes. Despite their greater use of materials compared to absorption-based processes, adsorption-based processes, together with ion exchange technologies, have the highest exergy efficiencies of the DAC technologies investigated. Moreover, the results highlight the importance of limiting material consumption and electrifying large-scale DAC plants, which cannot run exclusively on waste heat from industrial processes.

IPCC第六次评估强调需要采取紧急措施去除大气中的二氧化碳，以实现本世纪末1.5℃的目标。实现这一目标的一种选择是直接空气捕获 (DAC) 技术。这项工作评估了不同类别 DAC 技术的热力学性能，即基于吸附、基于吸收、离子交换和电化学。对每个类别的 DAC 流程进行火用分析，以确定系统内效率损失的热点。结果表明，在最先进的 DAC 工艺中，材料消耗占火用消耗的 5-40%。尽管与基于吸收的工艺相比，它们更多地使用材料，但基于吸附的工艺与离子交换技术一起，在所研究的 DAC 技术中具有最高的火用效率。此外，研究结果凸显了限制材料消耗和为大型 DAC 工厂供电的重要性，这些工厂不能完全依靠工业过程的废热来运行。