Effect of Humidity on the Energy and CO 2 Separation Characteristics of Membranes in Direct Air Capture Technology

Kamil Niesporek, Grzegorz Wiciak, Janusz Kotowicz () and Oliwia Baszczeńska ()
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Kamil Niesporek: Department of Power Engineering and Turbomachinery, Faculty of Energy and Environmental Engineering, Silesian University of Technology, 44-100 Gliwice, Poland
Grzegorz Wiciak: Department of Power Engineering and Turbomachinery, Faculty of Energy and Environmental Engineering, Silesian University of Technology, 44-100 Gliwice, Poland
Janusz Kotowicz: Department of Power Engineering and Turbomachinery, Faculty of Energy and Environmental Engineering, Silesian University of Technology, 44-100 Gliwice, Poland
Oliwia Baszczeńska: Department of Power Engineering and Turbomachinery, Faculty of Energy and Environmental Engineering, Silesian University of Technology, 44-100 Gliwice, Poland

Energies, 2025, vol. 18, issue 13, 1-19

Abstract: Membrane-based direct air capture of CO 2 (m-DAC) is a promising solution for atmospheric decarbonization. Despite growing interest, the impact of relative air humidity on the performance of m-DAC systems is often neglected in the literature. This study presents detailed parametric analyses that take into account humidity variability and several hypothetical scenarios regarding membrane selectivity toward water vapor. Specifically, cases were considered where the permeance of H 2 O relative to CO 2 was assumed to be 0.5, 2, and 5 times higher, which allowed for a systematic assessment of the impact of relative humidity on process performance. The calculations were carried out both for membranes with assumed separation parameters and for the PolyActive TM membrane, enabling a realistic evaluation of the influence of atmospheric conditions on the process. The results show that an increase in humidity in the analyzed range from 0 to 80% can lead to a rise in the energy intensity of the process by up to approximately 34%, and an increase in total power demand by around 29%. As humidity increases, key process parameters such as CO 2 purity in the permeate and recovery rate decrease. The water vapor content in the permeate in a single-stage membrane separation process can reach up to 60%. It is recommended to use gas drying systems and to develop membranes with low H 2 O permeance in order to reduce the energy cost of the process. The potential location of m-DAC systems should preferably be in regions with low air humidity. The study highlights the necessity of considering local climate conditions and the need for further research on membrane selectivity.

Keywords: membrane separation; direct air capture; carbon dioxide; relative humidity (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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