Session: 12-16-01: Decarbonization and Renewable Energy

Paper Number: 164515

Energetically Autarkic Direct Air Capture of Carbon Dioxide 

        To avoid catastrophic climate change, we must both reduce greenhouse gas emissions and actively remove hundreds of metric gigatons of CO2 from the atmosphere before the year 2100. Currently, CO2 direct air capture (DAC) technologies are limited by high costs due to low CO2 adsorbent capture capacities and lifetimes, as well as high energy consumption that necessitates energy storage or external power. DAC technologies dependent on external power are also likely to face insurmountable energy infrastructure scaling limits, prohibiting global deployment. Here, we demonstrate a stand-alone and economically feasible DAC system exclusively powered by solar energy. The device utilizes an ultrahigh capacity tetraamine-appended metal–organic framework adsorbent and employs a unique regeneration cycle synchronized with the natural diurnal cycle that obviates the need for energy storage or active air contactors. This approach results in adsorbent lifetimes > 8,000 cycles by avoiding excessively nonequilibrium processes and high temperatures that intensify adsorbent degradation rates in conventional DAC systems. This long adsorbent lifetime enables significant amortization of the capital cost. Our comprehensive technoeconomic analysis projects net CO2 capture costs of 86 $ tCO2^–1, below the U.S. ‘Carbon Negative Shot’ 2030 goal of 100 $ tCO2^–1. This system can overcome the material, land, and infrastructural scaling limitations impeding global deployment of contemporary DAC technologies and could meet the planet’s total 10+ GtCO2 year^–1 carbon capture requirements.

       Furthermore, it is extensively acknowledged that clean electricity is necessary for net carbon emissions in DAC, and thus DAC plants are built preferably close to wind or solar farms. Although clean electricity from dedicated solar farm-excluding those for grid decarbonization-is available for DAC, as identified in the carbon removal roadmap recently released by the U.S. Department of Energy, the potential of waste heat from photovoltaic panel for DAC has been rarely recognized and utilized. For a monocrystalline silicon photovoltaic (PV) panel, ~ 20% of solar irradiance is converted into electricity while the remaining 80% is converted into thermal energy, heating the PV panel to ~ 70°C at noon outdoors without concentrator and > 85°C with concentrator. This low-grade heat, usually dissipated to air, matches well with the regeneration temperature of the low-temperature amine-appended adsorbents. Surprisingly, PV technology matches well with DAC in terms of both quantity and quality of energy, showing the potential of photovoltaic-thermal (PVT) DAC to significantly reduce the energy consumption and cost of DAC. To prove the compatibility of PV and DAC technologies, we designed and demonstrated a photovoltaic-thermally driven DAC system that reduces energy consumption and cost by more than 50% compared to the aforementioned DAC system.

Presenting Author: Jian Zeng The Hong Kong University of Science and Technology (Guangzhou)

Presenting Author Biography: Dr. Jian ZENG has been an assistant professor with the Sustainable Energy and Environment Thrust in the Function Hub at the Hong Kong University of Science and Technology (Guangzhou) since October 2023. Before joining the HKUST (GZ), he was a postdoctoral scholar in the Lawrence Berkeley National Laboratory and University of California, Berkeley working with Profs. Ravi Prasher and Jeffrey Long. Dr. Zeng obtained his Ph.D. degree in Mechanical Engineering from the University of California, San Diego working with Prof. Renkun Chen, and M.S. and B.S. degrees both from South China University of Technology. Dr. Zeng’s group is dedicated to advanced thermal sciences and energy technologies for enhancing water-energy-climate nexus. We study the fundamental heat and mass transport mechanisms across different length scales for the applications in solar-thermal energy conversion and thermal management. We leverage the understanding of fundamental transport physics to designing next-generation Thermal Energy Storage, Carbon Capture and Conversion, Water Treatment and Water Harvesting, and Energy-efficient Building/Device/Personal Thermal-moisture Regulation.

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