Thermal Removal of Carbon Dioxide from the Atmosphere: Energy Requirements and Scaling Issues

I conduct a systems-level study of direct air capture of CO2 using techniques from thermal physics. This system relies on a combination of an efficient heat exchanger, radiative cooling, and refrigeration, all at industrial scale and operated in environments at low ambient temperatures. While technological developments will be required for such a system to operate efficiently, those developments rest on a long history of refrigeration expertise and technology, and they can be developed and tested at modest scale. I estimate that the energy required to remove CO2 via this approach is comparable to direct air capture by other techniques. The most challenging aspect of building a system that could remove 1 billion tonnes of CO2 from the atmosphere per year is the power demand of 112 to 420 GW during the wintertime operational period.