Direct Air Capture by Ion-Exchange Sorbent and Low-Grade Heat

Anthropogenic CO2 emissions are widely accepted as the primary driver of global climate change, leading to many adverse outcomes for humanity. While CO2 emissions are equally distributed within the atmosphere, the negative impacts of human-induced climate change are not, with marginalized people suffering the worst. While renewable energy technologies can reduce future emissions, large-scale atmospheric CO2 capture is needed to remove past and future emissions, especially since the transition to carbon-neutral energy sources will take many decades to complete. Current direct air capture (DAC) CO2 capture technologies suffer from high energy consumption per ton of CO2 captured, resulting in high capture costs. Advanced Cooling Technologies, Inc. (ACT) and Lehigh University (LU) began the development of a novel acid/base ion-exchange DAC system during the proceeding DOE STTR Phase I program. This system can utilize either a low-grade heat source (industrial waste heat or geothermal) medium or an electrically derived weak base solution to regenerate the capture sorbent. During Phase I, the project team demonstrated CO2 capture rates of greater than 90%, with thermal regeneration of the sorbent occurring at temperatures as low as ~50°C. This DAC system uses widely available commercial adsorbent resins, which reduce cost and help alleviate supply constraints. The system design and layout allow it to scale easily and be implemented as a modular system, minimizing manufacturing and deployment costs. ACT and LU's new ion-exchange DAC system captures CO2 in a fundamentally new way, which lends itself to improved plant efficiency. Current modeling predicts an energy improvement of 29% over stateof-the-art DAC technologies. These results suggest a pathway to full-scale levelized capture costs of less than $100/ton. Additional benefits of the technology are a smaller plant footprint and the ability to power the plant using 100% low-voltage electrical energy or a mix of low-grade heat and electricity. During the Phase II program, ACT and LU will develop the individual system-level components required for scaling the technology. After demonstrating the operation of these components and sub-systems, an integrated sub-scale test bed will be used to demonstrate system operation across dozens of capture and regeneration cycles. The team will use the data from these test bench tests to refine their full-scale system models. Finally, complete techno-economic and life cycle analyses will be completed to validate the technology's economic viability.