Exploratory Performance Modeling of the Sorbent-based Direct Air Capture System

Abstract

The continued growth in carbon dioxide (CO2) emissions will necessitate deployment of negative emissions technologies (NETs) to meet Paris stabilization climate targets [1]. Direct air capture (DAC) is a NET that can capture dispersed source CO2 already in the atmosphere [2] [3]. DAC systems would complement the application of CO2 capture and storage (CCS) applied for significant emissions reductions. Working DAC systems have been demonstrated at relatively small scales by several companies, including Climeworks, Global Thermostat and Carbon Engineering, proving the technical feasibility of such systems. However, the performance, cost, life cycle environmental impacts and efficacy of current DAC systems is still a subject of debate. There exists a growing need for understanding how DAC systems can be designed and employed to deliver cost-effective and environmentally sustainable negative emissions and be scaled up for rapid deployment. In this study, we explore the design space for a sorbent-based DAC system by developing a DAC performance model for three systems alongside existing models from literature [4] [5]. We identify process parameters such as cycle operation parameters, sorbent thermophysical characteristics and thermal energy supply for further sensitivity analysis that could improve the performance of the DAC system given suitable energy supply options. Our investigation into these process sensitivities yields an understanding of how DAC processes might be optimized for net negative CO2 emissions. Our key findings highlight low carbon intensive thermal energy options such as industrial heat pumps and natural gas fired boilers or natural gas combined heat and power plants as suitable options for integration with a DAC system to deliver net negative emissions and isolate key variables in heat pump systems for optimal negative emissions.