Passive Adsorptive Direct air capture (PADAC) using a Nature-assisted temperature Swing Process: A sustainable solution for residential CO2 emissions

Abstract

Numerous regions worldwide experience abundant natural sunlight and significant temperature differentials between night and day. We propose a novel system called Passive Adsorptive Direct Air Capture (PADAC), which leverages a natural temperature gradient to facilitate CO₂ adsorption and desorption cycles. Specifically, CO₂ is adsorbed during the cooler nighttime temperatures and desorbed during the warmer daytime temperatures. Our conceptual prototype was designed, developed, and tested in Morocco with a single adsorptive-desorptive cycle. To assess its global applicability, we selected several regions worldwide, where our system could be installed and work optimally, characterized by significant temperature fluctuations between day and night. This paper aims to demonstrate proof of concept to validate the feasibility of the PADAC process. The design of a pilot-scale experimental setup is presented, along with supporting experiments in the field that validate the proof of concept. We have experimentally demonstrated that the PADAC system can reach desorption temperatures of up to 93 °C, while its overnight temperature can drop to as low as 13 °C. These temperature ranges obtained by the Nature-assisted Temperature Swing Adsorption (Na-TSA) process, are optimal for the desorption and adsorption processes of most solid adsorbents. We have found that the PADAC achieves an efficiency of approximately 52 % in delivering the required temperature range for desorption. This innovative approach addresses the high energy costs typically associated with DAC by utilizing free thermal energy from natural temperature variations between night and day, with the main purpose of offsetting up to 1 t of CO₂ per person per residence.