Exploring the impact of hourly variability of air condition on the efficiency of direct air capture
This week, we deep dive into a paper recently published in the Chemical Engineering Journal. The study was led by Howoun Jung, affiliated with the Korea Institute of Energy Research in Daejeon (Republic of Korea) and the University of Southern California in Los Angeles (US).
This study investigates how hourly fluctuations in ambient air conditions—specifically temperature and humidity—affect the performance of Direct Air Capture (DAC) systems, which are technologies designed to remove CO₂ directly from the atmosphere. The research focuses on a DAC process utilizing Temperature-Vacuum Swing Adsorption (TVSA) and employs dynamic simulations combined with Bayesian optimization to assess performance across different climatic conditions.
The study reveals that hourly changes in ambient conditions can significantly impair DAC efficiency. Specifically, energy consumption can increase by up to 35.9%, and CO₂ capture productivity can decrease by up to 22.2% when compared to operations under constant, monthly-averaged conditions. High humidity levels are particularly detrimental, as they increase the energy required for water desorption, prolong desorption times, and elevate the workload on pumps, collectively leading to higher energy use and reduced productivity.
The adverse impacts of hourly variability are more pronounced in dry regions, where fluctuations in air conditions are more significant, leading to greater performance degradation. By re-optimizing operating parameters to account for ambient air variations, the study achieved approximately a 5% improvement in both energy consumption and productivity. This suggests that adaptive control strategies can partially mitigate the negative effects of environmental variability. Taken together, these results point to the suggestion that implementing advanced control systems that dynamically adjust operating parameters based on real-time or forecasted air conditions could enhance performance and economic viability. They also underscore how factoring in local climate variability in site selection for DAC facilities optimize efficiency.
Here is a list of the main takeaways of this paper:
- Hourly air condition variability significantly impacts DAC performance, increasing energy use by up to 36% and lowering CO₂ productivity by over 22%.
- Humidity is the most influential factor, as it extends desorption time and intensifies energy demands in TVSA systems.
- Dry regions experience more pronounced performance drops, due to greater fluctuations in temperature and humidity over the day.
- Static operational settings underperform in dynamic environments, highlighting the limits of designs based on monthly averages.
- Dynamic optimization of operating parameters mitigates losses, boosting efficiency by about 5% even under fluctuating conditions.
Read the full paper here: Exploring the impact of hourly variability of air condition on the efficiency of direct air capture