(628g) Feasibility of CO2 Direct Air Capture Integration in Data Centers

Global carbon emissions have increased exponentially since the industrial revolution, leading to a rise in global temperature. To meet the 2°C warming limit put forth by the United Nations, the International Panel on Climate Change has stated that substantial increases in negative carbon emissions by the end of the century are now necessary¹. Direct air capture of carbon dioxide is a promising negative emissions technology. However, due to the low atmospheric concentrations of CO₂ DAC technology is still energy-intensive and expensive². Targeting niche applications where existing airflow and waste heat can be used advantageously may lead to the rapid development that can make larger DAC commercialization more economically viable.

DAC integration in data centers is one such application. There are over 2,700 data centers in the United States with an average power usage effectiveness of 1.43³. The best facilities can approach values closer to 1.09, where a PUE of 1 means all power consumption is used for processing power rather than cooling. These lower PUE values are produced by pushing ambient air through the servers or using evaporative cooling⁴ rather than using traditional HVAC or cooling towers. Data centers currently use 200 TWh of electricity every year, 1% of the global energy demand⁵. This value is expected to increase to 7% of global demand by 2030. A substantial portion of that energy leaves data centers as thermal waste heat. This research aims to examine the feasibility of integrating data center airflow and waste heat into DAC systems.

Such a system must not interfere with the operation of servers and lead to a minimal increase in water and electricity usage. Therefore, the target is not to optimize the DAC process itself, but the operation of DAC within constraints placed by data center operation. This is made possible by using a series of staged vapor-liquid equilibriums to regenerate a liquid sorbent using only a 10°C differential that can be obtained from data center waste heat. Gas with a lower partial pressure of CO2 enters a reservoir and is adsorbed into a low-temperature liquid sorbent. This liquid sorbent then passes through a heat exchanger to a second hotter reservoir, where CO2 is released with a higher partial pressure than it first entered. This gas can be passed to the next stage until the desired CO2 concentration is achieved. ASPEN modeling is used to examine the energetics of using liquid sorbents in this staged “ladder” regeneration system and identify sorbents that minimize water loss in an air contactor. Results of promising sorbents are verified with experimental gas-liquid contactors and bench-scale prototypes of the regeneration system. This novel method of sorbent regeneration may provide an alternative for energy-intensive sorbent regeneration methods. Contactor design is optimized by testing a series of hollow fiber membranes in a lab-scale wind tunnel. The configuration with the lowest pressure drop and water loss will be ideal for DAC integration in data centers. Phosphate sorbents show promise in limiting water loss and reducing contact with more corrosive hydroxides in an expensive system.

[1] Masson-Delmotte, V., Zhai, P., Chen, Y., Goldfarb, L., Gomis, M. I., Matthews, J. B. R., Berger, S., Huang, M., Yelekçi, O., Yu, R., Zhou, B., Lonnoy, E., Maycock, T. K., Waterfield, T., Leitzell, K., & Caud, N. (2021). Working Group I Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change Edited by. www.ipcc.ch

[2] Holmes, G., & Keith, D. W. (2012). An air-liquid contactor for large-scale capture of CO 2 from air. Trans. R. Soc. A, 370, 4380–4403. https://doi.org/10.1098/rsta.2012.0137

[3] CloudScene, “Browse Markets,” n.d. (accessed April 2, 2021).

[4] StatePoint Liquid Cooling system for data centers - Engineering at Meta. (n.d.). Retrieved April 7, 2022, from https://engineering.fb.com/2018/06/05/data-center-engineering/statepoint-liquid-cooling/

[5]G Andrae, A. S., & Edler, T. (2010). On Global Electricity Usage of Communication Technology: Trends to 2030. Challenges, 6, 117–157. https://doi.org/10.3390/challe6010117