A research group led by China's East China University of Science and Technology and Tongji University has proposed a new system integrating liquid-based direct air capture (L-DAC) with diabatic compressed air energy storage (D-CAES).
“Previous studies focused on integrating CAES with post-combustion carbon capture. However, coupling L-DAC with D-CAES—especially using solvent-based capture for both atmospheric and point-source CO2—has never been explored, offering a groundbreaking framework for sustainable energy storage,” corresponding author, Yuxing Ding, told pv magazine.
“DAC is a key carbon dioxide removal with several advantages. One key advantage is its ability to capture CO2 directly from the air rather than point sources such as power plants or industrial facilities,” the group explained. “Integrating DAC with D-CAES offers several advantages. First, DAC can provide a source of CO2 for the D-CAES system, which can enhance the system's efficiency by increasing the mass flow rate of the working fluid. This can improve the overall performance of the D-CAES system and increase its energy storage capacity.”
Additionally, the team highlighted that integrating DAC with D-CAES can help reduce the system's overall carbon footprint by capturing and storing CO2 emissions from the air. The D-CAES emits CO2 by releasing air from storage via combustion, usually using natural gas or fuel. “This emission presents a significant environmental challenge, which requires further CO2 capture process to mitigate climate change impact,” the academics said.
The academics simulated the system in the Aspen Plus software to optimize it and asses its technical and commercial feasibility. In the simulation, the D-CAES system compresses clean air from the DAC system during periods of low energy demand, stores it in underground caverns, and releases it when electricity demand is high. The compressed air is expanded through an expander, driving a generator to produce electricity. The L-DAC side of the system, on the other hand, drives ambient air into gas-liquid contact with a sprayed aqueous alkaline solution. The CO2 reacts with the alkaline solution to produce a carbonate solution precipitated into solid carbonates.
Image: East China University of Science and Technology, Energy Conversion and Management: X, CC BY 4.0
The L-DAC process was modeled in a continuous flowsheet encompassing the K-cycle and Ca-cycle and was found to capture 1 Mt of CO2 from the atmosphere and eventually deliver 1.48 Mt of dry CO2 annually. In their modeling, the scientists assumed that the default air composition is 78% nitrogen, 21% oxygen, and 1% argon, ignoring other gases in small proportion. They also assumed the isentropic efficiency of the multi-stage compressors to be 75%, and the inlet temperature of the natural gas to be 32 C. The pressure at the inlet of the combustion chamber was assumed to be the same as the outlet pressure of the cavern.
Per their simulation results, the round trip efficiency (RTE) of the D-CAES system can reach up to 59.27%, delivering 206 MW of electrical energy. On the L-DAC system side, with an air travel distance (ATD) of 12 m, a CO2 capture rate of over 90% is achievable. “However, increasing ATD beyond this point does not significantly enhance the capture rate,” the researchers emphasized.
Furthermore, the group has also conducted an economic analysis of the system. It assumed the capex for the integrated system to be $1,118 million, including $879 million for L-DAC and $239 million for D-CAES. The annual fixed opex was assumed to be 3.7% of capex.
“The economic analysis reveals levelized cost of energy (LCOE) of 0.53 $/kWh for the D-CAES system, while the levelized cost of CO2 captured from air stands at 259 $/tCO2,” the scientists concluded. “Although the integrated system does not offer substantial cost advantages, it is crucial in advancing low-carbon energy systems. This study is a foundation for the environmentally sustainable commercial deployment of D-CAES systems.”
Their findings were presented in “An integrated solution to mitigate climate change through direct air capture and diabatic compressed air energy storage,” published in Energy Conversion and Management: X.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: editors@pv-magazine.com.
By submitting this form you agree to pv magazine using your data for the purposes of publishing your comment.
Your personal data will only be disclosed or otherwise transmitted to third parties for the purposes of spam filtering or if this is necessary for technical maintenance of the website. Any other transfer to third parties will not take place unless this is justified on the basis of applicable data protection regulations or if pv magazine is legally obliged to do so.
You may revoke this consent at any time with effect for the future, in which case your personal data will be deleted immediately. Otherwise, your data will be deleted if pv magazine has processed your request or the purpose of data storage is fulfilled.
Further information on data privacy can be found in our Data Protection Policy.