The Case for Onboard Carbon Dioxide Capture on Long-Range Vehicles

by Amanda Morris (Northwestern Now) Method can be implemented based on existing technologies -- Researchers argue that long-range vehicles, including cargo ships, should be powered by solid oxide fuel cells and use onboard carbon dioxide (CO2) capture; Depending on fuel type, this solution is CO2 neutral or even CO2 negative; Solid oxide fuel cells use conventional carbon-based fuels to power vehicles, but the byproduct is concentrated CO2 that can be easily captured; The team presents a novel dual-chamber tank that effectively stores fuel alongside captured CO2

The team presents its analysis in “Viability of vehicles utilizing on-board CO₂capture,” published today (Aug. 18) in the journal ACS Energy Letters. In the paper, the team looks at various factors, including fuel storage volumes and mass requirements for a wide range of vehicle classes — from light-duty passenger vehicles to tanker ships — and compares onboard CO₂capture to battery electric and hydrogen fuel cell options.

“It might be harder for people to see onboard CO₂capture as climate friendly because it uses conventional, carbon-based fuels,” said Northwestern’s Scott A. Barnett, senior author of the study. “People tend to assume hydrogen fuel cells and electric vehicles are more climate friendly. In reality, they often are not. Electricity might come from burning coal, and hydrogen is often produced by natural gas, which generates a lot of CO₂in the process.”

To store the CO₂on board, Barnett’s team has proposed a patent-pending dual-chamber storage tank. One chamber stores a carbon-based fuel. After the fuel cycles through the fuel cell to create energy, the CO₂byproduct is pressurized and introduced into the second chamber. The partition between the chambers can move — shrinking the fuel chamber as the fuel is used, making space for CO₂in the other chamber.

“The solid oxide fuel cell is critical because it burns the fuel with pure oxygen, yielding a concentrated CO₂product that is storable,” Schmauss said. “If we just burned the fuel with air, it would be heavily diluted with nitrogen, yielding too much gas to store. When the concentrated CO₂is compressed, it can be stored in a volume not much larger than that needed for the fuel, which saves space.”

“This technology really doesn’t have any major hurdles to making it work,” Barnett added. “You just have to replace the fuel tank with the double-chamber tank and add CO₂compressors. And, of course, the infrastructure eventually has to be developed to off-load the CO₂and either sequester or use it.” READ MORE