Session: 11-01 Carbon Capture and Sequestration

Paper Number: 114717

114717 - Evaluation of a Ph-Shifting Electrochemical Device for Oceanic Co2 Capture and Grid-Scale Load Shifting 

Carbon dioxide capture and removal technologies are critical to limit global warming to 2 °C. In this regard, ocean water CO₂ capture can complement Direct Air Capture (DAC) technologies. In addition to the atmosphere, the oceans are huge sinks for carbon and have to-date captured about 25% of all anthropogenically released carbon. This study proposes and evaluates the performance a new, reversible, electrochemical device that combines hydrogen and ferrocyanide redox salt looping to capture CO₂ from ocean water via pH-shifting. Ultimately, this device produces CO₂-lean water that can be released back into the ocean with a design that intrinsically offers operational flexibility/reversibility to enable grid-scale load shifting, which can enable deeper penetration of renewables in the grid. We developed an equivalent circuit model to predict the current-voltage performance of this oceanic carbon dioxide removal (CDR) device mediated by ferricyanide/ferrocyanide and H₂. Performance predictions are modeled as a function of key transport and thermodynamic conditions, specifically, for different mass transport rates of gases and liquid electrolytes and different extents of pH shift between acidification and basification steps.  Modeling results are compared to initial flow cell experiment results. Additionally, we apply this framework to determine parasitic energy demands for ocean water pumping, vacuum pumping for CO₂ removal, and gas compression of CO₂. Finally, by pairing electrochemical performance predictions with the California ISO “Duck Curve”, we demonstrate the effectiveness of the proposed reversible CDR device in load-shifting at the grid-scale. Our results show that the energy intensity for the reversible, oceanic CDR device has the potential to be reduced compared to present day DAC systems, but is highly sensitive to the energy intensity of ocean water pumping. Load-shifting capabilities in the proposed device provide additional benefits of powering CDR devices with renewable electricity while providing flexibility to manage grid-scale electricity demand. Overall, a reversible, pH-shifting based oceanic CDR device can provide holistic benefits of enabling CO2 capture with clean electricity.

Presenting Author: Rachel Silcox University of Michigan

Presenting Author Biography: Graduate Student Research Assistant at the University of Michigan - Ann Arbor