Direct Air Capture of Carbon Dioxide with Ocean Wave Energy

Project Overview

Recent studies have highlighted the urgent need to not only reduce carbon emissions, but also develop negative-emissions technologies that can remove carbon dioxide (CO2) from the air. Several companies (e.g., Carbon Engineering, Climeworks, and Global Thermostat) are actively working to develop direct air capture (DAC) technologies that use low-carbon electricity sources to power fans and blow massive quantities of air through sorbents to capture CO2. While functional, these installations have sizeable land-use footprints, high capital and operational expenses, and significant renewable electricity consumption demand. Accordingly, DAC by conventional methods is expensive at $94-$232 per ton of CO2 captured (state of the art).

In this project, we developed a new approach to direct air capture that makes use of renewable ocean energy and ocean CO2 sequestration. We designed and modeled a passive buoy module that can capture carbon dioxide from the atmosphere by harnessing ocean wave energy, ocean thermal energy, and solar thermal energy. This new approach to direct air capture has virtually no moving parts, making each buoy module robust, passively operated, and inexpensive to maintain. Furthermore, the CO2 captured by these remote ocean buoys can be sequestered in place by forming CO2 clathrates that sink in place to the bottom of the ocean. In this project, we analyzed literature on relevant oceanic and atmospheric conditions, designed a process-flow diagram and key fluidic components, modeled the airflow through the system using Gaussian processes (GP), determined the rate of water generation and carbon-dioxide capture in the system, and performed a preliminary techno-economic analysis. Based on the preliminary techno-economic analysis, our newly designed approach for DAC can be made economically competitive with further improvements and optimizations to floating oscillating water-column technology.

Mission Impact

This project is directly in line with LLNL's investment strategies for energy security and climate resilience, to "[l]ead in the science, methods, and technologies that reduce atmospheric carbon dioxide." The results of this feasibility study will set the stage for LLNL to forge a new arena of carbon-capture research based around ocean energy.