I’ve recently been working on building macro-energy systems models to understand the impact of direct air carbon capture systems on the electric grid. Over the last few months, I’ve worked to implement various DAC system designs in the GenX capacity expansion tool in Princeton’s ZERO Lab to measure how system wide emissions changed when DAC systems were built. My intermediate writeup for this research is below:

Full Report: https://drive.google.com/file/d/16l733O9esq-2Mi4DZYE_p2dFMYasA06R/view?usp=sharing

There are a few interesting preliminary findings in this report:

• Solid sorbent DAC systems drawing heat and power from the grid are often about 80% efficient in reducing emissions from a systems level perspective. This means that if a DAC system was rated to remove 1MtCO2 emissions in a given year, the electricity system’s total emissions would only reduce by 0.8MtCO2.. This difference is driven by the operational emissions from generating the heat required to run the DAC plant.
• The removal efficiency of DAC can be greatly improved by enabling DAC systems to take advantage of renewable power. As a high capital cost asset with slow ramping rates, it is difficult for the plant to take advantage of intermittent renewable resources. Given that the majority of DAC energy requirements are for heat, the DAC system can better utilize renewables by co-locating the plant with a thermal energy storage system(TES).
• Using a DAC + TES system design results in system wide emissions reductions greater than the rated capacity of the DAC plant because this TES system encourages the construction of more renewable power. Thus, by building a 1MT DAC plant with TES, system wide emissions are reduced by 1.5 MT of CO2. Though, this also results in higher costs.

These findings emphasize the need for policy reform in current IRA DAC tax credit structure, which encourage the building of DAC plants indiscriminate of system design or impacts to system wide emissions. I hope for this research to provide concrete recommendations for how such policy incentives for DAC development to be implemented going forward. My future research will examine the impact of alternative carbon capture technologies more deeply over the coming months, which will provide greater insight into how DAC technology compares with these other negative emissions pathways.