Cost and deployment consequences of advanced planning for negative emissions with direct air capture in the US Eastern Interconnection

Negative emissions systems differ from net-zero systems by deploying significantly more negative emission technologies. The emerging literature on negative emission power systems assumes straight transition pathways from the present systems to final negative emissions systems. Such straight transition paths are unlikely, as deployment of negative emission technologies such as direct air capture might occur via crash course to respond to climate crises and utilities are investing towards net-zero systems instead of negative emissions systems. In this paper, to inform policymakers of the different outcomes of planning for negative emissions systems at different timelines, we quantify the value of planning for a negative emissions power system beginning now versus after achieving a net-zero emissions system in 2050. We apply a macro-scale capacity expansion planning model to the Eastern Interconnection power system to quantify the technological deployments and cost consequences of these two decarbonization pathways to reach a negative emission power system. We find advanced planning for a negative emissions system favors more deployment of storage technologies, which increases system flexibility and allows for better utilization of renewable generation to reduce investments in other technologies, including transmission lines. This change in distribution of investments across technologies leads to small annual cost saving of $6 billion, or 1%. We also find that further delay in planning for a negative emission system after reaching net-zero by 5, 10, and 15 years could significantly increase total system cost by 29%, 35%, and 41% respectively due to higher deployment of negative emission technologies. Our results indicate that, given small annual cost saving from advanced planning for a negative emission power system, economically utilities are on the right path in planning for a net-zero power system by 2050. However, planning should not be delayed further after reaching net-zero to avoid missing cumulative emission targets or significant cost consequences.