Inspecting Alternative Decarbonization Pathways in an Open Energy Outlook for the United States

To prevent a global temperature rise greater than 1.5 Celsius, we need to achieve net-zero greenhouse gas (GHG) emissions by mid-century. The United States (US) was the second largest primary energy consumer and carbon dioxide emitter accounting for 17% of global primary energy supply and 14% of global GHG emissions in 2019. Policy implements, aimed at changing the way energy is produced and consumed, will be key to facilitate a rapid decarbonization transition. Energy system models (ESOMs) have been identified as powerful tools capable of examining future energy system evolution and testing effects of proposed policy. However, ESOMs are limited in their ability to model all aspects of the real world owing to structural uncertainties. If these uncertainties are unaccounted for, it can mislead decision makers into a false sense of certainty of the suggested system transformation.

The Open Energy Outlook (OEO) examines US decarbonization pathways across the energy system over a multi-decadal time span. We apply a method called Modeling to Generate Alternatives (MGA) to an open source energy system optimization model - Tools for Energy Model Optimization and Analysis (Temoa). This method allows us to systematically examine technology tradeoffs and address the underlying structural uncertainty. Here, we focus on alternative solutions under a scenario that achieves carbon neutrality by 2050. From a policy perspective, examining deep decarbonization alternatives with approximately the same system cost is worthwhile because sub-optimal solutions may be more desirable when weighing factors exogenous to the model like transition speed and public opinion. Preliminary results show a large range of potential future capacities for solar (1800-4200 GW) and nuclear power (50-750 GW) in the power system. Fossil fuel use across the energy system also spans a large range (5-70 EJ) indicating futures where widespread electrification or significant deployment of negative emissions technologies are both plausible. We also present results highlighting the tradeoffs between key technologies like electric vehicles and direct air capture/fischer-tropsch fuels and hydrogen and fossil fuel production.