Exploring Technology Pathways to Achieve Deep Decarbonization in the United States by Mid-Century

Abstract:

Our objective is to identify the US deep decarbonization technology pathways using Temoa, an Energy system optimization model (ESOM). ESOMs are used to explore future scenarios and associated outcomes over the next several decades. Most previous national-level work has focused on low carbon options in the electric sector, and only a few examine the US energy system in its entirety. Among those with a full energy system perspective, the analysis is generally limited to a small set of scenarios that vary a few key assumptions. Conventional scenario analysis does not adequately address large future uncertainties.

We use a technique called modeling to generate alternatives (MGA) to systematically explore the decision space under a stringent carbon cap scenario (95% reduction in 2050 below the 2017 emissions level). MGA is an algorithm designed to produce solutions that have similar system costs but are very different in decision space.

The key mechanisms by which decarbonization is achieved are (1) a fully decarbonized electric sector through massive deployment of nuclear and renewables, including bioenergy with CCS (BECCS), (2) displacement of fossil fuels in the end-use sectors by electricity, hydrogen, synthetic gas, and biofuels, and (3) the deployment of more energy efficient devices in the end-use sectors. The residential and commercial sectors are characterized by a close to full-scale electrification of services. In the transportation and industrial sectors, a combination of electrification and penetration of carbon-free fuels (including synthetic fuels derived from hydrogen) drives down emissions. A low carbon electric sector can be achieved by a variety of ways that are different in their configurations but have similar costs. Our analysis suggests important tradeoffs in the presence of a stringent carbon cap. One tradeoff is between nuclear and solar PV coupled with battery storage. Our MGA results demonstrate that even when nuclear costs overruns are ignored, there are cost-competitive substitutes to nuclear.