They conclude that widespread electrification of transportation and other sectors is required, along with decarbonized electricity becoming the dominant form of energy supply. This transformation, they write, which poses challenges and opportunities for economic growth and climate policy, demands technologies that are not yet commercialized and coordination of investment, technology development, and infrastructure deployment.

Pacala and Socolow proposed a way to stabilize climate using existing greenhouse gas (GHG) mitigation technologies, visualized as interchangeable, global-scale ‘wedges’ of equivalent emissions reductions. Subsequent work has produced more detailed analyses, but none combines the sectoral granularity, physical and resource constraints, and geographic scale needed for developing realistic technology and policy roadmaps. We addressed this gap by analyzing the specific changes in infrastructure, technology, cost, and governance required to decarbonize a major economy, at the state/provincial level that has primary jurisdiction over electricity supply, transportation planning, building standards, and other key components of an energy transition.

...Previous modeling work we performed for California’s state government formed the analytical foundation for the state’s AB32 implementation plan in the electricity and natural gas sectors. California has also set a target of reducing 2050 emissions 80% below the 1990 level, consistent with the IPCC emission trajectory for a 450 ppm carbon dioxide equivalent (CO₂e) stabilization path that avoids dangerous anthropogenic interference. Working at both time scales, we found a pressing need for methodologies that bridge the analytical gap between planning for shallower, near-term GHG reductions, based entirely on existing commercialized technology, and deeper, long-term GHG reductions, which will depend substantially on technologies that are not yet commercialized.Williams et al.

Their model divided California’s economy into six energy demand sectors and two energy supply sectors, plus cross-sectoral economic activities that produce non-energy and non-CO₂ GHG emissions. They constructed a baseline scenario from government forecasts of population and gross state product, combined with regression-based infrastructure characteristics and emissions intensities to calculate a 2050 emissions baseline of 875 Mt CO₂e.

In the mitigation scenarios, they used backcasting, setting 2050 emissions at the state target of 85 Mt CO₂e as a constrained outcome, and altered the emissions intensities of new infrastructure over time as needed to meet the target, employing seventy-two types of physical mitigation measures.

Short-term measure selection was driven by implementation plans for state policies; long term rates of technology introduction were constrained by physical feasibility, resource availability, and historical uptake rates rather than relative prices of technology, energy, or carbon as in general equilibrium models. They did not include technologies expected to be far from commercialization in the next few decades. Mitigation cost was calculated as the difference between total fuel and measure costs in the mitigation and baseline scenarios. They also did not assume explicit lifestyle changes such as vegetarianism or bicycle transportation which could have a significant effect on mitigation requirements and costs; behavior change in their model is wrapped into conservation measures and energy efficiency.

Among the other major findings of the study are:

• Three major energy system transformations were necessary to meet the target: (1) energy efficiency had to improve by at least 1.3% yr⁻¹ over 40 years; (2) electricity supply had to be nearly decarbonized, with 2050 emissions intensity less than 0.025 kg CO₂e/kWh; and (3) most existing direct fuel uses had to be electrified, with electricity constituting 55% of end-use energy in 2050, compared to 15% today.

• Without electrification, the other measures combined produced at best 2050 emissions of 210 Mt CO₂e, about 50% below the 1990 level.

• The largest share of GHG reductions from electrification came from transportation, in which 70% of vehicle miles traveled—including almost all light duty vehicle miles—were powered by electricity in 2050, along with 20% from biofuels and 10% from fossil fuels.

• “Smart charging” of electric vehicles was essential for reducing the cost of electrification, by raising utility load factors and reducing peak capacity requirements through automated control of charging times and levels.

• Biofuels made a 6% contribution to the 2050 emissions reduction when feedstocks were constrained to be carbon neutral.

• Assuming perfect renewable generation forecasting, breakthroughs in storage technology, replacement of steam generation with fast-response gas generation, and a major shift in load curves by smart charging of vehicles, renewable energy could contribute a maximum of 74% of the total required.

• The largest share of GHG reductions from energy efficiency came from the building sector, through a combination of efficiency improvements in building shell, HVAC systems, lighting, and appliances.

• Achieving the requisite infrastructure changes necessitates major improvements in the functionality and cost of a wide array of technologies and infrastructure systems, including but not limited to cellulosic and algal biofuels; CCS; on-grid energy storage; electric vehicle batteries; smart charging; building shell and appliances; cement manufacturing; electric industrial boilers; agriculture and forestry practices; and source reduction/capture of high global warming potential (GWP) emissions from industry.

Not only must these technologies and systems be commercially ready, they must also be deployed in a coordinated fashion to achieve their hoped-for emission reduction benefits at acceptable cost. For example, switching from fuels to electricity before the grid is substantially decarbonized negates the emissions benefits of electrification; large-scale deployment of electric vehicles without smart charging will reduce utility load factors and increase electricity costs; without aggressive energy efficiency, the bulk requirements for decarbonized electricity would be doubled, making achievement of 2050 goals much more difficult in terms of capital investment and siting.

—Williams et al.

Net mitigation cost to California came in at 1.3% in 2050 ($65 billion or $1,200 per capita). The transportation sector bore the highest share of these costs, reflecting the cost of fleet electrification.

The second model result deserving special attention is the expanded role of electricity, which increases from 15% to 55% of end-use energy, essentially switching places with petroleum products, which fall from 45% to 15%. If electricity does become the dominant component of the 2050 energy economy, the cost of decarbonized electricity becomes a paramount economic issue. Our results show that generation mixes dominated by renewable, nuclear, and CCS, in the absence of cost breakthroughs, would have roughly comparable costs, raising the present average cost of electricity generation by a factor of about two, a result also noted by other researchers. These findings indicate that minimizing the cost of decarbonized generation should be a key policy objective.

...For electrified transportation, the inherently higher efficiencies of electric drive trains would still allow a net reduction in fuel costs even with electricity prices doubled and oil prices at $100/barrel, as well as shifting cash flows away from foreign oil imports toward domestic purchases of electricity. On the other hand, electrification of direct fuel uses will increase residential, commercial, and industrial sector costs, especially for heating, emphasizing the need for energy efficiency and design of new infrastructure in these sectors to minimize lifecycle costs. Because much of the required technology and infrastructure for the energy-system transformation is not yet commercialized, comparative lifecycle costs are highly uncertain.

—Williams et al.

Resources

• James H. Williams, Andrew DeBenedictis, Rebecca Ghanadan, Amber Mahone, Jack Moore, William R. Morrow III, Snuller Price, and Margaret S. Torn (2011) The Technology Path to Deep Greenhouse Gas Emissions Cuts by 2050: The Pivotal Role of Electricity. Science doi: 10.1126/science.1208365