• DOE should give greater emphasis to the transport sector relative to the stationary sector.

• Among the transport strategies, DOE will devote its greatest effort to electrification of the vehicle fleet, a sweet spot for pre-competitive DOE R&D.

• Within the stationary heat and power sector, the DOE-QTR finds that the Department should increase emphasis on efficiency and understanding the grid. It states that the Department’s role as a source of information and as a convener of interested parties, two functions that are often underestimated, are unique and indispensable in advancing energy technologies.

• The need for the Department to develop stronger, more integrated policy, economics, and technical analyses of its research and development activities.

The QTR has been, at its core, about developing the principles that will guide difficult choices between different technically viable approaches that cannot all be pursued. Mere technical promise—that something could work—is an unjustifiably low bar for the commitment of DOE R&D funds. As every dollar matters, DOE’s research portfolio will give priority to those technologies most likely to have significant impact on timescales commensurate with the urgency of national energy challenges.

...we will apply two themes to the development of the overall R&D portfolio. First, we will balance more assured activities against higher-risk transformational work to hedge against situations where reasonably assured paths become blocked by insurmountable challenges. Second, because the Department neither manufactures nor sells commercial-scale energy technologies, our work must be relevant to the private sector, which is the agent of deployment.

In the transportation sector, DOE will focus on technologies that significantly reduce oil consumption and diversify fuel sources for on-road transportation. DOE recognizes that technology developments can help make vehicles more efficient and alternative fuels more economic, but the deployment of any technologies it helps develop is largely determined by policies, such as Corporate Average Fuel Economy standards. Impartial DOE research can help inform these standards. In setting priorities for our R&D activities, DOE will support technologies that can integrate with existing energy infrastructure to ease market adoption.

Furthermore, DOE will only support technologies that emit less carbon than incumbents—in keeping with our national energy goals. Recognizing the differences in the fleet, DOE will establish separate technology priorities for heavy-duty and light-duty vehicles.

There is significant headroom for DOE to work on increasing conventional vehicle efficiency by improving the internal combustion engine, by lightweighting, and by improving the aerodynamics of heavy-duty vehicles. Electrification is the next greatest opportunity to dramatically reduce or eliminate oil consumption in the light-duty vehicle fleet. DOE’s most significant role in transport research is here. DOE’s investment strategy does not preclude the market from selecting mild or strong hybrid, plug-in hybrid, battery-electric, or even fuel cell vehicles as the end point for electrification.

Finally, DOE will support development of domestically produced, infrastructure-compatible biofuels to reduce carbon emissions from liquid transportation fuels where electrification is not viable (heavy-duty vehicles, marine, and air). Although biofuels have other economic or security advantages, DOE understands that any drop-in liquid fuel will not insulate consumers from the global oil price.

As a result of this Review, we find that DOE is underinvested in the transportation sector relative to the stationary sector (energy efficiency, grid, and electric power). Yet, reliance on oil is the greatest immediate threat to US economic and national security, and also contributes to the long-term threat of climate change. Vehicle efficiency has the greatest short- to mid-term impact on oil consumption. Electrification will play a growing role in both efficiency and fuel diversification. DOE has particular capabilities in these areas. Within our transportation activities, we conclude that DOE should gradually increase its effort on vehicle efficiency and electrification relative to alternative fuels.

—QTR

Inspired by the Quadrennial Defense Review, the DOE-QTR was recommended by the President’s Council of Advisors on Science and Technology (PCAST) as an initial step toward a government-wide Quadrennial Energy Review to help formulate a national energy policy.

Vehicle efficiency. The QTR notes that improving vehicle efficiency is the most effective short-term route to reducing liquid fuel consumption. DOE can have the greatest impact in three efficiency technologies, according to the report: greater efficiency of internal combustion engines (ICEs); reductions in vehicle weight (lightweighting); and improved aerodynamics.

The performance, low cost, and fuel flexibility of ICEs makes it likely that they will continue to dominate the vehicle fleet for at least the next several decades, according to the report. ICE improvements can also be applied to both hybrid electric vehicles (HEVs) and vehicles that use alternative hydrocarbon fuels.

Increased efficiency and reduced emissions of ICEs can be realized through technologies that improve engine design and better integrate systems, potentially doubling the fuel economy of light-duty vehicles and increasing heavy-duty vehicle fuel economy by 60%, DOE said. In addition, the application of high-performance computing (HPC) and simulations to engine design can reduce the time and cost of integrating new technologies. As ICE technologies are proven and refined, the primary barriers to their adoption include cost, consumer acceptance, resource constraints, capital requirements, and turnover rates.

A 10% reduction in weight in a conventional ICE vehicle can improve fuel economy by 6%–8%, while the same lightweighting of a battery-electric vehicle increases its range by up to 10%. Weight can be reduced through decreasing vehicle size, innovative chassis design, or by introducing lightweight materials; consumer expectations make the latter two approaches more likely in the short term, the report notes.

Aerodynamics has a large impact on vehicles with a large frontal area and highway-dominated driving patterns in large-vehicle classes, such as tractor trailers, pickups, sport utility vehicles, and passenger vans.

Better aerodynamics could improve on-road truck fuel economy by more than 10%; they require a combination of modeling and real-world validation. The headroom for passenger cars is much smaller due to the smaller frontal area, a drive cycle not dominated by highway driving, and current light-duty vehicle designs that are already quite aerodynamic.

DOE said it will strive to balance its vehicle efficiency R&D efforts between technical issues faced by light-duty and heavy-duty vehicles. While light-duty vehicles are responsible for a larger fraction of national fuel consumption, they are more easily electrified than heavy-duty vehicles. The more limited technical options for heavy-duty vehicles motivates an intense focus on conventional efficiency.

Within the vehicle efficiency portfolio, ICE improvements will receive the greatest emphasis. This is both because it contributes to light-duty and heavy-duty vehicle sectors and because DOE’s capabilities are well-aligned with the field’s technical needs.

Vehicle Electrification. DOE’s electrification strategy is focusing on light-duty vehicles. DOE will focus on partial electrification because hybrid electric (HEVs) and plug-in hybrid electric (PHEVs) can access existing infrastructure. DOE says it can re-evaluate the relative priority in its portfolio of full electrification compared to partial electrification as batteries and charging infrastructure advance, and once penetration of EVs into the light-duty vehicle fleet is significant.

Batteries present the greatest technical challenge in vehicle electrification, the QTR report says. High-cost (currently about $650/kWh of usable energy) and low-energy density are the primary drawbacks of today’s lithium-ion batteries; significant advances in energy density, performance, and cost are required for the cost-effective deployment of EVs. Those technical barriers contribute to the primary market barriers for EVs: vehicle cost and range anxiety. Further, there are physical limits to the storage capacity that can be used; the required, but unusable, capacity dictates a heavier and more costly battery.

DOE’s goal is to reduce battery costs through a combination of better materials, optimized battery designs, and improved manufacturing. Near-term improvements will likely be the result of improved lithium-ion batteries. More dramatic advances in energy density, weight, cycle life, and power rates can be achieved through novel chemistries, such as metal polymer and lithium-sulfur batteries. While some next-generation batteries have shown promise in the laboratory, they require significant R&D before they can become commercial products.

Although DOE sees that it support of fuel cell research has led to significant progress in recent years, it notes that significant further improvements in key technologies remain to be demonstrated to meet program goals. If those program goals are met, the cost of driving (vehicle plus fuel) for FCEVs will likely be comparable to other alternative technologies (including vehicle efficiency improvements, electrification from HEVs to PHEVs to AEVs, and biofuels). However, those other alternative technologies are currently economically superior and will continue to improve rapidly.

DOE says it will maintain a limited program of fundamental R&D in fuel cells for transportation and in hydrogen production and storage.

DOE will develop technical capability in power electronics and electric motors via research in high-temperature capacitors, low-loss soft magnetics, wide-bandgap semiconductor materials, and their integration into low-cost power conversion devices and systems operated at high temperatures.

Alternative hydrocarbon fuels. DOE notes that liquid hydrocarbon fuels will remain important to the transportation sector for the foreseeable future, in heavy-duty vehicles, as well as air, marine, rail, and niche markets if not in light-duty vehicles.

Noting that there are numerous fuel pathways emerging, DOE says that it will not support R&D on fuel pathways that have greater life cycle carbon emissions than conventional fuels. The greenhouse gas emissions of gas-to-liquids (GTL), coal-to-liquids (CTL), and coal-and-biomass-to-liquids (CBTL) without carbon capture outweigh the potential benefits for petroleum displacement.

DOE also notes that the abundance, low cost, and domestic supply of natural gas makes it an increasingly attractive candidate for captive fueling applications (i.e., fleets). DOE will support the development of new technologies that may make natural gas more applicable for transport.

Resources

• Report on the First Quadrennial Technology Review