Summary

The energy security, environmental, and economic issues associated with the transportation sector and with light-duty vehicles can be addressed in a number of ways. An important part of the nation’s approach to reducing petroleum consumption and the environmental impact of light-duty vehicles is to improve automotive technology in a variety of ways that lead to higher fuel economy vehicles that are affordable. In addition, vehicles that can use alternative sources of energy, such as electricity or hydrogen, can have low greenhouse gas (GHG) and other emissions. Since the early 1990s the nation has formed government-industry partnerships to help accelerate the research and development (R&D) for light-duty vehicles (see Chapter 1).

This report by the National Academies of Sciences, Engineering, and Medicine (the Academies) Committee on the Review of the Research Program of the U.S. DRIVE Partnership, Phase 5 (the committee), presents the results of a review of the U.S. DRIVE (Driving Research and Innovation for Vehicle Efficiency and Energy Sustainability) Partnership, which was formed in 2011. U.S. DRIVE is very much in line with the partnerships that preceded it, namely, the FreedomCAR and Fuel Partnership and, prior to that, the Partnership for a New Generation of Vehicles (PNGV).¹ The PNGV focused on achieving a significant increase in fuel economy for a family sedan and resulted in unveiling three concept vehicles at the end of that program. Under President George W. Bush, a shift in the program took place toward addressing the challenges of developing technologies for hydrogen fuel as well as for fuel cell vehicle technologies. The FreedomCAR and Fuel

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¹ The focus of the committee’s review of technologies for light-duty vehicles is on the Department of Energy’s (DOE’s) research and development (R&D) programs that support the goals of U.S. DRIVE.

Partnership was established to address these challenges and to advance the technologies sufficiently so that a decision on the commercial viability of hydrogen fuel cell vehicles (HFCVs) could be made by 2015. As the Obama administration took office in early 2009, a redirection began to take place, with reduced R&D on hydrogen and fuel cell vehicles and increased attention directed toward technologies for the use of electricity to power light-duty vehicles, with emphasis on plug-in electric vehicles including plug-in hybrid electric vehicles (PHEVs) and all-electric vehicles (or battery electric vehicles [BEVs]). The Academies reviewed the PNGV seven times, from 1993 to 2001; the FreedomCAR and Fuel Partnership three times, between 2004 and 2010; and the U.S. DRIVE Partnership in 2011-2012. The U.S. DRIVE Partnership is considered a continuation of the FreedomCAR and Fuel Partnership and hence the current review a fifth (Phase 5) review.² The Partnership provides a forum to discuss precompetitive, technology-specific R&D needs; identify possible solutions; and evaluate progress toward jointly developed technical goals.³ This process helps to inform the Department of Energy (DOE) on the precompetitive R&D that is carried out by DOE’s Vehicle Technologies Office (VTO) and the Fuel Cell Technologies Office (FCTO). U.S. DRIVE and its member partners focus on precompetitive R&D that can help to accelerate the emergence of advanced technologies that are commercially feasible.

The U.S. DRIVE vision is that “American consumers have a broad range of affordable personal transportation choices that reduce petroleum consumption and significantly reduce harmful emissions from the transportation sector.” Its mission is as follows: “Accelerate the development of pre-competitive and innovative technologies to enable a full range of efficient and clean advanced light-duty vehicles, as well as related energy infrastructure” (U.S. DRIVE, 2016).

The guidance for the work of the U.S. DRIVE Partnership as well as the priority setting and targets for needed research are provided by 12 joint industry/government technical teams, and working groups are formed as needed to address crosscutting issues. This structure has been demonstrated to be an effective means of identifying high-priority, long-term precompetitive research needs for each technology with which the Partnership is involved (see Chapters 1 and 2).

Technical areas in which R&D as well as technology validation programs have been pursued include the following:

• Internal combustion engines (ICEs) operating on conventional and various alternative fuels,
• Automotive fuel cell power systems,
• Hydrogen storage systems (especially onboard vehicles),

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² See previous reports for background on the partnerships, the various technical areas, and issues that the partnerships have addressed (NRC, 2001, 2005, 2008, 2009, 2010, 2013). The background and introduction presented here derive and cite much from the previous Academies’ review (NRC, 2013).

³ The committee views precompetitive government R&D on technology as long-term, high-risk work with regard to its potential transition into commercial viability.

• Batteries and other forms of electrochemical energy storage,
• Electric propulsion systems,
• Hydrogen production and delivery, and
• Materials leading to vehicle weight reductions.

In each of these technology areas, specific research targets have been established, although some targets and time frames are undergoing revision. U.S. DRIVE oversight is provided by an Executive Steering Group (ESG), which is not a federal advisory committee as defined by the Federal Advisory Committee Act (FACA). It consists of the DOE’s Assistant Secretary for Energy Efficiency and Renewable Energy (EERE) and a vice-presidential-level executive from each of the Partnership companies. The DOE EERE efforts are divided between the VTO and FCTO. The Partnership collaborates with other DOE offices within EERE and outside of EERE, as appropriate, and other agencies such as the U.S. Environmental Protection Agency, the U.S. Department of Defense, and the U.S. Department of Transportation on safety-related activities.

The U.S. DRIVE partners presently include three automotive companies, five energy companies, two electric power companies, and the Electric Power Research Institute, with the DOE providing the federal leadership.⁴ Several associate members are also associated with the technical teams. The Partnership does not itself have a budget or conduct or fund R&D, but each partner makes its own decisions regarding the funding and management of its projects (see Chapters 1 and 2 for more detailed discussion of the organization of the Partnership).

This Summary provides overall comments and a brief discussion of the technical areas covered more completely in this report and presents the committee’s main findings and recommendations.

OVERARCHING RECOMMENDATIONS

There are a number of issues that indicate to the committee that it is an opportune time for the Partnership to take stock of its strategic position and its focus. Significant technological advances are occurring in the private sector, for example, with the emergence of a variety of plug-in electric vehicles, with offerings of fuel cell vehicles, and with rapid advances in technology for autonomous vehicles. The U.S. petroleum import situation is changing rapidly, with the United States becoming much less dependent. In some cases, the technology targets are too near term for a precompetitive focus, and perhaps targets should be set for at least 2025, if not 2030, to develop those high-risk technologies that the private sector will not pursue. The Partnership is revisiting many of its technical targets. For hydrogen fuel cell vehicles, a critical barrier is the deployment of a hydrogen infrastructure, which is currently outside the precompetitive focus of the Partner-

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⁴ Note that Tesla was a partner until it withdrew from the Partnership in July 2016.

ship. Although the committee has avoided making budget recommendations, new targets and timelines and changes in emphasis or on new technologies may obviously affect the distribution of DOE funding, although that will have to be determined by DOE.

Progress and Barriers

Given that the Partnership exists primarily as a technical information exchange and serves as just one of the many inputs to DOE programs, where the budgets for all this activity reside, it is difficult to ascertain exactly which achievements are directly attributable to the Partnership. The Partnership points to the DOE FCTO/VTO Annual Merit Review for details on all its initiatives, where a wealth of valuable information can be found.

Nevertheless, significant progress has clearly been made since the National Research Council (NRC) Phase 4 review in the period 2011-2012 in many of the technical areas, including such areas as advanced combustion, hydrogen fuel cell durability and cost, and electric drive systems (motor, power electronics, and battery) and cost, the details of which can be found in Chapter 3. At the same time, market introduction of improved hybrid electric vehicles (HEVs) and BEVs, both by automotive manufacturers represented in U.S. DRIVE and others, indicates that much of this technology is migrating out of the precompetitive realm and into the marketplace. The HFCV, currently being introduced in limited numbers by foreign original equipment manufacturers (OEMs), and anticipated by 2020 by one U.S. OEM (GM⁵), is expected to follow a path to commercialization with its own unique challenges, including, for example, infrastructure development. Since the Partnership is exclusively dedicated to precompetitive R&D, it is important that, informed by the cradle-to-grave (C2G) studies, the portfolio of projects be regularly reviewed to ensure that the focus remains on precompetitive challenges and relevant technology enablers. The C2G studies are important to determine the full life-cycle impacts of different advanced vehicles and their fuel/energy sources (e.g., hydrogen, electricity, hydrocarbon fuels, etc.).

While some of the remaining challenges are purely technical, cost remains a formidable barrier for essentially all the technologies under development. The other notable barrier is the infrastructure challenge confronting hydrogen. Policy matters and deployment are by definition beyond the scope of the Partnership, but lack of infrastructure is arguably the biggest challenge to the widespread deployment of hydrogen fuel cell vehicles, and continued emphasis by DOE on infrastructure enablers as well as an implementation plan is vital, whether within the Partnership or not.

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⁵ See, for example, R. Truett, “Fuel Cell Puzzle Comes Together,” Automotive News, October 11, 2016, http://www.autonews.com/article/20161011/BLOG06/310119999/fuel-cell-puzzle-comes-together.

Adequacy and Balance

During the past few years, the DOE EERE budget devoted to hydrogen and fuel cell-related activities, which include both stationary and automotive applications, has remained stable at around $100 million per year, while the budget devoted to non-hydrogen-related vehicle technology has gradually increased. For the fiscal year 2016, hydrogen and fuel cell-related work was $101 million per year and the VTO funding was $310 million per year.

Much of the VTO funding is for electric drive vehicles, especially batteries. Part of the VTO funding is for technologies for medium- and heavy-duty vehicles. Since fuel cell vehicles are inherently electric vehicles, much of the work on electric drivetrain and improved batteries is equally applicable to both plug-in electric vehicles and HFCVs. While the $100 million devoted to purely hydrogen and fuel cell technologies is a much smaller share of the total EERE budget, it is still felt by the committee to be appropriate as a share of the overall effort for projects supporting U.S. DRIVE targets and goals. Within that overall effort, priorities for funding may shift among technical areas as technical challenges change. Furthermore, there is hydrogen-related work in other parts of DOE outside of EERE, for example, the Office of Basic Energy Sciences, the Office of Fossil Energy, as well as the Advanced Research Projects Agency-Energy.

Management, Strategy, and Priority Setting

Prior reviews of the U.S. DRIVE Partnership have been critical of both the target setting process and the decision-making process, due to the lack of an overall total vehicle systems analysis approach. Prior reviews have found that systems analysis has been applied very effectively at the subsystem or micro level, but that overall total systems analysis guiding high-level Partnership direction was lacking. The Partnership has taken steps to improve both of these processes. In 2015 the Partnership established a target setting task force (TSTF) that operates in concert with the vehicle systems analysis technical team and the new C2G analytical working group. The committee applauds the creation of the C2G working group and the TSTF, as well as the adoption of a more robust target setting process based on total system analysis. These recent changes in approach appear to address the criticisms of previous reviews and are most welcome.

Overall, the Partnership has an increasingly robust consensus process for developing goals and targets and for providing guidance and input to DOE to inform the management of relevant DOE projects, and this process benefits greatly from the recent addition of overall strategic analysis. However, the supervision of those projects and the decisions made within them are a DOE EERE responsibility and not that of the Partnership.

The Partnership points to the types of decisions that are made by the Partnership as being, for example, focused within the portfolio, such as a decision (by the ESG) to emphasize work on low-carbon fuels.

Given these limitations on the scope of decision making within the Partnership, particularly those due to FACA, the committee feels that the processes applied within the technical teams, and overall at the ESG and the Joint Operations Group level, are robust and appropriate, and that the Partnership has successfully fulfilled its mandate for technical information exchange.

Finding S-1 (2-1 in Chapter 2). The committee finds that the response to prior recommendations regarding management of the Partnership, particularly the creation of the target setting task force and the cradle-to-grave (C2G) working group, and the adoption of a portfolio-based strategy, are welcome improvements, and the Partnership is well managed. However, the increased engagement by the Executive Steering Group has improved from unacceptable to barely adequate. Furthermore, the Partnership currently regards the C2G working group as only a “temporary, task-specific” group.

Finding S-2 (3-43 in Chapter 3). The cradle-to-grave life-cycle analysis model provides a major step forward in the ability of the U.S. DRIVE to advise the industry and the Department of Energy on program and policy choices. This model provides the capabilities and insights that will give the Partnership a useful management tool and, with further development, a strategic and policy capability.

Recommendation S-1 (2-1 in Chapter 2). The Executive Steering Group should meet more regularly than annually, perhaps at least quarterly, and participate directly in the portfolio analysis and target setting process for revised 2020 and new 2025 goals. Furthermore, the recently published cradle-to-grave study on vehicle-fuel pathways and follow-on work by the target setting task force and cradle-to-grave working group should be used proactively and specifically to help shape the overall Office of Energy Efficiency and Renewable Energy portfolio, and the cradle-to-grave working group should be transitioned from temporary to permanent status.

Recommendation S-2 (3-32 in Chapter 3). The cradle-to-grave model should be continually updated and, where possible, tailored to improve its ability to support senior policy makers. Resources appropriate to this task should be provided. This updating will be an ongoing project, and the Partnership should consider upgrading the ad hoc working group to a technical team.

Finding S-3 (2-2 in Chapter 2). Given the reality that the Partnership does not direct or manage DOE-funded programs, overlaps with other DOE programs, and has no budget, there remains considerable ambiguity over the precise scope of the Partnership and its relationship with other DOE activities.

Recommendation S-3 (2-2 in Chapter 2). The Partnership is urged to provide more transparency and clarity regarding those Department of Energy projects deemed wholly or partly within the U.S. DRIVE portfolio and the achievements truly attributable to the Partnership.

Strategic Issues Looking Forward

Three trends have emerged since the NRC Phase 4 review of the Partnership took place that could have strategic implications in the future:

Recommendation S-4 (4-1 in Chapter 4). The Executive Steering Group should identify appropriate changes in Partnership focus to reflect the impact of new personal mobility models, shrinking opportunities to achieve the aggressive greenhouse gas goals, the transition of many candidate technologies into the competitive domain, and the significant infrastructure challenges in providing hydrogen at fueling stations at a competitive cost—in particular, while retaining the focus on precompetitive technology enablers.

ADVANCED INTERNAL COMBUSTION ENGINES AND EMISSION CONTROLS

As noted in NRC (2013), advanced combustion and emission controls for ICEs are important because ICEs for transportation systems are going to be the dominant automotive technology for decades, whether in conventional vehicles, HEVs, PHEVs, or biofuel or natural gas vehicles. There is still much opportunity to reduce the fuel consumption and environmental impact of ICE-powered vehicles, so it is important to keep an active research program in this area. Developing the enhanced understanding and tools to do this pushes the state of the art in all engineering sciences.

Finding S-4 (3-2 in Chapter 3). The advanced combustion and emissions control technical team (ACECTT) has established stretch efficiencies goals for 2020 for peak and intermediate engine loads for the three types of engine power train systems they expect to be most prevalent in the near term: hybrid applications, naturally aspirated engine systems, and downsized boosted engine systems. The ACECTT is also engaged in research activities in chemical kinetic development and promoting a more fundamental understanding of the interaction between fuel characteristics—such as Research and Motor Octane number, heat of vaporization, and so on—and different engine operating conditions. This work is aimed at facilitating the integration of advanced kinetically controlled combustion processes, that is, low-temperature combustion, as part of the engine’s operating map, which is considered a longer-term technology.

Finding S-5 (3-3 in Chapter 3). The ACECTT focus for both near- and longer-term research is centered on conventional four-stroke engine architectures. However, work on alternative engine architectures is taking place. Some of that work is under DOE funding, and claims are being made in the literature of potential efficiency and environmental impact improvements for these different engine architectures.

Recommendation S-5 (3-1 in Chapter 3). The advanced combustion and emissions control technical team should be proactive in seeking out and assessing data on the performance of alternative engine architectures that will allow benchmarking against those within their current research portfolio.

FUELS FOR INTERNAL COMBUSTION ENGINES

The committee was told that the VTO plans to “downselect” a specific spark ignition candidate fuel by 2017 and demonstrate an optimized kinetically controlled engine-fuel system by 2025. This is a very aggressive set of objectives. In the view of the committee, meeting the timing of the goals identified by DOE for advanced engine-fuel combinations, although well intended, will be difficult.

Although the current portfolio of projects will provide technical data to aid in making the selection, the process of choosing an optimized engine-fuel system will be a challenge. Each potential combination will have benefits and drawbacks. It is not too early in planning to identify the process and criteria for selecting an optimum system. In addition, outside the Partnership, DOE has established a Co-Optima initiative. Last, what are the plans for promoting the use of such an engine-fuel combination in commercial vehicles?

Finding S-6 (3-9 in Chapter 3). DOE has set an aggressive timeline for identifying an “optimized kinetically controlled” engine-fuel system. The Co-Optima program will presumably help in developing the data to establish such an optimized system, but DOE has not yet addressed how such a system would be implemented in the light-duty vehicle fleet.

Recommendation S-6 (3-2 in Chapter 3). The Department of Energy (DOE) should further explain how the Co-Optima program will lead to the introduction of an optimum engine-fuel system in commercial practice. The introduction of high-efficiency, low greenhouse gas (GHG) internal combustion engine technology into the marketplace may require fuel formulations that are different from today’s commercial fuels. Engine manufacturers will not introduce vehicles that utilize advanced combustion systems without the assurance that suitable fuels are available for the new combustion technology. Reaching consensus between the DOE’s Co-Optima program and U.S. DRIVE on the concept of an optimum engine and fuel is necessary, but not sufficient. A plan for introduction of advanced combustion systems and fuels designed to increase transportation energy efficiency and reduce carbon dioxide (CO₂) emissions is required.

FUEL CELLS

HFCVs have been in a development phase by the major automotive companies for decades. Their attractiveness when compared to conventional ICE technology is based on the direct conversion of chemical (hydrogen) to electrical energy via an electrochemical process and reduced environmental impact provided that the hydrogen is derived from “green” primary energy sources. The efforts to develop HFCVs by the major automotive companies have been significant, as is evident from the magnitude of the investments made by the individual automotive OEMs, the number of patents issued, and the engineering accomplishments to date. Notably, within this review period, a number of foreign OEMs (Toyota, Hyundai, and Honda) have either initiated membrane-based fuel cell vehicle sales or leases to the general public in the United States or have announced that vehicles will be available within the next few years. General Motors, Ford, and Fiat Chrysler, all three U.S. DRIVE Partnership members, do not currently have vehicle offerings, yet GM has been cited in the open literature as stating they

are “on track” to produce their Gen 2 HFCV by 2020.⁶ Recent activities by the aforementioned OEMs, foreign and domestic, demonstrate that HFCVs are in the late stages of development and are now ready for customer engagement, albeit at a modest level owing to limited production volume and hydrogen delivery and refueling infrastructure issues.

In addition to the infrastructure barrier, technical challenges remain before widespread market penetration and consumer acceptance of HFCVs are realized, but the current introduction of a limited number of HFCVs is encouraging. Such challenges have been outlined in prior Academies reviews (Phases 1 through 4) and though many have been resolved, meeting cost and fuel cell durability targets simultaneously remains the most critical barrier to overcome if HFCVs are to become viable, both technically and commercially. DOE is developing additional activities at the national laboratories with the creation of consortia that will help focus and coordinate the R&D.

Finding S-7 (3-16 in Chapter 3). Since the NRC Phase 4 review, Toyota, Hyundai, and Honda have made available within the United States a limited number of fuel cell vehicle sales or leases to the general public. U.S.-based OEMs, with significant input from the Partnership, although in different states of development, have advanced fuel cell technology to the point that at least one U.S. DRIVE Partnership OEM (General Motors) is anticipating a rollout of its fuel cell vehicle in 2020. The development and deployment of roadworthy fuel cell vehicles is a major accomplishment and one that will help to identify remaining technical, cost, manufacturing, and infrastructure challenges. Though the cars are still in the late stages of development, the fact that the cars have advanced to this point is due in part to R&D coordination by the Partnership and its prior organizations, as well as from decades of funding of pertinent research projects by the DOE and Partnership members.

Finding S-8 (3-17 in Chapter 3). With the U.S. OEMs in different states of fuel cell vehicle development, and with competitive dynamics emerging, selected Partnership (fuel cell) goals and targets are relevant to only some of the OEM members (e.g., platinum loadings). Furthermore, it appears that there is a fine line between what might be considered near- and long-term projects based on the state of development of a given OEM’s technology.

Recommendation S-7 (3-5 in Chapter 3). The Partnership should evaluate projects for their near-term or long-term potential impact and assign technology readiness levels to them. The Partnership should continually assess its process for

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⁶ See, for example, B. Snavely, “GM, Honda to make hydrogen fuel cells at Michigan factory,” USA Today, January 30, 2017, http://www.usatoday.com/story/money/cars/2017/01/30/general-motorshonda-fuel-cell-deal/97240096/ or R. Truett, “Fuel Cell Puzzle Comes Together,” Automotive News, October 11, 2016.

prioritizing projects and should continue to address the longer-term, precompetitive (lower technology readiness level) objectives.

ONBOARD HYDROGEN STORAGE

The mission of the hydrogen storage technical team is to “accelerate research and innovation that will lead to commercially viable hydrogen-storage technologies that meet the U.S. DRIVE Partnership goals.” Vehicle driving range and fueling time are important customer attributes for fuel cell vehicles. The objective is to achieve a driving range of at least 300 miles for a full range of light-duty vehicles and at the same time meet performance, packaging, cost, rapid fueling time, and safety requirements.

Finding S-9 (3-21 in Chapter 3). All the goals for onboard hydrogen storage have not been met, and basic scientific research has not produced an easy solution to date. Yet, onboard hydrogen storage is an issue for several technical teams and working groups beyond the hydrogen storage technical team, for example, the materials technical team, the fuel cells technical team, the hydrogen codes and standards technical team, and the hydrogen delivery technical team. As the technologies continue to mature, the need to merge activities can be expected to increase because vehicle performance parameters might be achieved through a wider range of options than gravimetric and volumetric hydrogen storage density alone.

Recommendation S-8 (3-9 in Chapter 3). The hydrogen storage technical team should increasingly work with the other technical teams even beyond those areas where overlap currently exists.

HYDROGEN

Regardless of the source of hydrogen, it is clear that for there to be the possibility of widespread penetration of HFCVs into the light-duty fleet, there must be the availability of hydrogen for refueling. Hydrogen production by natural gas reforming is currently a cost-effective option for near-term hydrogen requirements, and it also provides a pathway to reduced GHG emissions. To further reduce GHG emissions, the use of renewable sources of energy, such as biomass, wind, and solar, is required. Development of such technologies is the focus of the long-term R&D. However, delivery and dispensing of hydrogen is still prohibitively expensive and requires technological advances to meet the overall cost targets for the HFCV option to be viable in the future. Pressures of 700 bar for compressed hydrogen gas in onboard storage tanks is currently the accepted option for onboard storage. The delivery and dispensing of hydrogen needs to meet the corresponding requirements, that is, even higher pressure (e.g.,

875-900 bar) at the pump. Thus, the R&D focus has been to develop low-cost compression technologies and materials and concepts for high-pressure hydrogen storage and transport. There are several hurdles with this approach, and alternative new concepts need to be continuously developed.

While electricity infrastructure required for plug-in electric vehicles and related vehicle technology options already exist, hydrogen infrastructure is practically nonexistent. Therefore, market introduction of HFCVs faces a daunting challenge. Moreover, with ongoing improvements in engine and battery technologies, HFCVs will face increased competition, for example, with increasingly improved HEVs. The lack of hydrogen infrastructure can derail HFCV deployment. Some states, like California, Connecticut, and New York, along with companies like Toyota and Honda, are promoting infrastructure build-out by providing funding. But to date there are very few operating fueling stations to support the projected market for HFCVs. High station cost is an obvious barrier.

Finding S-10 (3-22 in Chapter 3). U.S. DRIVE does not have a cost target for dispensed hydrogen; it is instead considered within the scope of the U.S. DOE R&D program. The DOE cost target for dispensed hydrogen of less than $4/kg H₂ is based on its calculation of threshold cost.⁷ Since DOE calculated this cost in 2011, there have been changes in the base case values such as the fuel economy for hybrid electric vehicles.

Recommendation S-9 (3-10 in Chapter 3). The hydrogen threshold cost calculation, published by the Department of Energy in 2011, should be revised by taking into consideration the advances in competing hybrid vehicle technologies as well as any progress made with vehicular hydrogen fuel cells. This should be carefully assessed and addressed by the appropriate U.S. DRIVE teams as well as the Executive Steering Group to incorporate the implications in the Partnership plans.

Finding S-11 (3-29 in Chapter 3). Although industrial gas companies currently have the most experience with hydrogen production, delivery, and infrastructure, they are not core members of the Partnership; some of them serve as associate members of technical teams, but not on a consistent basis.

Recommendation S-10 (3-16 in Chapter 3). U.S. DRIVE should consider having industrial gas companies involved in hydrogen infrastructure activities as permanent members rather than as temporary associate members.

Recommendation S-11 (3-15 in Chapter 3). The Executive Steering Group should address issues (e.g., how will fueling stations be installed and by whom,

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⁷ Threshold cost is calculated so as to be competitive with other transportation options that are expected in 2020.

who will produce hydrogen, how will investments occur in fueling infrastructure without sufficient fuel cell vehicles on the road and vice versa, etc.) related to hydrogen infrastructure and assess U.S. DRIVE’s role to formulate an action plan to address the issues and barriers.

ELECTRIC PROPULSION AND ELECTRICAL SYSTEMS

The electric drive (consisting of an electronic motor and an electronic controller) is a critical part of electrified power trains for light-duty vehicles. Therefore, a key objective of the U.S. DRIVE Partnership is the development of technologies addressing the electric drive component cost, weight, and size to help expedite electrified power train market penetration. Several motor configurations and design variations are under investigation to address the high cost of rare earth magnets. Significant progress was reported by the Partnership in power electronics. This was achieved by using innovative packaging and integration of classic inverters and converters and also by exploring the use of wide bandgap (WBG) devices for automotive power electronic systems. Also, pursuing WBG devices with the vigor and intensity shown in the DOE programs is commendable due to the size, weight, and efficiency benefits of using these devices in electrified vehicles. Given the inherent cost advantage of gallium nitride (GaN) devices grown on silicon (Si) substrates compared with silicon carbide (SiC) on SiC substrates (due to the much higher cost of SiC compared to Si), it is expected that GaN will ultimately be preferred among these two competing technologies for automotive applications. Historically, SiC devices have been the focus of research for many years, as they possess higher voltage and temperature capabilities than GaN devices. Operating at these high levels of temperatures requires other circuit components to be also capable of these temperatures, which is cost prohibitive for automotive applications but not so for other cost-tolerant applications, such as for defense.

Finding S-12 (3-33 in Chapter 3). Only a few projects are exploring GaN, with the majority focusing on SiC. Given GaN’s potential cost advantage, it is expected to ultimately be the preferred choice for automotive applications.

Recommendation S-12 (3-20 in Chapter 3). The U.S. DRIVE Partnership should increase the focus on the advancement of gallium nitride technology in order to accelerate its readiness for commercial implementation.

ELECTROCHEMICAL ENERGY STORAGE

Improving electrochemical energy storage technologies, such as batteries, is needed for achieving the goals of the U.S. DRIVE Partnership. Batteries and supercapacitors are used in all electric drive vehicles including HEVs, PHEVs, BEVs, and HFCVs.

High cost remains the main impediment to significant market penetration of plug-in electric vehicles, which use large batteries. There is also a need to improve battery performance characteristics, that is, energy density, specific energy, operation at extreme temperatures, charging and discharging rates, cycle, and calendar life. These improvements in performance and cost reduction need to be realized while addressing the inherent safety issues associated with lithium batteries. Lithium-ion battery performance, cost, and safety are being addressed by DOE and other government entities, automotive OEMs, and battery manufacturers. DOE is exploring additional battery chemistries in order to surpass the performance and reduce the cost relative to lithium-ion batteries.

Finding S-13 (3-36 in Chapter 3). After a 20-year gap, a new set of energy storage goals and targets for the various electric vehicles was established in 2012. These targets are to be realized in the year 2020. This was a very positive step; however, all of the goals and targets are not in one place and there are several inconsistencies in the target values in various publications. It may be time to revisit the goals and targets given the advances in battery technology and vehicle implementation in the last 4 years.

Recommendation S-13 (3-23 in Chapter 3). U.S. DRIVE should establish a single, authoritative website for energy storage targets and goals for the various electric vehicle applications that is prominently and easily accessible to all. The dates that targets and goals were set or reviewed without change should be provided. The site should provide a roadmap of energy storage needs for several (rolling) decades into the future for use by research organizations and investigators for various applications and differing time frames.

GRID IMPACTS OF ELECTRICITY AS AN ENERGY SOURCE FOR VEHICLES

The convenience, affordability, and environmental impacts of electric energy have become an important consideration for the U.S. DRIVE Partnership. The environmental and energy security benefits from plug-in electric vehicles will increase in proportion to their use, commonly measured in electric vehicle miles traveled. And so, the availability and cost of recharging options weighs importantly in consumer decisions to purchase and use plug-in electric vehicles. Hydrogen fuel cell vehicles also rely on the electric grid, since the electrolysis of water could be used to produce hydrogen fuel. In addition, these vehicles could serve as a backup electric supply with a typical automotive power train, about 70 kW, able to serve a small cluster of homes.

Finding S-14 (3-38 in Chapter 3). The electric grid is beginning a period of disruptive change brought on by (1) technological opportunity, especially in micro-

electronics, deep learning, and robotics; (2) the global need to reduce the carbon emissions from electricity production; (3) marketplace demand for new and more efficient energy services; and (4) threats from outsiders to the security of a more automated grid linked to external devices. As a consequence, the electric grid will continue to evolve in ways that are not predictable to either the incumbents or the disruptors. State regulatory authorities will shape the pace and direction of this transition to a greater extent than the federal government.

Recommendations S-14 (3-25 in Chapter 3). The U.S. DRIVE partners should closely monitor the evolution of the electric grid to understand how (or whether) vehicle design can enable effective participation in the emerging electric marketplace in a way that increases the market share of nonpetroleum vehicles such as hydrogen fuel cell vehicles and (possibly) battery electric vehicles.

STRUCTURAL MATERIALS

As noted and discussed in Taub and Luo (2015), a major approach for improving vehicle efficiency, and thus fuel economy, is reducing the vehicle mass. A midsize family car weighs about 1,450 kg, and it takes a weight reduction of approximately 150 kg, or 10 percent, to achieve a 3 to 6 percent improvement in fuel economy. Following the global oil crisis of the 1970s, the weight of automobiles decreased consistently for about one decade. This was followed by a period of stable oil prices and, in the North American market, a shift to larger and heavier vehicles. Since the 1990s, engineering improvements in vehicle structural efficiency have continued, but the improvements have been offset by increased safety features and other consumer-driven content, such as convenience features and infotainment systems. More recently, higher fuel economy standards are being adopted worldwide, and the newest vehicle models are exhibiting weight reductions of 5 to 10 percent or more.

Finding S-15 (3-40 in Chapter 3). The U.S. DRIVE materials technical team (MTT), like the FreedomCAR and Fuel Partnership before it, has adopted a stretch goal of 50 percent reduction in vehicle weight (versus 2002 comparable vehicles) with equal affordability (emphasis added). Previous NRC (2010, 2013) committees found this goal to be unrealistic. The present committee agrees with that assessment. Further, during this review, the MTT reported a revision to the target by setting the comparator as a 2015 vehicle. The committee feels that this makes the target even more unrealistic.

Finding S-16 (3-41 in Chapter 3). The committee was pleased to see the MTT reported adoption of a midterm target for 2020 of an 18 percent weight glider reduction to be achieved at <$11/kg saved (<$5/pound) saved while maintaining equal vehicle-level performance (crash; noise, vibration, and harshness; durabil-

ity; reliability; and recyclability).⁸ However, the 2016 DOE Annual Merit Review referred to a 30 percent reduction by 2022 relative to a 2012 baseline. This is not realistic given the 2020 target. When designing a new vehicle, the options available for weight reduction are compared with other fuel economy improvement solutions including increased power train efficiency, vehicle electrification, decreased tire rolling resistance, and improved aerodynamics. It appears to be more appropriate for the Partnership to set a long-term target for weight reduction, in a similar manner.

Recommendation S-15 (3-29 in Chapter 3). U.S. DRIVE should set the long-term target for the cost of weight reduction to be consistent with the long-term cost targets for the other technical teams. The committee also recommends continuing the practice of setting midterm targets. In doing so, it is important for all Department of Energy and U.S. DRIVE sources to reference a consistent set of targets.

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⁸ The glider is the vehicle structure excluding the power train. Historically, weight reductions are easier to achieve in that part of the vehicle.