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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report 3 Vehicle Subsystems The long-range goals of the FreedomCAR and Fuel Partnership—to transition to a transportation system that uses sustainable energy resources and produces minimal criteria or net carbon emissions on a life-cycle or source-to-wheels basis—are extremely ambitious. The difficulties are compounded when the additional constraints associated with the Partnership are imposed: energy freedom, environmental freedom, and vehicle freedom. These goals and associated constraints effectively eliminate the continued simple evolution of the gasoline-fueled internal combustion engine (ICE) vehicle as a possible answer. “Sustainable energy resources” and “energy freedom” both suggest non-petroleum-based alternative fuels or electricity. The emphasis on “net carbon emissions” and “environmental freedom” suggests that carbon dioxide (CO2) and other emissions from the production and consumption of alternative fuels or electricity should be reduced, through highly efficient processes, to minimize adverse environmental effects. Finally, “vehicle freedom” implies that the fuel and onboard energy conversion systems should not limit the options and choice that buyers expect to have available in their personal vehicles. These goals, if attained, are likely to require new transportation energy carriers (fuel[s] and/or electricity) utilized in more efficient power plants in lighter vehicles having reduced power requirements and equivalent utility and safety. This chapter discusses the vehicle systems technology areas that the Partnership is addressing in its research and development (R&D) programs, which include the following: (1) advanced combustion, emission control, and fuels for ICEs; (2) fuel cells; (3) hydrogen storage on the vehicle; (4) electrochemical energy storage or technologies for storing electricity onboard a vehicle; (5) electrical propulsion systems; and (6) materials for reducing the weight of the vehicle. The
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report reader is referred to the presentations from the Partnership to the committee on the various technical areas: these can all be found in the project’s public access file, available through the National Academies Public Access Records Office. Chapter 4 will address issues associated with hydrogen and biomass-based fuels. ADVANCED COMBUSTION, EMISSIONS CONTROL, AND HYDROCARBON FUELS Introduction Steady progress is being made in the advancement of power plants that rely on energy carriers other than liquid hydrocarbon (HC) fuels. However, one unique characteristic of mobility applications is that the energy being supplied to the power plant needs to be carried around with the vehicle. As weight and volume are important parameters in vehicle design and function, it is critical to have the highest possible energy per unit of mass and per unit of volume within the vehicle’s fuel system. Here, the fuel system includes all aspects of carrying the energy on the vehicle—that is, the fuel tank or containment system (battery pack, or hydride material) and supporting structures are included in this weight and volume assessment. On this basis, liquid HC fuels are very effective energy carriers for mobility systems. Using the metrics of energy density (watt-hour per liter [Wh/L]) and specific energy (watt-hour per kilogram [Wh/kg]) of a vehicle’s complete fuel system highlights differences compared to conventional vehicles and the challenges of implementing alternative energy carriers to mobility systems. When one makes these comparisons, it is important to consider not only the energy density of the vehicle’s fuel system but also the efficiency of converting the energy carried on the vehicle to motive power (power that causes motion) at the wheels of the vehicle. Liquid HC fuels have very high energy density and specific energy relative to batteries and hydrogen systems, but the efficiency of the ICE is typically lower than that of systems using electric motors and power electronics and fuel cell systems. Thus the concentrated effort to improve the engine and power-train efficiency is easily understood. However, the energy density and specific energy of liquid HC fuels is so great that even considering these efficiency differences, a typical vehicle carrying a liquid HC will have significantly higher capability than that of an electric or hydrogen-powered vehicle in terms of deliverable work to the wheels per unit of mass and volume of vehicle energy storage onboard the vehicle. For example, comparing an ICE with an efficiency of 40 percent to a hydrogen fuel cell vehicle (HFCV)1 with an overall power-train efficiency of 65 percent results in a work capacity of the liquid-fueled ICE vehicle that is approximately 1 It has been assumed that the 2015 hydrogen storage targets of 1,300 Wh/L and 1,800 Wh/kg have been met in performing this analysis.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report 4.5 times higher per unit of volume of “fuel storage” and approximately 4 times higher per unit of mass of “fuel storage” than those of the HFCV. It seems likely that there will be certain applications, such as extended operation at higher loads or very long range transport, that will favor using a liquid HC as the on-vehicle energy carrier. In addition, as new power plants with alternative energy carriers are developed, produced, and introduced into the market, there will be a significant time delay associated with their market penetration. As noted in Chapter 1, in the United States the vehicle fleet turnover in recent years is estimated to be about 15 years.2 Consequently the turnover time for completely new vehicle architectures to achieve significant market penetration will be measured in multiple decades (Bandivadekar et al., 2008; Weiss et al., 2000). During this transition the dominant power plant for mobility systems will continue to be ICE vehicles fueled with a hydrocarbon fuel (e.g., gasoline, diesel fuel, or biofuel).3 Consequently, it is important to maintain an active ICE and liquid fuels R&D program at all levels: industry, government laboratories, and academia, to expand the knowledge base to enable the development of technologies that can reduce the fuel consumption of transportation systems powered by ICEs. The near-term introduction of such technologies into existing production facilities will reduce the growth in transportation petroleum use during a transition to alternative power plants and power-train configurations. This is the focus of the Partnership’s advanced combustion and emission control (ACEC) technical team. The overarching goals, technical targets, and program structure of the ACEC technical team are basically the same as reported in the Phase 2 review of the program (NRC, 2008). The technical team has established the following technical engine target goals for 2010: Engine peak brake thermal efficiency (BTE): 45 percent Nitrogen oxides (NOx) and particulate matter (PM) emissions: Tier 2 Bin 5 (T2B5) Power-train cost: <$30/kW The general focus of the ACEC technical team’s work to achieve these targets continues to be lean-burn, direct-injection engines for vehicles fueled by diesel, gasoline, and biofuel or other alternative fuels, provided appropriate carbon emission mitigation is accomplished during their production. Within this broad area specific foci include the following: 2 Of course, this can vary depending on the economic expectations of consumers, who may change their behavior depending on the state of the economy. 3 In this discussion, hybrid vehicles are included as ICE power trains fueled with a liquid HC fuel. In the hybrid, the energy source is the HC fuel; the hybridization allows more optimal use of the engine and vehicle power-train system.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report Low-temperature combustion (LTC) Control Expanding the load range Coupling to fuel characteristics Transient operation Combustion mode switching Aftertreatment Diesel particulate filter (DPF) modeling Lean NOx traps Selective catalytic reduction (SCR) NOx reduction Potential catalyst identification for HC NOx catalysis Tool development Improved computational fluid dynamic (CFD) capabilities Improved diagnostics capabilities Comparison of CFD and experiment In this quest, all aspects of the engine and power train are under investigation. Individual subsystems and processes, such as injection systems, turbochargers, combustion chamber system optimization, the enhanced use of alternative combustion processes (such as low-temperature combustion) and exhaust-gas energy recovery, are actively being investigated. All aspects of the engine operation are being pursued. The electrification of auxiliaries, matching the engine operation to the fuel characteristics, and reducing friction through advanced lubricants are subjects of investigation. Advanced sensors and total power-train system optimization will be enablers for integrating alternative combustion processes into the engine operational map. This will enable optimal matching of the engine and the exhaust aftertreatment systems. In addition, improvements in the aftertreatment systems, particularly lean NOx systems, will be a critical component of meeting the technical team’s targets. Current exhaust-gas aftertreatment systems increase fuel consumption. More effective exhaust emission systems will have a double benefit. They will reduce the fuel consumption associated with their use, and they will allow the engine to be tuned differently with an attendant increase in efficiency. Hydrogen-fueled ICEs have also been investigated. Such technology could allow a broader use of hydrogen within the transportation system and thus allow the implementation of a hydrogen infrastructure while chemical-electric conversion power plants penetrate the market. However, the hydrogen-fueled ICE vehicle will have similar energy density and specific energy constraints as those of an HFCV, described above. In all these endeavors, the key hurdle continues to be detailed fundamental understanding of the chemical, thermal, and physical processes taking place within the power train and combustion system. Good progress is being made by the ACEC technical team in meeting the technical targets. A peak thermal efficiency for an ICE of 43 percent has
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report been achieved. A peak engine efficiency of 45 percent has been achieved for a hydrogen-fueled ICE. The operational range for LTC has been enhanced through active cylinder valve actuation and intake boosting. The technical team reported achieving engine loads of 16 bar (1.6 MPa) indicated mean effective pressure (IMEP) with homogeneous charge compression ignition (HCCI) using a combination of exhaust-gas recirculation (EGR) and intake boost. Additional sensing devices are being developed and integrated into the engine cylinder and power train that facilitate better control of the in-cylinder conditions and power-train energy flow management, which is a necessity for the integration of LTC operation into the engine map. To maximize the gains in reducing fuel consumption and emissions, every aspect of the ICE power train and aftertreatment system must be optimized for every operating condition in the vehicle’s duty cycle. This requires accurate control and manipulation of all engine control parameters for each operating condition. The fundamental research being performed by the ACEC technical team is generating the knowledge base necessary for the identification of how to optimize the combustion process at any operating condition. This understanding is being incorporated into detailed CFD simulations, which in turn accurately replicate the experimental results with minimum adjustable numerical tuning. The predictive capabilities of the current CFD codes are very good. In fact, the codes are now being used to guide experiments and, more importantly, to identify the combination of engine control parameters that will optimize the engine and power-train performance at different operating conditions, including the use of different combinations of fuels. This is a significant technical accomplishment. The simulation currently being used is KIVA III, developed by the U.S. Department of Energy (DOE). KIVA is an open-source-code program, which allows researchers to incorporate new understanding directly into the code for any aspect of the thermophysical processes occurring within the engine: for example, improved kinetic schemes for different fuel types, or new submodels that more accurately represent liquid fuel-combustion chamber surface interactions can be implemented into the code and then exercised for more detailed predictions of combustion results. However, KIVA III is more than 10 years old and lacks important, modern numerical technologies such as parallel computing. Having an up-to-date, open-source-code CFD program for researchers to use is a critical aspect of achieving the improvement potential of the ICE and aftertreatment power trains. To conduct such a program successfully requires close coordination among industry, government laboratories, and academia. The ACEC technical team continues to do a good job with this close coordination. The organizational structure of the team’s activities involves memoranda of understanding (MOU) between companies and government laboratories, working group meetings, regular intergroup reviews, and an annual peer-reviewed research meeting. The technical team’s responses to the recommendation of the previous review were good (DOE, 2009c).
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report The energy companies continue to be engaged, and the program of Fuels for Advanced Combustion Engines (FACE), organized under the Coordinating Research Council (CRC), is supplying an important database on the impact of fuel characteristics on engine-emission processes and alternative combustion process facilitation. The technical team has had difficulty specifically addressing its cost target. The team has assumed that the base engine cost will be $20/kW, and the incremental cost for the technology improvements, which includes enhanced aftertreatment, will be $10/kW. The team has not been able to confirm these estimates with public domain data. Consequently, it has adopted a strategy of determining the technical feasibility of the power train and aftertreatment system, and from there it will work on reducing costs by system improvements (i.e., reduce engine-out emissions, maximizing use of LTC, improving aftertreatment robustness to poisons and thermal degradation, reducing precious metal content). Funding The FY 2009 funding level for the ACEC technical team was $25.4 million, with the requested level for FY 2010 being $27 million: the funds appropriated for FY 2010 were $34 million. A breakdown of how the FY 2009 funding was dispersed among different organizations and technologies is shown in Figure 3-1. Adjustments and New Issues Since the National Research Council’s (NRC’s) Phase 2 review of the FreedomCAR and Fuel Partnership research program (NRC, 2008), changes in the country’s energy situation have occurred. The biofuels program has grown significantly. Estimates that up to 30 percent of U.S. liquid HC energy could be displaced by domestically produced biofuels have appeared in the literature.4 A genetically modified alga has attracted attention as a way to enhance the recycling of power plant’s CO2 emissions into a viable transportation fuel.5 The prospect of enhanced electric storage capacity has spurred the interest in plug-in hybrid electric vehicles (PHEVs). And, new, more stringent emission regulations for NOx and PM are scheduled to go into effect after 2010. All of these will impact the ACEC program. The ACEC technical team has acknowledged these changes and addressed them in its future plans. For example, the team is now engaged in fundamental combustion, emission, and kinetic studies of fuel derived from biomass. This work 4 See for example <http://www.altdotenergy.com/2009/02/sandia-gm-study-finds-large-scale-biofuel-is-sustainable/>. 5 See for example <http://www.exxonmobil.com/Corporate/energy_climate_con_vehicle_algae.aspx>.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report FIGURE 3-1 DOE advanced combustion engine research and development funding, FY 2009. SOURCE: Advanced Combustion and Emission Control Technical Team, Presentation to the committee, August 4, 2009, Southfield, Michigan. is aimed at understanding the fundamental changes that occur in ignition and emission-formation processes when different compounds, such as methyl esters that are found in biofuels, are used in the engine. The auto-ignition characteristics of many oxygenates, which occur naturally in biofuels, may offer advantages in expanding the range of low-temperature combustion or in expanding the optimal-efficiency regions in engine maps. The new emission standards will require that the vehicle emission target will need to be changed from Tier 2 Bin 5 to Tier 2 Bin 2. With this change will come new challenges in lean NOx aftertreatment, specifically mitigating the impact of sulfur poisoning and the associated degradation of the system performance that occurs with repeated desulfurization. Pending fuel economy standards will impact the vehicle mix as the on-the-road light-duty vehicle fleet turns over. Vehicles will become smaller and lighter. Thus the requirements for the engines and power trains will change. For example, the optimal engine for a PHEV will be significantly smaller than the engines typical in vehicles today. All of these changes will force an evolution in engine and power-train design, and consequently, the optimal power-train configuration, operating scenario, and fuel characteristics will also evolve. It is likely that the operational targets for the engine and power train will become more fluid. To the committee the foregoing considerations raised the question of whether system-level modeling could be used as a tool to evaluate the optimal power train, engine map, and fuel characteristics for different scenarios of vehicle, power train, and fuel mixes as the energy market and government regulation evolve.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report Recommendations Within the scope of the FreedomCAR and Fuel Partnership objectives, the funding level and work allocation for the continued development of the ICE and vehicle electrification seem appropriate. The ACEC technical team is doing a good job of maintaining a close and constructive working relationship with the stakeholders within the vehicle and energy community. It is critical for the technical team to maintain this collaboration and to look for ways to make it even stronger. The largest barrier to implementing advanced combustion, aftertreatment, and fuel technologies continues to be an insufficient knowledge base. Not only topic-specific understanding but also an understanding of the system-level interactions among the energy carrier, the energy release process, and the final emission cleanup are critical to continued improvement of the ICE power train.6 Continued close collaboration between the DOE and industry is necessary to allow newly developed technologies to transition into the industrial laboratories and to lead to the identification of new areas where enhanced understanding will be the most beneficial. Recommendation 3-1. The DOE should continue to support financially, be active in, and work to further enhance the collaborations among the national laboratories, industry, and academia in order most effectively to direct research efforts to areas where enhanced fundamental understanding is most needed to improve internal combustion engine and aftertreatment power-train performance. Recommendation 3-2. The DOE should continue to support the development and dissemination of the open-source-code computational fluid dynamics program KIVA. This tool is critical to integrating the new understanding of combustion and emission processes into a framework that allows it to be used to guide further research and identify fuel and engine operating conditions that will maximize reductions in fuel consumption over the entire operating range of the engine. Recommendation 3-3. The advanced combustion and emission control technical team should engage with the biofuels research community to ensure that the biofuels research which the team is conducting is consistent with and leverages the latest developments in the field of biofuels R&D. Recommendation 3-4. As the vehicle mix within the on-the-road light-duty vehicle fleet is likely to change with the implementation of the new fuel economy standards, the advanced combustion and emission control technical team should 6 As with the discussion in this section, hybrid and even plug-in hybrid power trains are included in the general classification of power train.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report interface with the system modeling technical team to make sure that their research programs are consistent with the changing demands for the optimal matching of the engine operational regimes, power management, and emission control that will be imposed on the internal combustion engine and hybrid power trains as the vehicle characteristics evolve. FUEL CELL SUBSYSTEM The fuel cell power-generation subsystem—containing the fuel cell stack and its balance of plant (BoP) consisting of the supporting air and fuel supply, thermal management, and controls—is arguably the most complex and challenging element of the entire hydrogen-fueled vehicle. As this technology is not yet fully developed, advancements are needed to meet the established efficiency, durability, lifetime, and cost targets. Although there are multiple approaches and engineering configurations under development by the original equipment manufacturers (OEMs; the automobile manufacturers), the burden of successfully accomplishing all advancements by any one organization is challenging, since much of the effort is high-risk and demands the assignment of critical resources. The Department of Energy has been proactive in providing fuel cell R&D support for the precompetitive scientific and engineering initiatives that are high-risk and enabling by providing funding to appropriate organizations such as universities, national laboratories, and the private sector. In many cases involving private-sector developers, R&D activities have the added benefit that the initiatives may lead to supply chain development. Such support has been available through the open solicitation process for nearly 8 years under this current program (FreedomCAR and Fuel Partnership) and a number of years prior in forerunner efforts such as the Partnership for the Next Generation of Vehicles (PNGV). The recent years have witnessed funding activities on fuel cells through multiple DOE organizations, including the Office of Energy Efficiency and Renewable Energy (EERE), Basic Energy Sciences (BES), the Small Business Innovation Research (SBIR) office, and more recently, with coordinated efforts with the National Energy Technology Laboratory (NETL) and the National Renewable Energy Laboratory (NREL). During this period, multiyear development programs have resulted in awards in support of fuel cell R&D efforts. In this program alone, the 8 years of funding has resulted in three cost-shared solicitations, resulting in many R&D contracts ranging from early programmatically focused efforts, to “go/no-go” milestone-based R&D. As a result of these programs, the core technology has advanced in such areas as fuel cell membranes, catalysts, operating modes, durability, lifetime, and the scientific evaluation of the factors limiting performance (e.g., gas quality), to name a few, while projected costs have continually decreased. The activities have been coordinated directly by the fuel cell technical team organized under the FreedomCAR and Fuel Partnership Executive Steering Group (ESG).
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report With respect to this review, since FY 2007 approximately $140 million (see Figure 3-2) has been appropriated in total to support the attainment of the fuel cell technology roadmap R&D (DOE, 2009a) objectives so that the Partnership’s chances of meeting the 2010 targets and the 2015 commercialization-readiness decision goal are enhanced. In order for this decision to be reasonably made (i.e., for the OEMs to decide by 2015 whether or not to initiate the next steps in the process of developing commercially viable vehicles based on a hydrogen fuel cell power-generation subsystem), much of the technology must be demonstrated to be operational in vehicles, or at least it must be significantly beyond laboratory scale. The attainment of, or progress toward, 2010 targets, as shown in Table 3-1 for selected fuel cell stack targets, can also be considered as a measure of progress of the program. The 2010 goals assessment is also a measure of ascertaining whether the R&D topics initially deemed to be the highest priority are still appropriate. In such cases, the DOE go/no-go decision-making process can be and is employed. The committee’s assessment is that the fuel cell technical team is well coordinated and is aligned with respect to the achievement of the goals and the longer-term, high-risk technology challenges, especially as the OEMs are now road testing prototype HFCVs. In light of the prior funding of this program as reported in this review period (2007-2009) and the advancements reported to the committee, at the time of this assessment the success of the program could have been put in jeopardy as a result FIGURE 3-2 Fuel cell budget, FY 2007 through FY 2009 (in millions of dollars per year). SOURCE: C. Gittleman (GM) and K. Epping Martin (DOE), “FreedomCAR Fuel Cell Technical Team,” Presentation to the committee, August 4, 2009, Southfield, Michigan.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report TABLE 3-1 Selected Fuel Cell Stack Targets and Progress Currenta 2010 Target 2015 Target Lifetime (hr) 1,977 5,000 Catalyst loading (mg/cm2) 0.15 0.30 0.15 Efficiency at 25% rated power 59%b 60% 60% Projected system costs (500,000 units produced per year; $/kW) ~60-70 45 30 Power density (W/L) without storage 224 325 Specific power (W/kg) without storage 406 325 a As reported to the committee at its August 4-5, 2009, meeting and by S. Satyapal, DOE, Hydrogen Program Overview, Annual Merit Review and Peer Evaluation Meeting, May 18, 2009, Washington, D.C. Available on the Web at <http://www.hydrogen.energy.gov/pdfs/review09/program_overview_2009_amr.pdf>. b Based on laboratory results from 3M and not full-size modules. of the zeroing of the primary budget line items related to the fuel cell development activities (in the FY 2010 administration’s budget request). If vehicle fuel cell development is to continue, such funding must remain intact and must be directed at the R&D that can help enable OEMs to develop the complete vehicle fuel cell power-generation subsystem. More specifically, as stated in its recommendations, the committee believes that technologies needed for vehicle fuel cell systems—and not just fuel cells for stationary, auxiliary power, or portable applications—should be pursued. Vehicle fuel cell requirements can be, and usually are, different and more challenging with respect to cost, reliability, and manufacturability when compared to the other nonvehicle applications. Furthermore, continued funding, especially of the high-risk concepts, will help facilitate next-generation technologies. The fuel cell stack is composed of layers of catalyzed proton-conducting membranes and electrode assemblies (MEAs) that react supplied hydrogen fuel with oxygen from the air. The MEAs must operate under all environmental conditions and have nearly turnkey operating characteristics. The continued refinement of prior generations of the MEAs is a major issue, as neither the earlier nor current versions have been shown to meet simultaneously the 2015 targets for performance, lifetime, reliability, and cost. However, significant progress has been and continues to be made, as evidenced by field and laboratory testing. Table 3-1 presents selected fuel cell stack targets, the current status, and the progress against such targets as reported by the DOE and the Partnership. Even with such data, complicating the comprehensive understanding of the status of the fuel cell technology is the fact that the OEMs have their own respective (proprietary) fuel cell activities and engineering approaches, which may or may not be synchronized with the DOE-funded development efforts. With that said, what has been reported is that, overall, the OEMs have shown increased power density for the fuel cell stack and BoP, while at the same time the packaging and operating modes have become quite sophisticated. Manufacturing aspects of the power-generation
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report System Controllers. System controllers need to control the vehicle in response to the driver’s commands. During acceleration an HEV or BEV should have the “feel” of conventional vehicles, although the high torque produced by electric motors, especially at low speed, is probably an advantage. The controller will also need to control regenerative braking to minimize energy drain from the battery or the fuel cell. It should be pointed out that there is little activity in this area of electrical systems in the Partnership, and this is justified in the committee’s view because technology development is in the “competitive areas” of each OEM. The exception to this is a remarkable drive for the compressor expander motor (CEM) of the air supply system for a fuel cell balance of plant as discussed below.21 Compressor Expander Motor for Fuel Cell Vehicles. The CEM project incorporates a high-speed drive (165,000 rpm) with a fairly low projected cost. At a production of 500,000 annual units, the projected cost of the CEM is $293 and the cost of the controller is $303, with a total cost of $705 including assembly ($31) and a markup (15 percent for the CEM and 10 percent for the controller). Information provided subsequent to the meeting shows that this is a system similar to a 100,000 rpm demonstration unit from Honeywell. Such speeds are certainly unusual in automotive electric motor applications but, if successful, are very useful for keeping the weight and volume of the system down. The motor is a permanent magnet brushless motor with 2 poles, thus requiring switching devices operating at a minimum of 2,750 hertz (Hz). This is based on a design at Honeywell for motors in excess of 200,000 rpm (requiring a minimum switching frequency of 3,333 Hz). Although the details of the motor and motor controller are proprietary, the motor controller and motor are reported to have efficiencies of greater than 90 percent and greater than 93 percent, respectively, for a combined efficiency near 85 percent, which is truly remarkable at such speeds and frequencies. The motor stator and motor controller can be liquid- or air-cooled, but the rotor must be air-cooled. The cost does not include the entire cooling system cost, as the cooling system is shared with the vehicle’s traction drive motor. Because of the critical importance of the CEM for HFCVs, the committee encourages continued support for further testing of this integrated subsystem—in particular with respect to noise and vibration as well as durability at conditions that can be expected in the automotive environment. In the opinion of the committee, this is the kind of stretch technology that is needed to reduce component size and material cost. 21 B. James (Directed Technologies, Inc.), “Mass Production Cost Estimation of Direct H2 PEM Fuel Cell Systems for Automotive Applications,” Presentation to the committee, October 26, 2009.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report Recommendations Recommendation 3-19. The Partnership should continue to focus on activities to reduce the cost, size, and losses in the power electronics and electrical machines. Recommendation 3-20. The Partnership should conduct a project to evaluate the effect of battery charging on lithium-ion battery packs as a function of the cell chemistries, cell geometries, and configurations in the pack; battery string voltages; and numbers of parallel strings. A standardized method for these evaluations should be developed to ensure the safety of battery packs during vehicle operation as well as during plug-in charging. Recommendation 3-21. The Partnership should consider conducting a project to investigate induction motors as replacements for the permanent magnet motors now almost universally used for electric propulsion. STRUCTURAL MATERIALS The challenge to the materials technical team is to generate a cost-neutral 50 percent vehicle weight reduction. The 50 percent weight reduction is critical to reaching FreedomCAR goals for fuel consumption and emissions. However, the target of no cost penalty for such a large weight reduction was unrealistic when set, and it remains unrealistic. A similar conclusion was stated in the Phase 2 report (NRC, 2008). What is missing at this juncture is a projection of what the cost penalty will likely be. For example, Berger et al. (2009) considered an aggressive weight-reduction program that yielded a 37 percent reduction (230 lb) in the Golf V body-in-white (BIW) which generated a 112 percent ($1,088) increase in cost. In other words, each 1 percent weight reduction in the BIW yielded a 3 percent increase in cost. Computer simulation was used to ensure that stiffness and crashworthiness requirements were met. An additional 50 percent weight savings of 115 lbs may be possible from downsizing brakes, suspension, engine, power train, and wheels and tires. But the associated cost savings are unlikely to make up the needed $1,000 plus. A full vehicle study is needed by FreedomCAR to assess the estimated overall cost penalty. Based on the above study, the outcome may be a penalty well over $500. What is also missing at this juncture is how the cost penalty changes as a function of the percent of weight reduction, assuming that the most effective mix of materials is used at each step in the weight-reduction process. This information will be needed in case the overall system-level targets for FreedomCAR need to be reset.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report Weight Reduction Calculus The impact of weight reduction on fuel consumption is well understood, and automotive OEMs have worked for many years to develop effective vehicle weight-reduction technologies. Consider, for example, a vehicle that is driven 12,000 miles per year having an average fuel economy of 25 mpg (0.04 gal/mi). The vehicle is then redesigned to achieve a 10 percent weight reduction using lightweight materials and/or better structural utilization. Fuel consumption would then be expected to be reduced by at least 6 percent, resulting in a new fuel economy of at least 26.6 mpg. The total of 480 gal used annually at 25 mpg would be reduced to 451 gal. For gas priced at $2.50/gal, the annual fuel costs of $1,270 at 25 mpg would be reduced by $72.50 due to the weight reduction. When computed over 6 years using an 8 percent discount rate for future savings, the resulting net present value (NPV) for the redesign is $335. Thus, there would be an NPV incentive of more than $100 to the buyer if the one-time, up-front added material costs were under $200. This is an example of the value of developing weight-reducing technologies not only to the entire industry, but to the nation as well. For example, if each passenger car in the United States was reduced in weight by 10 percent, the expected annual savings in fuel would be more than 4.5 billion gallons, based on the 2006 vehicle fuel usage statistics. There would be large additional savings in societal value resulting from reduced pollution and reduced dependence on foreign oil that are not reflected in consumer (commercial) value of $289 computed above. Also, there does not need to be a trade-off between increased fuel economy and safety. Mass reduction is an important means of improving fuel economy. But mass is not the same as size, and with efficient designs, low-mass cars can be made safe by improving crash-management design and reducing the frequency of accidents through improved accident-avoidance systems in vehicles and on highways. Mass Decompounding A weight-reduction process known as mass decompounding can be utilized when brakes, suspension, and power train can be redesigned to gain secondary weight savings as a result of the primary weight savings made in the structure through the use of lightweight materials. A lighter vehicle can perform equally well with smaller brakes, a less hefty suspension, and a smaller engine. During the past year, the materials technical team arrived at a useful rule of thumb in which 1.0 to 1.5 lb of secondary weight savings should be achievable for each 1 lb of primary weight saved, provided that the entire vehicle can be redesigned to take advantage of the savings. The relationship for the amount of secondary weight savings was determined from an analysis of teardown data from two vehicle databases by the materials technical team. If it is assumed that each 1.0 lb of lightweight material generates 1.25 lb of secondary weight savings on average, then a current vehicle weighing
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report 3,000 lb will require 667 lb of primary weight savings to meet the 50 percent weight reduction goal of 1,500 lb. Magnesium Power-Train Components The targets for the project on magnesium power-train components have been to replace aluminum components with magnesium for a minimum weight savings of 15 percent and a cost penalty of less than $2.00 for each pound saved. This project was completed in September 2009. The mass reduction achieved was 29 percent for the magnesium components and 7.8 percent for the engine subsystem, which exceeded the weight-savings goal. The cost penalty was found to be $3/lb at current magnesium prices. Although over the cost target, the outcome was judged as demonstrating that magnesium was both technically feasible and potentially cost-effective in these applications. Polyolefin Feedstock Cost has been a limiting factor in the use of commercial carbon-fiber-reinforced composites in the design of automotive structures and body panels. Importantly, the materials technical team has shown that major cost savings appear possible through the use of polyolefin for the feedstock in making carbon fibers.22 As with all lightweight materials applications, the trade-offs between cost and weight will need to be reevaluated as the price of oil changes. If the price of oil doubles, the cost of polyolefin will increase significantly, since polyolefin comes mostly from oil or perhaps natural gas. If the price of oil doubles, for example, the incentive to use carbon fibers in cars will increase because of the reduction in weight, but the cost of the polyolefin and therefore the carbon fiber will also increase. The DOE needs to understand the trade-offs there. Recycling End-of-Life Vehicles New materials present challenges to recycling. ANL is developing a one-fifth scale pilot operation to assess how to recover residual metals and polymers from the residue from shredders. A second pilot operation is to begin in the first quarter of 2010 to evaluate the recycling of polyurethane foams by converting them to polyols. The FreedomCAR and Fuel Partnership also needs to consider how to recycle carbon-fiber-reinforced composites including carbon-fiber hydrogen tanks. 22 See <http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2009/light-weight_materials/lm_05_warren.pdf>.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report Response to the Phase 2 Recommendations A recommendation from the Phase 2 report (NRC, 2008, p. 9) is as follows: Recommendation. The materials research funding should largely be redistributed to areas of higher potential payoff, such as high-energy batteries, fuel cells, hydrogen storage, and projects associated with infrastructure issues. However, materials research for projects that show a high potential for enabling near-term, low-cost mass reduction should continue to be funded. The response of the Partnership was as follows:23 Strategic lightweighting is an important enabler for reducing fuel consumption. We recommend that lightweighting materials research funding not be redistributed to support other technology areas. We agree that materials research for projects that show a high potential for enabling near-term, low-cost mass reduction should continue to be funded. Recommendations The materials needed to make the required weight reductions—high-strength steels, aluminum, titanium, magnesium, and fiber-reinforced composites—are available. The key issue is not improving their performance but getting the weight reductions needed at an acceptable cost. The structural materials efforts and budget should reflect this reality. The resources required in the future may be less or more if major pilot programs are needed. Systems analysis is an approach that can highlight where critical cost reductions are needed. The polyolefin feedstock is a good example of what can be achieved. The high cost of aerospace-quality carbon fiber is a major impediment to achieving cost-effective compressed hydrogen storage. Recommendation 3-22. The materials technical team should develop a systems-analysis methodology to determine the currently most cost-effective way for achieving a 50 percent weight reduction for hybrid and fuel cell vehicles. The materials team needs to evaluate how the cost penalty changes as a function of the percent weight reduction, assuming that the most effective mix of materials is used at each step in the weight-reduction process. The analysis should be updated on a regular basis as the cost structures change as a result of process research breakthroughs and commercial developments. 23 See J. Quinn (GM) and J. Carpenter (DOE), “Materials Tech Team Peer Review Report,” Presentation to the committee, August 4, 2009, Southfield, Michigan.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report Recommendation 3-23. The magnesium castings study is completed, and no further technical effort is anticipated by the Partnership as recommended in the Phase 2 report. However, magnesium castings should be considered in completing the cost reduction recommendation listed above. Recommendation 3-24. Methods for the recycling of carbon-reinforced composites need to be developed. REFERENCES Anderson, B., and I. Wade, 2001. Metal resource onstraints for electric vehicle batteries, Transportation Research Record D 6: 297-324. ANL (Argonne National Laboratory). 2009. Technical Assessment of Cryo-Compressed Hydrogen Storage Tank Systems for Automotive Applications. Report ANL/09-33, by R. K. Ahluwalia, T. Q. Hua, J.-K. Peng, Argonne National Laboratory, Argonne, Illinois; S. Lasher, K. McKenney, and J. Sinha, TIAX LLC, Cambridge, Massachusetts. Argonne, Ill.: ANL. Federal Grant Number DE-ACO2-06CH11357. Available on the Web at <http://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/cyro_compressed_auto.pdf>. Bandivadekar, A., K. Bodek, L. Cheah, C. Evans, T. Groode, J. Heywood, E. Kasseris, M. Kromer, and M. Weiss. 2008. On the Road in 2035: Reducing Transportation’s Petroleum Consumption and GHG Emissions. Report No. LFEE 2008-05 RP (July). Cambridge, Massachusetts: MIT Laboratory for Energy and the Environment. Berger, Lutz et al., 2009. “Super LIGHT CAR—the Multi-Material Car Body.” Presented at the 7th European LS-DYNA Conference. Available on the Web at <http://www.dynalook.com/european-conf-2009/B-V-03.pdf>. Department of Energy (DOE). 2009a. Hydrogen, Fuel Cells and Infrastructure: Multi-Year Research, Development and Demonstration Plan. DOE/GO-102003-1741. Washington, D.C.: U.S. Department of Energy, Energy Efficiency and Renewable Energy (original edition, 2004; revised April 2009). Available on the Web at <http://www.eere.energy.gov/hydrogenandfuelcells/mypp/>. DOE. 2009b. Hydrogen Program. “Announcement for H Prize.” Available on the Web at <http://www.hydrogen.energy.gov/news_h-prize_administrator.html>. DOE. 2009c. Actions and Evidence Report, April 2. Submitted to the National Research Council (NRC) Committee on Review of the FreedomCAR and Fuel Research Program, Phase 3, documenting responses by DOE to recommendations in the Phase 2 report [see NRC, 2008]. DOE. 2009d. 2009 Annual Progress Report, DOE Hydrogen Program. DOE/GO-102009-2950 (November). Washington, D.C.: Office of Energy Efficiency and Renewable Energy. Available on the Web at <http://hydrogendoedev.nrel.gov/pdfs/progress09/2009_doe_hydrogen_program_annual_progress_report_cover.pdf>. El-Rafaie, A., and F. Johnson. 2009. “Scalable, Low-Cost, High Performance IPM Motor for Hybrid Vehicles.” Presentation at the DOE Annual Merit Review, May 22. Available on the Web at <http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2009/advanced_power_electronics/ape_08_elrefaie.pdf>. Howell, D. 2009. Annual Progress Report for 2008, Energy Storage Research and Development (January). Washington, D.C.: U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy. Available on the Web at <http://www1.eere.energy.gov/vehiclesandfuels/pdfs/program/2008_energy_storage.pdf>. James, B., and J. Kalinoski. 2009. “Mass-Production Cost Estimation of Automotive Fuel Cell Systems.” Presentation at DOE 2009 Annual Merit Review, May 21, Arlington, Virginia. Available on the Web at <http://www.hydrogen.energy.gov/pdfs/review09/fc_30_james.pdf>.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report Kim, G., and K. Smith. 2008. “Three-Dimensional Lithium-Ion Battery Model.” 4th International Symposium on Large Lithium Ion Battery Technology and Application, Tampa, Florida, May 12-14. NREL/PR-540-43166. Available on the Web at <http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/43166.pdf>. Nozawa, N., T. Maekawa, S. Nozawa, and K. Asakura. 2009. Development of Power Control Unit for Compact-Class Vehicle, SAE 2009-01-1310, April. NRC (National Research Council). 2008. Review of the Research Program of the FreedomCAR and Fuel Partnership, Second Report. Washington, D.C.: The National Academies Press. Rogers, S. 2009. “Advanced Power Electronics and Electric Machines.” Presentation at the DOE Annual Merit Review, May 21. Available on the Web at <http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2009/advanced_power_electronics/ape_0_rogers.pdf- 916.8KB> Satyapal, S. 2009. “Hydrogen Program Overview.” DOE Annual Merit Review and Peer Evaluation Meeting, May 18. Available on the Web at <http://www.hydrogen.energy.gov/pdfs/review09/program_overview_2009_amr.pdf>. Sinha, J., S. Lasher, and Y. Yang. 2009. “Direct Hydrogen PEMFC Manufacturing Cost Estimation for Automotive Applications.” Presentation at the DOE 2009 Annual Merit Review, May 21, Arlington, Virginia. Available on the Web at <http://www.hydrogen.energy.gov/pdfs/review09/fc_31_sinha.pdf>. Taylor, J. 2009. “Development, Test and Demonstration of a Cost-Effective, Compact, Light-Weight, and Scalable High Temperature Inverter for HEVs, PHEVs, and FCVs.” DOE Annual Merit Review and Peer Evaluation Meeting, May 21. Available on the Web at <http://www1.eere.energy.gov/vehiclesandfuels/pdfs/merit_review_2009/advanced_power_electronics/ape_07_taylor.pdf>. TIAX. 2009. Technical Assessment of Compressed Hydrogen Storage Tank Systems for Automotive Applications. Report to United States Department of Energy, Office of Energy Efficiency and Renewable Energy; Hydrogen, Fuel Cells and Infrastructure Technologies Program; Part 1 (Volume 1), December 10. Federal Grant Number: DE-FC36-04GO14283, Stephen Lasher, Kurtis McKenney, and Jayanti Sinha, TIAX LLC, Cambridge, Massachusetts, Reference: D0268; Rajesh Ahluwalia, Thanh Hua, and J-K Peng, Argonne National Laboratory. Weiss, M. A., J.B. Heywood, E.M. Drake, A. Schafer, and F.F. AuYeung. 2000. On the Road in 2020: A Life-Cycle Analysis of New Automobile Technologies. Cambridge, Massachusetts: MIT Laboratory for Energy and the Environment. Xu, J., H.R. Thomas, Rob W. Francis, Ken R. Lum, Jingwei Wang, Bo Liang. 2008. A review of processes and technologies for the recycling of lithium-ion secondary batteries, Journal of Power Sources 177 (2008) 512-527.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report ANNEX TABLE 3A-1 Technical System Targets: Onboard Hydrogen Storage for Light-Duty Vehicles Storage Parameter Units 2010 2015 Ultimate System Gravimetric Capacity Usable, specific-energy from H2 kWh/kg 1.5 1.8 2.5 (net useful energy/max system mass)a (kg H2/kg system) (0.045) (0.055) (0.075) System Volumetric Capacity Usable energy density from H2 kWh/L 0.9 1.3 2.3 (net useful energy / max system volume) (kg H2/L system) (0.028) (0.040) (0.070) Storage System Costb $/kWh net 4 2 TBD (and fuel cost)c ($/kg H2) (133) (67) $/gge at pump 2-3 2-3 2-3 Durability/Operability Operating ambient temperatured °C −30/50 (sun) −40/60 (sun) −40/60 (sun) Min/max delivery temperature °C −40/85 −40/85 −40/85 Cycle life (1/4 tank to full)e Cycles 1000 1500 1500 Cycle life variationf % of mean (min) at % confidence 90/90 99/90 99/90 Min delivery pressure from storage system; FC = fuel cell, ICE = internal combustion engine Atm (abs) 4FC/35 ICE 3FC/35 ICE 3FC/35 ICE Max delivery pressure from storage systemg Atm (abs) 100 100 100
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report Storage Parameter Units 2010 2015 Ultimate Charging/Discharging Rates System fill time (for 5 kg H2) Min (kg H2/min) 4.2 min (1.2 kg/min) 3.3 min (1.5 kg/min) 2.5 min (2.0 kg/min) Minimum full flow rate (g/s)/kW 0.02 0.02 0.02 Start time to full flow (−20 °C)h s 5 5 5 Start time to full flow (20 °C)h s 15 15 15 Transient response 10%-90% and 90%-0%i s 0.75 0.75 0.75 Fuel Purity (H2 from storage)j % H2 99.99 (dry basis) 99.99 (dry basis) 99.99 (dry basis) Environmental Health and Safety Permeation and leakagek Scc/h Meets or exceeds applicable standards Meets or exceeds applicable standards Meets or exceeds applicable standards Toxicity — Safety — Loss of usable H2l (g/h)/kg H2 stored 0.1 0.05 0.05 a Generally the “full” mass (including hydrogen) is used, for systems that gain weight, the highest mass during discharge is used. b 2003 US$; total cost includes any component replacement if needed over 15 years or 150,000 mile life. The storage system costs are currently under review and will be changed at a future date. c 2005 US$; includes off-board costs such as liquefaction, compression, regeneration, etc; based on H2 production cost of $2 to $3/gasoline gallon equivalent untaxed, independent of production pathway. d Stated ambient temperature plus full solar load. No allowable performance degradation from −20C to 40C. Allowable degradation outside these limits is TBD. e Equivalent to 100,000; 200,000; and 300,000 miles respectively (current gasoline tank spec). f All targets must be achieved at end of life. g For delivery the storage system, in the near term, the forecourt should be capable of delivering 10,000 psi (700 bar or ca. 70 MPa) compressed hydrogen, liquid hydrogen, or chilled hydrogen (35 to 77 K) and up to 5,000 psi (350 bar or ca. 35 MPa). In the long term, it is anticipated that delivery pressures will be reduced to between 50 and 150 atm for solid state storage systems, based on today’s knowledge of sodium alanates. h Flow must initiate within 25% of target time. i At operating temperature.
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Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report j The storage system will not provide any purification, but will receive incoming hydrogen at the purity levels required for the fuel cell. For fuel cell systems, purity meets SAE J2719, Information Report on the Development of a Hydrogen Quality Guideline in Fuel Cell Vehicles. Examples include: total nonparticulates, 100 ppm; H2O, 5 ppm; total hydrocarbons (C1 basis), 2 ppm; O2, 5 ppm; He, N2, Ar combined, 100 ppm; CO2, 1 ppm; CO, 0.2 ppm; total S, 0.004 ppm; formaldehyde (HCHO), 0.01 ppm; formic acid (HCOOH), 0.2 ppm; NH3, 0.1 ppm; total halogenates, 0.05 ppm; maximum particle size, <10 μm; particulate concentration, <1 μg/L H2. These are subject to change. See Appendix C on Hydrogen Quality, to be updated as fuel purity analyses progress. Note that some storage technologies may produce contaminants for which effects are unknown; these will be addressed as more information becomes available. k Total hydrogen lost into the environment as H2; relates to hydrogen accumulation in enclosed spaces. Storage system must comply with CSA/NGV2 standards for vehicular tanks. This includes any coating or enclosure that incorporates the envelope of the storage system. l Total hydrogen lost from the storage system, including leaked or vented hydrogen; relates to loss of range. SOURCE: DOE (2009a).
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