Review of the Research Program of the Partnership for a New Generation of Vehicles Third Report (1997) / Chapter Skim
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4: POWERTRAIN DEVELOPMENTS
4: POWERTRAIN DEVELOPMENTS
Pages 50-85
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From page 50... ...
The candidate systems and subsystems have not changed during the past year. They are as follows: four-stroke CIDI engines gas turbines Stirling engines fuel cells reversible energy-storage devices electrical and electronic power-conversion devices Reversible in this context means that the device can both accept and provide energy, not that it is reversible in a thermodynamic sense.
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From page 51... ...
However, CIDI engines also suffer from size, weight, noise, and cost penalties that have limited their market acceptance in passenger cars unless their purchase is encouraged by a substantial fuel cost differential. Eliminating these disadvantages, while retaining or increasing the superior fuel economy of these engines, represents major challenges on several fronts.
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From page 52... ...
Because the HEV programs preceded PNGV, these hybrid vehicles are required to double fuel economy rather than meeting the PNGV Goal 3 vehicle target of tripling fuel economy. Technical Targets The critical characteristics of a CIDI engine, suitable for application to a Goal 3 vehicle, are shown as a function of PNGV milestone targets in Table 4-1.
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From page 53... ...
Fuel economy targets for the CIDI engine have been moderated in recognition of the likelihood of having to meet the increasingly stringent emissions standards shown in Table 4-2. The CIDI team believes that the most technically challenging aspect of the CIDI program will be meeting the NOX emission standards; however, possible stringent fine-particulate standards could also become a significant barrier for diesels.
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From page 54... ...
reduce emissions from the CIDI engine, including reducing NOx emissions. Incylinder combustion control will require a sophisticated, high-pressure, fuelinjection system that is matched to the engine's in-cylinder flow field over the entire operating range of the engine.
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From page 55... ...
High-Pressure Fuel-Injection Systems and Combustion Fundamentals Significant advancements in the fuel-injection system's ability to control the fuel injection rate to match it to in-cylinder combustion processes are required for
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From page 56... ...
Both types of injection system are being aggressively developed, and the prognosis is good for successful deployment to an engine in the required time frame. In 1996 the PNGV program established a 4-year combustion CRADA, with an initial allocation of $700,000/yr, plus matching funds from industry, to address the in-cylinder combustion processes of fuel injection, air-fuel mixing, combustion, and emission formation.
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From page 57... ...
This is an 83 percent increase in fuel economy as compared to state-of-the-art fuel injection gasoline engines. It should be noted, however, that these fuel economies are for the "1/3 Euromix" driving cycle, which is said to be less severe than the American federal urban driving cycle used for EPA fuel-economy estimates.
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Recommendations Based on its review of the program status and progress for CIDI engines, the committee makes the following recommendations. Recommendation.
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From page 59... ...
The alternative is to develop a ceramic material with the potential to meet both the cost-and high temperature objectives. Program Status and Progress Previously Identified Barriers In its second report, the committee reported that gas turbines represent a promising technology for hybrid vehicles and that considerable progress had been made in the previous year, especially in turbo-alternator design, bearings, combustors, heat recovery, and controls.
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From page 60... ...
The designs have different target characteristics based upon two different hybrid-vehicle performance and control strategies. The Teledyne design power is 55 kW to 60 kW and its efficiency at one-third power, required to meet the Goal 3 vehicle fuel economy target, is 43 percent.
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Assessment of the Program Considerable progress in the last year has moved the gas turbine closer to being a successful PNGV engine candidate. Gas-turbine manufacturers project that they can meet or approach the PNGV weight, volume, and efficiency goals.
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In summary, much progress has been made, but even the most optimistic projections for the required development time puts the gas turbine well beyond the time frame for PNGV concept vehicle demonstrations. Recommendations Based on its review of the program status and progress for gas turbines, the committee makes the following recommendations.
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From page 63... ...
The HEV program will provide a benchmark for the performance of these components, as well as an assessment of the critical issue of working-fluid containment. The potential of this power plant in the PNGV program will be much easier to assess when this information is available.
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From page 64... ...
is the best candidate among established fuel cell technologies for a hybrid vehicle. It can operate at about 80°C and its efficiency, specific power, and power density (operating on a hydrogen fuel)
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The efficacy, efficiency, and durability of these fuel-processor technologies when operated with gasoline are yet to be established, as is their effectiveness in reducing CO to the required levels, and the dependence of the fuel processor efficiency on part-load and transient conditions. Electrochemical Cell Stack In programs funded under the DOE HEV program, now part of PNGV, and by the OEMs outside of the PNGV program, several fuel-cell power plants in the 10-kW to 30-kW range have been developed, built by subcontractors to Chrysler, General Motors, and Ford, and operated with methanol or hydrogen fuels.
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From page 66... ...
Because commercial phosphoric acid fuel cells presently cost more than $1,000/kW on a larger, less constrained scale, major efforts will have to be made to find low-cost component materials and to develop low-cost manufacturing methods for PEMFCs. Substantial cost reduction can be anticipated to accrue from highvolume production using automated processes (for fabricating key components like bipolar plates, membranes, and electrodes, and for assembly of cell stacks)
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From page 67... ...
research laboratories are in the forefront of fundamental and applied research investigations to advance PEMFC technology, and International Fuel Cells, a subsidiary of United Technologies, appears to be only behind Ballard in technology development and demonstration. Assessment of the Program PNGV and worldwide progress in automotive fuel-cell technology have been impressive in a number of important areas, especially in improving the power density of the fuel-cell stack and in lowering the projected costs.
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From page 68... ...
system returns 95 percent of its input energy, and conversion of electrical to mechanical energy reaches 81 percent efiTiciency, the fuel-cell system would have an overall efficiency of only 36 percent. This is below the projected values of 37 percent for gas turbines and 43 percent for CIDI engines.
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From page 69... ...
Efforts to develop more cost-effective materials and high technology automated techniques for manufacturing and assembling key fuel-cell components, such as bipolar plates, membranes, electrodes, end-plates, and sealants, should have higher priority than costly and possibly premature efforts to demonstrate integrated fuel-cell power plants in parallel efforts. BATTERIES Technical Targets Batteries, especially some of the advanced batteries currently under development for electric vehicle propulsion, have the potential to meet the energy storage requirements of HEVs.
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kW30- 70 Discharge power density kW/L0.781.6 Discharge specific power kW/kg0.631.0 Cost $/kW127.7 Durability (100 Wh) cycles50,000120,000 Lifetime yr1010 Operating temperature °C-40 to 52-40 to 52 Survival temperature °C-40 to 66-40 to 66 Note: The fast-response power plant is assumed to react very much like a conventional automotive engine, responding very quickly to vehicle power demands.
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From page 71... ...
SAFT Lithium-Ion Program Status and Progress The SAFT technology meets all major HEV battery target performance goals except for cost, including goals for energy density, power density, and cycle life, at the 0.85-Ah cell level. The project is on schedule and within budget.
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From page 72... ...
It is not clear whether the current programs will be able to demonstrate battery performance and cycle life close to those needed to meet PNGV goals. It is also unclear whether the program's nickel metal hydride batteries will approach, much less exceed, the very promising performance reported by DAUG (a batterydevelopment organization owned jointly by Daimler-Benz and Volkswagen in Germany)
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From page 73... ...
The ability of these cells to deliver and absorb 10 s current pulses at the nominal 15 C rate (discharge of the nominal capacity in 1/15 of an hour) has been established, but the battery power density projected from cell data appears limited to about 0.4 kW/kg.
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From page 74... ...
One possible exception is DAUG's successful development of a 14-Ah nickel metal hydride high power cell technology, but DAUG does not appear to have immediate plans for commercializing this technology. Thus, the hybrid/high power battery developments funded under the DOE HEV program and PNGV represent leading-edge efforts to achieve the challenging technical targets for power density, shallow cycle life, and high "round-trip" efficiency with potentially affordable battery systems.
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This support should be provided at least until the capabilities of the lithium-ion and/ or nickel metal hydride batteries to meet PNGV goals can be predicted with confidence. Recommendation.
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The fast-response power plant is assumed to react very much like a conventional automotive engine, responding very quickly to vehicle power demands. This type of power plant places the least demand on the flywheel system.
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Recommendation. After appropriate vehicle system trade-off studies have been conducted, performance objectives should be created that satisfy the requirements of the fast-response power plant vehicle system, and a plan should be developed for evaluating and integrating a flywheel subsystem in post-2000 concept vehicles.
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From page 78... ...
Based on the testing of unpackaged single cells, they project the following performance characteristics at 2.75 V: specific energy of 4.1 Wh/kg, energy density of 5 Wh/L to 7 Wh/L, specific power (to half maximum voltage) of 1,100 W/kg, and power density of 1,500 W/L.
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From page 79... ...
The prospects for developing batteries (particularly the high performance nickel metal hydride and lithium-ion batteries) that meet the PNGV technical goals for energy storage, both for the slow-response and fast-response engines, are excellent.
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Work on ultracapacitors for HEV applications should be limited to basic and applied research studies at universities, national laboratories, and industrial R&D centers and should be directed toward making fundamental advances and breakthroughs. ELECTRICAL AND ELECTRONIC POWER-CONVERSION DEVICES Program Description and Requirements All of the PNGV vehicle configurations involving electric motor drives, energy recovery, flywheels, or fuel cells require electric motors/alternators, power electronic inverters, and sophisticated electronic controllers.
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From page 81... ...
It appears to the committee that this team is relying heavily on other electric-vehicle and HEV programs to guide their efforts in developing technology for the Goal 3 Vehicle. Chrysler is using its experience with the Patriot concept HEV; General Motors is using its experience from the Impact concept electric vehicle and the production of the EV- 1; and Ford is using experience from the Ecostar and other advanced vehicle studies.
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From page 82... ...
What was learned during development of the Patriot vehicle is useful to the PNGV program, especially in the design of the power controller. It must be noted, however, that manufacturability and cost were not major considerations in the Patriot vehicle program.
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Of these, the efficiency of the energy storage device is critical. The battery technology now available cannot accept a high charging current efficiently.
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Recommendations Based on its review of electrical and electronic power conversion device programs and progress, the committee makes the following recommendations. Recommendation.
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From page 85... ...
Presentation to the Committee Subgroup on CIDI Engines, Ford Scientific Research Laboratory, October 22, 1996. NRC (National Research Council)
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