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Appendix F: Vehicles
Appendix F: Vehicles
Pages 218-304
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From page 218... ...
Potential effects on safety, fuel economy, and vehicle costs are discussed for scenarios where mass reduction is accomplished entirely through material substitution and smart design that can reduce mass without changing a vehicle's functionality or safety performance and maintains structural strength. Fuel Economy Benefits The engineering rule of thumb, assuming appropriate engine resizing is applied and vehicle performance is held constant, is that a 10 percent curb weight reduction results in a 6-7 percent fuel consumption savings (NHTSA-EPA, 2010)
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From page 219... ...
In comments to various U.S. Corporate Average Fuel Economy (CAFE)
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report Assessment of Fuel Economy Technologies for Light-Duty Vehicles pointed out the importance of secondary weight reduction "as the mass of a vehicle is reduced .
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. NHTSA/EPA issued the proposed rule "2017 and Later Model Year Light-Duty Vehicle Greenhouse Gas Emissions and Corporate Average Fuel Economy Standards" (NHTSA/EPA, 2011c)
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Vehicle manufacturers have an incentive to provide their cars with low rolling resistance tires to maximize fuel economy during certification. The failure of owners to maintain proper tire pressures and to buy low rolling resistance replacement tires increases in-use fuel consumption.
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From page 223... ...
EPA mileage labeling, however, does include air conditioner use, and new fuel economy and greenhouse gas regulations credit improved air conditioner efficiency. Multiple technologies exist for improving the efficiency of air conditioning systems, in particular in the compressor, air handling fans, and refrigeration cycles.
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• Energy generation (vehicle specific) -- Vehicles with batteries for energy storage (HEVs, plug-in hybrid electric vehicles [PHEVs]
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Engine Friction Reduction Engine friction is an important source of energy losses. Engine friction reduction can be achieved by both redesign of key engine parts and improvement in lubrication.
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BMW has demonstrated this technology on a gasoline engine vehicle and projects fuel consumption reduction of 2-3 percent on the U.S. combined cycle at a power level of about 100 W (BMW, 2009)
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The committee's goals can only be achieved with aggressive policies, including stringent efficiency standards. Such policies will influence manufacturers to emphasize fuel economy improvements over performance improvements.
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From page 228... ...
Table F.2 contains cost estimates for the manufacturing cost (without retail price equivalent) for a high-volume Prius powersplit system (2025 costs calculated based on 2008 current cost estimate and assuming 2 percent annual cost reductions through 2025 for the electric air conditioning, high voltage cables, and the body/chassis/special components and 1 percent annual cost reductions for the other components)
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From page 229... ...
TABLE F.3 Cost Estimates of Efficiency Technologies for Selected Future Hybrid Electric Vehicles VW VW VW VW Polo Golf Passat VW Sharan VW Tiguan Touareg Curb weight average, lb 2,390 2,803 3,299 3,749 3,513 4,867 System power, kW 64.6 77.8 101.2 151.1 114.6 271.8 ICE power, kW 51.7 62.3 80.9 120.9 91.7 271.8 Traction motor power, kW 12.9 15.6 20.2 30.2 22.9 54.3 High voltage battery capacity, kWh 0.74 0.86 0.99 1.12 1.05 1.43 Cost Estimates (€) Torque converter -- baseline (credit)
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From page 230... ...
starting with 2020. -- Electric air conditioning compressors are used on hybrid and electric vehicles in order to maintain air conditioning while the engine is shut off (hybrids)
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TABLE F.4 Cost Evolution for Hybrid Electric Vehicle Efficiency Technologies Alternator Torque Service and Enable Conv. Battery Regulator Body Brake Electric AC Auxiliary Voltage Power Dist.
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• Motor/generator/gears were estimated to cost $1,100 in 2008 and $940 in 2025 (1 percent annual cost reduction from 2008)
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TABLE F.7 Calculated Incremental Manufacturing Cost -- P2 Hybrid Electric Vehicle Technology VW VW VW Polo Golf VW Passat VW Sharan VW Tiguan Touareg Curb weight average, lb 2,390 2,803 3,299 3,749 3,513 4,867 System power, kW 64.6 77.8 101.2 151.1 114.6 271.8 ICE power, kW 51.7 62.3 80.9 120.9 91.7 271.8 Traction motor power, kW 12.9 15.6 20.2 30.2 22.9 54.3 High voltage battery capacity, kWh 0.74 0.86 0.99 1.12 1.05 1.43 Calculated Cost (€) Case subsystem 60.99 65.90 73.00 85.62 77.04 124.31 Launch clutch subsystem 40.16 42.98 47.08 52.24 48.95 68.04 Oil pump and filter subsystem 24.12 25.87 28.43 31.95 29.66 42.72 Traction motor/generator subsystem 79.97 86.59 95.43 117.52 102.06 170.54 Power electric 43.36 51.33 53.07 57.42 54.38 67.86 Control modules (motor/trans)
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From page 234... ...
While the calculated cost for the larger motors are significantly lower than MIT's, they are higher than the DOE 2015 goal for PHEV motor costs. F.1.3.3 Electric Traction System Efficiency Average electric motor efficiency over the test cycles was determined by the Ricardo simulation models and the EPA Energy Audit data.
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From page 235... ...
TABLE F.9 Comparison of Motor System Cost Estimates HEV PHEV-10 PHEV-30 PHEV-60 BEV FCEV Size (kW) 25 38 40 42 85 90 MIT 2030 cost $600 $800 $800 $800 $1,400 $1,400 DOE 2015 goal ($12/kW)
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FIGURE F.1 2007 Camry Hybrid motor-inverter efficiency map. SOURCE: Ricardo (2008)
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EI Energy required to accelerate the vehicle, that is to overcome the inertia of the vehicle, which is made up of the vehicle mass plus the rotational inertia of tire/wheel/axle assemblies EHC the energy required to provide hill-climbing ERR Energy required to overcome the rolling resistance 237
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For example, the same vehicle load reduction assumptions (weight, aero, rolling resistance) were applied to all of the technology packages.
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efficiency, -- Pumping losses, -- Engine friction losses, -- Engine braking losses, and -- Idle losses; • Transmission efficiency; • Torque converter efficiency; • Electric drivetrain, such as -- Battery storage and discharge efficiencies, -- Electric motor and generator efficiencies, and -- Charger efficiency (BEV only) ; • Fuel cell stack efficiency, such as -- Also the FCEV battery loop share of non-regenerative tractive energy; • Fraction of braking energy recovered; and • Fraction of combustion waste heat energy recovered.
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. The simple averages were compared to sales-weighted average numbers from EPA's 2010 Fuel Economy Trends Report, (EPA 2012)
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From page 241... ...
-- Cost of reducing a pound of weight, with separate inputs for HSS, aluminum, and carbon fiber. -- Cost of aero improvements -- Cost of tire rolling resistance improvements • Other data: -- Baseline vehicle weight is the average of the loaded vehicle weight for the 3 different models of cars or light trucks.
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From page 242... ...
: - Control electronics cost: $150 - Wiring: $200 - Blended brake control: $100 - DC-DC converter: $75 - Integration of motor into transmission: $50 - ICE size reduction: $100 credit - Elimination of starter/alternator: $100 credit - Elimination of torque converter: $75 credit • Calculations: -- Motor size = Total propulsion power times motor % of total propulsion power (kW) -- Battery size = Motor size divided by the battery power-to-energy ratio (kWh)
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From page 243... ...
• Calculations: -- Motor size = Total propulsion power times motor % of total propulsion power (kW) -- Battery size = Energy consumption times desired range divided by battery depth-of discharge -- BEV cost = (HEV cost minus ICE tech, turbo, and waste heat recovery costs)
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From page 244... ...
-- Battery size = BEV energy consumption times desired battery range divided by battery depth-of-discharge -- Fuel cell system power = Total propulsion power times fuel cell system size as % of total propulsion power -- H2 storage (kg) = Vehicle H2 consumption rate converted to kg/mile times desired range -- FCEV cost = (HEV cost minus ICE tech, turbo, and waste heat recovery costs)
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From page 245... ...
For this project, CAFE fuel economy was estimated using what can best be described as a twostep process. In the first step, the tractive energy required to navigate the CAFE driving cycles using a given vehicle is estimated.
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From page 246... ...
Both the simulation model and the two-step model include an explicit estimation of tractive energy impacts due to changes in vehicle road load characteristics. As is the case with actual CAFE compliance, CAFE fuel economy is estimated as the weighted average of energy (and fuel)
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From page 247... ...
F.2.2.2 Summary of CAFE Procedures 13 CAFE testing consists of two driving cycles, one nominally intended to represent city driving and one nominally intended to represent highway driving. The ability of either cycle to accurately reflect current driving behavior is limited, and for this reason the advertised fuel economy of a vehicle is based on both CAFE and supplemental testing, but CAFE compliance is limited to these two driving cycles alone.
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Average city cycle fuel consumption (gallons per mile, the inverse of fuel economy) is multiplied by 0.55, 248
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From page 249... ...
F.2.2.3 Tractive Energy Estimation As described above, the first step in the two-step modeling approach consists of the estimation of the tractive energy required by a specific vehicle to navigate the CAFE driving cycles. For a given set of vehicle characteristics and a specified driving cycle, the tractive energy required to navigate the driving cycle is defined precisely by physics and can thus be calculated accurately (without actually testing the vehicle)
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From page 250... ...
It is generally represented as: R = (r0 + r1v + r2v2) × mg where r0, r1, r2 = tire rolling resistance coefficients, v = vehicle velocity, m = vehicle mass, and g = gravitational acceleration (9.80665 meters per second squared)
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From page 251... ...
. Tractive energy requirements are sensitive to driver behavior, both in terms of the driver's ability to adhere to the driving cycle and in terms of driving behavior between defined cycle seconds, but fuel economy testing allows for only minor deviations from driving cycle speed/time definitions.
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From page 252... ...
Therefore, these calculations are discussed briefly here. Such calculations are also useful in understanding the tractive energy impacts of changes in vehicle load characteristics (e.g., rolling resistance, aerodynamic drag, vehicle mass)
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Closed throttle coasting is not typically a zero energy mode. 20 Road load forces are defined as the sum of rolling resistance and aerodynamic drag forces, signifying those forces that arise independent of the specific motive force demands of a driving cycle.
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From page 254... ...
During tractive energy analysis, each component of a driving cycle (meaning, in the case of this project, each second of the driving cycle) is determined to be in one of these energy modes, so that when integrated across the entire cycle, the energy input and output fractions are clearly identifiable, as are the individual motive, rolling resistance, and aerodynamic drag-induced components of those fractions.
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From page 255... ...
As discussed above, the tractive force relationship is: F=R+D+M If we implement a reduction of 40 percent in the rolling resistance force component, the new total tractive force becomes: Fnew = (0.6 × R) + D + M and the impact on the total tractive force is: (Fnew/F)
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From page 256... ...
For example, if we compare the tractive energy for the same vehicle used in the arithmetic example above, we find that a 40 percent reduction in vehicle mass (a net mass reduction of 39.16 percent) with no additional rolling resistance or aerodynamic drag influences decreases motive force by 43.3 percent, as compared to an expectation of 39.16 percent in the absence of any shift in powered 23 In the case of rolling resistance, the increase is relative to the tractive energy that would be expected after the change in vehicle mass is applied, not relative to a pre-mass reduction baseline.
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From page 257... ...
While it is not critical that the reader understand these various nuances, it is important that they recognize that such nuances exist and have the potential to induce "synergistic" effects on tractive and braking energy requirements. F.2.2.4 Energy Input and Fuel Economy Estimation Following the "first step" estimation of tractive energy requirements, the modeling process employed for this project implements a "second step" that involves "working backwards" from the wheels of a vehicle through the various energy transfer mechanisms (and their associated losses)
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From page 258... ...
Calculation ID Estimate Units Energy Path Component Description A 0.2 kWh/mi CAFE tractive energy requirement B 0 kWh/mi Braking energy recovered C 0 kWh/mi Waste heat energy recovered D 0.2 kWh/mi Required energy from transmission (= A − B − C) E 88% Transmission efficiency F 0.227273 kWh/mi Required energy from torque converter (= D/E)
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From page 259... ...
Motor losses Energy lost in the conversion of electrical energy to mechanical energy. a For this project, this includes only accessories that are operational during the CAFE driving cycles.
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From page 260... ...
Multiplier applied to the baseline vehicle mass (affects both motive and Vehicle mass multiplier rolling resistance forces)
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From page 261... ...
The actual simulation modeling results obtained for model baseline development and validation also assumed the implementation of idle-off engine technology on all six ICE vehicles. The modeling, thus, predicted increased fuel economy for the six vehicles (relative to the baseline simulation modeling results presented in Table F.15)
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From page 262... ...
All project scenario impact data are evaluated relative to this baseline. Hybrid Electric Vehicles The energy transfer path for HEVs, as implemented for this project, includes all of the various components and energy loss mechanisms specified for ICE vehicles.
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Toyota Yaris 41.3 41.2 41.9 +0.2 −1.4 Toyota Camry 33.2 32.0 32.9 +3.8 +0.9 Chrysler 300 26.1 25.5 25.8 +2.4 +1.2 Saturn Vue 29.0 28.8 28.4 +0.7 +2.1 Dodge Grand Caravan 24.0 23.1 23.8 +3.9 +0.8 Ford F-150 17.7 17.6 19.6 +0.6 −9.7 TABLE F.17 Hybrid Electric Vehicle Energy Losses Vehicle Component Energy Loss Mechanism Brief Description of Loss Mechanism Internal combustion Gross (indicated) efficiency Energy lost in the thermal conversion of fuel energy to mechanical engine energy.
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From page 264... ...
. Interim Joint Technical Assessment Report: Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards for Model Years 2017-2025.
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From page 265... ...
. Vehicle mass multiplier Multiplier applied to the vehicle mass of the corresponding ICE scenario (allows for ICE/HEV differentials, affects both motive and rolling resistance forces)
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From page 266... ...
A summary of the energy transfer pathways modeled for BEVs is presented in Table F.20. Because there are "extra" CAFE compliance credits available to producers of BEVs, it is important to understand how the CAFE fuel economy estimates that are modeled for BEVs in this project compare to the "creditable" fuel economy of such vehicles.
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a For this project, this includes only accessories that are operational during the CAFE driving cycles. 31 All BEV fuel economy estimates for this project are reported as miles per gasoline gallon equivalent.
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From page 268... ...
Such effects are explicitly considered in a separate portion of the project. To avoid any confusion, the CAFE fuel economy estimates also exclude any non-petroleum credits, instead representing measured CAFE fuel economy exclusively.
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. Braking losses are adjusted automatically for impacts associated with regenerative braking as well any changes to vehicle mass, rolling resistance, and aerodynamic drag parameters.
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From page 270... ...
Tractive energy requirements for the LEAF over the CAFE driving cycles were estimated using the tractive energy model employed for this project, in conjunction with estimated rolling resistance, aerodynamic drag, and mass parameters for the LEAF, as reported by Nissan or available through the EPA's "Test Car" dataset. 34 Following the calculation of the tractive energy estimate, the nominal energy loss parameters established for currentgeneration BEVs were applied to derive an estimated CAFE fuel economy for the LEAF.
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From page 271... ...
Since the fuel economy estimates developed for this project are based on measured CAFE fuel economy, the lack of official standardized factors for adjusting measured CAFE poses no significant difficulty. However, readers should recognize that at some point, upstream adjustment factors relating the production and distribution of hydrogen to the production and distribution of gasoline are likely to be developed, and these factors, combined with FCEV credits for reduced petroleum usage, will dictate the difference between measured and creditable CAFE fuel economy.
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From page 272... ...
The FCEV processing logic effectively "builds off" the vehicle load (mass, rolling resistance, and aerodynamic drag) logic for ICE vehicles and the e-machine logic for BEVs, so that FCEV modeling scenarios can generally be viewed as incremental to corresponding ICE and BEV efficiency scenarios.
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From page 273... ...
. Braking losses are adjusted automatically for impacts associated with regenerative braking as well any changes to vehicle mass, rolling resistance, and aerodynamic drag parameters.
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From page 274... ...
To select a specific nominal value for current systems, as well as validate all other nominal values for FCEV componentry, the FCEV model employed for this project was used to estimate CAFE fuel economy for the current Honda FCX and Mercedes F-Cell fuel cell vehicles. The tractive energy requirements for both vehicles over the CAFE driving cycles were estimated using the tractive energy model employed for this project, in conjunction with estimated rolling resistance, aerodynamic drag, and mass parameters for the two vehicles as reported by Honda and Mercedes, or available through the EPA's "Test Car" dataset.
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From page 275... ...
, While precise acceleration curves for individual vehicles can vary (and can be modeled in detail by simulation models using component technology definitions) , the modeling approach employed in this project is based on more aggregated energy losses and is unable to predict technology-specific variations in acceleration curve shape.
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From page 276... ...
Peak power at the wheels is then converted into peak required engine (or alternative energy source) power in exactly the same manner as described above for the "second step" of the CAFE fuel economy modeling process employed for this project.
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From page 277... ...
In all cases, the predicted performance cycle power is calibrated to match the rated power of each vehicle platform engine, and all alternative scenario and vehicle architecture estimates are evaluated on a relative basis only, so that all unbiased estimation error will "cancel out" in across-scenario comparisons. F.3 BATTERY VEHICLES Electric vehicles have been around since the 19th century and originally were more popular than gasoline vehicles.
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From page 278... ...
Improvements in battery technology will be critical to the success of EVs. F.3.2 Batteries for Plug-In Hybrid and Electric Vehicles Lead acid batteries have been the dominant technology for starting engines and powering accessories for a century.
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The processing of these materials is subject to considerable cost reduction, as is the cell manufacture.
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From page 280... ...
The production process for flat plate cells differs from that for cylindrical cells, but it is anticipated that the cost will follow a similar learning pattern as the 18650 cell. An initial high cost is expected to be followed by cost reductions from improved production efficiency in cells and materials as the process matures.
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From page 281... ...
Actually there are no pure spinel structures present in Li-ion batteries; spinel-like would be more accurate. SOURCE: Transitions to Alternative Transportation Technologies; Plug-in Hybrid Electric Vehicles.
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From page 282... ...
The new layered nickel-manganese-cobalt oxide materials, now under development, offer similar improvements in cathode performance but will require sophisticated production processes. These materials will be more expensive at the start but can be expected to show significant cost reduction as demand increases.
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From page 283... ...
be required. A battery recycling effort will be needed when large numbers of battery packs reach the end of their useful lifetimes.
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From page 284... ...
49 ARPA-E's BEEST Program: Ultra-High Energy, Low Cost Energy Storage for Ubiquitous Electric Vehicles, presentation to the committee by David Danielson, Program Director, ARPA-E, March 21, 2011. 50 Dudata, M., et al., Semi-Solid Lithium Rechargeable Flow Battery, Advanced Energy Materials, Vol.
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F.3.5.1 Battery Cost Battery cost is a key issue for the success of the electric vehicle. Lower cost electrode materials will be an important step.
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From page 286... ...
F.3.5.2 Battery Performance Battery performance must be improved if BEVs are to widely replace ICE vehicles. The present average auto has a range of about 300 miles on a tank of gasoline.
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From page 287... ...
These rare earth magnets were invented and produced initially at General Motors Research Laboratories, which developed and patented a high-flux magnet material using rare earth materials termed "MagnaQuench" for neodymium-iron-boron (NdFeB)
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From page 288... ...
Recently Toyota announced that it has developed a new material that has equivalent or superior capability in as a substitute for the rare earth materials in electric motors for its line of EVs (Reuters, 2012)
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From page 289... ...
If EV performance and cost follow the path shown in Table F.28, the cost penalty of a 100-mile range EV compared to a conventional drivetrain vehicle will shrink from its current level of about $16,000 to $2,000-$3,000 by 2030, and the EV will become the less expensive than its conventional counterpart by 2050. In addition, the gasolineequivalent fuel economy of such a vehicle -- already high at about 150 mpg (EPA test)
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From page 290... ...
Future improvements in the performance and cost of HEV batteries will apply to FCEVs as well. Battery Power Electric Motor/ Transmission Electronics Hydrogen Fuel Cell Storage System Power FIGURE F.8 Typical FCEV powertrain schematic.
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From page 291... ...
Further reductions in the cost of fuel cell systems are expected to result from downsizing associated with improved stack efficiency and improved response to load transients. Significant additional cost reductions will result if vehicle loads (weight, rolling resistance, and aerodynamics)
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From page 292... ...
previously estimated 2005 fuel cell costs to be $67/kW. But recent technology developments aimed at cost reduction and improved detailed cost analyses (James et al., 2010; Carlson et al., 2005)
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From page 293... ...
energy losses during fueling, de-fueling, and long-term parking are minimal; and (4) compressed storage has been demonstrated in fleets of FCEVs.
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From page 294... ...
. F.4.1.6 Vehicle Safety The two primary features that distinguish FCEVs from conventional ICE vehicles with respect to safety are high-voltage electric power and hydrogen fuel.
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From page 295... ...
. Therefore, for purposes of this report, technology-driven cost reduction from 2020 to 2030 of 2 percent per year is midrange, and 3 percent per year is optimistic.
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1. Storage -- reduced cost of carbon fiber -- new production and processing methods 2.
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From page 297... ...
. Therefore both midrange and optimistic cost estimates for 2050 include the 1 percent per year cost reduction rate associated with maturing technologies after 2030.
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From page 298... ...
Storage systems get smaller as vehicle demand for fuel is reduced with improved vehicle efficiency (vehicle weight, aerodynamics, rolling resistance and powertrain efficiency)
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From page 299... ...
As before, additional cost reductions result when the variable fraction of the storage system cost is scaled to accommodate the downsizing of storage associated with continually improving vehicle efficiency. The optimistic estimate for 2050 hydrogen storage cost assumes a more aggressive technologydriven 2 percent per year cost improvement applied to the variable cost fraction for an additional 10-year 54 The committee received confidential input from vehicle manufacturers and suppliers.
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From page 300... ...
However, it is noted that a reduction in storage cost associated with achievement of a targeted <$10/kg carbon fiber and pressure shift to 50 MPa would be consistent with a cost reduction of 35-40 percent, the optimistic technology-driven projection in Table F.32. F.4.2.6 Trade-Offs with BEVs FCEVs, like BEVs, are electric vehicles having no GHG emissions.
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From page 301... ...
TABLE F.34 Details of the Potential Evolution of a Midsize Fuel Cell Vehicle, 2010-2050 2010 2030 mid 2030 opt 2050 mid 2050 opt Fuel cell efficiency 53 55.3 57.5 59.6 61.6 Fuel economy, test mpge 94.1 125.8 149.5 170.4 211.3 Fuel cell power required, kW 110.8 91.6 85.6 81 71.2 Hydrogen required for 390 mile (test) range, kg 4.3 3.1 2.6 2.3 1.9 Fuel cell cost, $/kW 50 33 27 27 22 Variable hydrogen tank cost, $/kg 469 424 383 347 283 Incremental cost versus baseline, $ 8,554 3,747 2,133 3,281 1,961 Incremental cost versus conventional, $ 8,554 1,314 −62 −378 −1,442 F.5 REFERENCES Aachen.
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From page 302... ...
2010. Interim Joint Technical Assessment Report: Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards for Model Years 2017-2025.
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From page 303... ...
2010b. Interim Joint Technical Assessment Report: Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy Standards for Model Years 2017 2025.
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From page 304... ...
2009. Carbon Fiber Technology Development, ORNL presentation report.
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