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4 Heavy-Duty Hybrid Vehicles Introduction several prototype heavy-duty hybrid vehicles in a variety of classes for a range of applications. Tests to date with these The objectives for introducing hybrid architectures into vehicles have confirmed that these trucks are capable of the powertrains of heavy-duty trucks and buses are much the delivering significant improvements in fuel economy falling same as those for introducing them into passenger vehicles predominantly in the range of 40 to 60 percent depending on and light-duty trucks. More specifically, the introduction the truck class and the specific technologies that have been of either electric or hydraulic propulsion equipment makes applied (Table 4-1). The reports straddle the 21CTP target of it possible to operate the diesel engine at or near its condi- 60 percent fuel economy improvement that will be discussed tions for maximum efficiency and/or lowest emissions to in more detail later in this chapter. However, larger increases spend more of its operating time while under conditions in fuel economy exceeding 100 percent have already been of reduced fuel consumption and emissions. In addition, demonstrated in some special applications such as the Class the electric/hydraulic equipment is used for acceleration 6/7 hybrid utility trucks that are particularly good candidates and theÂ recoveryÂ of braking energy, making it possible to for this technology (van Amburg, 2006). reduce the required engine rating and, in some cases, to turn Funding agencies for hybrid truck projects under the the engine off during idling conditions. In addition to the 21CTP umbrella have included DOE, DOD, and EPA. The opportunities for improved fuel economy, heavy-duty hybrid DOE-funded projects have focused on trucks with hybrid- trucks also are capable of delivering significant reductions in electric powertrains, while the EPA-funded effort has been emissions (Barker and Hitchcock, 2003). devoted to hybrid-hydraulic configurations as shown in Table The architectures developed for hybrid heavy-duty 4-1. The DOD-funded projects are distinguished from the v Â ehicles (HHV) have much in common with the configura- DOE and EPA projects by the special requirements asso- tions adopted for passenger vehicles and light-duty trucks. ciated with military vehicles, often including significant For hybrid-electric powertrains, both parallel and series amounts of auxiliary electric power. hybrid configurations have been developed for different In the face of changing priorities in the larger FCVT applications. In parallel hybrid systems, the electric or program, DOE has diverted nearly all of its hybrid-electric hydraulic motor is coupled to the same driveshaft as the technology investments to light-duty vehicles since FY2006. engine so that the motor can add torque when needed to assist As a result, the requested R&D budget for heavy-duty hybrid with acceleration. The motors can also act as generators or development in the DOE budget for 21CTP activities was as hydraulic pumps in the case of hydraulic systems to pro- reduced to zero in both FY2007 and FY2008. The only vide regenerative braking force that recovers energy to help remaining research projects on heavy hybrid propulsion recharge the system batteries or as accumulators respectively. systems are two congressionally directed activities (DOE, In series hybrid architectures, all of the mechanical power 2006b). The committee was advised that this termination from the engine is converted to electricity or pressurized hydraulic fluid which is then delivered to one or more electric Kevin Beaty, Eaton Corp., and V.K. Sharma, International Truck, or hydraulic motors that drive the wheels. âHybrid Technology Program Review,â Presentation to the committee, During the past several years up to and including FY2007, Washington, D.C., February 8-9, 2007. funding has been dedicated to the development of hybrid Ken Howden, DOE, FCVT, â21st Century Truck Partnership,â Presenta- truck components and systems as part of the 21CTP ini- tion to the committee, March 28, 2007, Washington, D.C. tiative. This investment has resulted in the completion of Ken Howden, DOE, FCVT, â21st Century Truck Partnership,â Presenta- tion to the committee, March 28, 2007, Washington, D.C. 56
HEAVY-DUTY HYBRID VEHICLES 57 TABLE 4-1â Reported HHV Fuel Economy Improvements â¢ Develop a new generation of drive unit systems that have higher specific power, lower cost and durability Developer and Vehicle Fuel Economy Improvement (percent) matching the service life of the vehicle. Develop a Eaton Electric Hybrid drive unit that has 15 years of design life and costs no â UPS P100 Delivery Vana 36 (in field) more than $50/kW by 2012. â Adv. Technology HEVb 47 (on dynamometer) â HTUF Utility Truckc 67-150 (in field) â¢ Develop an energy storage system with 15 years of Oshkosh Electric Hybrid design life that prioritizes high power rather than high â AHHPS Refuse Truckd 36 (in field) energy, and costs no more than $25/kW peak electric EPA Hydraulic Hybrid power rating by 2012. â Urban Delivery Vane 39-74 (in field) â¢ Develop and demonstrate a heavy hybrid propulsion aData from Kevin Beaty, Eaton Corp., and V.K. Sharma, International technology that achieves a 60 percent improvement in Truck, âHybrid Technology Program Review,â Presentation to the commit- fuel economy, on a representative urban driving cycle, tee, Washington, D.C., February 8, 2007, Slide 5. while meeting regulated emissions levels for 2007 and bData from Beaty and Sharma presentation, Slide 20. cData from Beaty and Sharma presentation, Slide 8. thereafter. dData from Nadr Naser, âOshkosh Truck CorporationâAHHPS,â Presen- ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ tation to the committee, Washington, D.C., February 8, 2007, Slide 16. However, summary presentations by government staff eData from Charles Gray, Jr., âEPAâs Transportation R&D,â Presentation have shown significant changes in program goals over time. to the committee, Washington, D.C., March 28, 2007, Slide 24. Skalny presented information which showed that the original fuel economy improvement targets when 21CTP was estab- lished, following the earlier Review of the DOE Office of Heavy Vehicle Technologies (National Research Council, of funding was necessitated by the sharp reduction in the 2000) were between 100 and 200 percent improvements total 21CTP initiative funding that was enforced beginning for heavy-duty hybrid vehicle demonstrations, depending in FY2007, requiring deep cuts in even successful project upon the application. Rogers reported a goal of âup to a areas. In contrast, funding has continued for hybrid truck 100 percent improvementâ in fuel economy without refer- projects supported by DOD and EPA, although this hybrid ence to a driving cycle. The current official 21CTP goal of work apparently falls outside of the 21CTP initiative. demonstrating 60 percent improvement in fuel economy on The 21CTP Roadmap (DOE, 2006a) identifies the major a representative urban driving cycle neither defines the cycle challenges for hybrid truck commercialization to be: nor does it identify the vehicle class or intended use. This gradual reduction in the fuel economy improvement target â¢ System reliability during the past seven years has the effect of aligning the goal â¢ System cost more closely with what available electric or hydraulic hybrid â¢ System integration into the vehicle. technology can achieve in Class 5/6 urban delivery vehicles, as summarized in Table 4-1. Based upon these commercial issues, it identifies the Some insight into the background of these changing top priority areas for HHV funding to achieve the 21CTP program objectives was provided by the 21CTP manage- goalsÂ as: ment in response to a question posed by the committee. The committee was informed that âthe change in goals is mainly â¢ Drive unit reliability attributable to a change in focus at the government level soon â¢ Drive unit cost after the development of the 2000 roadmap, in which govern- â¢ Energy storage system reliability ment agencies (DOE in particular) were encouraged by the â¢ Energy storage system cost Administration to focus more on component technologies â¢ Demonstrated ability to meet heavy-duty 2007 emis- and less on vehicle/system technologies.â sion standards The timetable for hybrid truck development is very brief â¢ Demonstrate 60 percent improvement in fuel economy, (truncated beyond 2007) as a result of the decision to termi- compared to current production heavy duty vehicles. nate further research in the heavy hybrid propulsion area. Paul Skalny, DOD (U.S. Department of Defense), U.S. Army Tank AutoÂ The 2012 goals stated in the 21CTP 2006 Roadmap for heavy-duty hybrid vehicles are as follows: motive Research and Development Command, âBriefing to the National Academiesâ Committee to Review the 21CTP,â Presentation to the commit- tee, March 28, 2007, Washington, D.C. Susan Rogers, DOE, FCVT, âHeavy Hybrid Propulsion Overview,â Presentation to the committee, February 21, 2007, Washington, D.C. Charles Gray, Jr., âEPAâs Transportation R&D,â Presentation to the DOE, FCVT, Response to committee query on âPartnership History, committee, March 28, 2007, Washington, D.C.; Paul Skalny, âBriefing to Vision, Mission, and Organizationâ section of âResponses to NAS Queries the National Academiesâ Committee to Review the 21CTP,â Presentation to on 21CTP Management and Process Issues,â transmitted via e-mail by Ken the committee, March 28, 2007, Washington, D.C. Howden, March 27, 2007.
58 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP FIGURE 4-1â Network chart for heavy hybrid propulsion. SOURCE: DOE, 2006b, Figure 3.1-4. Fig 4-1, bitmapped The Heavy Hybrid Propulsion Network Chart (Figure 4-1) Demonstrating the cost-effectiveness of a heavy-hybrid for the heavy-duty hybrid truck program provided in the vehicle within a specific period (typically, the objective is FreedomCAR and Vehicle Technology (FCVT) Multi-Year a payback period less than two years) is a major factor in Program Plan (MYPP) document (DOE, 2006b, Fig. 3.1-4) determining the commercial success of heavy-duty hybrid shows that heavy-duty hybrid R&D efforts supported by trucks. Key obstacles to achieving cost effectiveness include DOE are being brought to a close in early 2008. (1) high costs of the non-optimized, hybrid components used in the demonstration vehicles to date; (2) the large variety of potential low-volume applications (buses, garbage trucks, Goal 1: Develop a New Generation of Drive delivery trucks, etc.) that result in high initial development Unit Systems and investment costs; and (3) the lack of a recognized This goalâs full title is âDevelop a new generation of p Â rocedure/standard for demonstrating the fuel savings, which drive unit systems that have higher specific power, lower are highly dependent on the vehicle duty cycle. cost, and durability matching the service life of the vehicle. Meeting the aggressive cost target of $50/kW is proving Develop a drive unit that has 15 years design life and costs no to be one of the most difficult challenges for the develÂopers more than $50 kW by 2012.â Goal 1 and Goal 3 (60 percent of heavy hybrid propulsion systems. On the positive side, improvement in fuel consumption) are identified by 21CTP information presented to the committee indicates that 21CTP as separate goals, but they are closely interrelated. That is, funding has helped manufacturers to reduce the produc- the achievement of a commercially-viable hybrid truck for any application depends on achieving significant improve- Arthur McGrew, GM Allison Transmission, âAH2PS: Motor and Power ments in both fuel economy and emissions at a cost that is Electronics Development,â Presentation to the committee, February 8-9, low enough to justify the associated cost premium. In addi- 2007, Washington, D.C.; Kevin Beaty, Eaton Corp., and V. K. Sharma, tion, the equipment must be sufficiently rugged and durable International Truck, âHybrid Technology Program Review,â Presentation to to perform reliably during the full design life of the truck in the committee, February 8, 2007, Washington, D.C., Slide 20; Nadr Naser, âOshkosh Truck CorporationâAHHPS,â Presentation to the committee, adverse environmental conditions. February 21, 2007, Washington, D.C.
HEAVY-DUTY HYBRID VEHICLES 59 tion cost of the hybrid propulsion equipment. For example, Looking beyond the cost targets, DOE contractors have a representative of Allison Transmission reported to the reported progress toward achieving substantial increases in committee that the companyâs DOE-supported project had the power density of the hybrid-electric drivetrain hardware. yielded component improvements that could achieve a 40 For example, Allison Transmission reported that their engi- percent decrease in electric machine costs and a 50 percent neers had succeeded in improving the power of their Dual reduction of power electronics costs, yielding an aggregate Power Inverter Module (DPIM) by 200 percent compared cost reduction of 14 percent for the hybrid-electric drivetrain to the previous generation of power electronics. A 30 to 40 system. Furthermore, it is likely that increases in the annual percent improvement in the motor power density was also production of hybridized versions of passenger vehicles and reported in the same presentation. light-duty trucks will help to bring the cost of hybrid-electric Very little evidence was presented to the committee to drivetrain equipment down the learning curve in ways that substantiate any significant progress made by 21CTP-funded will directly benefit heavy-duty truck hybrid powertrain researchers toward achieving the desired reliability target equipment as well. of 15 years design life for the hybrid propulsion powertrain Despite this progress, the 21CTP management reported to equipment. In fairness, the number of prototype heavy hybrid the committee that, as of 2006, industrial partners working on trucks currently in the field is very low, making it particularly electric-based hybrid propulsion systems âhad achieved costs difficult to gather any meaningful reliability data. However, of between $600 and $1,000 per kilowatt with the energy there are promising reports indicating that hybrid powertrain storage system as the major cost item.â This same document equipment can be designed to operate reliably over long reports that â. . . industry may be able to achieve a target periods of time under adverse environmental conditions. For of $300 per kilowatt by 2012â and that the threshold for example, a 2006 NREL-funded study of the maintenance achieving high-volume sales is expected to be âin the range records of hybrid passenger buses used in regular revenue of $100 to $200 per kilowatt.â If this threshold is correct, it service in New York City indicated that the hybrid buses suggests that the official 21CTP goal of reaching $50/kW delivered approximately 5,000 Miles Between Road Call may be more ambitious than necessary to achieve commer- (MBRC), exceeding the New York City Transit minimum cial success. Regardless of the ultimate cost objective, it is requirement of 4,000 MBRC (Barnitt and Chandler, 2006). clear that significantly more progress is required in the area of cost reduction in order to achieve dollar-per-Âkilowatt val- Goal 2: Develop an Energy Storage System ues that would make hybrid powertrains attractive to buyers with 15 Years of Design Life that Prioritizes of heavy-duty trucks in the absence of direct subsidies or High Power rather than High Energy, and appropriately targeted tax credits.10 Costs no more than $25/kW Peak Electric One notable exception to the cautious pronouncements Power Rating, by 2012 about the cost of heavy-duty hybrid truck technology was the more optimistic outlook articulated by representatives of Current State of Electrical Storage Technology for Eaton Corp. and International Truck and Engine indicating Transportation Use that series hydraulic hybrids can be sufficiently low in cost to achieve a payback period of two to three years.11 EPA has indicated that the cost premium for installing a hydraulic- The ideal electrical energy storage system for heavy-duty hybrid drivetrain into a Class 6 urban delivery van on a mass hybrid trucks would have the following characteristics: production basis could be as low as $600 (Nikkel, 2006). However, this promising news is tempered by the fact that the â¢ High Volumetric Energy Density (energy per unit limited energy storage capacity of hydraulic accumulators volume) constrains the usefulness of hybrid-hydraulic technology in â¢ High Gravimetric Energy Density (energy per unit of heavy-duty trucks primarily to those with significant start- weight, Specific Energy) stop duty cycle requirements, such as refuse trucks.12 â¢ High Volumetric Power Density (power per unit of volume) DOE/FCVT, response to question 1 in âAdditional Hybrid System Ques- â¢ High Gravimetric Power Density (power per unit of tionsâ section of âResponses to NAS Queries on 21CTP,â transmitted via weight, Specific Power) e-mail by Ken Howden, August 28, 2007. â¢ Low purchase cost 10DOE, FCVT, Response to committee query on âPartnership History, â¢ Low operating cost Vision, Mission, and Organizationâ section of âResponses to NAS Queries on 21CTP Management and Process Issues,â response to committee query, â¢ Low recycling cost transmitted via e-mail by Ken Howden, March 27, 2007. â¢ Long useful life 11Kevin Beaty, Eaton Corp., and V.K. Sharma, International Truck, âHy- â¢ Long shelf life brid Technology Program Review,â Presentation to the committee, February â¢ Minimal maintenance 8, 2007, Washington, D.C. â¢ High level of safety in collisions and rollover accidents 12Charles Gray, Jr., âEPAâs Transportation R&D,â Presentation to the committee, March 28, 2007, Washington, D.C. â¢ High level of safety during charging
60 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP â¢ Ease of charging method Comparing Published Energy Storage Data â¢ Minimal charging time Metrics for energy storage components vary quite sig- â¢ Storable and operable at normal and extreme ambient nificantly in published data, making accurate comparison of temperatures energy storage technologies difficult. For example, capacity â¢ High number of charge-discharge cycles, regardless of specifications, often expressed in ampere-hours (Ah), vary the depth of discharge with the interval used to discharge the battery during testing. â¢ Minimal environmental concerns during manufactur- Testing with longer intervals typically exhibits much higher ing, useful life, and recycling or disposal capacities than with shorter intervals for the same battery. The interval used for a capacity test is usually expressed by Unfortunately, every commercially viable battery tech- the time used during testing to discharge the battery, and is nology being pursued must trade off compromises of these often expressed as a âC-rate.â 1C represents discharge of attributes. The optimal electrical energy storage system for a the rated energy capacity in one hour, 2C corresponds to given application will highly depend on the weighted values discharge in 0.5 hours, and 0.5C (or C/2) corresponds to of these attributes as they relate to the specific application. discharge in two hours. For example, if a battery is rated with an energy capacity of 5 Ah, the 1C rate would be 5 amps, the Trading Off Attribute Priorities for an Application C/2 rate would be 2.5 amps, and 2C would be 10 amps. In addition to the inconsistencies associated with the Battery-only electric vehicles (EVs), hybrid electric C-rate, the amp-hour rating does not usually allow easy vehicles (HEVs), and plug-in HEVs (PHEVs) have some- analysis of the instantaneous power available for accelera- what distinct requirements. An EV developer might place tion or the ability of the battery to store energy quickly to the highest priority on an energy storage system that has the recover braking losses. highest energy density or specific energy, to assure maxi- Power density specifications are suitable for comparison mum range between charges for a given size of system. The of the short-term power delivery capability for an energy instantaneous power available would likely be less important storage system, as a function of its mass or volume. In than mileage or range to the EV developer, but the relative contrast, energy density specifications are suitable for com- priorities would be reversed for the HEV developer. How- parison of long-term available stored energy capacity of an ever, systems with higher energy capacity also tend to have energy storage system, as a function of its mass or volume. higher available power for acceleration but with more mass However, even these metrics (when provided) possess vari- than is desired for HEV applications. ability in how they are derived, particularly the percentage The EV developer might also interpret system safety and and rate of discharge over the measurement interval. This environmental concerns somewhat differently from an HEV measurement renders the task of comparing energy storage developer. Because a battery-only vehicle usually has a much device technologies difficult at best, based upon the informa- larger battery than an HEV, and because it carries more tion provided to the committee. electrical energy and caustic chemicals on-board, it may Appendix F of this report reviews the state-of-the-art in carry higher battery-related safety risks than an HEV with batteries for light-duty vehicles. a smaller battery. However, the HEV includes an internal combustion engine (ICE) that carries additional safety risks associated with its energy storage system (i.e., gasoline fuel Battery Technology for Heavy-Duty Applications tank) that drivers of conventional ICE-based vehicles have Unique challenges exist for the application of energy lived with for many years. s Â torage components in heavy-duty hybrid trucks, includ- An HEV seeks to recover as much of the braking energy ing batteries, ultra-capacitors, hydraulic accumulators, as possible to recharge the battery. If the battery system or flywheels. Light-duty EVs and HEVs focus on energy has insufficient ability to be rapidly charged, the friction capacity for long battery range, or rapid power charging and brakes will be used and significant energy will be lost to discharging capabilities for acceleration and braking energy heat. Because regenerative braking is a primary method recovery, or a combination of both. It is currently impracti- to charge the battery in an HEV, the efficiency is critically cal for heavy-duty vehicles and trucks to carry sufficiently important to an HEVâs performance characteristics. Because large battery packs or electric power sources (e.g., fuel the electric motor is also used significantly to assist the inter- cells) to provide the required power levels for an all-electric nal combustion engine during acceleration, specific power powertrain (without ICE). Therefore, vehicle manufacturers and power density will become important considerations. and researchers are focusing on hybrid powertrains based PHEVs have battery energy storage characteristics that on diesel-electric architectures that require batteries with can have more in common with either typical EV or HEV high power capability to assist in vehicle acceleration, rapid requirements, dependent on whether the PHEV powertrain charging, and efficient recovery of braking energy. design is dominated by the electric motor or by the internal combustion engine.
HEAVY-DUTY HYBRID VEHICLES 61 TABLE 4-2â Current Status of FreedomCAR Energy Storage Goals and NRC Evaluation FreedomCAR Energy Storage Goal (units) 2010 Goal (end of life) 2005 NRC Review Current Status Discharge Power (kW) 25 (18 sec) 25 25 Available Energy (Wh) 300 300 300 Calendar Life, years 15 10 10-15 Cost Goal (at 100,000 units/year) 500 1,200 750-900 Regen Pulse, kW 20 (10 sec) 20 20 Cycle Life, cycles 300 k 300 k+ 300 k+ Maximum System Weight, kg 40 32 25 Maximum System Volume, liter 32 33 20 Cold Cranking Power, kW at â30Â°C 5 for 2 sec 3-5 3-5 Operating Temperature Range, Â°C â30 to +52 +10 to +40 â10 to +40 SOURCE: National Research Council, 2005. The charge rate and level of charge acceptance needed â HEVs (power-assist hybrid electric vehicles) to maximize the capture of braking energy in a heavy-duty â PHEVs (plug-in hybrid electric vehicles) vehicle is much greater than the comparable requirements â FCVs (fuel cell hybrid vehicles) for a light-duty vehicle, due to the difference in vehicle â EVs (battery electric vehicles) mass and inertia. A popular way to reach the higher power capacity required for heavy-duty truck applications is to The stated 2010 FreedomCAR research goals associated over-size the battery. For light-duty hybrid vehicles there are with energy storage (Table 4-2) are intended to enable reli- storage systems available with sufficiently high charge rates able HEVs that are durable and affordable, with an electric that avoid the need to over-size the battery. Over-sizing the drivetrain energy storage system that exhibits: energy storage system to obtain the necessary power capacity is undesirable in several regards including the unnecessary â¢ 15 year life expenses of additional mass, volume, and heightened envi- â¢ Capacity of 300 Wh ronmental and safety concerns. â¢ Discharge power of 25 kW for 18 seconds The additional mass in the heavy-duty vehicle makes â¢ Cost of $20/kW them less practical as battery-only EVs due to the required â¢ 100 Wh/kg by 2012 battery size for reasonable performance, given the current â¢ 150 Wh/kg by 2015 state of the art, while battery-only power remains more viable for the light-duty vehicle. The DOE PHEV battery goal is focused on cost reduction with a target of $200 to $300 per kWh by 2014. 21CTP Goals TARDEC Program Goals and Activities During meetings with DOE and 21CTP management, the committee was informed that essentially all DOE-sponsored TARDEC Program Goals.14 The energy storage program goals effort associated with batteries and other forms of energy established by the US Army Tank-Automotive Research, storage is focused on light-duty vehicles under the Freedom- Development and Engineering Center (TARDEC) are to: CAR and Fuel Partnership.13 Based upon materials submitted to the committee (Howell â¢ Reduce the current $115,000 per 30 kWh pack cost to and Habib, March 2007), the FreedomCAR Program charter $58,000 related to energy storage is to: â¢ Accelerate the technology and automate the manufac- turing process â¢ Research and develop electrochemical energy storage â¢ Improve the temperature stability and safety technologies which support the commercialization â¢ Develop enhanced materials of (light-duty) hybrid and electric vehicles, with the â¢ Produce affordable battery packs for HEV dash followÂing target applications: m Â obility, silent watch, and pulse power for weapons 14DOD, TARDEC (U.S. Army Tank-Automotive Research, Develop- ment, and Engineering Command), âEnergy Storage Research Projects, 13Personal communication, Rogelio Sullivan, Ken Howden, and Ed Wall, TARDEC Ground Vehicle Power & Mobility,â received by the committee DOE, FCVT, during committee meeting, August 28, 2007. from Ken Howden, DOE, FCVT, August 31, 2007.
62 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP â¢ >3 kW/kg by 3/2009 age pack as a standard, economy-of-scale would suggest the â¢ 150 Whr/kg by 3/2009 opportunity to further reduce cost by using multiple 25kW packs for heavier-duty vehicles. However, the shift in focus TARDEC ManTech Objective (MTO) Program. Within toward technologies that favor high power over high energy the MTO program, TARDEC is pursuing opportunities to is not currently a high priority in the light-duty segment encourage battery technology suppliers, especially Li-ion where cost reduction and reliability are the driving factors at cell and battery manufactureres, to produce safer, more this time. In principle, a shift toward higher power capability reliable, lower-cost cells and batteries for heavy-duty HEB would not detract from the normal use of battery pack in full applications. Included in these goals is earlier demonstration hybrid light-duty applications. of higher energy capacity compared to that currently being However, for PHEVs, the DOE target of $200-300 per demonstrated under the FreedomCAR program. kWh re-emphasizes the need for energy capacity optimiza- TARDEC desires to achieve the goal of 150 Wh/kg by tion, as expected for PHEVs. The market expectation for March 2009, whereas the FreedomCAR goal is to achieve battery-only range with a PHEV will be much higher than 150 Wh/kg by 2015. TARDEC reports that it has demon- 2010 expectations for HEVs. Although these cost goals are strated more than 100 Wh/kg in FY2008,15 whereas the founded on reasonable market expectations, they may prove FreedomCAR program has targeted the demonstration of to be difficult to achieve by the targeted dates. 100 Wh/kg by 2012. Specific Energy. Specific Energy goals of 100 Wh/kg by 2012 and 150 Wh/kg by 2015 seem achievable, considering FreedomCAR Electrochemical Storage Program the rapid pace of development, the high levels of public and The FreedomCAR program appears to be exploring a commercial business interest, and that TARDEC has already greater breadth of technologies than the Army TARDEC achieved the 2012 goal. program. Because the focus is light-duty vehicles, all of the stated goals seem to be extremely cost-driven, because the Shift to High Power from High Energy. During the period energy storage system remains a significant percentage of when California initially imposed its zero emission vehicle the cost of an HEV, and an even higher percentage of PHEV standards, battery-only EVs received significant development and EV cost. attention by the auto industry. In those cases, gravimetric energy density was a primary concern because acceptable 15 Year Life. Battery life is critically important to avoid the vehicle range was one of the most important EV attributes replacement of the energy storage system before the end of being addressed, due to the battery limitations at the time. the useful life of the vehicle which would represent a very Advancements in Ni-metal-hydride battery technology in the significant repair/replacement cost and increase the recycling late 1990s allowed light-duty EVs such at the electric-powered challenges. The need to replace the energy storage system Toyota RAV4 to achieve reasonably acceptable range. Gravi- once in a vehicleâs life would more than double its effective metric power density is a focus of light-duty HEV electrical cost. Therefore, the goal of achieving battery lifetimes that storage system. Heavy-duty HEVs require even higher power match or exceed that of the vehicle may be necessary for so the shift in priority for improved gravimetric power density owner acceptance in large volume production. for such applications is quite appropriate. Higher power density will support further improvements Capacity Goals. The FreedomCAR energy capacity goals of in light-duty HEV fuel efficiency as less reliance on the 300 Wh and power capability goal of 25 kW for 18 seconds internal combustion engine for transient power is achieved, may be appropriate for the anticipated battery-only range of enabling further engine downsizing. As power density a light-duty HEV, but they may fall short of the needs for increases, the maximum charging rate and charge acceptance heavy-duty HEVs, unless two or more of the target battery tend to increase as well, facilitating greater ability to recover packs are used for the application. brake energy. Therefore, progress made toward higher power density, which is necessary for efficient heavy-duty HEV Costs. The targeted energy storage system for 2010 has a applications, will also benefit light-duty HEVs. Li-ion tech- cost target of $20/kW pack so the battery pack would cost nology appears to be the leading candidate for significant $500, making the cost reasonable for a light-duty HEV. The progress in energy storage system power density, but signifi- achievement of this goal opens the door for energy storage cant cost, durability and safety issues exist. packs with peak power ratings higher than 25 kW. However, if the light-duty HEV industry adopts a 25 kW, 300 Wh stor- Durability and Safety Issues for Li-ion Battery Systems. Safety remains a significant issue for Li-ion battery systems. 15DOD, TARDEC (U.S. Army Tank-Automotive Research, Develop- Overcharging, fast charging, fast discharging, crushing, ment, and Engineering Command), âEnergy Storage Research Projects, projectile penetration, external heating, or external short- TARDEC Ground Vehicle Power & Mobility,â received by the committee from Ken Howden, DOE, FCVT, August 31, 2007. c Â ircuiting, can cause the battery pack to heat up. If heat gen-
HEAVY-DUTY HYBRID VEHICLES 63 eration exceeds heat dissipation capability, thermal runaway Enhanced Lead-acid Batteries. Enhanced Lead-acid batteries can occur. Elevated temperatures can cause leaks, gas vent- are also under development. The company FireflyÂ® Energy, ing, smoke, flames, or even ârapid disassemblyâ to occur. Inc., is introducing a new carbon-graphite foam-based con- Intelligent monitoring and control of the charging and struction that significantly reduces the volume, mass, and discharging processes is being developed to manage many cost of a lead acid battery, while reportedly improving its of the concerns associated with thermal runaway. However, cycle life, durability, recycle ability, and temperature range. vehicle collisions and projectiles that can cause the battery TACOM is currently evaluating this advanced lead-acid solu- case to be breached are inspiring the need for new construc- tion for potential heavy-duty hybrid applications. tion materials that are less prone to mechanical and thermal issues. Assessment of 21CTP Energy Storage Research Programs Other battery technologies, such as LiFePO4 and Li- titanates, are also being pursued because they offer some FreedomCAR Light-Duty Energy Storage Effort. Review of advantages over Li-ion approaches, but have other features the material provided by DOE on the ongoing FreedomCAR which render them less attractive than Li-ion. Some new research and development effort for light-duty vehicles sug- technologies are becoming available that offer promise for gests that the program is addressing the needs, goals, and greater safety with fewer environmental concerns. sizing for light-duty HEVs. However, it is clear that the capa- bilities needed for heavy-duty use may differ significantly Future Development Trends. There are several promising from light-duty applications. Therefore, a clearer assessment new technologies which are currently under development and by DOE as to how the technology may be transitioned from will be evaluated to determine the extent to which they can light- to heavy-duty is needed. provide improvements over conventional Li-ion approaches. The features that allow these technologies to be directed TARDEC Energy Storage Research Projects. TARDECâs toward higher power density for use in heavy-duty hybrids Energy Storage Research Projects appear to be focused on should be explored. incremental improvements in lead-acid, Ni-metal-hydride, Li-ion, and Ni-Zn batteries that can be introduced into Lithium Nano Titanate. Altair Nanotechnologies, Inc., is planned military-specific hybrid electric applications. Power marketÂing a battery called NanoSafeÂ® that offers extremely density and energy density trade-offs appear to be appropri- fast charging without thermal runaway, along with other ately considered. The near-term focus is to address durabil- safety improvements. NanoSafeÂ® is a lithium nano titanate ity and safety issues related to Li-ion batteries, due to the battery system. Altair Nanotechnologies recently dem- specific requirements of military applications. The urgency onstrated a 10-minute charge cycle for an 18-kWh pack, of this matter as well as the need for Li-ion-type energy and using a 125-kW-rated, high-voltage charging station from power density characteristics for next-generation military AeroVironment, Inc. combat and tactical vehicles underscores the need for sig- 50Â°C lithium titanate batteries under development by nificant financial support in the future. the company Enerdel are identified in the FreedomCAR summary. Allison and Eaton Heavy-Duty Hybrid Programs under 21CTP. The Allison Two Mode Hybrid Bus Program and Ultracapacitors. Ultracapacitors represent an alternative way the International/Eaton Advanced Technology HEV were to achieve the desired power density levels in combination identified as examples of successful developments con- with other batteries. Ultracapacitors are inherently high in ducted under the 21CTP programs. The Allison Two-Mode instantaneous power availability, compared to batteries. Cur- system incorporates a lead-acid battery system and the rently, ultracapacitors are very expensive, but the technology International/Eaton system uses a 70 kW NiMH battery. is advancing quickly and production costs are continuing to Based upon materials provided to the committee, it appears decrease. that the successful development effort was targeted more Ultracapacitors offer more than 10Ã the power density of toward advanced motor, drive and power electronics systems, todayâs batteries, but far less energy density, making them although early Eaton plans call for Li-ion batteries. However, unsuitable as battery replacements. However, hybrid energy future cooperative programs have identified the desire for storage packs containing both batteries and ultracapacitors Li-ion battery systems. are under development. Practical production vehicle systems must trade off the associated costs of system with both high Energy Storage Funding energy density and high power density. However due to the high factor of fuel in the operational cost of heavy-duty The annual energy storage funding under the DOE Freedom- vehicles, the use of ultracapacitors may prove to be cost CAR budget has been fairly stable (~$17 million) in FY2005, effective. Ultracapacitors have extremely long useful life and FY2006, the FY2007 request and the FY2008 request, related are inherently safer than most practical batteries. to High Power Energy Storage. However, significant increases
64 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP in Advanced Battery Development have been requested for eral, it appears that as a minimum, lithium-ion technology FY2007 ($7.6 million, up from $1.4 million in FY2006) and is necessary to achieve the stated heavy-duty roadmap goals. FY2008 ($18.2 million, up from $1.4 million in FY2006). However, until sufficient effort is conducted to truly evaluate These increases are targeted toward higher energy storage the light-duty progress in a commercial heavy-duty environ- capacity systems that would be necessary for PHEVs. ment, the committee cannot gauge the real progress. No information was provided to the committee concern- ing the funding allocations that have been directly attribut- Findings and Recommendations able to the energy storage system development under the TACOM budget line items. Finding 4-1. Challenges with lithium-ion anode/cathode materials and chemical stability under high power condi- tions will likely preclude achieving the 15-year durability Appropriateness of the 21CTP Research Areas of Focus targets by 2012. The committee agrees that the following issues need to be addressed to advance the state of the art in energy storage Recommendation 4-1. Much closer interaction between systems for heavy-duty vehicle applications: military and commercial suppliers is recommended to identify the highest-priority areas for further research in an â¢ Cost, both procurement and life cycle attempt to expedite the development of commercially viable â¢ Weight and space claim battery or battery/ultracapacitor systems that can accomplish â¢ Life expectancy in a specific heavy-duty drive cycle the unique high-power needs of heavy-duty vehicles. â¢ Energy and power capacity for a heavy-duty hybrid application Finding 4-2. There are significant differences associated â¢ Suitability for the heavy-duty vehicle environment and with the use of battery energy storage systems in heavy-duty cooling techniques vs. light-duty applications. â¢ Architecture/modularity â¢ Safety/failure modes Recommendation 4-2. Due to these differences and the â¢ Maintainability much lower production volumes for heavy-duty applications, â¢ Supplier base for the energy storage components. it is appropriate to continue funding and conduct sufficient research and development to demonstrate prototypical Continued focus on solving the cost, durability, safety, bat- s Â uccess in heavy duty applications, or identify areas for tery management system, and reliability issues associated continued research. with Li-ion batteries appears to be appropriate. However, due to the unique requirements for very high power capac- Finding 4-3. The information exchange between DOD, DOT, ity for certain heavy-duty applications, additional focus on DOE appears to be rather casual due to completely separate ultracapacitors or other very high power capable technolo- funding mechanisms, priorities, and testing methods. gies seems appropriate. Although the stated intent for transfer of technology Recommendation 4-3. Jointly funded programs that priori- from light-duty to heavy-duty appears logical, the unique tize research, build on the success of each agencyâs programs, requirements for heavy-duty application may require sig- and thereby necessitate technology transfer between the part- nificantly different trade-offs. This appears to be the focus ners would significantly improve the technology transfer and of the TACOM programs, but the cost issues for military reduce the chance for âreinventing the wheelâ or duplicating acceptance may be significantly different than commercial othersâ mistakes. heavy-duty service. Finding 4-4. The metrics used for comparing battery tech- Progress Toward Achieving the Stated Goals. TARDEC nologies differ from manufacturer-to-manufacturer, agency- appears to have established more aggressive technical goals to-agency, and even for different evaluations within a given than those stated in the 21CTP 2006 Roadmap. For instance, agency. Terminologies also vary in definition. Many existing TARDEC reports that it has already achieved and exceeded standards for measuring battery parameters are technology the 2012 FreedomCAR goal of 100 Wh/kg. However, the specific, making accurate comparison of different technolo- cost and durability targets have not yet been confirmed. gies difficult or impossible. The Roadmap stated goal is to develop an energy storage system with 15 years of design life that prioritizes high power Recommendation 4-4.Â Metrics should be standardized or rather than high energy, and costs no more than $25/kW peak modified to enable more accurate comparisons across differ- electric power rating by 2012. It is difficult to extrapolate the ent battery technologies for transportation use. Universal ter- progress made in the light-duty sector with respect to the minologies should be defined, published, and recommended achievement of goals in a heavy-duty environment. In gen- for adoption by the various battery manufacturers.
HEAVY-DUTY HYBRID VEHICLES 65 Finding 4-5. Very little data are published about batteries van by Eaton and International Truck and Engine achieved when used in conjunction with ultracapacitors for heavy- an improvement in fuel economy between 60 and 70 percent duty HEV applications in this program. Recent develop- during lab testing using an EPA city driving cycle. ments show great promise with this technology, especially One of the most aggressively developed applications for for heavy-duty applications requiring high power output for heavy-duty hybrid truck technology has been urban transit acceleration and fast charging for braking energy recovery. buses. Tests conducted by the U.S. National Renewable Energy Laboratory (NREL) on the hybrid-electric buses Recommendation 4-5. Expanded research effort and associ- developed by Orion Bus and BAE Systems demonstrated ated funding focus should be focused on ultracapacitors or that the buses achieved an average fuel economy improve- supercapacitors as âhybridâ storage systems, in combination ment of 45 percent compared to conventional diesel engines with batteries. when driving over the cityâs most severe duty cycles (Green Car Congress, 2006). It is also worth noting that Eaton has reported progress in Goal 3: Develop and Demonstrate a Heavy the development of parallel hybrid-electric powertrains for Hybrid Propulsion Technology That Achieves Class 8 heavy-duty commercial highway trucks that have a 60 percent Improvement In Fuel Economy, demonstrated fuel economy improvements of 5 to 7 percent on A Representative Urban Driving Cycle, over long-haul routes during independent tests (Eaton Corp., While Meeting Regulated Emissions Levels 2006). Although this percentage improvement is not as high for 2007 and Thereafter as for the other heavy-duty trucks and buses cited above, it is The hybrid truck development projects funded by DOE still noteworthy because of the much higher annual fuel con- as part of the 21CTP initiative have demonstrated signifi- sumption associated with Class 8 long-haul trucks compared cant progress toward achieving the 60 percent fuel economy to any other type of heavy-duty truck (Eaton Corp., 2006). improvement target for some specific truck classes and Eaton claims that the fuel savings provided by their hybrid applications. In order to evaluate this progress, it is impor- drivetrain can deliver a cost savings of approximately $9,500 tant to recognize that heavy-duty trucks experience a much per long-haul truck per year. Overall, the progress achieved wider range of driving cycles than passenger vehicles or by truck manufacturers and suppliers toward meeting the light-duty trucks. For example, a Class 6 urban delivery 60 percent fuel economy improvement objective in Goal 3 van experiences typical driving cycles that are much dif- is substantial. ferent from those of Class 8 long-haul commercial trucks. Past DOE-supported heavy-duty hybrid truck develop- Because large numbers of accelerations and braking decel- ment efforts appear to have been almost completely biased erations associated with truck applications such as delivery toward achieving improved fuel economy with compara- vans or refuse trucks are well-suited to demonstrating the tively little attention being given to opportunities for major advantages of hybridization, most of the 21CTP-funded reductions in emissions. Despite references to emissions development of hybrid trucks has been focused on these reductions in the basic mission of the truck partnership, applications.16 In fact, even Goal 3 itself has been formu- the briefings that the committee received summarizing the lated in terms of an âurban driving cycleâ to highlight these accomplishments of recent hybrid truck development proj- applications. ects made almost no mention of targets or achievements in An example of a heavy-duty hybrid truck that has demon- the area of emissions reductions. strated greater than 60 percent improvement in fuel economy In response to a question about this apparent omission, is a Class 6/7 utility truck developed using Eaton parallel the committee was informed that âthe emissions of heavy- hybrid-electric drivetrain technology. In tests conducted by duty vehicles are not measured on a chassis dynamometer the Hybrid Truck Users Forum (HTUF), the prototype hybrid and regulated on a grams/mile basis like passenger cars and utility truck demonstrated higher-than-expected fuel econ- light trucks.â17 This is unfortunate, because features such as omy improvement of between 62 and 150 percent on four electric creep (movement under electric power alone) are different mission duty cycles. As a second example, a series expected to make it possible to turn off engines for extended hydraulic hybrid system installed in a Class 6 UPS delivery periods during congested traffic or loading queue conditions, creating opportunities for substantial emission reduction during these conditions. The limitations imposed by existing 16Susan Rogers, U.S. Department of Energy, âHeavy Hybrid Propulsion procedures for certifying truck engines make it difficult to Overview,â Presentation to the committee, February 8, 2007, Washington, D.C.; Arthur McGrew, Allison Transmission, General Motors ÂCorporation, fairly evaluate the full benefits of heavy-duty hybrid trucks, âAH2PS: Motor & Power Electronics Development,â Presentation to the committee, February 8, 2007, Washington, D.C.; Kevin Beaty, Eaton Corp., and V.K. Sharma, International Truck, âHybrid Technology Program R Â eview,â Presentation to the committee, February 8, 2007, Washington, D.C.; 17DOE, FCVT, 21CTP, response to committee query (Question 15 in Nader Nasr, Oshkosh Truck Corporation, âAdvanced ProductsâAHHPS,â âHybrid Electric Vehicle Systemsâ section), transmitted via e-mail by Ken Presentation to the committee, February 8, 2007, Washington, D.C. Howden, March 27, 2007.
66 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP providing the basis for a separate recommendation (4-8) the engine design for integration into a hybrid powertrain.18 presented later in this section. This is noteworthy in view of the major impact that engine In summary, there is an acknowledged risk that heavy- performance characteristics have on the achievable fuel duty truck hybrid propulsion technology will not be success- economy and emissions of heavy hybrid trucks and buses. fully commercialized on a broad scale without continuing Progress toward the successful development of hybrid coordinated governmental support at both the federal and truck technology would benefit from improved coordina- state levels. As stated by the 21CTP management team: tion among the governmental agencies that are funding this âCurrently, the development of hybrid technology for vari- workâDOE, DOD, and EPAâas well as among the national ous vehicle platforms represents a high technical risk and is labs, universities, and subcontractors who are carryÂing out cost-Âprohibitive. Government-industry sharing of these risks this R&D. Although it has been pointed out to the committee and costs may accelerate introduction of these vehicles. This that some communication and technical interactions already evaluation is consistent with the stated 21CTP âStrategic occur as part of 21CTP activities and technical conferences,19 Approachâ that calls for efforts to âpromote research focused the overall development program would benefit from closer on advanced heavy-duty hybrid propulsion systemsâ as well technical coordination among the various projects. In light as to âpromote the validation, demonstration, and deployment of the limited resources that are available to support R&D of advanced truck and bus technologiesâ (DOE, 2006a). projects in this area, the importance of gaining the high- est value from these investments by sharing information Finding 4-6. R&D on heavy-duty hybrid trucks and buses w Â herever possible and avoiding unnecessary duplication has demonstrated significant progress, achieving 35 to takes on added urgency. 47Â percent fuel economy improvements in hybrid-electric Looking elsewhere among the 21CTP programs for best delivery vans and urban buses, with specialized applications practices in developing system approaches, the idle reduc- and the hydraulic hybrid delivery van in the 50 to 70 percent tion program reviewed in Chapter 6 deserves special atten- range (60 percent is the present 21CTP target). Commercial tion. In particular, the nighttime idle reduction initiative has success has already been achieved with hybrid electric urban been particularly successful in demonstrating how several buses, albeit with major governmental subsidies. Despite the agencies and stakeholders can coordinate their activities to promising progress, significant hurdles still remain to achiev- aggressively move new technology developments out of the ing the fuel economy improvement targets for a broader laboratory and into marketplace.20 This has been accom- range of heavy-duty hybrid vehicle (HHV) applications, plished using an effective combination of technology devel- reducing the cost, and improving HHV reliability sufficiently opment, field validation, certification testing, and tax credit to achieve broader commercial success. In addition, there are incentives. In addition, this initiative has included customer opportunities for achieving significant system-level improve- education and incentive programs that have involved govern- ments that would make HHVs more attractive to OEMs and mental agencies at both the state and federal levels working users, such as the merging of hybrid propulsion and idle together with equipment manufacturers.21 reduction features, including start-stop operation and creep- The considerable progress achieved in the idle reduction ing under all-electric power. area deserves to be studied to determine whether its success can be replicated in other areas such as hybrid trucks using Recommendation 4-6. Development and demonstration of some of the same techniques. This approach makes particular heavy-duty hybrid truck technology should be continued sense for the hybrid truck area because hybrid drive and idle as part of the 21CTP program in order to reduce barriers reduction technologies directly overlap in some key areas to commercialization. These development projects should such as creep idle. include efforts to capitalize on opportunities for system- There is also a need for this coordination to extend beyond level improvements made possible by HHV technology in the agencies to Congress itself. For example, the tax credits order to extract the maximum possible value from any new hybridized propulsion equipment that is installed in future 18Gurpreet Singh, DOE, FCVT, âOverview of DOE/FCVT Heavy-Duty trucks and buses. Engine R&D,â Presentation to the committee, Washington, D.C., February 8, 2007. 19Ken Howden, DOE, FCVT, âPartnership History, Vision, Mission, and Systems Development and Organization,â Presentation to the committee, February 8, 2007, Washing- Project Coordination ton, D.C. 20Mitchell Greenberg, EPA (U.S. Environmental Protection Agency), The decision by the government to focus 21CTP devel- âEPA SmartWay Transport Program: Overcoming Technology Deployment opment efforts on component technologies has resulted in a Challenges,â Presentation to the committee, March 28, 2007, Washington, reduction of emphasis on coordinated systems development. D.C. 21Glenn Keller, Linda Gaines, and Terry Levinson, DOE, Argonne For example, there is little indication that any significant por- tion of the substantial 21CTP investment in advanced com- National Laboratory, Center for Transportation Research, âIdle Reduction Technologies,â Presentation to the committee, February 8, 2007, Washing- bustion engine development has been directed to optimizing ton, D.C.
HEAVY-DUTY HYBRID VEHICLES 67 specified for hybrid trucks in the Energy Policy Act of 2005 in identifying and overcoming key hurdles to the successful (Public Law 109-58, August 8, 2005) are due to expire on commercialization of HHV technology. December 31, 2009. There is a high likelihood that the timing of this expiration and uncertainty about its renewal will com- HHV Certification Test Procedures plicate the market acceptance of hybrid trucks introduced by manufacturers during the coming years unless early action Lack of fuel economy and emission certification test is taken to clarify renewal plans. A very similar problem has procedures for heavy-duty hybrid trucks has been a deterrent afflicted the wind power industry because of the series of to their commercialization. Although the U.S Energy Policy expirations and renewals of tax incentives in that industry, Act of 2005 provided direct tax credits for hybrid trucks that creating a âfeast-or-famineâ market environment (Pellerin, deliver improved fuel economy, there was no practical way 2005). Closer coordination between the agencies and Con- for truck purchasers to derive these direct tax credits until gressional offices would help to prevent this problem from mid-2007.23 harming the hybrid truck market in a similar fashion. EPA is aware of the lack of fuel economy and emissions Industry also has an important role to play in order to test and certification procedures for heavy-duty hybrid ensure that an appropriate systems perspective is main- trucks. Currently, EPA is developing a procedure to directly tained in the 21CTP programs. In 2006, DOE established measure fuel economy and emissions of complete heavy-duty a subgroup activity named the Validation Working Group vehicles, including hybrids; when finalized, this procedure is made up of 21CTP member volunteers. The purpose of this expected to provide a measurement method and certification subgroup is to focus attention on vehicle system technolo- procedure for obtaining tax credits for heavy-duty hybrid gies that are evaluated as having the greatest potential for trucks.24 Unfortunately, EPAâs development of fuel economy positive impact on fuel economy and emissions combined and emissions test procedures for heavy-duty hybrid trucks is with high cost effectiveness. The Validation Working Group expected to be a time-consuming process, requiring vehicle- is intended to actively seek out opportunities to conduct in- level testing on heavy-duty chassis dynamometers. This pro- service demonstrations of these promising technologies in cess is particularly challenging because the number of large order to encourage their commercial adoption. The Hybrid chassis dynamometers available in the United States that are Truck Users Forum (HTUF) established with the support of suitable for heavy-duty trucks is quite limited. the U.S. Army National Automotive Center (NAC) and the EPA, in response to a U.S. Supreme Court ruling in a Hewlett Foundation is playing a similar role.22 lawsuit brought by the state of Massachusetts in April 2007, is developing programs to utilize its experience with fuel Finding 4-7. Progress in the development of HHV technol- economy and CO2 measurement protocols as part of its ongo- ogy under the 21CTP program has been hindered by the ing deliberations on potential greenhouse gas regulations for decision to focus on component-level technology rather vehicles under the Clean Air Act. Whether this program will than systems. Successful development and commercializa- accelerate the development of fuel economy and emissions tion of HHV technology requires coordinated, customized test procedures for heavy-duty hybrid trucks is not known development of the combustion engine, electrical/hydraulic at this time. drive equipment, mechanical powertrain, and controls as components of an integrated system, in order to realize its 23Note added in proofâFollowing the public release of this report, the full potential. In addition, the coordination of HHV project activities among the 21CTPâs federal partners (DOD, EPA, following information came to the committeeâs attention: In 2007, the Internal Revenue Service set forth interim guidance that provides a means and DOE) has not matched the level achieved in other 21CTP to obtain tax credits for new qualified heavy-duty hybrid motor vehicles, programs such as nighttime idle reduction, making it more based on their improved fuel economy. Internal Revenue Service Notice difficult to achieve ambitious HHV technology targets. 2007-46, issued June 4, 2007, and entitled âCredit for New Qualified Heavy-Duty Hybrid Motor Vehicles,â provides procedures for a vehicle Recommendation 4-7. Coordination of all 21CTP heavy- manufacturer to certify to the IRS that the city fuel economy of a heavy-duty hybrid vehicle was measured in a manner that is substantially similar to the duty hybrid truck development and demonstration activities manner in which city fuel economy is measured under 40 CFR (Code of should be strengthened across components, programs, and Federal Regulations) Part 600 (in effect August 5, 2005). This notice allows agencies to maximize the system benefits of this technology the manufacturer to use any procedure that the manufacturer reasonably and to accelerate its successful deployment in commercial determines to be substantially similar to procedures under 40 CFR Part trucks and buses. In addition to improved cross-agency 600. In addition, the IRS will not challenge a manufacturerâs determination of city fuel economy. A manufacturer following this procedure still needs coordination, HHV stakeholder-based organizations includ- a certificate of conformity that the vehicleâs internal combustion engine ing the Validation Working Group and the Hybrid Truck meets the EPA emission standards for heavy-duty engines. Therefore, no Users Forum should be engaged more aggressively to assist credit is available for possible reductions in actual vehicle emissions with hybrid operation. As a result, simplified emission control systems cannot be considered for hybrid heavy-duty vehicles. 22HTUF is available at http://www.calstart.org/programs/htuf/. Accessed 24Note added in proofâThe committee was unaware of this fact at the June 2, 2008. time of the reportâs public release.
68 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP Finding 4-8. Emissions of heavy-duty trucks are currently of the entire heavy-duty vehicle propulsion system and its measured and certified by EPA for each engine type rather accessories could potentially yield significant fuel savings than for any truck as a complete unit. Current procedures do from the following techniques beyond those achievable with not allow either the fuel economy or emissions of complete WHR alone. These revisions include the following: hybrid propulsion systems to be certified, and so neither the fuel economy improvements nor emissions reductions of â¢ Application of the basic hybrid-electric vehicle con- hybrid trucks are appropriately recognized. Prior to mid- cept, allowing the main diesel engine to be downsized 2007, these procedures served as deterrents to commercial- and peak power demands to be supplied by the electric ization of HHV technology since there was no practical way motor and battery storage system. for truck purchasers to derive any direct tax credits for buying â¢ Extensive use of high-voltage, electrically driven hybrid trucks as called for in the U.S. Energy Policy Act of accessories on an on-demand basis. 2005, which expires in 2009. Developing the necessary test â¢ Elimination of a separate engine-driven alternator. procedures is expected to be a complex and lengthy process, and EPA has not been able to devote sufficient resources to In light of these developments, the 21CTP management developing such procedures in a timely manner.25 has made statements indicating that they are reconsidering some of their earlier conclusions about the benefits of hybrid- Recommendation 4-8. Since tax credits for hybrid trucks ization for heavy-duty Class 8 long-haul trucks.27 However, established in the Energy Policy Act of 2005 expire at the there is no indication that any documented study is yet avail- end of 2009, and there are not established engineering test able in the public literature to prove that opportunities for procedures, DOE should work with EPA and stakeholders to significant fuel economy/emissions improvements in hybrid accelerate the development of fuel economy and emissions Class 8 long-haul trucks really exist. certification procedures for heavy-duty hybrid vehicles so that the actual benefits of hybridization can be recognized Finding 4-9. Recent statements by representatives of some and rewarded to further encourage commercial adoption. heavy-duty truck OEMs have reported that there are oppor- tunities for fuel economy improvements between 5 and 7Â percent in hybridized versions of Class 8 long-haul trucks, Hybridization of Long-Haul Trucks yielding annual fuel cost savings exceeding $9,000 per year. 21CTP investments in heavy-duty hybrid truck devel- This result runs counter to generally-held opinions about opment activities have been predominantly focused on the low potential of hybrid versions of Class 8 long-haul truck types other than Class 8 long-haul trucks because trucks for substantial fuel savings, and no documented study stakeÂholders originally identified long-haul trucks as poor results have been made available to the committee to firmly candidates for significant fuel economy improvements in substantiate the recent claims. comparison to other truck types and classes.26 However, as noted earlier in this chapter, recent statements by some Recommendation 4-9. The committee recommends that truck manufacturers and OEM suppliers are suggesting that the potential benefits of hybrid Class 8 long-haul trucks be the potential fuel economy benefits of hybridization for evaluated as part of the 21CTP program by conducting a Class 8 long-haul trucks may be much larger than previously documented study using a combination of analytical simula- expected (Eaton Corp., 2006). tion and experimental data. If the results of the study confirm Some opportunities for fuel-economy improvement in the recent claims of substantial fuel economy opportunities long-haul trucks can be derived from engine-off operation in hybrid long-haul trucks, the 21CTP program management under idle and low-speed creep conditions, as well as energy is encouraged to find ways to contribute directly to the accel- recovery from regenerative braking. Additional improvement erated development of the necessary hybrid technology and has been proposed using waste heat recovery (WHR) from a its successful demonstration in prototype vehicles. Rankine cycle using a turbine generator to provide electric power to supplement the main engine shaft power, providing References a predicted fuel efficiency boost of 15 to 20 percent to the diesel engine (Regner et al., 2006). Barker, W., and D. Hitchcock. 2003. Potential Emissions Reductions of Â Diesel/Electric Hybrid Pickup/Delivery Vehicles in the Houston/Â As discussed in Chapter 3, Cummins engineers have Galveston Region, Presented at Hybrid Truck Users Forum, San Antonio, reported that, in addition to the WHR technology, a revision Tex., Oct. 23. Available at http://files.harc.edu/Projects/Transportation/Â FedExTechnicalBriefing.pdf (accessed May 12, 2008). 25Note added in proofâCurrently, EPA is developing a procedure to directly measure fuel economy and emissions of complete heavy-duty vehicles, including hybrids. 27DOE, FCVT, response to Question 14 in âHybrid Electric Vehicle 26DOE, FCVT, 21CTP, response to committee query (Question 2 in Systemsâ section of âResponses to NAS Queries on 21CTP Idle Reduc- âHybrid Electric Vehicle Systemsâ section), transmitted via e-mail by Ken tion, Hybrid Vehicles, and Parasitic Losses,â forwarded via e-mail by Ken Howden, March 27, 2007. Howden, 21CTP program director, March 27, 2007.
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