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3
Engine Systems and Fuels
INTRODUCTION
The 21st Century Truck Partnership (21CTP) includes specific goals in the areas of engine systems and fuels. This chapter contains comments on the goals and the related research programs, including aftertreatment systems, the High Temperature Materials Laboratory of the Oak Ridge National Laboratory (ORNL), and health concerns related to diesel emissions.
Three specific goals were set for engine systems and fuels (DOE, 2006, p. 2), which can be summarized as follows:
Achieve 50 percent thermal efficiency, while meeting 2010 emission standards, by 2010;
Research and develop technologies to achieve 55 percent thermal efficiency by 2013; and
By 2010 identify and validate fuel formulations making possible 5 percent replacement of petroleum fuels.
The goals discussed in this chapter are exclusively focused on heavy-duty diesel engines. Prior to the formation of the 21CTP, the responsibilities for heavy-duty and light-duty truck technology were merged within the U.S. Department of Energy (DOE) Office of Heavy Vehicle Technologies (OHVT). One of the objectives that the OHVT inherited, and which was subsequently included in the 21CTP, was the development of diesel engine enabling technologies, to support large-scale industry dieselization of Class 1 and 2 light-duty trucks capable of achieving 35 percent fuel efficiency improvement over comparable gasoline-fueled trucks, while meeting applicable emission standards (National Research Council, 2000, p. 14). Because this program was a legacy of earlier vehicle research at DOE, none of the objectives of the 21CTP were associated with this program, although the accomplishments of this program were frequently cited by DOE officials in presentations to the committee. DOE believed that this program was beneficial for the heavy-duty diesel programs due to the synergy from light-duty to heavy-duty diesel engines.1 No further discussion of the light-duty diesel program will be presented here, even though it was funded in fiscal years (FY) 2000 through 2004 (as shown in Table 1-6 in Chapter 1 and in more detail in Appendix C).
GOAL OF THERMAL EFFICIENCY OF 50 PERCENT
Introduction
The first overarching technology goal of the 21CTP is stated as follows:
Develop and demonstrate an emissions compliant engine system for Class 7-8 highway trucks that improves the engine system fuel efficiency by 20 percent (from approximately 42 percent thermal efficiency today to 50 percent) by 2010. (DOE, 2006, p. 14)
This goal was further defined in terms of Major Activity and Milestone 3 as follows:
Demonstrate engine efficiency of 50 percent with 2010 emissions compliance through integration of advanced fuel injection, new combustion regimes, exhaust-heat recovery, aftertreatment, advanced controls, low-friction features, air handling, thermal management, and advanced materials. (DOE, 2006, p. 21).
Background and Analysis
The 21CTP developed an energy audit of a typical Class 8 tractor-trailer combination vehicle traveling on a level road at a constant 65 miles per hour (mph) with a gross combination weight (GCW) of 80,000 lb, as shown in Figure 3-1. Baseline
1
Personal communication to the committee from Ken Howden, U.S. Department of Energy, Office of FreedomCAR and Vehicle Technologies, August 29, 2007.
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FIGURE 3-1 Energy audit of a typical Class 8 tractor-trailer combination on a level road at a constant speed of 65 mph and a GVW of 80,000 lb. SOURCE: DOE, 2006, p. 7.
TABLE 3-1 Baseline and 21CTP Target Values from the Energy Audit Shown in Figure 3-1
Base
Target
Percentage Reduction
Total Energy Consumption
380 kW
225 kW
40%
Engine Power Required
160 kW
112.8 kW
30%
Thermal Efficiency
42%
50%
—
Auxiliary Loads
15 kW
7.5 kW
50%
Drivetrain
9 kW
6.3 kW
30%
Rolling Resistance
51 kW
30.6 kW
40%
Aerodynamic Losses
85 kW
68 kW
20%
and 21CTP target values from the energy audit shown in Figure 3-1 are also listed in Table 3-1.
The following observations can be derived from this energy audit:
Improvements in engine efficiency offer the largest potential reductions in fuel usage. Reductions in rolling resistance and aerodynamic losses offer lesser reductions in fuel usage.
The engine power output of 160 kilowatts (kW), which is required by the vehicle at 65 mph, is about 42 percent of the total fuel energy consumption rate of 380 kW (which equates to 6.8 mpg). Therefore, the thermal efficiency is 42 percent, which is representative of today’s typical diesel engine thermal efficiency at the 65 mph road load operating condition.
A 20 percent improvement in engine thermal efficiency from the current baseline of 42 percent will yield the 50 percent thermal efficiency objective.
Increases in fuel economy, expressed in miles per gallon (mpg), will be directly proportional to improvements in thermal efficiency. However, fuel usage in gallons is inversely proportional to miles per gallon. Therefore, a 20 percent improvement in thermal efficiency will result in only a 16.7 percent reduction in fuel usage, as shown below.
Thermal efficiency = (work output)/(fuel energy input) ~ miles/gal ~ mpg
Fuel usage ~ 1/mpg
Percentage change in fuel usage = (1/mpgimproved − 1/mpgbase) × 100
Percentage change in fuel usage = (1/1.2 − 1/1.0) × 100 = −16.7 percent
This result illustrates an inconsistency in a presentation to the committee,2 which erroneously suggested that a 20 percent improvement in engine thermal efficiency would yield a 20 percent reduction in fuel usage.
For consistency with DOE, the following terminology is used in this report:
Individual vehicle fuel consumption is expressed as gallons per mile (gpm). (Note: Alternative units such
2
Vinod K. Duggal, Cummins Engine Company, Inc., “Diesel Engine R&D and Integration,” Presentation to the committee, Washington, D.C. February 9, 2007, Slide 11.
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as liters/100 km or gallons/ton-mile may be more descriptive, but the committee did not use them.
Individual vehicle fuel economy is expressed as miles per gallon (mpg).
Total annual vehicle fuel consumption is expressed in total gallons consumed and is equal to total vehicle miles traveled divided by the average mpg.
Program Status
The 21CTP selected the engine manufacturers Cummins, Caterpillar, and Detroit Diesel as the industry partners for the demonstration of 50 percent thermal efficiency at 2010 emissions. Although Volvo/Mack was also identified by DOE as another industry partner in the 21st Century Truck Partnership Roadmap, Volvo/Mack does not appear to have been funded and has not reported any results. Work on the 50 percent thermal efficiency objective began with the initiation of the 21CTP in 2000 and continued until 2007, when DOE concluded this activity.
The 21CTP funding for the demonstration of 50 percent thermal efficiency at 2010 emissions is shown in Table 3-2. A total of $116 million was spent on the program for demonstration of 50 percent thermal efficiency at 2010 emissions, with $55 million provided by DOE and $61 million provided by the industry partners. The industry partners performed all of the work in this program. DOE did not provide the committee with a breakdown of specifically how the government money and the industry money were spent.
Although it was not clearly stated by the 21CTP, the committee assumed that achieving this goal required testing a complete engine system on an engine dynamometer and demonstrating that the resulting thermal efficiency and emissions, measured according to standardized test procedures, met the specified goals. To assess the status of this goal, the committee summarized the results reported by each industry partner in Table 3-3.3
These results show that none of the industry partners achieved the goal of measuring 50 percent thermal efficiency at 2010 emissions from a complete engine system. With respect to the 50 percent thermal efficiency goal, each partner either failed to test a complete engine system on an engine dynamometer and used analysis to project results, or failed to achieve the 50 percent thermal efficiency goal with a complete engine system.
The technologies used in the demonstration engines, which were modified from production baseline engines, are listed in Table 3-4. These technologies were identified by the industry partners and are categorized according to the features that were intended to be used for this demonstration and are listed under Major Activity and Milestone 3 (DOE, 2006, p. 21).
TABLE 3-2 21CTP Funding for the Demonstration of 50 Percent Thermal Efficiency (U.S. dollars)
DOE
Participant
Total
Cummins
19,032,087
20,471,307
39,503,394
Caterpillar
19,353,158
22,854,337
42,207,495
Detroit Diesel
16,906,376
17,496,651
34,403,027
Total
55,291,621
60,822,295
116,113,916
SOURCE: Ken Howden, DOE, FCVT, DOE responses to committee queries on 21CTP engine systems and fuels, March 28, 2007.
Although the details of the technology features are vague in many cases, significantly different approaches were taken in several areas. Cummins used a high-pressure (HP) common rail fuel, system while Caterpillar and Detroit Diesel did not specify the fuel injection system. Another possible significant difference is that Caterpillar used variable intake valve actuators while Cummins and Detroit Diesel did not specify this feature. Exhaust Gas Recirculation (EGR) systems differed, with Cummins using high pressure loop EGR while Caterpillar used low-pressure (LP) EGR. Detroit Diesel did not specify the EGR system. Turbocharging systems also differed. Cummins used variable geometry turbo-charging while Caterpillar used a series LP compressor, HP compressor, HP turbine, and LP turbine. Detroit Diesel did not specify the turbocharging system.
Each of the industry partners used a waste heat recovery (WHR) system in an effort to approach 50 percent thermal efficiency. Cummins applied a Rankine cycle WHR system with a turbine-driven generator, which would ultimately drive an electric motor geared to the engine-output shaft. In contrast, Caterpillar and Detroit Diesel used turbocompounding WHR systems.
The Cummins results, which indicated that 50 percent thermal efficiency could be achieved when a Rankine cycle WHR system with a power output of 57 hp was added to the engine power output of 378 hp, are questionable due to two key technical issues.
The “Rankine cycle WHR System Test Block” schematic provided by Cummins shows 60°F cooling water provided for the Rankine cycle WHR system. This unrealistically low temperature cooling water, which would not be available on Class 7 or 8 trucks, would improve the efficiency of the Rankine cycle WHR system (Van Wylen, 1961, pp. 282-284).
An appropriate heat sink for such a Rankine cycle system might be air at an 80°F temperature. Such a heat sink temperature would require the design of special heat exchange systems and a system to provide the air for cooling. Thus, the change in Rankine cycle heat sink temperature would be accompanied by addi-
3
Ken Howden, DOE, FCVT, DOE responses to committee queries on 21CTP engine systems and fuels, March 28, 2007.
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TABLE 3-3 Reported Results of Thermal Efficiency Testing
Measured Test Results
Cummins
Caterpillar
Detroit Diesel
Engine alone
43.2% at 378 hp
Not Specified
Not Specified
WHR
57 hp at 60°F cooling water for Rankine Cycle
Not Specified
Not Specified
System (Engine + WHR)
Not tested (WHR device was not integrated with engine-output shaft)
47.4% Thermal Efficiency
48.4% Thermal Efficiency
Analytical Projections (Reported as Peak Efficiency)
50% Brake Thermal Efficiency
50.5% Thermal Efficiency (Nelson, 2006a)
50.2% Thermal Efficiency
Baseline Engine
Engine Model
MY2000ISX 450
2007 C15 15L Engine
Not Specified
Rated Power
450 hp @ 2000 rpm
550 hp @ 1800 rpm (est.)
Peak Torque
1650 ft-lb @ 1200 rpm
1850 ft-lb @ 1200 rpm and 1850 ft-lb @ 1100 rpm
1534 ft-lb @ 1237 rpm
Thermal Efficiency
42%
Not Specified
Not Specified
Test Speed/Load Condition
“Typical Cruise”a
“Key fuel economy point”a
Not Specified
Test Conditions
SAE J1349 (Net Power)
SAE J1995 (Gross Power)
EPA Certification Procedures
Technology Demonstration Engine
System Tested
Engine and Rankine cycle WHR System were not mechanically connected
Implied to be total engine and turbocompound system
Implied to be total engine and turbocompound system
Test Speed/Load Condition
Peak Torque
Peak Torque (1200 rpm, 1,850 ft-lb)
Not Specified
Test Condition Power
435 hp
Not Specified
Not Specified
Issues with Results
Rankine cycle is used to produce electricity. Losses in the conversion of electricity to engine shaft power do not appear to be included
Rankine cycle used 60°F cooling water. Significantly higher temperatures would be expected in a vehicle, with subsequent deterioration
aGurpreet Singh, DOE, FCVT, “Overview of DOE/FCVT Heavy-Duty Engine R&D,” Presentation to the committee, Washington, D.C., February 8,of the Rankine cycle efficiency 2007.
tional energy losses required for cooling the system condenser.
A driveline electric motor consuming the electric power generated by the Rankine cycle WHR system and geared to the engine-output shaft would be required to utilize the WHR power in a Class 7 or 8 truck. Instead of testing a driveline electric motor and gear set to transmit the electric motor power to the output shaft of the engine, a load bank (i.e., resistors) was used to consume the electric power generated. The efficiency of the electric motor and the gear set do not appear to have been included in the calculation of the power that the WHR system could add to the engine shaft power.
Several features identified in the Major Activity and Milestone 3 were not included in the test engines, as shown in Table 3-5, and were not addressed by the industry partners. The most notable features not included were “new combustion regimes” and “advanced materials.” This was of significant concern because DOE had funded extensive research work in the 21CTP focused on low-temperature combustion within the category of “new combustion regimes” and high-temperature materials within the category of “advanced materials.”
Other features were not applied consistently by the industry partners; selected features were used by some partners and were not used by other partners. These areas included “advanced fuel injection,” “advanced controls,” “low-friction features,” “air handling,” and “thermal management.” Several examples illustrate this issue:
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TABLE 3-4 Technologies in Demonstrator Engines for Thermal Efficiency Testing
Features
Cummins
Caterpillar
Detroit Diesel
Engine
MY2000 ISX 450
2007 C15 15L Engine
Not Specified
Advanced Fuel Injection
High-pressure common rail fuel system replaced the HPI fuel system
NA
NA
New Combustion Regimes
NA
NA
NA
Exhaust-Heat Recovery
Rankine cycle with load bank to simulate a driveline motor consuming electric power
Turbocompound
Turbocompound
Aftertreatment
Simulated by increasing back pressure on the exhaust
High efficiency aftertreatment includes dual DPF and dual NRT
High-efficiency NOx aftertreatment
Advanced Controls
Engine calibration was tuned with the hardware set to achieve target emission levels
Variable intake valve actuators
NA
Low-Friction Features
Optimized lube and water pumps
Low-friction components
NA
Air Handling
NA
Reduced flow restriction, High-Efficiency air systems (series turbocharging)
NA
Thermal Management
NA
Reduced heat rejection
NA
Advanced Materials
NA
NA
NA
Other Features
Compression Ratio
Increased compression ratio
Increased compression ratio
Cylinder Pressure
NA
Increased peak cylinder pressure capability
NA
Charge Cooling
NA
High efficiency compact Intercooler and Aftercooler
NA
EGR
High-pressure loop EGR with EGR cooler
Low pressure (LP) EGR picked up after DPF; includes CGIC (EGR cooler)
NA
Turbocharging
Variable geometry turbocharging instead of fixed geometry turbocharging
High Efficiency Air System with series LP compressor, HP turbine and LP turbine
NA
Other
Exhaust—WHR cooler
System optimization (peak cylinder pressure, CR, etc.)
NA
CAC—WHR cooler
Coolant—WHR cooler
WHR system boost and feed pumps, turbine/generator
Test cell coolers to control engine coolant
NOTE: CAC, charge air cooler; CGIC, clean gas induction cooler; DPF, diesel particulate filter; IMT, intake manifold temperature; NRT, NOx reductionand IMT to target conditions trap; WHR, waste heat recovery.
Variable valve actuation was used only by Caterpillar. The role of this feature for improving thermal efficiency was not defined. Furthermore, the committee was not informed of the extent to which the absence of this feature on the engines of the other two industry partners contributed to their failure to achieve the 50 percent thermal efficiency goal.
Only Caterpillar stated that it incorporated reduced heat rejection in its engine, but the means by which this was achieved was not defined and the role of this feature for improving thermal efficiency was not provided. Caterpillar subsequently reported to the committee that it had prepared air gap pistons and exhaust port liners, but that they had not been tested. The committee did not receive an explanation of why, after nearly 7 years with thermal management as a key feature to be included in this project, these items were not included in the Caterpillar test engine. In contrast, the engines of the other two partners did not include this feature and the committee did not receive an explanation of why this feature was not included in their programs. Likewise, the committee was not informed of the extent to which the absence of this feature contributed to their failure to achieve the 50 percent thermal efficiency.
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TABLE 3-5 Status of Achieving 2010 Emissions Standards at 50 Percent Thermal Efficiency
Cummins
Caterpillar
Detroit Diesel
Emissions Standards
Test Conditions
Assumed to be the same single point used to measure thermal efficiency
—
—
EPA FTP Heavy Duty Transient Test Cycle, Supplemental Emission Test (SET) consisting of the 13 mode ESC (European Stationary Cycle), and NTE (Not to Exceed) Limits.
Engine-Out Emission Test Results
NMHC (nonmethane hydrocarbon)
—
—
—
—
CO
—
—
—
—
NOx
1.39 g/bhp-h
2.5 g/bhp-h
—
—
PM (particulate matter)
<0.1 g/bhp-h
—
—
—
Exhaust Emission Test Results
NMHC
—
—
—
0.14 g/bhp-h
CO
—
—
—
15.5 g/bhp-h
NOx
—
—
—
0.20 g/bhp-h
PM
—
—
0.006 g/bhp-h
0.01 g/bhp-h
Exhaust Emission Analytical Calculations
NMHC
—
—
—
—
CO
—
—
—
—
NOx
0.209 g/bhp-h
0.17 g/bhp-h
0.2 g/bhp-h
—
PM
<0.01 g/bhp-h
<0.01 g/bhp-h
—
—
Assumptions for Analytical Calculations
NOx
85% effectiveness with urea-SCR aftertreatment
93-97% conversion efficiency demonstrated with SCR aftertreatment (Nelson, 2006a)
95.3% urea SCR efficiency assumed, but higher efficiency has been measured
—
PM
90% effective PMI filter
—
—
—
Aging Used for Aftertreatment System
Above Performance assumptions “consistent with an aged cycle.”a
“The effect of aging was accounted for by only using a 5% degradation factor for the NOx aftertreatment”a
“These are technology evaluation/demonstration projects, and hence, did not require the protocol of durability or aging required for product development.”a
—
DPF Loading
Assumed to have average loading
—
—
—
Fuel Economy Penalty
Reflected in base engine performance. Aftertreatment system was simulated by increased back pressure on the exhaust.
The fuel economy penalty for the back pressure of 13 kPa of the aftertreatment system was accounted for by actually having the aftertreatment installed
“The fuel economy information is competitive information, and, therefore, not public domain.”a
—
DPF Regeneration
—
Passive regeneration ability of the DPF allows it to be self-regenerating
—
—
NOTE: —, no information provided to the committee.
aGurpreet Singh, DOE, FCVT, “Overview of DOE/FCVT Heavy-Duty Engine R&D,” Presentation to the committee, Washington, D.C., February 8, 2007.
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TABLE 3-6 Improvements Proposed for Reaching 50 Percent Thermal Efficiency
Feature
Cumminsa
Caterpillarb
Detroit Dieselb
Breathing
NA
NA
Variable breathing
Fuel Injection
NA
Higher injection pressure
Heat Insulation
NA
Add air gap pistons
NA
Add exhaust port liners
Parasitic Losses
NA
NA
Parasitic loss reduction
Turbocharger
NA
Redesign the LP stage turbine to reach the 80% analytical predictions
Increased efficiency
Add the redesigned HP stage compressor to reach 80% analytically predicted level
WHR
NA
Redesign turbocompound mechanically to eliminate rubbing friction caused by undamped shaft dynamics
NA
Aftertreatment
NA
NA
Backpressure reduction
aCummins analytically projected 50 percent thermal efficiency, but it did not demonstrate 50 percent thermal efficiency with one complete engine system. Improvements are likely to be required by Cummins to resolve issues noted in Table 3-3 in order to achieve 50% thermal efficiency.
bImprovements provided by each company.
In defining the goals of the 21CTP, DOE indicated that all of these areas would have a significant role in improving engine thermal efficiency, yet several of the features received little or no attention in the attempted demonstration of 50 percent thermal efficiency. Although DOE has provided significant funding in several of these areas in the 21CTP in addition to the funding for the achievement of 50 percent thermal efficiency at 2010 emissions, the results from this work were not included in the unsuccessful attempts by the three industry partners to achieve the important goal of 50 percent thermal efficiency. Advanced development within companies usually lags national laboratory research. However, not including many advanced features in the test engines was of particular concern, because the engine manufacturers were known to have had past experience and development activities in most of these areas.
DOE should review the original features expected to be included in the 50 percent thermal efficiency engine and determine the justification for omitting some of the features from the demonstration engines. DOE should also determine how the results of their funding of research in several of these areas, especially in the categories of “new combustion regimes” and “advanced materials” could have been incorporated in an engine that might have had a greater potential to achieve 50 percent thermal efficiency.
None of the industry partners demonstrated compliance with the 2010 emissions regulations. Meeting the 2010 standard while achieving the 50 percent thermal efficiency goal implied that any thermal efficiency penalty incurred by meeting the 2010 emissions standard would inherently be included in the thermal efficiency measurement. Comparisons of the test procedures used to confirm that the demonstrator engines met the 2010 emissions standard and the emission control systems used, as reported by the industry partners, are shown in Table 3-5.4 “Meeting the 2010 emissions standard” implies that: (a) emission levels from the test engine and aftertreatment system, when tested on the EPA FTP Heavy Duty Transient Test Cycle, the Supplemental Emission Test (SET) and the Not To Exceed (NTE) tests, are adequately below the applicable standards to account for the statistical variability of emission results from in-use production engines, and (b) the complete test engine and aftertreatment system has been aged on a durability cycle to simulate 435,000 miles for HHDDE as prescribed by the EPA regulations. The table indicates that an inconsistent approach was taken by the three industry partners in demonstrating 2010 emissions.
As described earlier, none of the partners achieved the goal of 50 percent thermal efficiency at 2010 emissions standards. Instead, the industry partners presented discussions on potential improvements that might be used to reach the stated goals. These potential improvements, as reported by the industry partners, are summarized in Table 3-6.5 As indicated in the table, Caterpillar and Detroit Diesel projected that significant design changes would be required to reach the goal of 50 percent thermal efficiency at 2010 emissions. In contrast, Cummins analytically projected 50 percent thermal efficiency, but it did not demonstrate 50 percent thermal efficiency with one complete engine system. Improvements are also likely to be required by Cummins to resolve the issues noted in Table 3-3. EPA test procedures are the industry standard and should be used for emissions testing, in order to achieve 50 percent thermal efficiency with one complete engine system.
4
Ken Howden, DOE, FCVT, DOE responses to committee queries on 21CTP engine systems and fuels, March 28, 2007.
5
Ken Howden, DOE, FCVT, DOE responses to committee queries on 21CTP engine systems and fuels, March 28, 2007.
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Finding 3-1. Although DOE has concluded that the 50 percent thermal efficiency goal has been achieved, the experimental test results show that none of the industry partners achieved the goal of 50 percent thermal efficiency at 2010 emissions standards with a complete engine system. Each partner either failed to test a complete engine system on an engine dynamometer and used analysis to project results or failed to achieve 50 percent thermal efficiency at 2010 emissions standards with a complete system. Details of the analytical projections were proprietary and were not provided to the committee. Moreover, the work that was accomplished was at the intrinsically more efficient peak torque condition rather than at an engine speed and load representative of 65 mph road load.
Recommendation 3-1. Objective and consistent criteria should be used to assess the success or failure of achieving a key goal of the 21CTP such as the attainment of 50 percent thermal efficiency. Detailed periodic technical reviews of progress against the program plan should be conducted so that deficiencies can be identified early and corrective actions implemented to ensure success in accomplishing program goals. DOE should continue to work toward demonstrating 50 percent thermal efficiency at the peak efficiency condition as well as representative 65-mph road load engine speed and torque condition. DOE should also consider reducing the number of industry contracts on specific engine projects that are funded so that only the engine systems most likely to meet the goal, based on system modeling and analytical projections, will be developed and tested experimentally.
Finding 3-2. The goal of achieving 50 percent thermal efficiency at 2010 emissions was not clearly specified by the 21CTP. Each of the three industry partners used a different test procedure for measuring thermal efficiency (see Table 3-4). Likewise, none of the industry partners demonstrated 2010 emissions using the required EPA test procedures with aged engine and aftertreatment systems. A goal of this importance should be specified by standard test procedures so that the results are verifiable and compatible with industry standards.
Recommendation 3-2. Future work to achieve the goal of 50 percent thermal efficiency at 2010 emissions should be specified by industry standard test procedures. SAE J1349 Engine Power Test Code is the industry standard for net power ratings and should be specified for the thermal efficiency portion of this goal (SAE, 2004). Test results should clearly provide all of the engineering details required to interpret the results.
Finding 3-3. Some of the technical features used to approach the goal of 50 percent thermal efficiency, as shown in Table 3-4, differed among the three industry partners, and no explanation or technical analysis was provided to justify the different approaches. Furthermore, the effectiveness of the individual features used on the demonstration engines could not be determined due to the lack of analysis or system modeling. A validated system model should have been used to compare test data with analytical projections to determine if each feature was performing as expected.
Recommendation 3-3. Prior to beginning future test phases of this program to achieve 50 percent thermal efficiency, system modeling should be used so that the preferred technical approaches could be selected and test data could be compared with analytical projections to determine if the expected results have been obtained.
Finding 3-4. Although DOE stated that the 2010 emissions standard was achieved in the demonstrator engines attempting to achieve 50 percent thermal efficiency, only steady-state emissions at one test condition were reported rather than test results from the EPA specified test procedures for the 2010 emissions standard. In some cases, the emissions were estimated from engine-out emissions and assumed aftertreatment efficiency.
Recommendation 3-4. Achieving compliance with 2010 emissions with a “one-off” prototype engine designed to demonstrate 50 percent thermal efficiency may be too stringent a goal for the 21CTP. The emission objective levels should be revised to be the demonstration of emissions at a single point, where the emission level selected to be demonstrated should have the potential for meeting the 2010 emissions as specified by EPA test procedures.
Finding 3-5. Although industrial partners reported on their progress, the presentations were high level summaries with critical engineering information omitted, thereby making the assessment of accomplishments relative to goals difficult.
Recommendation 3-5. DOE should work to develop a review process that will allow future review committees to evaluate “sensitive” information so quantitative assessments of progress can be made.
Engine System Life and Durability
Tests with single, one-off demonstration engines fail to demonstrate the system life required for introduction into the heavy-duty truck marketplace. The demonstration of system durability for a 400,000- to 1,000,000-mile system life target represents a serious “real world” hurdle for the introduction of such hardware.
DOE and the industry partners will need to address the system life target of heavy-duty diesel engines as they are developing experimental, one-off demonstration engines with improved thermal efficiency. At a minimum, a roadmap of required technical actions to achieve system life targets
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after demonstrating thermal efficiency objectives in a one-off, demonstration engine should be provided.
A Novel Potential Energy Recovery Concept
In reviewing the Cummins WHR concept of the Rankine cycle using a turbine generator to provide electric power to supplement the main engine shaft power, the committee found that an interesting, and potentially relevant, extension of this concept was contained in a Cummins presentation on exhaust energy recovery at the 2006 Diesel Engine Emission Reduction (DEER) Conference (Nelson, 2006b). This presentation suggested the following features for a potential energy recovery concept:
An on-vehicle high-voltage bus, departing from the typical 12 VDC systems
Incorporating technology common with Hybrid Electric Vehicles (HEV), including battery storage and power conditioning.
Opportunities for high voltage accessories, including:
Driveline motor/generator
Coolant pump(s)
Power steering
Electric fans
Air compressor, and
Heating, ventilation, and air conditioning (HVAC)
This brief presentation suggested that a significant revision of the entire propulsion system and its accessories could potentially yield fuel savings from the following techniques:
Using the HEV concept could allow the main diesel engine to be downsized and peak power demands could be supplied by the electric motor and battery storage system
Extensive use of high voltage, electrically driven accessories on an on-demand basis
Elimination of a separate engine-driven alternator
This significant revision of the entire propulsion system and its accessories should be studied for its potential in providing fuel savings as a means for meeting the goal of the 21CTP. The study should include analysis of the cost-benefit of each of the opportunities listed above. These opportunities are discussed further in Chapter 4, under the heading “Hybridization of Long-Haul Trucks.”
Fuel Economy Losses Related to Oxides of Nitrogen (NOX) and Particulate Control
One of the key challenges with regard to maintaining and improving fuel economy for heavy-duty truck engines is to minimize the fuel economy losses associated with adding NOx and particulate control systems to these engines to meet future emissions standards. The impacts on fuel economy associated with the addition of these emission control systems are difficult to quantify for specific engines from the data that were presented to the committee. The industry partners indicated that the details of these emission control systems are proprietary and have chosen not to specify their configurations or their performance explicitly.
Several of the slides presented indicate the general trends of the adverse impact on fuel economy that can occur due to the additional emission control systems without further improvements in the thermal efficiency of the engine. Engine efficiency improvements, which had been occurring at the level of one half a percent per year, decreased significantly as the model year 2002 was approached.6 Figure 3-2, which is reproduced from Duggal, shows trends for the impact of emission standards for model year 2002 and beyond on engine efficiency.7 A 3 percent decline in absolute engine efficiency is associated with the introduction of cooled EGR to meet the 2002 emissions standard. An additional 1.5 percent degradation in engine efficiency is forecasted to occur with increased EGR to meet the 2007 emissions standard. Improvements in the engine configuration were portrayed as having the capability to recover this absolute 4½ percent engine efficiency decrease at the 2007 emissions standard. Figure 3-2 also predicts a 2 percent absolute engine efficiency degradation because EGR levels will again be increased to meet the 2010 emissions standard.
Because of the lack of detailed information, it is not possible to determine the precise fuel economy degradation that had been encountered by the engine manufacturers as they changed their configurations to meet the emission standards. DOE should ask the manufacturers to supply this information to assist in determining the size and cause of these fuel economy degradations associated with the successive changes in required emission standards (such as increases in back pressure before regeneration and quantity of fuel used to regenerate the diesel particulate filter [DPF]). Such information would allow the DOE to evaluate the potential beneficial impact of the technologies being developed by the 21CTP program.
An additional concern is associated with the cost and energy content/requirements (because urea is made from natural gas) of reagents for reducing NOx levels with Selective Catalytic Reduction (SCR) NOx removal systems. It is not clear how the cost or energy content/requirements of such reagents is being related to the efficiency targets for the 21CTP. Because the reagent use is directly proportional to the pre-SCR NOx levels in the exhaust, one must know these details to outline reagent use and cost. Discussion with regard to SCR reagent usage was absent from the presentations and
6
Vinod K. Duggal, Cummins Engine Company, Inc., “Diesel Engine R&D and Integration,” Presentation to the committee, Washington, D.C., February 9, 2007, Slide 8.
7
Vinod K. Duggal, Cummins Engine Company, Inc., “Diesel Engine R&D and Integration,” Presentation to the committee, Washington, D.C., February 9, 2007, Slide 16.
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FIGURE 3-2 Heavy truck engine technology roadmap showing the effects of emission regulations on thermal efficiency. SOURCE: Vinod K. Duggal, Cummins Engine Company, Inc.,“Diesel Engine R&D and Integration,” Presentation to the committee, Washington, D.C., February 9, 2007, Slide 16.
only the NOx removal effectiveness was discussed in information presented for the SCR systems. If DOE determines that reagent costs or energy is significant, it should specify a procedure to include these effects in thermal efficiency and vehicle fuel economy goals and economic assessments.
The data presented for the 50 percent thermal efficiency goal by the industry partners projected the performance of such emission control systems for the configurations used in the specific engine tests. In some cases, the operating condition chosen for the test caused exhaust temperatures to be sufficiently high to continuously regenerate the DPFs. Thus, no fuel economy degradation was associated with the level of fuel economy demonstrated. This circumstance appears to be an optimistic assumption with regard to overall usage of a heavy-duty truck. It appears reasonable that DPFs would require periodic regeneration, especially in city use or operating without a loaded trailer, and thus the potential for degradation in overall engine efficiency.
A January 31, 2007, Associated Press article (Robertson, 2007) quoting Freightliner executives highlighted additional costs associated with meeting new emissions standards. In that article, Freightliner Corporation stated that some fuel economy penalties were associated with meeting the 2007 emissions standards. These fuel economy degradations were not quantified in their corporate statement.
Thermal Efficiency Goal at Full Load Versus Road Load
The 21CTP goal for the three industry partners was to demonstrate 50 percent thermal efficiency. Although the specific engine speed and load conditions for this demonstration were not specified, each of the industry partners reported that their best thermal efficiency was measured at, or near, the peak torque condition of the engine, as indicated in Table 3-3.
The peak torque condition where the best thermal efficiency was demonstrated is not consistent with the typical 65 mph road load engine operating condition that was specified as the focus of Class 8 trucks for the 21CTP. This discrepancy in operating conditions is illustrated in the energy audit of a typical Class 8 tractor-trailer combination on a level road at a constant speed of 65 mph and a GVW of 80,000 lb as shown previously in Figure 3-1.
To meet the goals of the 21CTP goal, this audit shows that the 50-percent thermal efficiency goal is required at the road load power at 65 mph rather than at the peak torque condition. The road load power required at 65 mph is 214 hp (160 kW), as shown in Table 3-7. At the peak torque condition for these engines, approximately the same power is generated as at the rated power condition, which is attributed to the significant torque rise of these engines.
The decrease in thermal efficiency at the 65 mph road load power condition versus the peak torque condition can be significant. This reduction is illustrated on a typical fuel consumption map for a production DDC Series 60 12.7L engine shown in Figure 3-3 (from Merrion, 1994). The 65 mph road load operating condition (speed and power) for typical drivetrain parameters for a fuel-efficient Class 8 truck is shown on this fuel consumption map. As indicated in the figure, a 2.5 percent decrease (1.1 percentage point
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TABLE 3-7 Comparison of Engine Rated Power and Road Load Power
Engine
Rated Power
Road Load Power
Road Load Power as Percent of Rated Power
Cummins ISX
450 hp
214 hp
48%
Caterpillar C15
550 hp
214 hp
39%
Detroit Diesel
NA
NA
NA
NOTE: NA, Not available to the committee.
FIGURE 3-3 DDC Series 60 12.7L brake-specific fuel consumption map. SOURCE: Based on Merrion, 1994, modified by the committee. Reprinted with permission from SAE paper 940130. Copyright 1994 by SAE International.
decrease) in thermal efficiency occurs from the peak thermal efficiency condition to the road load condition, as shown in Table 3-8.
The 21CTP stated that “difference in peak thermal efficiency and road-load thermal efficiency is common, [but] it is not a universal rule.”8 However, subsequent data provided by several of the industry partners, also shown in Table 3-8, indicated that the decrease in thermal efficiency at the 65 mph road load engine operating condition versus the peak thermal efficiency can be significant. The available data from the 21CTP as well as published data indicate that up to a 7 percent decrease (3.4 percentage point decrease) in thermal efficiency can be expected at the 65 mph road load condition versus the peak thermal efficiency condition.
A convenient method for defining the road load condition would be to use one of the operating conditions from the SET (Supplemental Emission Test) which is the 13-mode steady-state emission test established to help ensure that heavy-duty engine emissions are controlled during steady-state type driving, such as a line-haul truck operating on a freeway. This test is based on the European Union’s 13-mode ESC (European Stationary Cycle) schedule, commonly referred to as the “Euro III cycle.” This cycle is shown schematically in Figure 3-4.
Because road load power required at 65 mph is approximately half of the rated power, and rated torque of the engine, 13-mode test point A50 (60 percent engine speed, 50 percent load) would appear to be an appropriate choice to approximate the 65 mph road load condition, although this would need to be confirmed for each engine under consideration. The 60 percent of rated engine speed for test point A50 is similar to the speed for the peak torque condition that had been used for the demonstration of peak thermal efficiency by the industry partners.
Finding 3-6. Achieving the 21CTP’s goal of 50 percent peak thermal efficiency is not expected to result in the Partnership’s goal of 50 percent thermal efficiency for a typical Class 8 tractor-trailer combination on a level road at a constant speed of 65 mph and a GVW of 80,000 lb. Even if 50-percent thermal efficiency were to be achieved at, or near, the peak torque condition, up to a 7 percent improvement (3.4 percentage point improvement) task would still remain to achieve 50 percent thermal efficiency at the 65 mph road-load condition.
Recommendation 3-6. The 21CTP should clearly define, in addition to the peak thermal efficiency condition, the specific 65-mph road-load condition for demonstrating 50 percent thermal efficiency. The committee suggests using one of the 13-mode steady-state emission test points for approximating the 65-mph road load condition. For typical engines, drivetrains, and vehicles, emission test point A50 (60 percent engine speed, 50 percent load) would be appropriate, although the most appropriate point (or multiple points, if necessary) should be determined for the specific engine, powertrain, and vehicle configuration under consideration. The 21CTP should request each of the three current industry partners to test their experimental demonstration engines according to this recommendation.
A recent CRC study has proposed new cycles under development that may correlate better with actual in-use emissions and, possibly fuel usage, for heavy-duty diesel trucks (Tennant, 2007). This study found that their in-use operation
8
DOE, FCVT, 21CTP, response to committee query, transmitted via e-mail by Ken Howden, March 27, 2007.
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TABLE 3-10 Comparison of ASTM Specification for No. 2 Diesel Fuel and 100 Percent Biodiesel
D975-No.2 Diesel Fuel
D6751-Biodiesel (B100)
Units
ASTM Method
Applicability
Diesel fuel suitable for use in on-highway engines
Blend component up to 20 percent in any diesel fuel or home heating oil
°C
D93
Flash point
52 min.
130 min.
°C
D93
Water and Sediment
0.050 max.
0.05 max
percent volume
D2709
Distillation Temperature, 90% Recovered
282-338
Not Specified
°C
D86
Distillation Temperature, Atmospheric Equivalent, 90% Recovered
Not Specified
360 max.
°C
D1160
Kinematic Viscosity, 40°C
1.9-4.1
1.9-6.0
mm2/sec
D445
Ash
0.01 max.
Not Specified
percent mass
D482
Sulfur
0.0015 max.
0.0015 max.
percent mass (ppm)
D5453
Copper Strip Corrosion
No. 3 max.
No. 3 max
D130
Cetane Number
40 min.
47 min.
D613
One of the following:
Cetane Index
40 min.
Not Specified
D976
Aromaticity
35 max.
Not Specified
percent volume
D1319
Cloudpoint
Report
Report
°C
D2500
Ramsbottom Carbon on 10% Distillation Residue
0.35 max.
Not Specified
percent mass
D524
Carbon Residue 100% Sample
Not Specified
0.05 max.
percent mass
D4530
Lubricity, HRFF@60C
520 max.
Not Specified
microns
D6079
Calcium/Magnesium combined
Not Specified
5 max.
ppm (ug/g)
EN14538
Sulfated Ash
Not Specified
0.02 max.
percent volume
D874
Acid Number
Not Specified
0.50 max.
mg KOH/gm
D664
Free Glycerin
Not Specified
0.020 max.
percent mass
D6584
Total Glycerin
Not Specified
0.240 max.
percent mass
D6584
Phosphorus Content
Not Specified
0.001 max.
percent mass
D4951
Sodium/Potassium combined
Not Specified
5 max.
ppm
EN14538
Oxidation Stability
Not Specified
3 min.
hours
EN14112
SOURCE: DOE responses to committee queries on engine systems and fuels, delivered by Ken Howden, DOE, FCVT, via e-mail, July 27, 2007.
explained in this chapter, these engines are modifications of existing production diesel engines with conventional combustion systems using high pressure, common-rail fuel injection systems, advanced turbocharging systems and cooled EGR, along with PM and NOx aftertreatment systems. The production engines were originally developed for the current ASTM specification for No. 2 diesel fuel and the modified versions of these engines for the 21CTP program were tailored for the same fuel specification.
The second part of Goal 1 deals with 5 percent replacement of petroleum fuels with non-petroleum fuels. DOE explained that their Fuel Technologies R&D program consists of two components: Advanced Petroleum-Based Fuels (APBF) and Non-Petroleum-Based Fuels (NPBF).12 The specific activity of the NPBF component that applies to this objective is research to resolve barriers pertaining to use of non-petroleum fuels as direct replacements of conventional fuels. Fuels and fuel sources under consideration by DOE include:
Biodiesel primarily, but also biomass-to-liquids (BTL)
Oil sands and shale oil
Biodiesel is a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils such as soybeans or animal fats, designated B100 and meeting the requirements of ASTM International Specification D6751. This standard specification for biodiesel was issued in 2002. The specification for biodiesel fuels does not depend on the feedstock and/or processing method. The specification is designed to ensure safe operation in a compression-ignition engine (Hoar, 2007). Biodiesel is not raw vegetable oil; it must be produced by a chemical process that removes glycerin from the oil. Table 3-10 show a comparison of the biodiesel specification, ASTM 6751, with ASTM 975 for conventional No. 2 diesel fuel.
As noted in Table 3-10, many of the physical properties considered in these specifications for biodiesel meet or exceed the stringency of the conventional No. 2 diesel fuel specification. However, several physical properties specified for No. 2 diesel fuel, such as T90, aromaticity and ash, are not specified for biodiesel, thereby making transparent operation in current diesel engines problematic. Experience
12
Kevin Stork, DOE, FCVT, “Fuel Technologies R&D for Heavy Trucks,” Presentation to the committee, February 9, 2007, Washington, D.C.
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to date with biodiesel has shown some favorable properties (lubricity, sulfur content and lower particulate matter emissions) compared with conventional diesel fuel.
To date, EPA has considered biodiesel fuel as “substantially similar” to diesel fuel, which precludes producers from having to go through the laborious EPA fuel waiver request program.
Another potential shortcoming is that the biodiesel specification does not specify composition. Biodiesel fuel composition will depend on the source (rapeseed oil, soy oil, palm oil, coconut oil, waste cooking oil, etc.), and the production technology. Thus, the chemical composition of biodiesel fuels will vary greatly, and their composition will determine their effects on engine operation, deposits, emissions, etc., when blended into conventional diesel fuel. To eliminate some of these potential problems, refinery-based processes, such as Neste Oil’s Next Generation Biomass to Liquids (NExBTL) process (Schill, 2007) have been developed to process the biofuels feedstock in the refinery along with the petroleum. This could help ensure more uniform fuels with consistent properties when biodiesel is a refined component of diesel fuel.
In the United States and around the world, biodiesel production facilities are being built in large numbers. The Renewable Fuels Standard (RFS) of the Energy Policy Act of 2005 has had, and will continue to have a role in the increase in production facilities in the United States. Currently in the United States, there are more biodiesel production facilities than refineries making diesel fuel, and many more are being built and planned. However, their fuel production capacities are very small compared with refineries. In 2005, biodiesel production was less than one percent of refinery production of 2.8 million barrels per day of diesel fuel (EIA). The National Biodiesel Board estimated that 16,000 barrels per day would be produced in 2006 (Moran, 2006), which is significantly less than the several million barrels per day of refinery production of diesel fuel.
Hart’s International Fuel Quality Center/Global Biofuel Center recently projected that the world’s biofuel capacity could increase threefold from its current capacity of 5 billion gallons per year. Even if U.S. biofuels capacity increased similarly by 2010, it would only reach less than 3 percent of refinery production of diesel fuel, which would be insufficient to replace 5 percent of petroleum-derived diesel fuel. Therefore, it is highly unlikely that the goal of at least 5 percent replacement of petroleum fuels could be achieved by 2010 using biodiesel alone.
An additional and increasing concern with biofuels is the competition between biomass use for food and for fuel. This is already evident in the United States with the increased production of corn for ethanol taking away cropland from other products, such as soybeans, and resulting in increased prices for both soy and corn dependent food products.
The controversy over biofuels and ethanol continues to grow. As reported in the Ethanol and Biodiesel News of Sept. 11, 2007, a report by the Organization for Economic Cooperation and Development (OECD) unequivocally recommended that governments around the globe phase out their biofuels subsidies (Ngo, 2007). It characterized them as simply ushering in inefficient new sources of energy supply. The OECD report said biofuels would cut energy-related emissions by 3 percent at most, and that their cost greatly outweighs their benefits. The report’s authors stated, “When acidification, fertilizer use, biodiversity loss and toxicity of agricultural pesticides are taken into account, the overall environmental impacts of ethanol and biodiesel can very easily exceed those of petrol (gasoline) and diesel fuel.”
The authors of this report take no stance on the future of biofuels in the United States. However, as pointed out here and elsewhere in this section, there are many issues involving biodiesel that have to be resolved before it can become a viable commercial success. It is incumbent that the DOE stay in the mainstream regarding all of these issues.
DOE, especially at NREL, together with biodiesel suppliers and users are actively exploring the compatibility of biodiesel fuels with current and future engines. Potential biodiesel performance concerns that are being evaluated are:
Deposit control, especially in the fuel system and at the injector tips
Filter plugging and water separator performance, especially the influence of low temperature properties
Oxidation stability
NOx emissions
Impact of particulate properties on DPF performance, ash loading in the DPF and EGR cooler fouling
Impacts on lubricant performance
DOE did not report on the status or timetable of their efforts to resolve these concerns.
A major exploration of biodiesel fuel issues is currently being conducted by the Japanese Clean Air Program (JCAP), with which NREL has maintained close contact. DOE should explore more joint activities on biofuels with JCAP.
With modern diesel engines moving toward hot fuel circulation (via common rail systems), potential oxidation stability issues will need to be resolved. It is generally accepted that palm oil derived biodiesel (from Southeast Asia) has better oxidation stability than either rape methyl ester (from Western Europe) or soy methyl ester (from the United States). However, a recent study published by SAE (Goto and Shiotani, 2007) pointed out that oxidation stability worsens as the palm oil-derived methyl ester biodiesel fuel content increases, or the fuel temperature increases, with consequent loss of oxidation stability and fuel system corrosion.
The impact of biodiesel on exhaust NOx emissions is not clear. EPA’s position is that biodiesel increases NOx emissions; NREL’s position is that it has little or no effect. A recent paper (Sobotowski et al., 2007) supports EPA’s posi-
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tion. This issue will need to be resolved. The discrepancy may be related to the chemistry of the biodiesel fuels used in the various studies. To resolve the impasse between DOE and EPA, an independent body should look at all of the biodiesel studies to see if the chemistry of the fuel can be related to its impact on NOx emissions.
Today’s diesel fuel can be improved by blending with gas-to-liquid (GTL) components. This approach is used in Europe for premium quality diesel fuel. However, DOE did not comment on any work on diesel fuel blended with GTL components.
Independent of their source and the process for generation, biodiesel fuels should be characterized by their chemical and physical properties. These properties should be used to correlate with the fuel’s performance in engines and impacts on emissions.
A biodiesel blend, as distinguished from biodiesel fuel, is a blend of biodiesel fuel meeting ASTM 6751 with petroleum-based diesel fuel designated BXX, where XX is the volume percent of biodiesel. DOE is focused on ensuring that B20 is compatible with engines with diesel particulate filters/selective catalytic reduction/NOx absorber catalysts that will enter the market in the 2007-2010 timeframe.13 However, to date, the diesel engine manufacturers, through the Worldwide Fuel Charter, have recommended a maximum of five percent biodiesel (fatty acid methyl ester) blended in diesel fuel, and that ASTM Standard D6751 be followed. DOE must allay the engine manufacturers’ concerns about blends containing more than 5 percent biodiesel fuel before such blends can be accepted.
DOE has stated that they are not aware of operational issues for B20 or lower blends prepared from B100 that meets D6751, with one exception. Some biodiesel blends can cause cold temperature filter plugging even when the cloud point of the blend indicates it should be satisfactory. This may be caused by an impurity that is not currently limited in D6751. NREL and other participants at ASTM are working on this issue and expect to ballot a new requirement for the ASTM specification during 2008. DOE acknowledges that experience is still being gained, especially with 2007 and later on-highway engines. As more information is acquired, a further update to the specification may be required.14
DOE did not provide the committee with plans for achieving the goal of replacing 5 percent of petroleum fuel with non-petroleum fuels by 2010. This goal is highly dependent on three factors:
Biodiesel availability
Compatibility with existing engines
Fuel cost
Replacement of 5 percent petroleum fuel by 2010 is a very aggressive, if not unrealizable goal, especially considering that the most optimistic increase in biodiesel production capacity could only achieve replacement of 3 percent of petroleum fuels by 2010, as previously discussed. Regarding compatibility of the fuel with existing engines, DOE did not provide the committee with a timetable for the resolution of the issues associated with the use of biodiesel fuels or blends. Achieving this goal is also highly contingent on the acceptance of biodiesel blends by the diesel engine and trucking industries, especially from a cost and operational performance perspective. Current and proposed federal and state legislation contain tax incentives for the biodiesel industry that could assist with the acceptance of biodiesel fuels. Without these incentives it is unlikely that biodiesel will have a major impact.
Biodiesel fuels are in vogue because of their presumed benefits regarding greenhouse gases, especially carbon dioxide (CO2), reduction. A recent study from Wetlands International (Max, 2007) in the Netherlands has challenged that assumption regarding palm oil. It concluded that the CO2 reduction benefits of palm oil were overwhelmed by the CO2 released when swamps in Southeast Asia were drained to provide land for planting the palm trees. Although this will not apply in the United States, it lends a note of caution, and suggests that rigorous “well-to-wheel” analyses, especially in the generation of the crops providing the biodiesel feedstocks, are needed to thoroughly explore the benefits of biofuels. Land use issues must be incorporated into the “well-to-wheel” analyses.
The Low Carbon Fuel Standard (LCFS) concept is likely to be implemented in the United States and Europe.15 It essentially calls for a 10 percent reduction in carbon intensity of transportation fuels by 2020. Biofuels, including biodiesel, are one of the most likely near term options. DOE, EPA, and industry should work closely together on this standard as it is being implemented.
In addition to biodiesel as a potential replacement for petroleum fuels, DOE is also investigating oil sands and shale oil sources of fuel as part of its Non-Petroleum-Based Fuels (NPBF) efforts. DOE did not provide additional information on work directed toward these fuel sources, and did not provide any indication of the potential extent of the commercial use of these fuels by 2010.
Oil shale for many years has been a prominent potential source of oil. The resource base, primarily in arid Utah and Colorado, is very large. But it has not been commercially tapped to any extent because of environmental concerns related to water availability and surface mining. To lessen the concerns over surface mining, attention is being given to in-situ retorting to generate the shale oil.
In recent years, fuels made from Canadian tar sands have been commercialized and blended into diesel fuel. More than
13
Kevin Stork, DOE, FCVT, “Fuel Technologies R&D for Heavy Truck,” Presentation to the committee, Washington, D.C., February 9, 2007.
14
DOE responses to committee queries on third meeting, delivered by Ken Howden via e-mail July 27, 2007.
15
See http://www.energy.ca.gov/low_carbon_fuel_standard/index.html.
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one million barrels per day of fuels from Canadian tar sands are now being used in the United States. That volume was expected to grow; however recent environmental concerns in Alberta may limit the growth.
Finding 3-13. It is unlikely that the goal of identifying and validating non-petroleum fuel formulations, optimized for use in advanced combustion engines, will be achieved by 2010. DOE’s nonpetroleum fuels effort is focused on resolving biodiesel operational issues and commercialization barriers, but DOE did not provide a timetable for successful resolution of these efforts. DOE is also investigating oil sands and shale oil as other sources of petroleum fuel replacement. DOE did not present a plan for 5 percent replacement of petroleum fuels. The Renewable Fuels Standard of the Energy Policy Act of 2005 is likely to have a role in accelerating the availability of nonpetroleum fuels.
Recommendation 3-13. DOE should continue to work with biodiesel developers and users to ensure compatibility when biodiesel is blended with conventional diesel fuel and problem-free use of biodiesel fuels in diesel engines. Successful deployment will require resolving operational issues and updating the biofuel specifications. Development of refining technology to make acceptable diesel from shale oil or tar sands is not high-risk research suitable for federal funding and should be left to the private sector. DOE should develop specific plans, including key actions and timetables, for 5 percent replacement of petroleum fuels.
Fuels for Low-Temperature Combustion Regime Engines—Goal 2
The committee interpreted Goal 2 as being directed toward fuel properties of petroleum-based fuels that could have beneficial effects on engine efficiency and emissions, including aftertreatment performance with emphasis on engines with new low temperature combustion regimes. Directly addressing this goal is the other component of DOE’s fuel technology R&D program identified as Advanced Petroleum-Based Fuels (APBF).16
A key DOE project focused on this goal is the FACE (Fuels for Advanced Combustion Engines) project. This project, which operates under a Coordinating Research Council working group, was formed to better understand the fuel effects on LTC (low temperature combustion) engines. The fuel variables being investigated are cetane number, aromatic content, and T90 point. Fuels with variations in these properties are being distributed to teams researching multiple approaches to advanced combustion engines and aftertreatment systems. DOE stated that the engine hardware in these studies “may remain undisclosed,” which severely limits the usefulness of this project. Furthermore, because the committee is concerned about the viability of low temperature combustion (discussed in this chapter), the applicability of the results of this project may be limited.
Furthermore, the implication of the FACE project, which is exploring fuels significantly beyond today’s ASTM specification for No. 2 diesel fuel, is of serious concern. DOE did not address the concern that the FACE project may define optimum fuel properties for an engine with a new combustion regime that are not consistent with the properties of conventional diesel fuel defined in the ASTM specification for No. 2 diesel fuel. A potential implication of such a result is that an engine with a new combustion regime may require a separate fuel, which would entail significant problems in the refining, distribution, storage, availability and cost of a special diesel fuel for these engines. Additionally, if the emissions performance of vehicles with engines having a new combustion regime is contingent on use of specialized fuels, it is unlikely that the EPA would grant approval without guarantees of fuel availability.
The history of liquid fuel (both gasoline and diesel fuel) use in the United States shows little or no success for highly specialized fuels with limited sales potential. An example of this is the very limited availability of E85 fuel (85 percent ethanol, 15 percent gasoline) for the millions of recent model year vehicles that can utilize this fuel. Even assuming success of engines with low temperature combustion regimes, there will be very few vehicles in the marketplace with them for many years. Trucking companies are unlikely to buy vehicles with these engines without widespread availability of the specialized, reasonably priced fuel needed for these engines.
Refiners do not like to make small quantities of specialized fuels, especially if it requires capital expenditures. Production, distribution and storage of these fuels will cost more per gallon than for conventional diesel fuels. Refueling stations will not readily either give up an existing tank and pump, or install a new tank and pump, for a specialized fuel with small demand.
While it is important to continue with R&D to understand the optimum fuel properties for current and future engines, it will be more critical to be able to make the future engines operate on the conventional diesel fuel or gasoline that will be readily available for many years. The committee does not believe that specialized fuels will be commercially available for advanced combustion engines, especially with the low volume that will be required for many years for vehicles with these engines. To gain a better appreciation for the issues involved with use of a specialized fuel with advanced combustion engines, DOE should meet with at least several major oil companies to explore the practical realities of providing a special fuel.
With respect to the emission reduction portion of this objective, the difficulty in defining the properties of fuels
16
Kevin Stork, DOE, FCVT, “Fuel Technologies R&D for Heavy Trucks,” Presentation to the committee, Washington, D.C., February 9, 2007, Slide 4.
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for engines with new combustion regimes was pointed out in a recent paper published by SAE (Kalghatgi et al., 2007). The authors said that the debate over reducing engine-out emissions from diesel engines is tied to whether or not future engines, especially light-duty diesel engines, will require higher cetane number than currently is sold in the United States. If such engines need to promote premixed combustion, higher cetane number fuels will not help. These engines are expected to require lower cetane number fuel to allow time for thorough premixing of the air and fuel prior to the initiation of combustion.
Finding 3-14. DOE is exploring fuel properties of petroleum-based fuels that could have beneficial effects on engine efficiency and emissions, including aftertreatment. The committee is concerned about the viability of low temperature combustion regimes used in this effort, and that the applicability of the results of this project may be of limited value. The committee is also concerned that DOE’s work may define optimum fuel properties for an engine with a new combustion regime that are not consistent with the properties of conventional diesel fuel defined in the ASTM specification for No. 2 diesel fuel. A potential implication of such a result is that a future engine with a new combustion regime may require a separate fuel, which would entail significant problems in the refining, distribution, storage, availability and cost of a special diesel fuel for these engines.
Recommendation 3-14. The committee recommends against assuming that specialized fuels will be commercially available for future engines with new combustion regimes. Due to the issues concerning the viability of low temperature combustion regimes and commercially available specialized fuels, DOE should consider redirecting these efforts toward work with greater probability of contributing to the overall goals of the 21CTP.
Nonpetroleum Fuels for the Post 2010 Timeframe—Goal 3
The committee assumed that Goal 3 was intended to emphasize the development of nonpetroleum fuel formulations beyond biodiesel, previously addressed by Goal 1. The goal also addresses benefits of these fuels in providing additional fuel economy improvements and emission reductions. The discussion below will first address the potential fuel formulations followed by the potential functional benefits in fuel economy and emissions.
DOE’s report on their work on this objective to the committee provided little insight into the scope and magnitude of the effort. DOE briefly mentioned that they planned to investigate fuels with properties that capture synthetic fuels. Also briefly mentioned was their effort to resolve barriers pertaining to fuels derived from oil sands and shale oil. DOE has established a synergistic team with the Canadian Center for Upgrading Technology (NCUT) to improve the understanding and development of future fuels. The focus of this effort appears to be on oil sands.
There are many potential sources of non-petroleum derived diesel fuel, including; oil shale, coal, tar sands, natural gas and biomass. Technology exists to make diesel fuel with excellent properties from coal and natural gas. Some gas-to-liquids facilities have been commercialized outside the United States. None has been announced for construction in the United States.
Extreme caution has to be exercised when using diesel fuels made from these sources. For example, engine and fuel system failures have been reported (Peckham, 2007) with light-duty pickup trucks using diesel fuel derived entirely from tar sands. DOE’s Pacific Northwest National Lab is investigating this problem. Although it is unlikely that future diesel fuel will be produced entirely from tar sands, this failure indicates that a thorough investigation of this issue is required. James Eberhardt of DOE has cautioned that more attention needs to be paid to the molecular structure of these new fuels, rather than only the ASTM D-975 diesel fuel specifications.
The goal of identifying fuel formulations that will improve fuel economy and reduce emissions is optimistic, perhaps to the point of being unrealistic. The synthetic fuels being mentioned for this goal are all hydrocarbon-based fuels that would be expected to have combustion characteristics similar to conventional diesel fuel. It appears unlikely that the fundamental mechanisms that control the formation of HC, NOx, and particulate emissions in a diesel engine can be dramatically altered with a change in the fuel formulation to the extent that the emissions could approach zero.
Finding 3-15. DOE provided little insight into the scope and magnitude of the effort to address the goal of developing non-petroleum fuel formulations beyond biodiesel that could provide additional fuel economy improvements and near-zero emissions. DOE did not report any specific work plans, results, or timetables addressing this objective.
Recommendation 3-15. DOE should reaffirm that this goal should continue to be pursued. If the goal is considered to strongly contribute to the overall 21CTP goals, DOE should develop specific work plans and timetables for addressing this goal.
In 2005, Reaction Design of San Diego, Calif., a developer and licensor of commercial simulation software used for modeling the kinetics of fuel combustion, formed the Model Fuel Consortium (MFC).17 The activities of the MFC are directed toward the creation of new test-fuel formulations as well as the establishment of a database for certified fuel models that will be accessible by the various
17
Available at http://www.reactiondesign.com/support/open/mfc.html. Accessed May 30, 2007.
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members of the consortium. Model fuels are a unique mix of a few pure chemicals that are intended to reproduce the combustion behavior of more complex commercial fuels. The main computer codes used by the MFC are CHEMKIN and KINetics, both of which are commercially supported by Reaction Design.
It should be noted that this type of work has been going on in government and industry laboratories and academic institutions for many years and that it is exceedingly difficult to capture the detailed and complex kinetics of realistic fuels and their performance in actual engine combustion systems. Success is far from guaranteed. Nevertheless, improvements in this capability offer the promise of faster and more cost-effective evaluation of current and future fuel formulations in existing and new engine designs as well as in new combustion concepts.
In addition, the MFC and Reaction Design, with partners from Chevron and the University of Southern California, has been recently awarded a grant from the U.S. Department of Energy’s FCVT to study the combustion of various biofuels. The program is aimed at developing efficient, environmentally friendly transport fuels that will lessen the U.S.’s dependence on petroleum. The goals of the program are generally consistent but more aggressive than DOE’s 21CTP goal to optimize fuel formulations for current-generation diesel engines that incorporate some non-petroleum-based biofuel-blending components. A 5 percent replacement of petroleum fuels is an initial target with an additional 5 percent set for 2010 diesel engines. However, based on the impacts on refinery operations and fuel blending facilities, it is unlikely that this program will be able to influence the introduction of commercial fuels in time to impact 2010 diesel engines.
AFTERTREATMENT SYSTEMS
Introduction
The three goals discussed above in this chapter address exhaust emissions and aftertreatment, in terms such as “2010 emission compliant,” “emission-compliant, engine system thermal efficiency of 55 percent by 2013,” “reduce overall tailpipe emissions,” “lower engine-out emissions,” enhancement of aftertreatment performance for 2010 emission regulations,” and “lowering emission levels to near zero.” The following material discusses aftertreatment in the context of these statements.
Discussion
The 21CTP program on aftertreatment systems is vague and does not define the priority for exhaust aftertreatment. For instance, the Ed Wall presentation does not mention exhaust emissions as part of the top R&D objectives.18 Ken Howden, program director of the 21CTP, mentioned the phrases, “emit little or no pollution,” and “develop and demonstrate an emissions-compliant engine system”19 and stated that among the program’s significant accomplishments, “collaboration has enabled production diesel engines to meet stringent 2007 emissions while maintaining high efficiency.”20
Jim Eberhardt, Chief Scientist of the FCVT, said “DOE with industry is developing more sulfur tolerant catalysts under Combustion and Emission Control and Advanced Petroleum-Based Fuels-Diesel Emission Control (APBF-DEC) activities.”21
Gurpreet Singh listed, under barriers, “emissions: inadequate simulation capabilities, lack of readily implemented sensing, robust process control system” and “Fuels: need understanding of fuel property effects on NOx and particulate emission characteristics and implications on DPF operation.” Thus, the 21CTP and DOE’s role in the exhaust after-treatment arena is not very well defined, and measurement against specific objectives is not possible. In spite of these statements, some significant contributions have been made, as outlined by Singh.22
Ron Graves’s presentation thoroughly reviewed the status of several emissions treatment projects. The “Overview of Goals and Status of Major Engine Technology Projects with Industry” outlines several emissions and aftertreatment accomplishments and future goals.23
Duggal stated that the heavy-duty engine technology roadmap included potential improvements of “elimination of NOx aftertreatment.”24 and Kevin Stork stated that “balance point temperature (for DPF regeneration) decreased with B20- and B100-significant differences in regeneration rate, with blend levels as low as 5 percent (biodiesel).”25
The most significant review of aftertreatment programs was presented by Ron Graves26 in “Emission Control R&D
18
Ed Wall, DOE, FCVT, “DOE FreedomCAR and Vehicle Technologies Program,” Presentation to the committee, Washington. D.C., February 8, 2007.
19
Ken Howden, DOE, FCVT, “Partnership History, Vision, Mission, and Organization,” Presentation to the committee, Washington. D.C., February 8, 2007, Slide 2.
20
Ken Howden, DOE, FCVT, “Partnership History, Vision, Mission, and Organization,” Presentation to the committee, Washington. D.C., February 8, 2007, Slide 14.
21
James Eberhardt, DOE, FCVT, “Review of Findings from Previous Heavy Vehicle Review,” Presentation to the committee, Washington, D.C., February 8, 2007.
22
Gurpreet Singh, DOE FreedomCAR and Vehicle Technologies Program, “Overview of DOE/FCVT Heavy-Duty Engine R&D,” Presentation to the committee, Washington, D.C., February 8, 2007.
23
Ron Graves, DOE, ORNL (Oak Ridge National Laboratory), “Emission Control R&D for Heavy Truck Engines,” Presentation to the committee, Washington, D.C., February 8, 2007.
24
Vinod K. Duggal, Cummins, Inc., “Diesel Engine R & D and Integration,” Presentation to the committee, Washington, D.C., February 9, 2007.
25
Kevin Stork, DOE, FCVT, “Fuel Technologies R&D for Heavy Trucks,” Presentation to the committee, Washington, D.C., February 9, 2007.
26
Ron Graves, DOE, ORNL, “Emission Control R&D for Heavy Truck Engines,” Presentation to the committee, Washington, D.C., February 8,
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TABLE 3-11 Sectoral Breakdown of CRADA Partners in Emission Control Research
Sector
Share of Total Held by That Sector (percent)
Engine/Auto
28
Catalyst Suppliers
18
Labs and Government
21
Software/Consulting
18
Universities
15
SOURCE: Ron Graves, DOE, Oak Ridge National Laboratory, “Emission Control R&D for Heavy Truck Engines,” Presentation to the committee, Washington, D.C., February 9, 2007, Slide 7.
for Heavy Truck Engines,” which included the following statements:
Expected lower limits of engine-out emissions dictate aftertreatment requirements for NOx.
Progress in NOx control via in-cylinder processes has delayed need for exhaust aftertreatment until after 2007.
He also detailed the activities of CLEERS, DCT (Diesel Crosscut Team), and DOE labs use of CRADAs. Much has been accomplished through these cooperative groups, perhaps in part, because they are made up of the components shown in Table 3-11.
Finding 3-16. No specific goals have been outlined for 21CTP diesel engine aftertreatment systems but some goals have been set for eliminating aftertreatment. However, as discussed in this chapter, the goal of eliminating aftertreatment does not appear to be achievable in the foreseeable future.
Recommendation 3-16. Specific goals should be set for aftertreatment systems (improved efficiency, lower fuel consumption, lower cost of substrates, lower cost catalyst, etc.).
Finding 3-17. The CLEERS, DCT, and CRADAs have contributed to many successful projects and programs.
Recommendation 3-17. The 21 CTP should continue with the CLEERS, DCT and CRADA activities for aftertreatment systems.
HIGH TEMPERATURE MATERIALS LABORATORY
Introduction
The High Temperature Materials Laboratory was established 20 years ago as a National User Facility to provide specialized, in some cases one-of-a-kind (for example, aberration-corrected electron microscope with sub-Angstrom resolution) instruments for materials research and characterization. Its facilities have been utilized by participants of the 21CTP. Examples are given below.
The replacement value of the instruments in the facility is approximately $47 million. It is located at the Oak Ridge National Laboratory occupying a space of 37,511 square feet, which houses six centers:27
Materials Analysis Center
Mechanical Characterization and Analysis Center
Residual Stress Center
Thermography and Thermophysical Properties Center
Friction, Wear, and Tribology Center
Diffraction Center
The Laboratory makes available to researchers from universities, U.S. industries, and governmental agencies a skilled staff providing support in the use of the specialized equipment in the six centers. On average, 90 user projects are supported each year with projects lasting from a few days to as long as a few weeks. Access is available to qualified users through either proprietary or non-proprietary agreements. In the case of non-proprietary work, the results must be published in the open literature; in that case there is no cost to the user. Users who conduct proprietary work there are charged for total recovery of costs associated with time and resources. At one time, funding for work at the facility was included in the budgets of various DOE programs, such as the 21CTP. However, since FY 2003 it has been treated as a separate line item in the DOE budget. Funding for the User Program is allocated on an annual basis and is not prorated for each user project. The budget for FY 2007 is $4.1 million.28
21st Century Truck Projects29 That Rely on the High Temperature Materials Laboratory
Active 2007 Projects
Austenitic Stainless Steel Alloys for Exhaust Manifolds and Turbochargers.
The objective is to develop new materials to permit an increase in engine-out temperatures to improve engine efficiency. This is a CRADA between ORNL and Caterpillar. The DOE budget for 2007 is $185,000 with a cost share of $185,000 from Caterpillar.
2007, Slide 1.
27
Edgar Lara-Curzio, “The High Temperature Materials Laboratory,” Presentation to the committee, Washington, D.C., May 31, 2007.
28
Personal communication, Edgar Lara-Curzio, Re: 21st Century Truck Partnership Project Quad Sheets, to the committee, Washington, D.C., May 21, 2007.
29
As listed in DOE, 2007.
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Catalyst Characterization.
The objective is to develop catalyst devices that will meet diesel emissions regulations with minimal impact on fuel economy. The DOE budget for 2007 for this area is $230,000.
Catalyst via First Principles.
The object is to use theoretical models to help develop optimum catalyst systems. The DOE budget for 2007 is $195,000.
Characterization of Catalyst Microstructures and Deactivation Mechanisms.
The objective is to develop a better understanding of mechanisms that control aging and poisoning behavior of exhaust emission reduction catalyst materials. The DOE budget for 2007 is $200,000.
Friction and Wear Reduction in Diesel Engine Valve Trains.
The objective is to develop a high-temperature, repetitive impact test system and associated test methods, and apply them to the investigation of candidate materials and surface treatments for diesel engine valve train components. The DOE budget for 2007 is $130,000. This project is planned to continue through 2009.
Life Prediction of Diesel Engine Components.
The objective is to develop methods to assess and improve the durability (life) of advanced ceramic and titanium/aluminum diesel engine components (valves). Such advanced materials provide better engine efficiency through improved thermal management and reduced mass. The DOE budget for 2007 is $95,000.
Lightweight Valve Train Materials (Titanium).
The objective is to develop and validate by in-engine tests, the performance of advanced ceramic and titanium valves. This project is in cooperation with Caterpillar. The DOE budget for 2007 is $175,000.
Mechanical Reliability of Piezo-Stack Actuators.
The objective of the project is to evaluate piezoceramic materials and stack actuator designs for diesel fuel injectors and develop methods for improving system performance. The project is planned to continue through 2008. The DOE budget for 2007 is $305,000.
Micro-structural Changes in NOx Trap Materials.
The objective is to develop an understanding of the changes that occur in NOx trap materials during various modes of operation. There is no continuing DOE budget in 2007.
Nano-crystalline Materials by Machining.
The objective is to develop high performance metal matrix composites to reduce rotating mass in diesel engine components. The DOE budget for 2007 is $50,000.
Integrated Approach for Development of Energy-Efficient Steel Components for Heavy Vehicle and Transportation Applications.
The objective is to develop tools to simulate the formation and influence of non-homogeneous microstructures in steel processing for truck applications. Validation of the tools using production components is being carried out at Caterpillar. There is no DOE budget for 2007.
Thermomechanical Processing of Titanium and Titanium/Aluminum Sheet and Plate.
The objective is to develop new low cost titanium powder processing methods for application to large truck components (e.g., leaf springs) for weight reduction. There is no DOE budget for 2007.
Completed Projects
NOx Sensor Development
Advanced Machining and Sensor Concepts
Deformation in Ceramics
Durability of Diesel Engine Materials
Durability of Particulate Filters
High Density Infrared Technology for Surface Treatments
High Toughness Materials
Low Cost Manufacturing of Precision Diesel Engine Components
Mechanical Behavior of Ceramic Materials
Titanium Turbocharger Development
Walker Process for Stress Relief
Advance Materials for Friction Brakes
Attachment Techniques for Heavy Truck Composite Chassis Members
Basic Studies of Ultrasonic Welding for Advanced Transportation Systems
Counter Gravity and Pressure-Assisted Lost Foam Magnesium Casting
Effects of Ice Clearing Treatments on Corrosion of Heavy Vehicle Materials and Components
Friction Stir Welding and Processing of Advanced Materials
High Conductivity Carbon Foam for Thermal Control in Heavy Vehicles
Improved Friction Tests for Engine Materials
Research on Next Generation Truck Brake Materials
Brake Lining Coding and Marking
Finite Element Truck Crash Modeling
Integrated Braking Systems Analysis–Laboratory Efforts
Finding 3-18. The High Temperature Materials Laboratory is a valuable resource, providing specialized instrumentation and professional expertise in support of materials research. 21CTP projects have utilized the laboratory extensively; it has provided support to 35 different 21CTP projects since 2001. Whereas few advanced materials were actually utilized
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in the 21CTP project to demonstrate the major 50 percent thermal efficiency goal, it is expected to contribute to the 21CTP in valuable ways in the future.
Recommendation 3-18. The DOE should continue to provide 21CTP projects access to the HTML. Although HTML’s budget is not explicitly linked to the 21CTP, DOE should make every effort to maintain a stable budget for the HTML, in order to keep it at the “state of the art” level, and able to respond to the needs of the broader research community.
HEALTH CONCERNS RELATED TO EMISSIONS FROM HEAVY-DUTY VEHICLES
Introduction
The FreedomCAR and Vehicle Technologies (FCVT) program of the Office of Energy Efficiency and Renewable Energy (EERE), U.S. Department of Energy, conducts research to illuminate the health effects of emissions from heavy-duty vehicles. Its goals are twofold: (1) to provide a sound scientific basis underlying any unanticipated potential health hazards associated with the use of new powertrain technologies, fuels, and lubricants in transportation vehicles; and (2) to ensure that vehicle technologies being developed by FCVT for commercialization by industry will not have adverse impacts on human health through exposure to toxic particles, gases, and other compounds generated by these new technologies. In all, 105 papers from the FCVT Health Impacts Activity have been published in peer-reviewed literature since 1999 (Eberhardt, 2007).30
Discussion
The database upon which the health impact of diesel particulate is evaluated is generally recognized to be in need of updating. The pollutants of major concern are nitrogen oxides (NOx) and particulate matter (PM)—both PM10 (particles smaller than 10 millionths of a meter [micrometer] in diameter) and especially PM2.5 (those smaller than 2.5 micrometers). Both of these classes of pollutants will be reduced with new engine and aftertreatment technologies used with cleaner, low-sulfur diesel fuel. In terms of health impacts, there is the need for data about the health impacts associated with the mass and the precise chemical components of particles for engine systems designed to meet the 2007 and 2010 standards.
A major new study is underway to address the data gaps identified above. The Advanced Collaborative Emissions Study (ACES) is a multiyear, multisponsor program designed to investigate potential health effects of emissions from heavy-duty vehicles meeting the 2007 and 2010 US EPA emissions standards. DOE is a major funder of this program.31
ACES recognizes that any study must address emissions from the combined technologies of new heavy-duty diesel engines, aftertreatment, lubricants and fuels designed to meet the new standards. It is an animal study using rats and not focusing on the direct effects in humans.
The committee endorses the DOE funding of this study and recommends that this continues for the remainder of the study until results become available in the 2012-2013 period.
ACES is a cooperative, multi-party effort to characterize the emissions and assess the safety and potential health effects of these new, advanced engine systems and fuels. The ACES program is being carried out by the Health Effects Institute (HEI) and the Coordinating Research Council (CRC). Key stakeholders and funders of the effort include representatives of engine manufacturers, the petroleum industry, emission control manufacturers, EPA, DOE, CARB, and the Natural Resources Defense Council. ACES will utilize established emissions characterization and toxicological methods to assess the overall safety and potential health effects of production-intent engine and control technology combinations that will be introduced into the market during the time period.
The characterization of emissions from representative advanced diesel engine systems will include comprehensive analyses of the gaseous and particulate material, especially those species that have been identified as having potential health significance. This study will include a chronic bioassay of cancer end points similar to the standard National Toxicology Program (NTP) bioassay utilizing one rodent species (rats) and assessing cancer and noncancer end points (including respiratory, immunologic, and other effects for which there are accepted toxicological tests). These end points will also be measured in a short-term exposure study after completion of the bioassay using the then aged engine. It is anticipated that these studies will assess the potential health effects of these advanced diesel engines systems, will identify and assess any unforeseen changes in the emissions and effects as a result of the technology changes, and will contribute to the development of a data base to inform future assessments of the potential health risks relating to these advanced engine and control systems.
Major Project Elements and Timing
ACES is taking place in three phases:
In Phase 1, extensive emissions characterization (by the Southwest Research Institute) of four production-intent heavy heavy-duty diesel (HHDD) engines and
30
James Eberhardt, Chief Scientist, DOE, FCVT, “Overview of the Health Impacts of the Office of FreedomCAR and Vehicle Technologies Program,” Presentation to the committee, Washington, D.C., February 8, 2007.
31
Brent Bailey, “Diesel Emissions Research at CRC” (the ACES Diesel Project), Presentation to the committee, Washington, D.C., May 31, 2007.
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control systems designed meet 2007 standards for PM and NOx are being conducted and will be the basis for selecting one heavy-duty diesel engine/aftertreatment system for health-related studies (Phase 3). No results were available at the time of this report.
In Phase 2, extensive emissions characterization of a group of production-intent engine and control systems meeting the 2010 standards (including more advanced NOx controls) will be conducted.
In Phase 3, the selected 2007-compliant engine system would be installed in a specially-designed emissions generation and animal exposure facility (Phase 3A) and will be used in chronic inhalation study with health measurements at several time periods to form the basis of the ACES safety assessment (Phases 3B and 3C). This is will include a core 24-month chronic bioassay of cancer and noncancer end points in rats similar to the standard NTP bioassay. In addition to assessing potential carcinogenicity of whole diesel exhaust, this chronic bioassay would provide information on chronic toxicity through histopathological analyses of multiple organs at interim sacrifices and at the end of the study, on mutagenicity, inflammation, and other noncancer health end points that have been associated with exposure to diesel exhaust (Phase 3B). In addition, a short-term study (3 months exposure duration), measuring the same noncancer end points as in the chronic bioassay will be conducted in a different set of animals after completion of the chronic bioassay to determine whether the exhaust of the 2007 engine (Phase 3C) will produce emissions that are of concern from the human health standpoint. Due to program slippage, animal studies are now expected to start in the Fall of 2008 and may slip further.
Subsequently, subject to full evaluation of the 2007 engine tests, one (or possibly two) selected 2010-compliant engine system could be installed and characterized (Phase 3D) and evaluated in short-term health effects studies (Phase 3E) measuring the same end points measured after comparable exposure duration in the chronic bioassay and the subsequent short-term study with the 2007-compliant engine, as well as other established end points that require specific animal models or interventions. The schedule and organization of the study are shown on Figures 3-7 and 3-8, respectively. With respect to the ACES program, the committee supports
FIGURE 3-7 Overall schedule, CRC ACES study. SOURCE: Brent Bailey, Health Effects Institute, “Diesel Emissions Research at CRC” (the ACES Diesel Project), Presentation to the committee, Washington, D.C., May 31, 2007, slide 21.
FIGURE 3-8 Project organization, CRC ACES study. SOURCE: Brent Bailey, Health Effects Institute, “Diesel Emissions Research at CRC” (the ACES Diesel Project), Presentation to the committee, Washington, D.C., May 31, 2007, slide 21.
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continuation of this study, because of the vital information it provides.
Finding 3-19. ACES is a cooperative, multi-party effort to characterize the emissions and assess the safety and potential health effects of new, advanced engine systems, aftertreatment, fuels and lubricants. It is an animal study using rats and not focusing on the direct effects on humans. DOE is providing the major funding for this program.
Recommendation 3-19. The committee endorses the DOE funding of this study and recommends that this continue for the remainder of the study until results become available in the 2012-2013 time period.
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