California ARB releases draft assessment of heavy-duty truck efficiency technologies
15 June 2015
The California Air Resources Board (ARB) has published a Draft Technology Assessment: Engine/Powerplant and Drivetrain Optimization And Vehicle Efficiency that evaluates a range of technologies to increase fuel efficiency and reduce CO2 emissions from heavy-duty trucks. The release of the report coincides with the US EPA proposal for Phase 2 (post-2018) greenhouse gas (GHG) regulations that is expected to be released this week. In April, the California ARB published a related assessment of heavy-duty emission and fuel technologies.
Engine/powerplant and drivetrain optimization technologies evaluated in the report included:
- Advanced transmissions and engine downspeeding
- Waste heat recovery
- Engine downsizing
- Stop-start
- Automatic neutral idle
- Combustion and fuel injection optimization
- Higher-efficiency aftertreatment
- Reduced friction
- Auxiliary load reduction
- Air handling improvements
- Cylinder deactivation
- Stoichiometric gasoline direct injection
- Lean-burn gasoline direct injection
- Camless engines
- Opposed piston engines
- Free piston engines
- Advanced combustion cycles
In addition, a number of vehicle efficiency technologies have been evaluated:
- Aerodynamics
- Lightweighting
- Low-rolling resistance tires
- Automatic tire inflation
- Vehicle speed limiters
- Axle efficiency improvements
- Idle reduction
- Improved air conditioning
- Connected Vehicles
The assessment found that the evaluated technologies can produce significant reductions in fuel consumption. Table 1 summarizes the potential additional fuel consumption reduction (FCR) beyond Phase 1 GHG standards (i.e., model year 2018) compliant vehicle that incorporates all of the applicable technologies.
| Vehicle Category | FCR Potential, % |
|---|---|
| Heavy-Duty Tractor-Trailer (Class 7-8) Long Haul | 8 - 36 |
| Heavy-Duty Tractor-Trailer (Class 7-8) Short Haul | 8 - 33 |
| Heavy-Duty Vocational (Class 3-8) | 10 - 28 |
| Heavy-Duty Diesel Pick-ups and Vans (2b/3) | 3 - 23 |
| Heavy-Duty Gasoline Pick-ups and Vans (2b/3) | 10 - 27 |
The percent FCRs shown in the table correspond directly to potential reductions in CO2 emissions, and can be used to help inform the Phase 2 GHG standard setting process, said ARB in the report.
California air quality targets also require significant further reductions in emissions of criteria pollutants, particularly NOx emissions. In the past, many NOx reduction technologies (such as exhaust gas recirculation and retarded ignition timing) have resulted in increased fuel consumption and reduced fuel efficiency. However, the introduction of urea SCR technology in 2010 allowed for increased fuel efficiency (and reduced GHG emissions) while achieving low tailpipe NOx emissions, noted the report.
The California ARB will further discuss NOx control technologies for heavy-duty engines (both diesel and natural gas) as part of three separate upcoming technology assessment documents expected to be released later this year: (1) Lower NOx Heavy-Duty Diesel Engines, (2) Heavy-Duty Hybrid Vehicles, and (3) Low Emission Natural Gas and Other Alternative Heavy-Duty Fuel Engines.
Source: California ARB