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21st Century Truck Initiative/Partnership (21CTP)

Parasitic Losses

The industry participation in parasitic loss reduction research was to be through the truck original equipment manufacturers (DaimlerChrysler/Freightliner, International Truck & Engine Company, Mack Trucks, Oshkosh Truck, PACCAR, and Volvo Trucks North America), who would be working with their suppliers to develop the product and manufacturing technologies for aerodynamic drag reduction, accessory load reduction, and weight reduction. The truck manufacturers would be working with their suppliers on research to improve performance in these areas. The Department of Energy (DoE) would be working with truck and engine manufacturers through the FreedomCAR and Vehicle Technologies Program on several projects, including aerodynamic drag research and electrification of engine accessories. The Department of Defense would also be working in this area to reduce fuel consumption of tactical and utility vehicles.

The energy to move a heavy vehicle down the road includes energy losses associated with aerodynamic and rolling resistance, drivetrain and auxiliary loads. Collectively, these losses represent 40% (or 160 kWh) of the total energy. Improvements in aerodynamic drag and tire-rolling resistance have a significant impact on fuel efficiency. Improvements in driveline and accessory efficiency have a lesser influence on fuel efficiency. Proper management of thermal loads and overall vehicle weight also influence overall vehicle efficiency.

All vehicles would benefit from aerodynamic drag reduction. The higher the operating speed and the longer the drive duration, the greater the benefit will be. As of 2006 it was said that at highway speeds, approximately half of the fuel used to move the truck down the road (i.e., the energy to overcome aerodynamic and rolling resistance, drivetrain and auxiliary loads) aws used to overcome aerodynamic resistance. A 20% reduction in aerodynamic drag would result in savings in fuel consumption for steady highway travel in the range of 10 to 15%.

Auxiliary power management was a crosscutting technology area that addressed the efficient and practical management of both electrical and thermal management requirements for all classes of heavy vehicles. Auxiliary power was required during both drive and idle periods for heavy vehicles. Power requirements were derived from many vehicle functions, including engine and fuel heating, HVAC, lighting, auxiliary components (e.g., pumps, starter, compressor fans), and hotel loads (HVAC, computers, entertainment systems, and on-board appliances like refrigerators, microwaves, coffee pots, and hot pads), as well as work function loads such as trailer refrigeration and the operation of power lifts and pumps for bulk fluid transfer. As of 2006, up to 30 kW of auxiliary power was required for transit buses. Class 8 tractor-trailers required up to 15 kW of auxiliary power and an additional 30kW to power trailer refrigeration units.

A fully loaded tractor-trailer combination can weigh up to 80,000 pounds. Reduction in overall vehicle weight could enable an increase in freight delivered on a ton-mile basis. Practically, this would enable more freight to be delivered per truck and improves freight transportation efficiency. New vehicle systems, such as hybrid power trains, fuel cells and auxiliary power would present complex packaging and weight issues that would further increase the need for reductions in the weight of the body, chassis, and power train components in order to maintain vehicle functionality. Material and manufacturing technologies can also play a significant role in vehicle safety by reducing vehicle weight, and in the improved performance of vehicle passive and active safety systems.

Thermal management focuses on minimizing the auxiliary load requirements for heating, ventilation, and airconditioning (HVAC) systems while maintaining the thermal comfort of the vehicle occupants. Additional benefits in fuel efficiency could be achieved through the development of high-performance heat exchangers and cooling media (fluids), which would reduce the need for high-output engine water pumps. Numerous technologies were identified, including direct heating and cooling of the vehicle occupants, eliminating in-dash venting systems, reducing vehicle peak and steady-state thermal loads, and employing heat-generated cooling techniques. Technologies for reducing the vehicle thermal (solar) loads included advanced window glazing, thermal insulation, and ambient cooling and ventilation systems. Additionally, heat generated in the vehicle cabin could be used in various cooling techniques, including metal hydride systems, absorption, desiccant systems, and exhaust-heat waste-recovery systems.

Parasitic losses due to aerodynamic resistance, accessory loads, overall vehicle weight, under hood thermal loads, friction, and wear collectively and significantly reduce the overall efficiency of heavy vehicles. Three primary technology goals were identified for the partnership to address between 2006 and 2016. These were:

  • Develop and demonstrate advanced technology concepts that reduce the aerodynamic drag of a Class 8 highway tractor-trailer combination by 20% (from a existing average drag coefficient of 0.625 to 0.500).
  • Develop and demonstrate technologies that reduce essential auxiliary loads by 50% (from existing 20 horsepower to 10 horsepower) for Class 8 tractor-trailers.
  • Develop and demonstrate lightweight material and manufacturing processes that lead to a 15% to 20% reduction in tare weight (for example, a 5000-lb weight reduction for Class 8 tractor-trailer combinations).

The 21 Century Truck Partnership identified two other technology goals in the technical areas of 1) thermal management and friction and wear, and 2) rolling resistance. Initial goals were established in both of these areas. They were:

  • Thermal Management & Friction and Wear: Increase heat-load rejected by thermal management systems by 20% without increasing radiator size. Develop and demonstrate technologies that reduce powertrain and driveline losses by 50% thereby improving Class 8 fuel efficiencies by 6 to 8%.
  • Rolling resistance technology goal: 10% reduction in tire-rolling resistance values relative to existing best-in-class standards without compromising cost or performance.

The goal of the 21st Century Truck Partnership was to conduct research and development, demonstrations, validation and deployment of cost effective, reliable and durable technologies that reduce parasitic energy losses. The partnership would utilize a vehicle system approach to continually track overall benefits of individual technologies on overall vehicle efficiency and performance.

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Page last modified: 07-07-2011 02:41:30 ZULU