Integrating hybrid powertrains technologies


Rising fuel prices and environmental pressures are pushing fleets of all sizes to take a serious look at fuel economy and vehicle design alternatives. One of the areas attracting much interest is hybrid powertrain technology.

Some fleets, particularly those in vocational or pickup and delivery operations, have been early adopters of hybrid technology. However, hybrid powertrains hold promise for over-the-road applications, as well.

One of the leading fleets in North America investigating hybrid powertrain is the U.S. Army, through its U.S. Army Tank-Automotive Research, Development & Engineering Center’s National Automotive Center (TARDEC/NAC).

This organization has a cooperative affiliation with TMC (Technology & Maintenance Council), North America’s premier technical society for truck equipment technology and maintenance professionals.

At the TMC Fall Meeting and TMCSuperTech (National Technician Skills Competition), held Sept. 10 to 13 in Pittsburgh, PA, the results of TARDEC/NAC study on hybrid powertrain technologies for medium (Class 4 to 6) and heavy duty (Class 7 and 8) trucks and buses for North America was presented.

The study, conducted by consulting company Automotive Insight, was designed to assess the performance of hybrids in use within commercial and vocational applications as a benchmark reference for the introduction of hybrids and electric vehicles to the U.S. Military ground vehicle fleet.

TARDEC/NAC has a number of technology research initiatives ongoing, intended to develop, integrate and sustains the right technology solutions for all manned and unmanned Department of Defense ground systems and combat support systems to improve current force effectiveness, provide superior capabilities for the future force and reduce its energy consumption.


Study results

The study found that hybrid trucks and buses are growing due to a number of factors. Among them: government mandates, the price of fuel and more and more hybrid vehicle offerings, Automotive Insight’s Tom Smart told TMC meeting attendees.

Some of the key benefits of hybrid powertrains he noted:

- Fuel savings - up to 20 times more fuel efficiency annually compared to conventional powertrains. Actual savings will be dependent upon type of vehicle, routes and driver behavior, he pointed out.

- Quieter vehicle operation.

- Longer brake life and reduced brake maintenance because of regeneration (the recuperation of energy when braking).

- Fewer parts and components.

- The ability to generate power for onboard vehicle needs or at a work site.

The study reported there are hybrids vehicles being offered in all vehicle classes, with many retrofit options are available as well.

What’s more, suppliers are developing new batteries for hybrid systems that will help hybrids travel farther and perform better.

One of the challenges, the study found, is that because of the many different types of heavy and medium duty vehicles and their application, it is very difficult to develop a standard hybrid powertrain.



Also presenting at the TMC Fall Meeting was Bill Van Amburg of CALSTART, which serves as the leading catalyst organization for the global clean transportation technology industry.

CALSTART, in partnership with and under contract to the U.S. Army TARDEC/NAC, operates the Hybrid, Electric, and Advanced Truck Users Forum (HTUF) - a user-driven program that is speeding the commercialization of medium and heavy duty technologies.

He said that the next generation of commercial hybrid vehicles will have reduced weight, better engine-to-driveline calibration to optimize fuel economy; a more integrated powertrain; and onboard diagnostics.

Development of hydraulic hybrids is continuing, with the realization of 40 to 60 percent fuel economy improvements, he noted, and research is being done to integrate hybrid systems to be able to power such things as refrigeration units, liftgates, etc.

Hybrid vehicles use two sources of power to drive the wheels: a regular internal combustion engine and a hydraulic motor are used to power the wheels.