Hybrid-Electric Trucks on Army's Horizon.

• Author: Erwin, Sandra I.

Technology still not mature enough and too expensive, industry experts say

Ongoing efforts to expand the use of hybrid propulsion systems in military ground vehicles are gaining some momentum. But experts caution that the technology is not yet mature enough to allow the U.S. Army to make long-term buying decisions.

Both government and industry experts agree that the Army could save fuel and reduce air pollution by using hybrid propulsion systems. Another side benefit of hybrids is the availability of on-board power generation.

The most widely known hybrids are the so-called hybrid-electric systems, which are commercially available. A hybrid-electric vehicle combines two power sources. In most cases, the vehicle is powered by electric motors combined with a small, on-board combustion engine-generator.

Generally, hybrid systems feature a small conventional engine, such as a diesel or a fuel cell, which powers a generator, which in turn charges the battery. Because the internal combustion engine is smaller, the vehicle burns less fuel and emits less toxic fumes. The on-board generator means the battery constantly is recharged.

In an all-electric vehicle, the battery would have to be recharged approximately every 100 miles. With a hybrid system, the power still comes from the engine, while the batteries help it run more efficiently.

"The Army would like to contribute a reduction in emissions," said Harold Samborn, project leader at the Army's National Automotive Center (NAC), in Warren, Mich. The center, in partnership with private firms, is pursuing several projects to develop and demonstrate hybrid systems in military tactical and combat vehicles.

The umbrella program for these efforts is the so-called 21st century truck initiative, a government-industry venture seeking to develop fuel-efficient vehicles for commercial and military use. U.S. federal agencies and automotive firms are expected to invest $5 billion in this program during the next decade.

"We hope to have a variety of platforms that demonstrate advanced propulsion techniques, whether it's hybrid drive or fuel cells," said Samborn in a recent interview. "We may have alternative fuel vehicles running on natural gas. We may have several competing architectures for a particular technology, to see which one is most mature."

Last month, during the Society of Automotive Engineers annual truck and bus convention in Portland, Ore., the NAC show-cased a number of hybrid prototypes, such as a hybrid-electric 5-ton military truck, part of the Army's family of medium tactical vehicles (FMTV). Another prototype at the show was a commercial Class 8 Volvo tractor-trailer, which the NAC believes can be a test bed for the future introduction of hybrid drives into heavy military trucks.

"There are many hybrid systems out there, particularly in the automotive industry. But the heavy truck industry is...