Greener Army: high-tech vehicles promise fuel savings--years from now.

• Author: Rusling, Matthew
• Position: Tactical Vehicles

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The Army is channeling the majority of its investments in fuel-efficient technology into the Future Combat Systems. But that program is still years away from fielding, and energy savings may take a long time to materialize.

Army leaders have touted FCS as the Army's first major opportunity to introduce hybrid-electric engines into the fleet. Not only would hybrid-electric engines help to save fuel, but they would also serve as electricity generators that would power many of the devices that currently require bulky batteries and custom generators.

FCS is a $160 billion project to build a family of manned and unmanned ground and air systems, and sensors connected by a common network.

For the Army, trying to cut its fuel use to significantly lower levels is simply not possible with its current fleet. Its old, gas-guzzling engines can be tweaked, but real fuel economy requires a shift to hybrid-electric technology, experts said.

The FCS combat vehicles that are currently in development are in slated to arrive in 2015. They are being outfitted with "series" diesel-hybrid engines, which differs from what commercial hybrids use. A diesel engine on board turns a generator, which in turn charges batteries and powers electric motors that drive the tracks. The entire vehicle is electrically powered.

The Toyota Prius, by contrast, has a "parallel" gas-hybrid system, which is a more mature technology. Its computer gauges whether it is more efficient to use the batteries or the engine.

The FCS engine was custom designed to move a hefty vehicle that is expected to weigh at least 26 tons.

Both the FCS and the Prius use "regenerative breaking." When the driver hits the breaks, a mechanism is activated that converts some of the vehicle's kinetic energy into power that recharges the batteries.

The FCS non-line-of-sight cannon, a 155mm howitzer, already has the hybrid system embedded in its eight prototypes. It is now undergoing road testing, said Army spokesman Paul Mehney.

The diesel engine is removable. If the Army decides in the future to switch to a fuel cell or another engine, the transition should be simple, Mehney said.

There are no available statistics for how much fuel savings the entire FCS fleet will achieve once it arrives. The Army estimates that an FCS heavy brigade combat team will consume 29 percent less fuel than its current counterpart, Mehney said.

During a 1,864 mile mission lasting several days, a current heavy...