Mack Trucks was one of several manufacturers announcing breakthroughs for commercial hybrid operations. Hybrid ready-mix and dump trucks could be available in five years.

Since then, hybrid buses and delivery trucks have proven themselves useful in daily service. ZF and the Volvo Group are on the verge of having class-8 hybrid vehicles with capacities up to 80,000-pound gross vehicle weight. International Truck and Engine Co., working with ArvinMeritor, are preparing a hybrid over-the-road tractor for Wal-Mart.

Blending diesel and electric

The breakthrough is that modern nickel-metal hydride and lithium ion batteries have increased storage capacity, weigh less, have greater reliability and lower manufacturing, and thus replacement costs, than previous battery systems. Control units can process information much faster, allowing vehicles to achieve smoother transitions between the discharging and charging modes. And high-speed computer controls aided by proven engine sensors can blend diesel and electric power seamlessly, according to demand and conditions.

The result will be not only a more fuel-efficient engine that will reduce emissions, but a potentially lower-maintenance vehicle.

For example, lower brake maintenance costs will be a direct benefit. Currently, energy conversion for stopping is done by brake shoes creating friction between high-friction linings and the inside of the brake drums. Brakes convert kinetic energy to heat. With hybrids, the load on brakes will be lessened, as energy is converted to electricity, not heat.

In January, Mack Trucks rolled out a hybrid construction truck developed for the U.S. Air Force. It uses an Integrated Starter Alternator Motor (I-SAM) which offers fuel savings up to 35%. Hybrid technology for smaller construction vehicles will offer close to 50% savings.

Mack expects Granite models with the I-SAM hybrid driveline to enter production in 2009. The benefits for ready-mix trucks operating in urban environments should make them popular.

— Paul Abelson is a former director of the Technology and Maintenance Council of the American Trucking Associations. You can e-mail him at truck