Heavy-duty hybrids a non-starter

Hybrid-engine vehicles that run on both electric power and fossil fuel are in high demand for passenger cars these days. But don't expect to see heavy-duty trucks using Toyota Prius-style technology anytime soon, says a leading expert in the field.

"The concept of scaling up a Prius technology for a Class 8 truck is a non-starter," said David Alexander, an analyst at ABA research in Oyster Bay, New York, USA, who authored a report last year on the topic. "It's impractical and it won't happen."

The Prius, developed by Toyota Motor Corp., uses so-called parallel electric technology that depends on regenerative braking. A Prius captures energy when the vehicle slows, and it stores that energy in a battery for reuse when the car restarts and for low-speed operation.

"It's difficult for hybrids to work on Class 8 trucks because most of their operation involves cruising at 60 miles an hour or better," said Alexander in an interview.

Mid-sized trucks that handle local deliveries are more likely candidates for parallel electric hybrid technology, Alexander explained, because they make a number of stops and starts in the course of a day.

It's more likely that truck manufacturers will boost fuel economy by using hybrid technology to run ancillary systems like air conditioning units, cooling fans, or power steering. Alexander said trucks could use regenerative braking and battery storage to provide energy for ancillary features that now sap power from the engine. "It will not double fuel economy," he said of such design changes. "But five percent here and two percent there add up."