Solectria Class 7 Hybrid
Tom Berg
Equipment Editor
Thunk! That was the sound of the clutch pedal suddenly retracting. I had just switched on the ignition key of a modified Kenworth T300 and after a few seconds and a few glowing lights, the pedal made its sudden move. It pivoted against the floor beneath the dashboard, as if mashed by a ghostly foot.
"That's eerie," I said to my guide, Ricardo Espinosa, project engineer for the Solectria Class 7 Multi Mode Series Parallel Hybrid Drive System. It's an electronically controlled diesel-electric truck that was on a coast-to-coast tour during August. At startup, its automatic clutch disengages so the Cummins ISC under the hood can crank over. It did - with no input from me - and now the diesel idled more or less normally.
The truck was parked on Foothill Boulevard in Pasadena, Calif., one of the places that Espinosa and his crew had paused during their cross-country demonstration. They started at Solectria Corp.'s home in Woburn, Mass., north of Boston, and in a couple of weeks they had made about 30 stops and showed the truck to scores of people. Now it was my turn.
He released the parking brake and I punched the Eaton AutoShift's selector into D, then gave it some gas. We moved out, with the 210-hp engine working through the 6-speed automated mechanical transmission as smoothly as you'd expect. The clutch stayed engaged because the tranny float-shifted, and I didn't have to declutch when coming to a stop because it did that itself. The pedal stayed hidden until I switched off the ignition later on. When it thunked back into view.
No, it's not an auto-clutch from the new Eaton UltraShift, but one engineered by the Solectria team. Eaton has its own hybrid-drive project and Eaton people in Michigan were among those who inspected this truck. "They were impressed with what we did with the clutch," Espinosa said. Still, it's not the system's principal part.
The rest of the hybrid driveline includes two hefty AC electric motors, one behind the engine and another next to the driveshaft, plus a bank of 20 "ultra capacitors" stored against the front wall of the van body. The capacitors, acting as high-efficiency batteries, are charged by the engine-driven alternator. The driveline motors also act as generators, capturing the truck's kinetic energy - regenerative braking, it's called - and sending current to the capacitors. This occurred whenever I took my foot off the accelerator.
The truck can accelerate on engine power, on a "blend" of both engine and electric power, and on electric power alone. The first inkling that it's about to go all-electric is when the engine abruptly shuts off, sometimes while you're sitting at a red light. It's unnerving at first, then you quickly accept it. As the truck electro-accelerates, you hear an up-and-down whining from the motors as they go through the tranny's gears. That's eerie, too.
The engine restarts when the system's controls sense that the capacitors need more juice, which is fairly often. At freeway speeds the engine is the prime propulsion source, but on downgrades it goes back to idle and the motors take over. At stops, it may fast-idle to charge the capacitors as needed. It's all quite smooth, and it will work on trucks as heavy as 54,000 pounds gross.
With the boost from electric motors, hybrid autos get away with smallish engines, and the same would be true for cargo or vocational trucks. This T300 might use a Cummins ISB instead of the ISC. And the ultracapacitors would be sealed, shock-mounted and hung alongside the truck's frame rails, freeing the behind-cab area above the rails for whatever body is needed.
What's the point? Fewer exhaust pollutants - almost enough reduction to meet 2007 emissions limits with few, if any, changes to the diesel, Espinosa said - and less brake wear. And there's a 35% reduction in fuel consumption, which alone should pay for the system's extra cost in about three years, he said.
Cost for this prototype hybrid system for trucks was about $19,000.
Will you ever buy something like this? Could be. The Solectria team was showing the truck to several truck builders and there's some interest, Espinosa said.
The public seems ready, with Honda and Toyota selling more hybrid gasoline-electric cars than they expected. The industry's signing on, as FedEx and United Parcel Service are developing hybrid diesel-electric walk-in vans.
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