I knew Priuses store energy in the batteries but I wasn’t aware that was the key signifier of “hybrid.” I figured it meant a combination of gas engine and electric motor. In that sense, though, the new Cat dozer wouldn’t qualify either, because the engine runs the electric motors directly rather than switching on and off.

Great job discerning how significant the D7E project is to Caterpillar’s future. Carrying diesel-electric drive over into construction-size dozers is a major development with significance throughout the industry, as you aptly note in pointing out Volvo’s work on the concept.

It’s probably important to point out, though, that the D7E is not really a hybrid drive system, by most people’s definition of “hybrid drive.” ‘Course the definition itself is hardly absolute, but most agree that an electric drive system becomes a “hybrid” when it includes some sort of way to store energy that can be delivered later, when the engine needs a boost.

Cat engineers made this distinction themselves during the press introduction of the D7E. It’s certainly not much of a stretch to imagine a drive like that used here with a battery or other energy-storage system added to it. But in that respect, the Volvo concept probably qualifies more as a hybrid than the D7E.

I don’t know which — the D7E or the Volvo wheel loader — will be on a production line sooner. Both companies spoke of 2009 introductions, but the Volvo people suggested later in 2009, while Cat was speaking more in terms of early 2009. The coming quarter — Q1 2009 — will be an interesting time to be at construction equipment trade shows.

Larry Stewart