EVERYWHERE YOU TURN, HYBRIDS

January 17, 2007 Vol. 3, No. 2

The object of my attentions in this version of Product Watch — hybrid powertrains — is going to be an increasingly common one in the days to come. With the promise of fuel savings well above 30% and even 50% in some cases, it’s easy to see why. And that’s not to mention environmental and other benefits. It’s early days, however, and aside from some FedEx and UPS stepvans on the heavy side of light-duty being built and sold on a very limited basis so far, commercialization of the hybrid truck in North America is not yet reality.

Mack and Volvo aim to change that, and they’re doing it with heavy trucks, not medium- and light-duty machines as most other prototypes have been so far. Executives from the two companies were in Washington, DC late last week – along with yours truly — to show off their hybrid diesel-electric technology in a Mack Granite dump truck, and they say it will be ready for sale in 2009. They also claim a 30-35% fuel-economy improvement in a stop-and-go application like garbage trucks.

The internally developed I-SAM hybrid system at the heart of things is indeed commercially viable, say the companies, though Mack president Paul Vikner said with some passion that government funding is needed to “jump-start” the commercialization process.

The dump truck on display last week, at the Swedish Embassy and later for demo rides at RFK Stadium, was ordered by the U.S. Air Force. Four have been built to date for testing purposes, and more are on the way. Mack and Volvo engineers have collaborated on the project.

Development of the truck was carried out in close co-operation with the USAF which, several years ago, also contracted Mack to develop an aircraft refueller tank truck with hybrid diesel-electric drive. Its drive system is different from the newer I-SAM, using an electric motor aft of the transmission, much like a driveline retarder in reverse. The I-SAM answer puts the electric motor in between the engine and transmission as most others do.
I-SAM is the acronym for Integrated Starter, Alternator, & Motor.

Volvo is also developing similar hybrid technology for its construction equipment such as wheel loaders, by the way, in which the fuel savings might well reach 50%.

The I-SAM system is conventional in hybrid layout terms, consisting of an “electric machine” developing 161 hp and 590 lb ft of torque at its peak (94 hp and 295 lb ft
continuous) sandwiched between a Mack 315-hp MP-7 engine and a Volvo automated mechanical 12-speed direct-drive transmission based loosely on the Volvo I-Shift gearbox.
It’s a two-pedal system, having a clutch but no clutch pedal. The system does not employ batteries, instead using ultra-capacitors to store energy extracted from the heat of braking. They don’t store as much power as batteries, but in low-speed stop-and-go applications there’s no need for massive storage capacity – with that much braking going on, there’s more than enough energy recovery to keep things rolling.

In a demonstration ride, electric power launched the truck strongly with the diesel kicking in seamlessly at about 5 mph. The two can be combined after that point if required, as the need for power is transmitted from the throttle. Torque from the two power sources is blended very, very smoothly. A key point here is that a smaller-than-normal diesel can be spec’d for a given job because of the secondary power supply.

One of the advantages of the Volvo/Mack system, according to Guy Rini, Mack’s director of advanced propulsion systems, is relatively light weight. The use of ultra-capacitors instead of batteries saves many pounds, as does the Volvo transmission used where a full automatic would normally be spec’d. Rini says the net weight gain with the I-SAM is 800 lb, but it would be 1600 with the auto transmission.

Unlike some other hybrid systems I’ve seen – and driven, in the case of a ZF electric motor and transmission setup in an MAN medium-duty truck – the I-SAM system does not
automatically shut the diesel down at, say a stoplight. The fifth truck they build will have that feature, Rini told me, but that demands major modifications in the truck’s hydraulic and electrical systems. Specifically, that means electrification of engine-driven auxiliaries like the power-steering pump, air compressor, AC compressor, etc. That next phase will further contribute to improving fuel efficiency.

Asked about the price of a Granite equipped with I-SAM, Vikner said the companies really didn’t know yet. Leif Johansson, Volvo Group president and CEO, said it was entirely dependent on volume, and it’s much too early to have that pinned down. He added, however, that he expects customers to see a payback on the I-SAM system within two
years when the “right” sales volume is reached.

And will we ever see a similar hybrid system in a heavy-duty over-the-road truck? Rini said it will happen, but don’t expect more than single-digit fuel savings. Why not? Because there’s not enough braking going on, which means a smaller source of energy for those hungry batteries.