Will your next powertrain feature hybrid drive technology?

[kscarbel2]

Jack Roberts, Fleet Owner  /  September 6, 2016

A couple of weeks ago, in the wake of the release of the final rule for the U.S. Environmental Protection Agency's Phase 2 Greenhouse Gas regulations, I told Fleet Owner readers the different ways I thought that ruling would affect powertrain development over the next decade.

As I noted, one of the likely new technologies we'll start to see in the next decade will be hybrid-electric drivetrains, which will be optimized to give heavy duty trucks a big torque boost in lower gears to get the vehicle moving in a much more efficient manner.

Hybrid-electric drivetrains aren't new, of course. They first appeared in the late 1990s, most notably as a joint medium-duty offering from Eaton and International Trucks. In this incarnation, hybrid-electric drives functioned much as they likely will in the future, providing instantaneous electric torque to drive wheels. 

But, designers at the time also envisioned hybrid trucks as rolling power stations. The vehicles were outfitted with massive, heavy, battery packs that stored powered and enabled trucks to run a wide array of equipment with it. In most cases, this showed up on bucket trucks, or mobile drill rigs or service trucks. The idea seemed so promising at the time that light-duty OEMs quickly followed suit, with GM, in particular, offering hybrid-electric options for Silverado and Sierra pickup trucks. 

Alas, it all came to naught. As it happened, hybrid-electric drivetrains on the medium-duty side of the market proved to be too costly for municipal fleets to purchase in large numbers. Hybrid production never scaled up, and remained prohibitively expensive throughout its production run.

Another problem was maintenance. By and large, the systems were reliable. But when problems did occur, they proved difficult and expensive to repair. The trucks' complex high-voltage electrical systems were particularly tough to trouble-shoot and repair.

In the end, most fleets simply decided the fuel economy gains and modest convenience of having a mobile power pack didn't justify the added costs of the vehicles. Over time, they pretty much faded away.

But now, thanks to the EPA, hybrid-electric drives appear poised to make a come-back. And while I fully understand if you're not turning cartwheels at this bit of news, stop and consider that the hybrid-electric drives of the near future will not be the hybrid-electric drives of 20 years ago.

As is often the case, I felt that after-market suppliers actually ID'd the optimal hybrid-electric drive powertrain configuration.

At the height of trucking's hybrid drive flirtation, after-market suppliers began developing and selling hybrid modification kits that could be installed on a light-duty van or truck transmission to provide a "light" hybrid power boost when the vehicle was getting under way.

These systems did away with the heavy and complex battery packs featured on heavier trucks, and didn't bother with trying to store energy to use later on. The system was simplified and optimized to give the drivetrain a boost at low engine RPMs, and that was it.

I have a feeling this is the route Class 8 OEMs will take when they opt to add hybrid-electric drive lines to trucks as part of their GHG 2 strategy over the next decade.

Clearly, there simply isn't room for large battery systems on Class 8 trucks to be viable. And I don't need to point out that the weight penalty associated with those battery packs is a non-starter for fleets. 

But, a highly-optimized, light-hybrid system that can capture kinetic energy during braking and put that power to use to get heavy trucks up and moving quicker makes an awful lot of sense to me. Remember, fuel burn on a Class 8 truck increases exponentially when it is starting out in lower gears, and then drops off dramatically once the rig is up and moving in higher gears. 

Clearly, the systems will need to be carefully designed to keep weight and space requirements low. And it will need to be a robust system that is fairly easy to maintain and repair. 

But if those goals can be met, my suspicion is that hybrid-electric drivetrains may eventually prove to be a fuel-saving technology that fleets will feel is a winner.

[BC Mack]

The writer should visit a Transit bus garage and have a quiet word with the mechanics who fix the hybrids, may change his tune a bit..!!!

The power assist for acceleration from a stop and the braking retardation are the two good features.... just not sure if a highway semi could benefit carrying all that weight and cost, it may suit small/medium delivery trucks but he just said that isn't working out.

When we blow a DPIM or IGBT, my manager cringes... $$$

Remember, in the trademarked Allison system, the engine has no starter... you can't bump start them and pushing for more than a few feet with the axle still in causes considerable damage... so, operator mindset has also got to change.

I don't dislike them... just can't rave about the perceived cost savings vs. gains in greenhouse gas stuff.

Perhaps 10 years from now, they will develop something that works for a good price... even then, I will lease not buy.

BC Mack

[kscarbel2]

Getting a handle on hydraulic hybrid drivetrains

Jack Roberts, Fleet Owner  /  September 23, 2016

It's funny how in the age of social media and near-instant communication you rarely get a real, live, letter any more.  But that's exactly what happened on the heels of my recent Fleet Owner blog, when I noted that electric hybrid drive systems would, in all likelihood, be a part of the OEM formula for meeting Phase 2 Greenhouse Gas (GHG 2) regulations when they come into law a decade from now.

A letter from Lightning Hybrids CEO Tim Reeser noted that diesel-electric hybrids aren't the only option available to OEMs wrestling with GHG 2 powertrain requirements. Hydraulic-electric hybrid drivetrains also offer a significant low-end torque boost, to help trucks get up and moving more efficiently and burning less fuel in the process.

And Mr. Reeser is correct: I've been covering heavy trucks now for over 20 years. And all that time, I've never had the opportunity to test-drive a hydraulic hybrid drivetrain, or even inspect one up close. So I called Mr. Reeser to get a bit of a primer on these systems, which are already making inroads in refuse applications, due to the stop-and-start nature of that application.

Reeser told me that his company's system, is a relatively simple way of converting kinetic energy generated when a truck brakes into hydraulic energy, which is then released and used to provide extra torque when the truck gets under way again.

Here is a brief explanatory video from Lightning Hybrids:

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The system can be installed on a truck as an upfit, or retrofitted to older vehicles. (The company is currently in discussions with OEMs regrading offering it as an option on new vehicles.) The system consists of an dedicated, auxiliary hydraulic system, including a low-pressure holding tank, a high-pressure accumulator tank, a power transfer module, as well as an electronic control module and other components.

When the truck is moving down the road, the hydraulic fluid remains in the low-pressure storage tank until the vehicle's brakes are applied. At that point, the system uses the kinetic energy generated by the brakes to force the hydraulic fluid into the high-pressure accumulator tank, where it is stored until needed. When the brakes are released, the system's ECM reads all pertinent information off the vehicle's J1939 ECM, including throttle position, horsepower, torque, speed and other vital data, and immediately releases the hydraulic fluid at high pressure, where it flows into the system's power transfer module. This module is linked directly to the truck's transmission via a second driveshaft, where this additional torque is delivered directly to the drive axle, providing a significant low-end performance boost to the accelerating truck.

Reeser says battery capacity on electric hybrids limit the system's energy density to around 30 percent. But, he says, hydraulic hybrids capture close to 80 percent of the hydraulic fluid's energy density, resulting in a robust start-assist, which, he says, can yield fuel economy benefits from 15- to 35 percent for fleets – depending on application.

He notes that early hydraulic hybrid systems were much heavier and less reliable than systems available today. The industry has been able to leverage carbon fiber technology breakthroughs in natural gas fuel storage to develop new tanks and accumulators that weigh up to 1,000 pounds less than older systems. And recent advances in on-board vehicle control modules -- and his company's ability to tap effectively into those systems -- has resulted in consistently reliable, seamless performance for fleets and drivers alike.

For now, Reeser says Lightning Hybrids is beginning to work more closely with OEMs now that a clear GHG 2 pathway is visible, while also continuing to refine the technology. The results, he says, are promising, with next generation systems already 39 percent more efficient then their predecessors and costs steadily coming down to the point where he feels a 3 year return-on-investment for fleets will be feasible.

As I noted previously, it seems likely that hybrid drive systems will be an important tool to help OEMs meet GHG 2 regulations when they come into effect a decade from now. And although the public at large – and this writer – tend to think of electric systems when hybrids are mentioned, it's important to remember that hydraulic hybrids hold great promise as well for reducing emissions while boosting fuel economy in heavy truck applications.