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Beyond Tier 4 Engines

For almost two decades, you’ve heard the EPA talk about tiers and emission regulations for high-horsepower, off-highway diesel engines. You’ve adjusted as engine technology changed and widened your vocabulary with phrases like selective catalytic reduction and exhaust gas recirculation.

In 2014, Tier 4 Final came into effect for engines from 174 hp. to 750 hp., and next year it will extend below and above these outputs. This is the last scheduled emission regulation, which begs the question: Will Tier 4 Final be the last emission regulation? And what can you expect next in engine technology?

Tier 5 on the horizon

At this point, the EPA hasn’t issued anything saying there will be a Tier 5. But most industry experts believe there will be.

“Tier 5 is on the horizon,” says David Kohuth, product training specialist at New Holland. “I believe there will be a Tier 5,” confirms Antti Marttinen, manager of product management – global engine installations at AGCO. Cummins global off-highway communications director Kevan Browne agrees. “We are making plans now for a Tier 5, even though one doesn’t exist,” he says. “We are doing this on the basis that the European Union (EU) has proposed a Stage V. The proposal has gone to a high level, and we are almost 100% sure it will be introduced.”

Through Tier 4 Final and Stage IV, the EPA and the EU have aligned emissions regulations for high-horsepower diesel engines. “As Europe and North America are trying to synchronize as much as they can, we look at what we have compared to the EU and what they are doing at the moment,” explains Marttinen.

If you’ve kept up with your Tiers, you know Tier 4 and Tier 4 Final have reduced particulate matter (PM) and nitrogen oxide (NOx) emissions to near-zero levels. The proposed EU regulation will tighten NOx emissions to standards similar to the EPA and further reduce the particulate number by targeting the number of particulates, not just the mass or size.

“In addition to telling you the mass of particles you can emit, the EU is looking to establish a standard that says you can’t emit more than a certain volume of particles during a certain period of time,” explains Allen Schaeffer, executive director of the Diesel Technology Forum. The Diesel Technology Forum is a nonprofit educational organization that represents diesel engine and equipment manufacturers.

You’ll be relieved to hear that the solution for the further reduction is a known technology: a diesel particulate filter (DPF). At this point, only some Tier 4 Final engines use DPFs. “What Stage V will be is a DPF-enforcing regulation,” says Browne. “There is no other way.

“This regulation is about to be introduced for the European on-highway vehicles,” he adds. “All of the truck and bus engines will have to use a DPF.”

Diverging paths
The big question is whether or not the U.S. will join Europe on its particulate mission, or if the EPA will decide to tackle greenhouse gas emissions as it has already done for on-highway trucks. The EPA aims to reduce greenhouse gases by increasing fuel efficiency, which reduces carbon dioxide (CO2) emissions.

“For the U.S., there is speculation about CO2 control,” says Kohuth. “But the industry will probably go to the EPA and ask for harmonization with the EU Stage V to focus the development effort.”

While precedent would say that the EPA will align with the EU, the EPA’s recent focus on reducing greenhouse gases makes some experts question if the fifth round of emission regulations will diverge.

Schaeffer points to the recent work done by the EPA to reduce CO2 by targeting the three largest culprits: power plants, cars, and heavy-duty trucks. “By lowering fuel consumption, this also reduces the national dependency on imported oil, and this has to be an important consideration for the EPA,” says Browne.

So what would a greenhouse gas emission regulation look like for ag equipment? That answer is pretty foggy.

“The problem with off-road and off-highway applications is the sheer number and types of applications,” explains Marttinen. “Finding a regulation that could be applied to all of these different applications is difficult.”

Even if the EPA could find a regulation applicable to ag and off-road equipment, Schaeffer thinks it is probably unnecessary. “Off-road has not been in the scope of discussions from the EPA on CO2,” he says. “Keep in mind when we talk about lowering CO2 emissions we are talking about better fuel efficiency. Manufacturers have been focused on that forever.”

Schaeffer also does not believe there will be a Tier 5 – at least for a while – for three main reasons. First, the EPA is focused on the top three greenhouse gas emission offenders, and that doesn’t include off-road. Second, increasing fuel efficiency and reducing CO2 will be driven by competition among manufacturers. And last, the costs for further reducing particulates may outweigh the benefits. “What’s the cost and the benefit of that particulate level when you are already so close to zero?” he asks about the proposed EU regulation. “From here forward, the costs are astronomical vs. what you will achieve.”

If some form of greenhouse gas regulation was applied, Cummins says they will be able to leverage knowledge from the on-highway truck engines to off-highway equipment. The base engines are the same; the truck engines have just been adapted. “The changes we made were mostly around the combustion formula and the electronic control capability,” says Browne. “There wasn’t any major change to the architecture.”

Only time and the EPA can tell what Tier 5 will look like – or if it will form at all. But we do know a few things. Even if the EPA doesn’t pass further particulate matter reductions, this technology will most likely trickle down from Europe into the U.S. So you can expect to see DPFs on more or all engines in the future. Second, the industry will continue to work with the EPA to ensure possible regulations are feasible and realistic. And last, while the EU battles particulates and the EPA focuses on greenhouse gas emissions, the diesel engine industry will focus on making better engines.

Revving up innovation
“With Tier 4 covered, we have more available resources and time to look at innovative approaches that can save fuel, reduce after-treatment size, or introduce electrification to aspects of the engine operation,” says Browne. “It’s pretty exciting and will help drive innovation.”

“There is a lot of talk about hybrids,” says Browne. “But perhaps hybrid isn’t the only description. We are describing this process as electrification, because the hybrid is the full electrification of the machine.

“There are a lot of stops along the way to a full hybrid,” he explains. “Different systems and components will move you toward the end goal while giving you performance and fuel-efficiency benefits.”

Cummins’ CorePlus Motor Generator is one of these engine-mounted solutions. This component can be used in a hybrid system or on its own. The generator fits between the existing engine and transmission and hybridizes mechanical drivelines. In other words, it takes energy from the flywheel and sends it to battery storage. The CorePlus system captures 90 kilowatts at the peak and 30 kilowatts continuously for immediate use or battery storage. This provides fuel savings benefits, torque assist for the machine drive, and it generates extra electrical power when your machine needs it.

At this point in the game, Cummins is only producing engines, not full-hybrid systems. But they do pair up with innovative companies pursuing hybrid technology.
This year Oerlikon launched a diesel electric hybrid drivetrain with a new Cummins QSG12 engine. The system provides up to a 30% fuel economy improvement and, depending on the application, other benefits such as electrically driven auxiliary drives and the ability to add engine start/stop technology. The key is that the system, debuting in a 30-ton loader (shown above), uses ultracapacitors rather than lithium-ion batteries. “Ultracapacitors handle the cycles better than batteries would, making this system more suitable for really hardworking machines,” explains Browne.

AGCO is also working on overcoming hybrid challenges to find solutions. “Hybrid technologies already exist, it’s just the sheer cost,” says Marttinen. One AGCO solution is the Fendt X Concept tractor. This is a project incorporating high-power electricity into a tractor. At the rear end of the tractor, there is a plug for 130 kilowatts at 700 volts DC. That power can be used for implements that are able to run on high electricity.

“The growth of natural gas or biogas is growing for stationary use, but for ag machinery there are problems to overcome,” says Marttinen. “The operation time goes down because there isn’t room for large tanks.

“But we have done some concept studies on a biogas tractor,” he adds. Biogas can be produced from all organic materials, including farming by-products like manure and waste from crops.

The AGCO Valtra N101 biogas demonstration tractor’s dual-fuel engine functions like a diesel engine. The gas is injected with the air intake, and combustion occurs when a small amount of diesel fuel is injected into the cylinder. If biogas is not available, the engine can run completely on diesel fuel.

Without making any changes to the original diesel engine, 70% to 80% of the power is generated by biogas. The 100-hp. tractor can hold enough biogas for about four hours of work. The concept tractor is being tested in Sweden.

Other options
Electrification and biogas are more complex engine solutions, but you may see simpler solutions like Cummins’ Waste Heat Recovery system. This component takes waste heat out of the engine and uses it to drive an expander, which transmits that power back to the engine.

“From our testing, we’ve seen a 5% reduction in fuel use with just this device on the engine,” says Browne. This technology isn’t available in the off-road sector yet, but it is being tested in the on-highway market in trucks.

• Editor’s note: The main ag equipment manufacturers were contacted for this story. Those included were the ones who chose to comment on possible paths for Tier 5.

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