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Urban construction environments combine unique requirements for low emissions and noise with easier access to electric recharging, making them ideal for lower-power electrified equipment. (Volvo CE)

Electric machines find their niche

Many players in the off-highway market are announcing electrification efforts. But why? To date, global regulatory programs have spurred off-highway technological innovations, to improve fuel economy and reduce criteria pollutants. Think U.S. Tier 4 final, Euro Stage V and other global regulations.

But there’s more to it now.

“It is local restrictions and local market drivers,” Dr. Thaddäus Delebinski, business unit director, diesel systems for IAV, told Truck & Off-Highway Engineering. Crowded cities want clean air and quiet machines. This is reflected in more electrified buses and delivery vehicles. This trend is also affecting construction. For example, in some cities a construction company can only submit a quote if they are using quiet, zero-emissions equipment, according to Delebinski. This is especially true in urban areas in Northern Europe.

“That makes electrified power ideal in many cases,” he said. He also believes that this urban-centric perspective is pushing for development of smaller powered applications, typically under 56 kW.

He also noted that global emissions regulations for smaller engines, less than 56 kW, which today are not overly strict, will most likely get tighter at some point. “This means the aftertreatment and thermal management systems for smaller diesels will become quite complex and expensive, making either gasoline or especially electrified solutions more attractive,” he said.

This adds to the case for electrification of forklifts, smaller excavators, municipal tractors for lawn mowing, or multipurpose lawn care machines. Other off-highway applications that could be electrified include port drayage, aircraft support equipment, and most forms of material handling.

“It gets a little more difficult to make the case [for electrifying] larger power units up to 560 kW,” Delebinski said. But there are applications where fuel-cell-powered applications would still make sense, with ferries being an example.

He also sees electric hybridization as making sense in applications where energy recuperation is prevalent. This is true with new model hybrids for excavators with electric swing operation and wheel loaders with electric drive, for example, where stop/start movements of arms or the vehicle are ripe for recuperation.

“Overall, many of my colleagues are saying electrification will penetrate much faster than we think,” he said.

Recent hybrid, all-electric launches

One example of new hybrid technology, in the power range Delebinski mentions, is the 30-kW Kohler K-HEM hybrid power unit, introduced in January 2019. The K-HEM features a KDW 1003 18-kW diesel engine combined with a 48-volt electric motor that guarantees 15 kW of peak power and 9 kW of continuous power. Its design eliminates the need for exhaust-gas aftertreatment, according to the company.

The hybrid unit is designed to meet the needs of equipment with intermittent duty operation cycles and power peaks such as welders, mowers, or tractors with implements. It is also ideal for applications where continuous low-load operations prevent the engine from reaching temperatures that activate passive diesel particulate filters (DPFs), including forklifts or aerial platforms, Kohler claims.

“Kohler’s commitment is to support our customers in their growth and path to increasing electrification, not to force or drive their choices but to deliver the best of our engines in combination with electrical technology,” Paolo Fregni, advanced engineering manager, Kohler Diesel Engines, said to TOHE. He believes the major technical advances involve integrating diesels with electric power to improve power, torque, energy consumption, emissions, and total-cost-of-ownership.

Fregni also offers caution about off-highway applications as compared to commercial truck or light-duty passenger vehicles, where much of the world’s effort in electrification is being invested. “Energy recovery is less likely in off-highway because there are many different duty cycles and the missions of machines can be very different” and often depends on how the operator is using it, he said.

Nevertheless, there is a sense of excitement among some in the industry. “We are standing before a paradigm shift towards electromobility,” asserted Ahcène Nedjimi, electromobility specialist for Volvo CE. He agrees that electromobility is particularly useful in meeting the demands placed on vehicles by zero-emission areas as well as safety and silent zones. For example, he pointed out that the Norwegian capital Oslo plans to cut emissions by 95% by 2030, which is simply not achievable with current combustion-engine machines, he said.

“Noise reduction is another key factor for off-highway. This is because [electric] machines can work without causing disturbance to nearby residents. It’s a game-changer—contractors will be able to work whenever they want with greater flexibility,” he added.

Volvo CE’s actions confirm both this zeal and that smaller equipment is where electrification makes sense today. The manufacturer announced that by mid-2020 it will begin to launch a range of electric compact excavators, the EC15 to EC27 models, and compact wheel loaders, the L20 to L28 models. Both are described as ideal for working in inner-city environments.

The company is “stopping new diesel engine-based development of these models,” Nedjimi said. “The reaction has been great, and we are getting interest from customers all over the world, with surprising speed in the northern European market.”

The L25 wheel loader shown at the Bauma show promises up to 8 hours of operation, with off-board fast charging of up to 80% in 2 hours, or a recharge in 12 hours with a 230-V onboard charger.

Batteries and systems

But challenges to achieving that electromobility goal are many. “Substituting diesel-based machines with electric machines is not a simple task. Technologies with the internal combustion engine (ICE) have been developed over more than a century,” Nedjimi said. “This transition will require technological development, new business models, new driving behaviors, new policies, and new connections between industries.”

Current battery costs are as much an issue with off-highway as with other mobility sectors. While the vast amount of investment in batteries for light-duty passenger cars is bringing their costs down, adopting those batteries for off-highway is not simple. Cost, durability, and power density requirements are different in off-highway compared to the light-passenger market, according to Vinoo Thomas, director of electrified power business unit at Cummins Inc.

Off-highway customers are especially sensitive to initial cost and total cost of ownership. “You need to be below a certain price point kWh [pack costs] to make significant headway in off-highway construction,” he said, noting that cost figure depends on the application.

Duty cycles are also vastly different, with off-highway requiring higher peak loads much more often than passenger cars. This means off-highway packs need specialized thermal management systems. Durability requirements are more severe as well. Equipment—and their batteries—need to last a significant amount of time, up to 20 years in some cases. Maintenance costs of electrified equipment could provide an advantage. Electric drive systems are easier to maintain than diesel and gasoline ICEs.

Diversity in applications means “no one size fits all,” as Thomas puts it. “The proliferation of the machine types, the package requirements, and the other option requirements on different machines are just tremendous.”

Higher power density and smaller batteries are even more crucial for off-highway and commercial than light-passenger applications. An example of market movement is in Class 1-3 material handling. Lithium-ion replacing lead-acid batteries in this segment is an indicator of transition.

This gives Cummins an opportunity to build a unique advantage for commercial and off-highway battery packs. While not trying to invent its own battery cells, it is investing in its own battery pack design, according to Thomas.

“What we’re doing is adding on the structure, the cooling and the controls, to make application-specific battery packs. We are working with cell makers, but not creating cells ourselves. There is enough ‘secret sauce’ left in those other three elements that we believe we can create differentiated solutions for our customers,” he said.

The key to success will come in mass customization—a base platform tailored for different applications, with a common battery management system. “How you build the pack out then helps it go into multiple options and multiple pieces of equipment,” he said.

The strategy is similar to Cummins’ methodical platform-based approach used in, for example, its B-platform engine that has a current installed base of almost 600,000 units, according to Thomas.

Infrastructure challenges

Building effective battery-powered off-highway equipment is one thing. Developing suitable recharging infrastructure is another.

“The off-highway challenge is significantly different because you typically tend to deploy these pieces of equipment out in remote areas,” Thomas said. Easier access to recharging infrastructure is another reason to expect to see more pure electrification of off-highway equipment in urban settings—and not so for remote worksites.

“The last thing we want to do is deploy [electrified equipment] and then have a diesel generator provide the electricity. It defeats the purpose,” said Thomas.

For this reason, combined with other factors, off-highway electrification will remain in niches for the present. Kotaro Shiozaki, manager of engine planning, sales promotion department at Kubota Engine, expressed similar cautions to TOHE.

“Due to the high cost, we believe full-electric machines and diesel-electric series hybrids will not be a major solution in the market,” he said. “Those solutions will still be limited to some applications, such as aerial lift and forklift truck, which are used inside the building.”

For remote areas, where charging facilities are limited, machines will continue to be powered by internal combustion engines, according to Shiozaki. Kubota’s announcement of a micro-hybrid prototype engine at the Bauma event this past spring illustrates both its concerns and the opportunities it sees in electrification of limited applications.

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