Are Off-Highway Equipment and Heavy-Duty Trucks Going All-Electric Soon?
A host of car companies, countries, and localities are proclaiming they will no longer accommodate cars with internal combustion engines. They will either not build them or not let them drive in their area of control. But what about heavy-duty vehicles that handle construction, cement mixing, timber harvesting, and lifting or digging?
To get an idea of what the industry is thinking, Machine Design talked with experts from several companies heavily invested in off-highway vehicles and equipment: Bosch Rexroth, Parker Hannifin, and Volvo.
Will off-highway and construction equipment go to all-electric propulsion (replacing diesel and gasoline engines) and electric or electric-powered hydraulics for motion (controlling cherry-pickers, diggers, cranes) in the next 10 to 15 years? Why or why not?
Jenny Elfsberg, Volvo, Director Emerging Technologies: I am absolutely convinced all of our machines will be all-electric in the future. Either they will be battery powered or connect to the electric grid. To get there, we need to reinvent machines. We will see downsized machines, specialized “one-purpose” machines, and entirely new approaches, thanks to the electrification. It will entail digitization and automation, and changing the way we look at the entire design process. This transition will take years. That means combustion engines will remain important for many years to come, but they will be smaller and have smoother operation in a narrower band as they are designed to be more and more efficient. The fuel should be renewable, and so hydrogen will be an important parallel approach to electric when that becomes viable. The goal will be to get the most possible efficiency with electric power.
Terry Hershberger, Bosch Rexroth, Director Sales Product Management: Yes and no. Much of the answer to this rests in several areas including size and power requirements; tasks the machines will carry out, the functions the machine performs, including the duty cycle of the propulsion system; and, finally, the ability of storage technologies such as batteries that need to advance to provide the needed power to run the machines. Many machines have been running on battery power for years, not necessarily for propulsion, but as an electric motor driving the hydraulics. This includes aerial work platforms (AWPs).
We also know hydraulic pumps and motors have been effective and compact ways of transferring available energy for years. This will continue on the implement side/cylinder movement, due to the ability to transfer available power. However, on the propel side, the transition to electric will continue as technologies advance to provide a better way or an easy interface to amplify the torque of the electric motor via a gearbox or some other gear ratio to get the machine to move. Of course, the electric motor isn’t new to off-highway as the technology has been used in the mining industry for years. However, the challenge is to build the infrastructure for construction equipment in such a way that the components sized to make the machine move do not get in the way of what the machine needs to do. Hydraulic pumps and motors are well proven as trusted, effective, and compact ways of transferring available energy.
Again, much of the transition depends on power requirements, the main function of the machine, and the ability to store energy.
Eric Hendrickson, Parker Hannifin, Business Development Manager Vehicle Electrification: We will start to see a shift to all-electric off-highway vehicles. The reason is not a single technology or market-driving influence, but rather it is the convergence of many factors that will make electric off-highway vehicles more viable. These drivers include the ability of electric power to make vehicles more productive by using more efficient subsystems sized to do the work, recapturing energy and reducing reliance on fossil fuels. These abilities will be turbocharged by several technologies such as autonomy, artificial intelligence, fast charging, advances in batteries (energy density, charge acceptance rate, and price), high-efficiency electric motors and generators, and combined electrohydraulic actuators. Taken together, they make it easy to predict that electrification will be a reality in 10 to 15 years.
Volvo Construction Equipment’s concept vehicle, the EX2, is an all-electric compact excavator. According to the company, it delivers zero emissions, 10 times higher efficiency, and one-tenth the noise of its conventional counterparts. Instead of a combustion engine, it carries two lithium batteries, which store 382 KWh, enough for eight hours of digging. And instead of hydraulics moving the arm, electromechanical linear actuators handle the task.
Are diesel/hybrids an option for off-highway and heavy equipment? Haven’t they been tried and failed in the marketplace? What would make them viable from an engineering perspective?
Hendrickson: We will see more diesel hybrids entering specific markets. Parker Hannifin is engaged with several companies that manufacture relatively small off-highway construction equipment that are seeing the benefits and business case for developing diesel-hybrid products. These typically involve downsizing the diesel engine, adding a bellhousing-mounted motor/generator, and adding battery storage. Each vehicle has its intended use with distinct value propositions, but downsizing the engine, reducing or eliminating idling, reducing fuel consumption, adding an electric-only mode, and incorporating electrohydraulics are generally the main pathways for improving machine efficiency and productivity.
Elfsberg: Hybrids will play a role in the journey toward full electric. It can be electric, hydraulic, or mechanical hybrids, and depending on concept, they can all make sense. We have tested our concept machine (LX1) with several customers. The machine is a series hybrid with 98% new parts and radically improved fuel efficiency—50% better. Operators and site managers love the machine. We learned that the interest in electric and hybrid vehicles is sincere on their part, and now we are deciding how to go from the research labs to sellable machines.
When it comes to the hybrid technology, the challenge is larger than the technology. It changes much beyond the machine in operation, such as servicing and maintenance skills, as well as the business model. We have tested several different hybrid concepts and learned a lot and since we started to collaborate with others in our industry, we have learned how to take things further.
The LXI, another prototype from Volvo, is an electric hybrid wheel loader with 50% better fuel efficiency than a conventional version. It features electric drive motors mounted at the wheels, electric hydraulics, an energy storage system, and a significantly smaller diesel engine than that of a similarly sized conventional version. It can also do the work of conventional wheel loader one size larger.
What would be the major engineering challenges in making all-electric off-highway and construction equipment? How will each of those challenges likely be met? Or which ones will not likely be met over the next 10 to 15 years?
Hershberger: The challenges are in the energy-storage methods, limiting machine consumption of that stored energy, and the ability to quickly generate or replace that energy again. The major challenge comes down to the primary function of the machine. Is the primary function to propel, or is it to provide cylinder movements? Is the duty cycle of the machine set up so that the machine is always moving with implement-type motion or to position the machine and then do work such as lift and lower or extend and retract, then move again and repeat? The answers to these questions will shape how companies in this industry react in the next years.
One must also ask whether there will be electric actuators that can replace the power density of the hydraulics. For moving the vehicle, there seem to be trends toward electrics based on success in automotive and on-highway applications. But the use and power consumption rate for off-highway/construction equipment has to be evaluated. For actuators, this remains an open topic.
Elfsberg: There are many challenges, but the most manageable challenges are the technical ones. What is less mature and less manageable are the sales, marketing, aftermarket, and customer-acceptance dimensions. But we are working on those.
Of course there is fear and anxiousness when new technologies require new competencies, when the cost of the machine is high, but the total cost of ownership is low, minds change and a willingness to embrace the future and contribute to making this world a better place is needed. I can also say that Volvo Construction Equipment has been hesitating in bringing hybrids or full-electric machines to the markets because we need to secure safety, quality, and also business viability before we launch new things. But I think we, together with our competitors, have been hesitating longer than necessary. I hear many customers saying they want cleaner, less oil-dependent machines and they want them soon.
Hendrickson: I anticipate continued advancements in charging infrastructure, battery technology, and fast charging-technology that will overcome the major engineering challenges. In addition, off-highway and construction vehicles will benefit from advances in adjacent markets such as transit buses and Class 6, 7, and 8 trucks.
As with any new technology, the total cost is initially high. As electrification takes hold across many markets, the component costs will decrease. Higher levels of component integration into sub-systems will further drive down costs and further reduce vehicle weight and size.
Are there batteries, fuel cells, or other means of electrical storage with the power density to handle heavy mobile equipment such as bulldozers, cement mixers, and industrial cranes? Are there likely to be such sources in 10 to 15 years? What technology will they use? Hydrogen, molten salts, fuel cells?
Elfsberg: The best guess is that we will definitely need to use all alternatives and options, finding out which are the most suitable for each application. We will see more and more customization, including in the energy sources. For example, we have learned in uncovering our customers’ needs that some machines are already quite static, and become even more static if there are changes at the site. This opens the possibility of powering them by cables hooked into the grid. Or sites might develop their own local electric grid with storage, and this could include renewable energy such as wind and solar at the site.
Ten to 15 years from now we will see solutions we haven’t even considered yet, thanks to technologies being rapidly developed. Machine intelligence, machine electrification, and machine connectivity, along with additive manufacturing and the ability to tailor software for every application will drive completely new concepts. At the same time as these new developments happen, conventional machines with combustion engines are going to look quite the same as today. But the change is coming and we all need to invest and prepare for these future developments while taking care of today’s and tomorrow’s machines and customers.
The HX1 for Volvo is a self-driving, battery-powered load carrier. It’s part of a larger project that aims to cut carbon emissions on worksites by 95% and lower the total cost of ownership for mining companies by 25%. Other components of this project include a hybrid wheel loader and grid-connected (plug-in) excavator.
Hershberger: As technology advances, there will be successes in the on-highway sector regarding the ability to “power” vehicles such as Class 8 trucks, perhaps with hydrogen fuel cells. There will also be improvements in reliability and safety. We will also begin to see technology transfers into the off-highway sector in the categories of medium and larger construction vehicles. There are certainly hybrid technologies such as diesel or gasoline and electric that are already being used, but switching over to a hydrogen-based energy economy requires new infrastructure to produce and distribute the “fuel” to power these machines. This will take time, of course. Is this likely in next 10 to 15 years? If so, it has potential for placement. Storage and refueling technologies and replacement plans will remain the primary topics.