20 April 2023

Did you think that all it takes is changing an excavator’s diesel engine for an electric one? Well, it’s not that simple. The hydraulics can actually be adapted to the many advantages of the electric engine. Ongoing research at LiU is looking into this.

Two scientists in the hydraulic lab.
Liselott Ericson And Samuel Kärnell. Photo: Ulrik Svedin
Female scientist in the hydraulic lab. Photo credit Ulrik Svedin “The use of electric engines offers an array of possibilities that a diesel engine can’t match. But also some challenges,” says Liselott Ericson, senior associate professor in the Division of Fluid and Mechatronic Systems (FLUMES) at Linköping University.

How does hydraulics work?
“Traditionally, you have a pump, often driven by a diesel engine. It delivers a flow which makes pressure build up. That, in turn, creates a force that involves movement. Valves are then used to distribute and channel the flow to various functions,” Liselott Ericson explains.

In this context, LiU’s research focuses on mobile working machines, which includes everything from truck cranes to excavators. From a climate perspective, there are good reasons to change to electric engines, as construction machines cause around one percent of the world’s carbon dioxide emissions.

Electrification provides opportunity

“Many changes could be made to combustion engine machines to reduce CO2 emissions. In many cases, relatively small changes could reduce the machines’ energy consumption by around 20 percent, but electrification provides the opportunity for bigger changes,” says Samuel Kärnell, postdoc.

Removing diesel engines from heavy working machines opens up for changing the entire system, but currently much remains the same.

“Many of the existing electrically powered machines have basically only had their engines changed. The hydraulic system usually remains the same. But there’s great potential for improvement here,” says Samuel Kärnell.


female and male scientist by computor. Photo credit Ulrik Svedin Batteries currently represent a large share of the cost of an electrically powered machine. Reducing the machines’ energy consumption makes it possible to use smaller batteries. This will reduce the cost of the machine.

“People have been aware of the major losses often associated with conventional systems, but there has not been enough incitement to reduce costs. The situation is different now, as energy-saving measures can also reduce purchase prices of machines.

The largest laboratory in the country

LiU has Sweden’s largest university laboratory for hydraulics. Researchers here work to reduce energy loss in the systems. Sustainability and energy efficiency are important key concepts.

“Interest in electrically powered hydraulics has seen an exponential increase in later years. In our lab, we try out different solutions in collaboration with several large manufacturers of working machines,” Liselott Ericson explains.

Distributing the effect

The LiU researchers mention several factors that will be affected as the machines are electrified.
“One important aspect is that you can electrically regenerate energy that can be used to power the machines,” says Liselott Ericson.

Also, the effect can be more efficiently distributed to where it’s needed by installing several electrical engines in various places in the machine. Traditionally, a diesel engine has powered the entire system.

“We’re conducting several studies into how this can be used and what the effects may be. So far, we’ve seen that it can give energy advantages, but also problems with fluctuations in the system that have to be handled.”
Heavy batteries and hot components
Electrification also comes with other challenges. For example, batteries are still heavy, and components such as engines and batteries must not get too hot or too cold.

And then there is the noise. You might think that replacing the diesel engine with an electrical one would make for a quiet environment. This is only partly true. A quiet engine makes the noise from the hydraulics more noticeable.

A more high-pitched sound that humans find rather disturbing
“It’s a more high-pitched sound that humans find rather disturbing. So we’ll have to come up with solutions to reduce the noise from the hydraulics,” says Samuel Kärnell.

Both of them are equally fascinated by the technology involved in the hydraulics. Their enthusiasm for research and machines is evident when showing us around the lab.

Where does it come from?
“For me, it’s a fascination with developing the future. Hydraulics has an important place in this. As a researcher, I can see that there are clear energy losses that we can help identify and solve. That’s what drives me,” says Liselott Ericson.

World class

Hydraulic pump. Photo credit Ulrik Svedin LiU is at the forefront of research into hydraulic systems. The ongoing research is a collaboration with Swedish industry, which is also a global player in the area. Epiroc, Volvo and Hudiksvalls Hydraulikkluster, including Huddig and Hiab, are some examples of partners.

International meetings

LiU organises and regularly hosts Swedish and international conferences on hydraulic systems, open to both researchers and the industry. One such event is Hydraulikdagarna, to be held on 13 to 14 June 2023, in collaboration with the Swedish Fluid Motion Association.

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