A hydraulic pump powered by electricity

Fossil-free applies also to heavy mobile working machines. Liselott Ericson, Fluid and Mechatronic Systems, has received SEK 11.6 million from the Swedish Energy Agency to collaborate with industry in developing technology that uses a hydraulic pump in electrically operated working vehicles. 

Epiroc Scooptram powered by a battery Epiroc Scooptram, powered by electricity. Epiroc Rock Drills

“Previously, we aimed to reduce fuel consumption. The next step is to achieve completely fossil-free working machines, and get rid of the diesel engines”, says Liselott Ericson, senior lecturer in the Division of Fluid and Mechatronic Systems, Flumes. In a period dominated by the spread of the novel coronavirus, she is to initiate and drive a major research project in distance mode.

“Quite right – the start-up didn’t quite turn out as we expected: many of our collaboration partners are on furlough. But we have a realistic plan and viable work packages, so I’m sure everything will work out OK.”

Diesel-free

Two doctoral students are to be employed in the project, and the deadline for applying for these is 22 June. This means that those to graduate from Master’s programmes in the early summer can apply. “We have already seen that many people are interested”, she says.

Working vehicles are to be made diesel-free. However, the diesel in these machines doesn’t only drive the vehicle itself, but also the cylinders and the actuators needed to lift and lower the buckets, lifting arms and other tools, which often have heavy contents. Hydraulic systems are reliable and durable in demanding surroundings such as mines and building sites.

Flume´s hydraulic pump, length 16 cm. Photo credit FlumesIn a previous project, also financed by the Swedish Energy Agency, the LiU scientists designed an efficient hydraulic pump. They are now to investigate how the pump can be integrated with the electric motor in working machines, and how this affects the performance of the complete system. Their goal is that the electrically operated hydraulic pump will reduce the total energy need such that the machine can travel 5-10% further with the same battery capacity.

“When we integrate the pump with the electric motor, we can remove a power-transfer stage, since the electromagnetic forces in the electric motor and the hydraulic forces in the pump act on the same mechanical parts. This reduces the losses. Losses also arise in today’s diesel systems when two cylinders, one on each side of the bucket or lift arrangement, require different pressure levels. If we can achieve electrical operation, we may be able to have two electric motors and distribute the power as it is required”, says Liselott Ericson.

Electrohydraulic

The project, “Energy-efficient compact electrohydraulic solutions for components and systems in working machines” (abbreviated as “Ehydraulik”), will run for three years and is part of a Swedish initiative in vehicle research and innovation, FFI. The work will be conducted in close collaboration with the motor industry, and partners in the project include Volvo Construction Equipment, Epiroc Rock Drills, Volvo Personvagnar and Gnutti Carlo Sweden.

Translated by George Farrants

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