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Autonomous tractor with battery replacement robot

Imagine an autonomous self-driving battery-powered tractor harrowing in a field. When the battery runs low on power, it moves to a removable battery replacement robot beside the field. Then, after switching to a fully charged battery, the machine returns to the field to continue its work. It sounds like science fiction, but it is a possible scenario in a year.

The Swedish public inquiry, The road to fossil-independent agriculture, released in summer 2021, states that the development of fossil-free tractors and work machines is essential for achieving the climate goals. The report further states that “autonomous machines and new systems for cultivating the land are currently at the idea stage but should be a reality by 2045.

The investigators identify various scenarios how to achieve fossil-free agriculture, but in the end, it all comes down to what is politically, economically and practically possible.

“Investments in biofuels from forests seem advantageous in countries like Sweden and Finland,” says Ola Pettersson, senior project manager at RISE. “But as directives abroad point out a different path ‒ and machine developers need to invest in more significant market segments than just the Nordics ‒ the development within electrification advances.”


We want to prepare for electrification in agriculture and forestry and accelerate the development

The potential of electric autonomous machine systems has been investigated theoretically. Still, no electrically powered agricultural tractors or electric hybrids on the market can handle heavy fieldwork. However, this should be possible according to the made simulations.

“We want to prepare for electrification in agriculture and forestry and accelerate the development. For example, five years ago, it was considered impossible for aircrafts to be powered by electricity. However, many different electrified aircraft are now under development in the aviation industry,” says Jonas Engström, project manager for the project and operations manager for Testbed Digital Agriculture at RISE.

Battery replacement can be part of the solution for heavy machinery

The difficulty with electrifying heavy agricultural machinery is that they require significantly more energy than a car. A large battery becomes too heavy and expensive, while a smaller battery needs to be charged too often. To reduce weight and avoid downtime charging batteries in the machine during work, a solution is required with batteries that can be replaced directly in the field.

In a research project coordinated by RISE, a modular battery replacement system is being developed. The batteries are not built into a specific machine and can therefore be replaced when needed. For an autonomous machine system, the battery swap also needs to be done automatically.

Similar battery replacement systems, so-called battery swapping, are already available for vehicles in different parts of the world, although the existing solutions rely on stationary battery-swapping. Despite some of the leading companies in agricultural machinery have developed battery-powered concept machines, they have remained at the prototype stage. An essential part of moving forward is to solve how the devices should have access to batteries and cost-effectively charge in practice.

“Battery replacement is a technically efficient solution at low costs. With a mobile exchange station placed out in the field, we hope to find an automated solution that eventually can be realized in production”, says Ola Pettersson.

A battery replacement system also meets the needs of many seasonal work machines; ideally, machines with different seasons can use the same batteries.

“With a modular battery replacement system, it is possible for the farmer to order a certain number of charged batteries for the spring cultivation, which can be returned afterwards. Furthermore, the batteries can be switched between different machines. For a small farm, it could be enough with a couple of batteries for a few machines. With more batteries in circulation, the utilization and the economy will be better in the entire system,” says Jonas Engström.

Another great benefit of the battery system is that it also enables smaller machine manufacturers to access state-of-the-art battery systems. This is because work machines ‒ unlike passenger cars ‒ are produced in small series. Forest machines, for example, are only produced in about a hundred units per year, which makes development costs for a battery system excessive for both manufacturers and machine owners. Thus, this research project aims to eventually enable the introduction of battery-powered machines in industries where it is difficult today due to the high threshold costs when all manufacturers have to develop their own battery systems and bear the entire development cost.

Testbed for autonomous, electrified machines

The project will develop a prototype for a modular battery system, a mobile automatic battery replacement robot, and prototypes for an electrified forestry machine and an electrified, autonomous agricultural machine.

Parts of the project will occur at the testbed for digital agriculture that RISE with partners run at Ultuna, outside Uppsala.

“In the testbed, we test, among other things, new autonomous and electrified agriculture machine systems. We are already working with a prototype for a driverless electric tractor, Drever 120, which is the machine where we will demonstrate the battery replacement system,” says Jonas Engström.

How far in the future we may see the result of this research in terms of commercial driverless tractors that change the battery with the help of a robot in field operation is challenging to say. Due to agriculture’s large machinery and slow replacement rate, the combustion engine will continue to play a significant role for a long time to come. But the direction forward is still likely to be the electrification of work machines.

“The engine itself can be a combustion engine, maybe powered by on-farm-produced biogas. However, the transmission; the part that transmits power from the engine, can still be electrified,” predicts Ola Pettersson and adds that “biogas- or hydrogen fuel usually requires new machines. Still, there are examples of work machine trials that have undergone conversion. However, none of them is available in the market yet.”

“An electric machine has very high efficiency, and in addition, it controls its actions with higher precision than a machine with a combustion engine. Considering that accuracy is crucial for digitized autonomous field machines, it indicates that electrification in agriculture will dominate,” says Jonas Engström.

Increased profitability with reduced emissions

This project strengthens the Swedish vehicle industry’s international competitiveness by developing, applying, and demonstrating new energy-efficient and a fossil-free key technology for electric work machines. The project also includes investigating how a modular battery system can be spread and scaled-up.

Modular battery replacement system for fossil-free electric work machines

  • Development of a battery replacement system for work machines based on innovations from Powerswap AB and components from Micropower AB.
  • A prototype for an autonomous electric agricultural machine from Traktorarvid AB with components from Regal Components AB and Micropower AB, as well as control systems with open source code from RISE.
  • Electrification of a forestry machine from Malwa Forestry AB with components from Regal Components AB and Micropower AB.
  • Demonstration of the battery replacement system and the two electric machines in practical operation.
  • Investigation of how the battery replacement system can be scaled-up and spread to other applications and businesses and how it can affect the work environment and gender equality in machine-heavy industries.