Machinery

Background

Tractor swarms poised to take over

At a two-day forum organised by German Agricultural Society, DLG, 300 industry specialists met to discuss the challenges, opportunities and prospects for tractors. Their verdict was that wheeled tractors have now reached their limit and the future lies in swarm technology.

New large tractors are often prohibitively expensive, while their weight is too low to effectively convert their large engine power into traction. Increasing the weight to address this would, however, make tractors too heavy and bring the problem of soil compaction into play.

Significant cost increase due to emission standards

Joachim Pfannstiel-Wolf, a farmer on 1150 hectares, delivered an incisive, critical and somewhat sceptical presentation. Talking about his machinery, he mentioned that in the 1970s and 1980s his tractors cost the equivalent of € 695 per kW. In 2011 this was well in excess of € 875 per kW. He puts some of this significant cost increase down to more stringent emission standards. In recent years his machinery has become even more expensive, with costs now at € 950 per kW.

Reduction in profit per hectare

Mr Pfannstiel-Wolf stated that over all those years, the number of kW used per hectare has remained relatively stable – as has the tractor engine power. The increase in the purchase price has not been matched by an increase in the resale value of his tractors. All of this means his profit has fallen by € 50 per hectare. “The increase in the price of tractors is logical given the additional functionality and comfort. The result is that my drivers are glued to a screen and pay far less attention to the soil and their tyres, which is anything but a positive development.”

Limits of tractors reached

A critical appraisal of his 500-horsepower Fendt 1000 leads Mr Pfannstiel-Wolf to conclude that tractors have reached their maximum size. His arguments are clear. His main tractor used to be a Case IH Magnum 7220, which provided 74 kg per kW with a 2,000 kg front linkage combined with wheel weights. These days he often uses a Fendt 936, which can generate a maximum of 50 kg per kW despite 2,500 kg in the front linkage.

Text continues underneath image

The wheeled tractor has reached its limits in size and weight. For work not requiring lost of horsepower, swarms will be a serious alternative. - Illustration: Tony Tati
The wheeled tractor has reached its limits in size and weight. For work not requiring lost of horsepower, swarms will be a serious alternative. - Illustration: Tony Tati

The farmer continues: “A 14-tonne Fendt 1050 delivers no more than 38 kg per kW. You would have to increase its weight by 8 tonnes to get up to 60 kg per kW. Even if traffic regulations allowed for a weight like that, soil compaction would become an issue.”

This he demonstrated with the help of a figure. A 60:40 weight distribution would yield a pressure of 103 kPa at a depth of 40 cm under the rear-axle of the 1000 series, compared to 52 kPa underneath the old Magnum. The farmer lists the load capacity of his loam soil as 70-110 kPa and that of a sandy soil as no more than 50-70 kPa. On this basis, he characterises the current situation as problematic.

Switching to swarm technology

If tractors continue to increase in weight at the traditional rate, by 2030 the top model will come in at an impressive 33 tonnes at 800 horsepower. A graph by Agco’s Heribert Reiter shows combine harvesters are set to reach 50 tonnes with an output of 900 horsepower. According to Reiter, this is where the growth in machine size will level off. He believes the future is in small, autonomous robots cooperating in a swarm.

Fendt Xaver

Fendt is running a development project, Xaver, which has already shown good results. Compared to a standard tractor, Xaver robots are said to generate 95% less heat, produce 95% less noise, reduce soil compaction by 80% and save 70% on energy. It is also claimed that the robots are more economical in the use of pesticide (reduced by half) and seed (reduction by 5%).

A downside is that a robot weighing no more than 40 kg itself will not be able to generate traction, meaning that soil tillage will still require the use of a tractor.

Text continues underneath image

Fendt’s Xaver system comprises 6 to 12 coordinated robots and a Cloud platform to plan, monitor and accurately document the planting process of corn. - Photo: Fendt
Fendt’s Xaver system comprises 6 to 12 coordinated robots and a Cloud platform to plan, monitor and accurately document the planting process of corn. - Photo: Fendt

New natural gas technology

If Roger Stirnimann and Danilo Engelmann of the Berner Fachhochschule in Switzerland have their way, gas-powered tractors will become available on the market. So far there have only been prototypes, such as the 2016 methane-powered New Holland. Applications have been limited to CNG-engines (compressed natural gas), for which natural gas is filled into tanks under high pressure. These only permit a limited range.
Stirnimann and Engelmann predict liquid natural gas (LNG) will offer opportunities. LNG involves filling natural gas into insulated double-walled tanks under extremely low temperatures, which has a significantly higher energy density. A litre of diesel delivers 35.7 MJ and weighs 0.83 kg per litre, which translates to 43 MJ per kilogram.
A litre of CNG (now outdated) weighs 0.14 kg and yields 6.44 MJ, or 46 MJ per kilogram. The new LNG weighs 0.41 kg per litre and delivers at least 18.86 MJ, which comes to at least 46 MJ per kilogram. Stirnimann and Engelmann are confident the first LNG-powered tractor prototypes are only a matter of time.

Conceptual shift

Professor Thomas Herlitzius agrees that a tractor remains the only option for applications requiring traction. He is involved in Feldschwarm, another development project. He is convinced that a conceptual shift from large machinery to swarm technology is on the cards. As machines increase in productivity, they are also becoming heavier. But utilisation is falling, with machines clocking up fewer operating hours in a year.

Tractor manufacturers must therefore reduce weight and increase power density, which pushes tractor prices up further still. Prof Herlitzius believes a shift to swarm technology is inevitable and thinks this could happen even before 2030.

Text continues underneath image

A ‘swarm’ of Yanmar tractors working as an autonomous team at Hokkaido University, Japan. - Photo: Yanmar
A ‘swarm’ of Yanmar tractors working as an autonomous team at Hokkaido University, Japan. - Photo: Yanmar

The farmer, Mr Pfannstiel-Wolf, is clearly less confident of this. His view is that although this might be possible in parts of the world, where plots are sufficiently large, this is not the case in the west of Germany. He draws a comparison with 2 robot vacuums he has been using in his home for the past year. “Watching them negotiate the legs of tables and chairs, I can’t even begin to think about operating 20 robots around a crowded area such as Düsseldorf.”

Also read: Hokkaido University creates this autonomous tractor swarm

A 15-tonne battery

Are all-electric drives possible? For small tractors, Dr Heribert Reiter at Agco believes they are the way forward. A 200-series Fendt (with an output of 70 horsepower) requires a battery with a 100 kWh charge to operate at 50% engine load for 4 hours. This translates to a battery with a volume of 0.3 m3 and a weight of 600 kg. This has prompted Fendt to develop the E100, a 200-series tractor with an electric drive. It believes there is a niche market for these, e.g. at waste collection sites.
However, wherever true pulling power is required, battery-powered tractors will still fall short. As an indication, a 1000-series Fendt (517 horsepower) operating fully electrically at 50% engine load for 12 hours would require a battery with a volume of 5 m3 weighing 15 tonnes. Combustion engines will therefore continue to be the default for now, as Reiter concludes. Key challenges developing electric tractors will be to keep cost down and significantly increase energy density.

Battery power is an option for smaller tractors like this Fendt E100. Big tractors would require too large batteries. - Photo: Bas van Hattum
Battery power is an option for smaller tractors like this Fendt E100. Big tractors would require too large batteries. - Photo: Bas van Hattum

Or register to be able to comment.