Robot Tractors!

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Guest Post by Dave Ward

Many readers of this blog will be familiar with the Eastern Daily Press, one of the Archant publishing group’s longest serving titles. It proudly claims to be the country’s largest circulation regional daily newspaper. However, I was told many years ago that it also happens to be the country’s ONLY regional daily newspaper – but never let a good selling point get in the way! Produced and printed in the city of Norwich, home to the UEA, it regularly features press releases from that famous institution, and also from the burgeoning “renewable” industry in the region. However they rarely question any such information provided – that is left to a handful of readers (like me) who take the time to write in. Even when we do, it’s almost a given that submissions will be edited (ostensibly to fit the limited space available), but also in subtle ways which alter the meaning. Despite numerous complaints about poor reporting standards they continue to trot out stuff like this:

Imagine a farm where driverless electric tractors roam the fields, day and night, before silently connecting themselves to solar-powered charging points ready for their next autonomous shift.”

Who on earth penned that! I’m not a farmer, but I’ve spent much of my time around small farms and do some work for one of them, so it’s immediately obvious that the writer hasn’t the faintest idea of the realities involved.

How do they “roam” day AND night, if relying on Solar Power? Certainly not with the capability of the John Deere SESAM prototype – 4 hours (max) use, followed by 3 hours charging. Look at any graph of solar output versus the time of day and the pronounced peak around midday is obvious. This would give the fastest charge times, but by late afternoon the battery would be flat, and solar output rapidly falling. It would (probably) be fully charged by mid-morning the next day, but then you would miss the peak charge opportunity whilst using it. Do they expect farmers to have several (very expensive) machines sitting around, charging when they can, just to get a semblance of normal diesel fuelled usage? And where are these solar panels going to be installed – not the fields being worked in, that’s for sure. The power requirements will be huge, and for Mr Fairman to compare them with robot vacuum cleaners or lawn mowers (both of which are considerably less powerful than their mains operated cousins) is disingenuous, to say the least.

With the demands of modern “just in time” harvesting & production, farmers have to be prepared to work from dawn to dusk (or even longer) during busy periods. To keep a conventional tractor (or combine) running all that’s needed is a fuel bowser, which can usually be towed to the site behind the 4×4 which the operator often travels in anyway. With the present state of battery technology the idea that fleets of tractors will be charging from solar panels is absurd. We are not talking about a 30 mile daily commute to work in a car. If, however, they make use of mains power it becomes (slightly) more sensible, but the “Eco” credentials go out the window. This approach would still require considerable investment – whilst 11kV power lines are never far from rural fields, voltage reduction transformers and charging equipment would be needed at frequent intervals. I’m willing to bet that large scale deployment of electrically powered farm machinery would put a strain on those local networks, as well. And surely they won’t be expected to supplement the grid, as is being talked about with cars? Can you imagine a farmer having to phone Birds Eye and explain that he can’t harvest their peas because the sun didn’t shine and/or the wind didn’t blow meaning his electric tractor battery is flat…

Electric tractors are not “silent” either – watch this promotional video and listen to it moving off at time 2:14. Now consider how happy you would be with several of them working nearby at 3:00am! There seems to be some discrepancy over the power output and range. The quote says “130kW of continuous power” – which would agree with “174hp” in this picture from the National Farmers Union (NFU):

Unfortunately, in the video an on-board information display shows two bar graphs of only 50kW each:

My basic maths makes that a total of 100kW, NOT 130 – which equates to 134hp. I’m unsure why each bar has a negative scale, but as there is a “Cooling” light below, it may indicate when battery power is being used for cooling? Furthermore, 100kW divided by 150kWhrs (if this is what the RHD display really means) equates to just 1½ hours at full power (or just over an hour for 130kW).

4 hours worth of operation means just 37.5kW / 50hp, and it won’t be pulling a 6 furrow plough on that. I appreciate full power is not always needed, but a conventional diesel fuelled machine can deliver it for as long as the tank will allow (and can then be re-fuelled in a matter of minutes). There may be limited opportunity for regenerative braking if towing on the road, but certainly not when working in fields. I can’t find fuel consumption figures in the publications for John Deere’s conventional range – rather odd considering it must be an important factor for the farmer. So without comparing similar engines fitted in other vehicles it is difficult to work out relative hourly operating costs – maybe that’s intentional?

There is also some ambiguity over where, in the existing range, this prototype fits in. According to that picture it is based on a 6 series chassis, and with 100kW, is comparable to the 6135M, for instance. This model has a 265 litre / 58 gallon fuel tank, which should give rather more than 4 hours endurance, I suspect! And yet in another video it sports a “7830” label, which doesn’t appear in the current JD brochure, but the “7” series range covers 210 to 310hp. The German text in the second clip mentions “400PS” (1PS = 0.986 horsepower), but which ever way you look at it a 100kW machine is not in the same ballpark. Pure electric cars may have startling acceleration, compared to similar petrol or diesel models, but they don’t do the sort of work a large tractor is expected to. The high starting torque available from electric drive systems might be beneficial in getting a multi-furrow plough started in a clay field, but sustained power after that is needed to get to the other end, and to do it over and over all day…

The proponents of electric vehicles constantly bang on about “revolutionary” advances in battery technology being “just around the corner” but similar claims have been made about other things in the past. Until they can offer the same energy density as conventional fuels the idea that we can simply replace I/C engines is pie in the sky, even disregarding where the extra electricity is supposed to come from.

There was a further section in the EDP article:

I suppose smaller autonomous battery powered agricultural vehicles, such as crop sprayers, might have a reasonable chance of success, as they don’t have to drag ploughs and heavy trailers around. Being able to operate at night also gives a better chance of applying their payload accurately, when winds are often lighter. But the NFU suggestion that technology could help farmers post-Brexit is rather wide of the mark, if John Deere are anything to go by. The company have been getting a lot of negative publicity lately regarding their policy of denying owners of their machinery access to technical information and diagnostic equipment. At least a conventional machine can be worked on (with pirated software), but what chance would even the most enterprising farm mechanic have with a fully electric machine? And the sight of a 750 volt battery sitting there with the connectors apparently covered in little more than some plastic film ought to ring alarm bells…

On the other hand, there may be the possibility for someone to “hack” an electric tractor and give it a Tesla style “Ludicrous” mode. The mind boggles…