Farming is blamed for around 10% of global emissions. As every industry strives to reduce its impact on climate change, farming is no different. We have heard a lot about the energy potential of cattle slurry. Now people are looking at the possibility of reducing emissions from farm machinery.
Electric tractors have been around for a surprisingly long time. Early models were usually confined to smaller garden models like lawnmowers and 4-8hp light machines. General Motors manufactured the successful Elec-Trak series throughout the 1970s and many of them are still used by smallholders in the US for planting, harvesting and tilling. There have also been innovative home-made models, even a solar powered small farm tractor, but these have been developed by enthusiasts rather than big companies.
Modern electric tractors use flywheel-mounted generators to produce current, which is then converted into direct transmission. It makes hydraulic gears and pumps unnecessary, as power is fed directly into specially-adapted implements. Power output can be isolated and controlled with great precision, which benefits efficiency. Electric tractors are therefore much cleaner than diesel models and they whirr like quieter versions of the turbines in a jet engine.
John Deere is currently leading the field of electric innovation and it recently unveiled its 200hp 7030E Sustainable Energy Supply for Agricultural Machinery (SESAM) range of electric machines. These will be available from 2018 and while their performance is impressive, especially in terms of torque, they need to be operated with specialist or converted PTO implements, which would make adopting them a very expensive gamble.
The SESAM carries a 130kWh battery pack which can generate 400-volt, 3-phase power and 230-volt DC power simultaneously. John Deere claims it has a 7 hour operating time between charges and can be field-ready again in 4 hours. This is better by far than any other high-power tractor has managed. Still, contractors and tillage farmers will have issues, as it is obviously more convenient to be able to bring fuel to the field than to drive back home for a four-hour charge after only a short day's work. A system where the battery could be changed would make this type of large tractor more viable.
So, regarding big machines, there is still a way to go. Nevertheless, it is good to see big companies like John Deere taking the threat of climate change seriously and adapting their machines to a clean energy future.
Medium sized electric tractors could be very useful on dairy and beef farms where the tractor rarely leaves the yard. Diesel power is not ideal for these machines because they are often only used for short durations. Batteries can run down from constant starting and stopping, while hydraulics can sustain damage from oil not being warmed sufficiently in winter. A reliable electric machine could be plugged in when not in use and would not suffer any adverse effects of short burst of activity.
For the moment farmers are reliant on oil, as electric technology receives much-needed refining. In its promo video for the SESAM, John Deere offers a glimpse of an integrated future in which farms generate their own power using wind turbines and biodigesters to feed charge-points for electric vehicles. These machines have their doubters, but it may be only a question of time before they prove themselves. It certainly is a compelling to think of a farming system operating completely on renewable energy.