Electric autonomous tractors in Swedish agriculture : A systems analysis of economic, environmental and performance effects

Abstract: Use of battery-electric vehicles has become common in different sectors, as a measure to reduce greenhouse gas emissions. Driveline electrification in agricultural machinery could reduce emissions and increase driveline efficiency, but implementation has been hindered by the low energy-carrying capacity of batteries compared with conventional fuels. Combining battery-electric drivelines and autonomous operation would provide important synergies by mitigating or eliminating many of negative aspects of electrification, while retaining the benefits from both systems.This thesis evaluated the potential and analysed the intricate workings of a battery-based autonomous electric vehicle system by applying systems analysis, economic analysis and life cycle assessment, through simulations and modelling. The vehicle system was evaluated on a theoretical Swedish grain farm of 200 ha using a conventional cropping system. Soil compaction, battery ageing, queueing dynamics, field trafficability, energy storage and weather effects were all included in simulations. This allowed comparison of performance, cost and environmental impacts for a conventional fieldwork tractor and a system with several smaller autonomous battery-electric tractors.The evaluation showed that the autonomous electric tractors were able to match or exceed the daily work rate of the conventional tractor, while reducing energy use (by 47-75%), lowering annual costs (by 32-37%) and reducing soil compaction. The environmental impact was generally also lower, with up to a 74% reduction in greenhouse gas emissions over the system’s life cycle. These results indicate great potential for autonomous electric tractors in future agricultural fieldwork, as combining the electric driveline and autonomous technologies allowed the benefits from both to be used to greater effect than either by itself.