Optimal design of a series hybrid powertrain for an agricultural tractor

Hybrid powertrains represent a potential solution to reduce the emissions of agricultural machineries and meet the restrictive standards introduced by the different governments with the aim to achieve Climate Neutrality. This study investigates a hybrid powertrain in the series architecture as it potentially better suits the requirements of agricultural applications, even though it has not yet been fully investigated in literature. A series hybrid powertrain model was built, then its control and components size were optimized for a vineyard/orchard tractor using real on-field data and a two level optimization procedure. This last is based on Dynamic Programming and the exhaustive search approach. Both environmental and economical aspects were taken into account in the optimization goals; in addition, powertrain volume constraints were introduced as they represent a key limiting factor for tractor hybridization. The average efficiency of the hybrid powertrain is higher than that of the conventional configuration. A sensitivity analysis was performed to understand the impact of different design parameters. This analysis showed that hybrid powertrains have enormous potential in the agricultural market, as this type of configuration was simulated in several scenarios for different European countries showing to be the most convenient. Moreover, this trend is expected to intensify with the upcoming emissions regulations and the increase in fuel prices through emission taxes.