Design, Development, and Evaluation of a PV_Bio-Gen Range Extender for an Off- Road Electric Tractor

Abstract

Transformation from fossil fuels to clean energy is necessary due to the stricter environmental protection policies. Hence, replacing conventional vehicles by electric vehicles (EVs) and renewable energy based vehicles would be as solutions in advance. However, some constraints are raised, e.g., low energy density of renewable energy sources and recharging time of batteries. Among various alternatives renewable sources, photovoltaic (PV) and biofuels seem to be more available in farm applications. The objective of this research is to retrofit an existing electric tractor into a series hybrid electric through the use of a PV system and a biogas fueled engine generator set (Bio-Gen). Moreover, some field measurements are carried out to define typical working cycles for farm hybrid vehicle application. Considering these points, the modeling, simulation and developing of an Extended- Range Solar Assist Plug-In Hybrid Electric Tractor (E-RSAPHT) are presented in this paper. Due to multi-power sources, a heuristic control strategy is developed to increase the operating time. Experimental results showed that the proposed system could improve energy autonomy and fuel efficiency. For typically evaluated toolbars, the operation ranges of the trailer, boom-type sprayer, and water-pump system were found up to 7.3, 8.7, and 14 hours, which correspond to a working range extended up to 292, 255, and 320% compared to the base system, respectively. The analysis illustrated that even for a 2100 kg electric farm vehicle, a downsized 4.4 kW Bio-Gen allows the hybrid electric system to supply the power demand compared to the conventional system by using the internal combustion engine (ICE).