Electrification of a diesel-hydraulic off-road machine

Abstract: This report is for the Master of Science thesis project undertaken for KTH Royal Institute of Technology in collaboration with the Forestry Research Institute of Sweden (Skogforsk) for the Forestry Master Thesis School. The aim of this project was to theoretically explore the possibility of replacing the hydraulic driveline with an electric series driveline and to understand the differences between using one or the other so that it can be convincingly concluded if a Diesel-electric driveline in Forestry forwarders is a worthwhile endeavour or not. In this report, the current status of the XT28 driveline is explored as well as improvements in terms of energy storage, energy recovery and controls are suggested. These two concepts are quantified and compared against a theoretical Diesel-Electric driveline, with details about its different parts from Power source to Motors and Gearboxes discussed at length. These three concepts are compared against each other in terms of Physical characteristics like mass, Performance characteristics like efficiency, energy recovery, energy storage capacity, etc. and Practical characteristics like cost. According to the results of the multiple weighted Pugh matrix comparisons, the theorized Diesel-Electric Driveline holds an edge over even the improved/idealised version of the current XT28 driveline, despite being hampered by the cost. In conclusion, electrification of XT28 is definitely a possibility for the future, only major concern being the high cost associated with it. The efficiency improvements possible through use of hybrid electric driveline are significant, with mass difference between the two concepts much lower than initially expected. However, since most of the performance will depend heavily on control systems and practical losses, the only way to concretely prove the efficiency advantage is through detailed computer modelling or manufacturing prototype.