A Shifting Industry: Developments in the electrification of Off-Highway Vehicles

Amidst growing environmental concerns, every individual entity is expected to contribute to preserve our planet. While personal transportation represents a big topic in environmental discussions, mining, construction, agriculture, keep being heavily reliant on diesel engines. Despite the adoption of recent technologies in terms emission control, vehicle manufacturers will be required by law to emit even less polluting agents. This dissertation aims to delve into the lesser-known world of Off-Highway Vehicles, also known as mobile working machines, by understanding how big of a share of the global economy it stands for, and the new challenges revolving around the transition towards cleaner builds faced by Original Equipment Manufacturers, with support from their suppliers. The consequences of this shift will be observed by focusing on a snow groomer application. Starting from the detailed description of the traditional diesel-hydraulic solution and its main working blocks, the analysis will then stem to two approaches aimed at vehicle electrification. The first approach consists of a single electric motor as replacement for the diesel engine, leaving its hydraulic system unchanged (BEV 2.0). The second one (BEV 3.0) will involve a more integrated strategy to electrification, featuring two separate motors replacing the hydrostatic traction, and a third one driving the implement pump train. The applied machine design process will be object of analysis, allowing transposition of hydraulic notions onto electric systems, and highlighting the different priorities these two powertrains demand. The manufacturer’s targets concentrate on battery range optimization, set at 4 hours of continuous work, as well as cost-containment while delivering vehicle performance on par with the traditional diesel-hydraulic model. The two electrified drivetrain solutions were compared through bench testing, to verify the efficiency of the hydraulic drive, quantifying the energy that could instead be redirected directly to the traction motors, and thus optimise operational range on BEV 3.0. Power losses in a hydraulic system become more critical in an electric powertrain, and particularly in an electro-hydraulic one, compared to a diesel-hydraulic topology, due to differences in energy density of the primary energy source, in this case, batteries. Battery technology has not yet reached the energy density potential that a tank full of fossil fuel already possesses, meaning that every single kWh the battery can provide has to be used as efficiently as possible to maximize vehicle operational range and ensure down times do not affect the final customer. This premise brought the manufacturer to test the latest iteration of the BEV 3.0 prototype directly on real life conditions, validating it performance-wise, and in vehicle behaviour terms. The terrain features of the test track allowed for realistic scope-of-use conditions, resulting in a truthful energy consumption analysis over work cycles. Gathered data allowed to perform optimization of the current topology, through a revision of the machine kit aimed at managing energy input more accurately with respect to an electric powertrain, and simplify the hydraulic system to further increase system efficiency.