Potential of Serial Hybrid Powertrain Concepts towards decarbonizing the Off-Highway Machinery

Today’s engines used in Agriculture, Mining and Construction are designed for robustness and cost. Here, the Diesel powertrain is the established mainstream solution, offering long operation times without refueling at any desired power rating. In view of the steps towards Carbon Neutrality by 2050 this segment of the Transportation Sector needs to reduce its CO2 emissions. Currently, the EU and US emissions legislations (EU Stage V / EPA Tier4) do not include a CO2 reduction scheme but is expected to change with the next update towards EU Stage VI / EPA Tier5 coming into effect 2030 and after. Larger power and operation range still require the use of renewable, liquid fuels or hydrogen. The cost-up of such fuels could be counterbalanced by more efficient engines in combination with a hybridized powertrain. The current paper therefore introduces a serial HEV solution for a large wheel loader application of ~20 t which is an example of a typical use-case from construction equipment industry. It utilizes a control strategy, which always operates at best system efficiency while also optimizing the thermal window of the aftertreatment system, thereby minimizing the emissions to levels below EUVII regulation limits for commercial vehicles. The strategy is verified using measured vehicle data, system simulation and validation on an engine test bench.