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 this is expected to change with the next update towards EU Stage VI / EPA Tier5 coming into effect 2030 and after. Applications demanding high power or long operational 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 12t tipping load, which is an example of a typical use-case from the construction equipment industry. A control strategy was developed to operate at best system efficiency while also optimizing the heat-up of the aftertreatment system for minimizing the emissions below EUVII regulation limits for commercial vehicles. The controls are verified by using an NRTC engine test cycle whereas the electric components are modeled but a real Diesel engine including aftertreatment system is used on the engine dynamometer side.