Emission reduction by hydraulic hybrids

Emissions of non-road machines are reduced by precise control of combustion process inside the engine and by after-treatment systems. One additional measure is the hybridization of the powertrain, which can be used to stabilize the engine load. This reduces harmful emissions because most nitrogen oxide emissions and particle emissions are related to sudden load and speed changes of the engine. In this study, four different hydraulic hybrid systems and their emission reduction potential are tested in one case study of a forwarder. The comparison study was done using a hardware-in-the-loop system (HIL) that consisted of a real-time simulation model, hydraulic secondary controlled loading system, real diesel engine, and emission measurement systems. The most efficient system (i.e., the system with the lowest fuel consumption) was the Four-pressure system. However, the difference between this system and the second-best system was negligible, and fuel consumption was about 40% less than with the reference system (a load-sensing system). Results showed that absolute emissions can be reduced by hybridization. Nitrogen oxide emissions were 15 25% lower and particulate matter emissions were 60 75% lower. The Four-pressure system had the lowest emissions. All studied hybrid systems resulted in reduction in fuel consumption and harmful emissions in the studied use case