Abstract
In recent years, much research has focused on reducing the power consumption of mobile hydraulic machines due to rising fuel costs, regulations on combustion engine emissions and the need to reduce the size and weight of the storage devices in hybrid drives. Current approaches to improve the energy efficiency of a hydraulic system can be classified into four basic groups: reduction of the energy demand, recovery of part of the supplied energy (ERS systems), regeneration of part of the supplied energy and reuse of the recovered and regenerated energy (hybrid systems). Today’s mobile hydraulic systems are often complex, perform different tasks and work under different load conditions, which makes it difficult to analyse energy losses. A study of the energy losses of a hydraulic system from different points of view, such as an energy balance for a complete machine cycle, an analysis of the individual cycle phases and a power analysis for the different operation quadrants of the actuators, can give an global picture of the energy losses, being very useful to rate its energy efficiency, identify main power losses and decide which of the different energy-saving techniques to apply. This paper describes the data collection process, its analysis from various points of view and the summary of the results in easy to understand charts as useful tools to identify and quantify the main energy losses. Only system architecture losses are considered. Losses in the ICE engine or the electric motor, hydraulic pump losses and mechanical losses are outside the scope of this study.
Highlights
Energy-efficient hydraulics has attracted considerable research interest over the last decades, the efficiency of todays mobile hydraulic systems is often still relatively low, even in those machines where efficient and well-sized individual components are used.Current approaches to improve the energy efficiency of a hydraulic system can be classified into four basic groups: reduction of the energy demand, recovery of part of the supplied energy (ERS systems), regeneration of part of the supplied energy and reuse of the recovered and regenerated energy.Table 1 shows different solutions for reducing the energy demand
This paper describes a multi-point-of-view analysis to identify the different sources of energy inefficiency in an existing hydraulic system
A mobile machine with load sensing architecture is studied, but other architectures or any industrial hydraulic application can be the subject for a similar analysis
Summary
Current approaches to improve the energy efficiency of a hydraulic system can be classified into four basic groups: reduction of the energy demand, recovery of part of the supplied energy (ERS systems), regeneration of part of the supplied energy and reuse of the recovered and regenerated energy (hybrid systems). In most current commercial applications today, the system architecture is based on one or several variable displacement pumps, each feeding several actuators through a proportional valve, using the concept of load-sensing (LS), a technology from the 1970s. The main weaknesses of this technology are the high throttling losses and the fact that the pump pressure must match the pressure demanded by the highest loaded actuator plus an additional LS overpressure, typically 10 to 30 bar
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