A New Approach for Measuring and Comparing the Energy Performances in Hydraulic Systems

The need for “green” energy management has sparked discussions on developing hydraulically actuated systems that are more efficient, consume less power, and are consequently more environmentally friendly. Numerous scientific papers and extensive research have been dedicated to this important topic. However, due to the variety of designs and different modes of operation, there is still no unified method to compare different systems with respect to energy management. In fact, terms such as “efficiency” and “energy regeneration” are often loosely defined and need to be revisited periodically. In this paper, we propose a new, physically meaningful indicator called the “Cyclic Performance Ratio” to measure the energy performance of hydraulic circuits. The goal is to establish a universal method that can be reliably used to compare industrial hydraulically actuated machines with respect to their energy efficiencies. Specifically, we aim to (a) precisely define the three possible modes of operation of hydraulic circuits, (b) establish the correct conditions under which the usual definition of efficiency can be applied in hydraulic circuits, (c) demonstrate that the current concept of efficiency cannot be used for operations where load energy is recovered, and (d) argue that the newly defined performance indicator correctly accounts for energy load recovery. Some examples are provided to show how the new indicator can be used with confidence in various applications.