Energy efficiency improvement of a vertical hydraulic system

Abstract

In recent decades, the development of hydraulic systems concentrated on efficiency and energy saving. Integration of modern control systems with today's hydraulic components, such as hydraulic power Pac and valves, creates unique opportunities to build energy-efficient hydraulic systems with flexible control ability. The hydraulic pump runs at full load in most cases as the hydraulic system might not run with a full load. An adjustable pump is an effective way to compensate for the varying load condition of a hydraulic system. However, the design of such an energy-efficient system is very complex as it requires matching the machine's primary power source. The carefully designed control system can further reduce energy consumption in modern hydraulic equipment and machinery. It can improve efficiency by using a bypass valve that can only open during the downward stroke. However, limited information is available to verify the benefit of using a bypass value to improve the energy efficiency of a hydraulic system with experimental testing. Therefore, the main objective of this study is to investigate the effect of the bypass valve in a conventional system and compare for the energy efficiency improvement experimentally. The study found that the energy efficiency is higher at lower pressure, and it gradually decreases when the operating pressure goes high. Energy efficiency is inversely proportional to the operating pressure for the larger load. When the cylinder load weight is doubled, the efficiency is also increased. Maximum energy efficiency can be achieved by keeping the pressure as low as possible to overcome the gravitational force and required velocity by keeping the maximum load on the cylinder.