Why hydraulic systems must be energy efficient
In the quest for a sustainable future, fluid power systems must be energy efficient. Improved energy efficiency is needed both to enable electrification and to lower the global demand for energy production, storage, and distribution. Three main drivers toward energy efficient fluid power systems are given in this article.
The global goal to limit temperature rise to 1.5 degrees Celsius requires massive carbon emission reductions. Countries aim for net-zero emissions by 2050, necessitating changes in production, movement, and consumption habits. Renewable energy sources, like wind, solar, and hydro, will play a crucial role, making electricity the primary energy form for industry, transport, and households.
Electrification of heavy machinery, such as wheel loaders and excavators, is vital. Shifting from diesel engines to batteries and electric motors places new demands on fluid power systems. Energy-efficient fluid power systems can perform the same tasks with significantly less energy, leading to considerable cost savings and reducing societal energy consumption. For example, improving an excavator's efficiency from 25% to 50% can greatly reduce energy input, benefiting both the environment and the economy.
Efficient fluid power systems are also key for eMobility. They reduce energy consumption, decrease battery charging times, and enhance productivity, easing the transition to electric machinery. Additionally, improved efficiency can streamline machinery design, reducing the need for cooling and auxiliary systems, which lowers installation and ongoing energy costs.
In conclusion, enhancing energy efficiency in fluid power systems is crucial for technological innovation and environmental stewardship. By prioritizing efficiency, we contribute to a sustainable and resilient future, driving forward a cleaner, greener planet.
The shift to throttle free control
We need to go throttle free. The main source of energy loss in traditional motion-controlled fluid power systems is the valves. More specifically the valves that throttle excess energy to control flow and pressure. Throttling control is like controlling your car or bike with the brakes. How often do you floor the throttle of your car and use the brake when you want to reduce the speed? Not often, right? And nobody wins Tour de France by constantly pedaling full speed and then adjusting their speed in the peloton using the brakes. Throttling, resistive or brake control is just “stupide” and waste of energy.
In aiming for throttle free control a couple of possibilities standout. One can go for direct pump control, meaning that each actuator is controlled by one or two pumps directly connected. Here the actuator control lies in how the pumps are controlled and hydraulic power sharing becomes rather complex.
An other solution is to use a common pressure rail system allowing hydraulic power recovery and power sharing. A transformer is used to control the speed and force of the actuator in a lossless manner, and the transformer recovers energy from lowering potential energy and breaking motions and supplies it back to the common pressure rail.
Transforming from Common Pressure rails
A combination of common pressure rails and transformers results in an energy efficient multi-actuator hydraulic system capable of precise motion control, energy recovery and power sharing. With a system architecture as shown below the central pumps can be operated under optimal conditions while the transformers efficiently move power in the system.
The common pressure rail structure enables the system to exploit both valve and transformer controlled actuators. This makes it possible to use valves for low power actuators without adding additional power units to the system.
In common pressure rail systems power can be drawn from the pressure rail or the additional accumulator bank during peak loading. This significantly reduces the peak power demands on the power units and allows that installed pump and engine capacity may be lowered.
