Efficiency How Digital Hydraulics Makes the Industry More Sustainable

Related Vendors

Danfoss Power Solutions

Danfoss Power Solutions GmbH & Co. OHG

FAULHABER Drive Systems

Wuxi InfiMotion Technology Co., Ltd.

Digital hydraulics increases machine efficiency and reduces emissions by up to 50 percent. There are three variants of the technologies. Alessandro Carmona from Danfoss Power Solutions explains how they work and when it’s better to electrify in a guest contribution.

According to the International Energy Agency, the highly criticized aviation sector caused nearly 1,047 million US short tons of carbon dioxide emissions in 2023. At the same time, a calculation supported by the fluid power industry, universities, and the European association CETOP shows that emissions from fluid-powered machinery amount to approximately 2,032 million US short tons of CO₂ per year—almost double the emissions of global aviation and five percent of global energy-related emissions. Even more astonishing is that over 40 percent of emissions from fluid-powered machinery (around 845 million US short tons) are due to losses. Useful work accounts for about 675 million US short tons of emissions, while electrical/combustion losses are responsible for 511 million US short tons of emissions.

The good news is that we have the opportunity to significantly reduce emissions, particularly in industrial hydraulics. The decarbonization of fluid power is achievable through energy-efficient digital hydraulics. With new components, systems, and architectures, efficiency can be increased by 50 percent and emissions reduced by one-third. Let's take a closer look at how this is possible.

What Are the Pros And Cons of Electrification?

But first, a word on electrification. It’s no secret that electric machines are much more efficient than hydraulic machines. So if we simply electrify, don’t we eliminate a large portion of those losses and therefore the emissions as well? While this is possible or even preferable in some applications, fluid power cannot be replaced in many other industrial applications, such as in process manufacturing, the primary metals industry, the marine and offshore sector, and the energy industry. Here, the strengths of fluid power are essential: high power and force density, flexibility and relatively low weight, inherent safety and robustness, as well as precise control of large forces.

Not all industrial sectors will stick with fluid power. In applications with rotating actuators or lower power/force requirements, switching to electric drives is generally possible. There are many examples of this in robotics and automation. However, for industries and applications where fluid power remains the best technical and commercial solution, manufacturers have a responsibility to provide low-emission and efficient solutions. We must fully embrace the opportunities of digitalization and electrification; and this is where digital hydraulics plays a key role.

What is Digital Hydraulics?

Variable speed drives, also known as VSDs, are one way to make industrial hydraulic applications more efficient. However, digital hydraulics goes beyond simply adding VSDs to the machine. It involves controlling the speed of the motor and pump within a new system architecture. A variable speed-controlled electric motor is combined with a fixed or variable displacement pump, and the speed of the motor and pump is used to directly control the flow and/or pressure, and ultimately the force and speed/position of an actuator.

This contrasts with conventional system architecture—a constantly rotating electric motor coupled with a fixed or variable displacement pump as well as pressure, flow, and directional valves—where pump displacement and valves control pressure and flow.

The conventional system always operates at its nominal speed, either 1,500 or 1,800 revolutions per minute, depending on the region. Excess hydraulic oil flow is redirected to the tank through a bypass or relief valve. This results in the high losses of conventional systems, especially when the machine’s duty cycle is characterized by varying pressure and flow requirements.

Digitization of the Drivetrain

How Artificial Intelligence Optimizes Drives

In a digital hydraulic system, the VSD is programmed to adapt to the load requirements of the current duty cycle, ensuring no energy is wasted. The pump and motor run and stop as needed, delivering power on demand, with a speed range from zero to typically 2,800 rpm. Compared to the conventional architecture, digital hydraulics reduces energy consumption by up to 70 percent, depending on machine utilization.

What Are the Advantages of Digital Hydraulics?

Energy efficiency is the main advantage of digital hydraulics. Saving energy lowers operating costs, allowing the technical changes to pay off. More efficient hydraulic systems generate less heat, which means the oil cooler can be downsized or even eliminated entirely. At the very least, this helps reduce oil volume and tank size, extending the lifespan of the oil and seals.

A variable speed often makes it possible to use a smaller (and therefore cheaper) pump: Since the system utilizes the full speed range of the motor (up to 3,600 rpm) instead of running at a fixed speed, the required pump displacement is reduced without changing the maximum oil flow available. This reduces the machine's CO₂ footprint.

Additionally, a smaller pump requires a smaller motor: a pump with a smaller displacement needs less torque to generate the same pressure. At the same time, the variable speed allows the utilization of the high overload capacity of electric motors to handle the short segment of the machine’s duty cycle with high torque. Both characteristics enable the selection of a smaller motor, further reducing overall operating costs and the size of the drive unit.

Additionally, machines with digital hydraulics operate more quietly: By adjusting the speed of the electric motor and pump to the work cycle, the baseline noise level is reduced.

Technology: What Types of Digital Hydraulics Are there?

A closer look at the technology reveals that there are several ways to design digital hydraulic systems for industrial applications. Danfoss, for instance, classifies them into three types:

• Induction motor solutions,
• Servo motor solutions and
• electrohydraulic actuators.

Induction Motor Solutions enhance traditional architectures by providing on-demand speeds. These open-loop systems consist of a hydraulic pump—typically a piston pump—an asynchronous induction motor, and a suitable frequency converter. These solutions are available as subsystems in the form of pump-motor units or integrated into complete hydraulic power units (HPU). Induction motor solutions are suitable for low dynamic and control requirements and are generally offered in low, medium, and high power ranges. Additionally, they can be easily retrofitted into existing machines with conventional hydraulic systems.

Servo Motor Solutions introduce new machine architectures that provide on-demand pressure and flow, along with closed-loop control. The hydraulic pump is typically an internal gear pump or piston pump, while the motor is a permanent magnet synchronous motor (PMSM) paired with a frequency converter. Servo motor solutions are suitable for high dynamic and control requirements and are generally offered in low and medium power ranges.

In addition to hardware, both system types require pressure and flow control as well as application software to enable the required dynamics and controllability. Induction and servo motor solutions are more suitable for traditional centralized architectures, meaning where a central hydraulic unit serves multiple actuators in the system.

For decentralized architectures, electrohydraulic actuators (EHAs) are the ideal choice. An EHA is a fully integrated linear drive consisting of a hydraulic cylinder with a position sensor, a PMSM servo motor with a speed sensor, a bidirectional four-quadrant internal gear pump, a manifold block with valves and sensors, a pressure accumulator, and a frequency converter with integrated software. EHAs are ideal for machines where most functions are electrified—meaning no hydraulic power unit is present. They are also excellent for isolated functions where the hydraulic power unit is not nearby or serves only one cylinder. Moreover, they are often used in environments requiring leak-free operation, such as the food industry.

Compared to a central hydraulic power unit, EHAs have lower oil volumes and a reduced risk of leaks. They require less space, offer quick setup and commissioning, and have lower maintenance requirements. Compared to electromechanical actuators, EHAs provide higher power density and force. There is no need for a load cell for force measurement, and they are resistant to external shocks and vibrations.

What Does the Future of Fluid Technology Look Like?

Fluid technology is moving towards efficient solutions and architectures closely linked with electric drive technology and digitalization. This requires new skills from component manufacturers, OEMs, and end users, as well as increased collaboration between industry and academia.

Partnership

Digital Solutions Aim to Optimize Industrial Production

Digital hydraulics is a significant advancement, helping to make the industry more efficient and reduce emissions without companies losing their competitiveness. The integration of digital control and on-demand power delivery in fluid power systems will play a crucial role in shaping industrial processes today and in the future.