Hydrogen – a technology with a lot of potentialWhen it comes to hydrogen, expert knowledge is in high demand

We have a long way to go before all the questions on the topic of hydrogen have been answered. This is because the production, supply and use of hydrogen still poses challenges for companies. But one thing is certain: hydrogen and alternative energy sources in mobile and industrial solutions have enormous potential. Potential for an environmentally friendly and emissions-free future in households, industries and transport.

But the topic of hydrogen quickly becomes complex. That's why it pays to have an expert at your side who offers innovative approaches to solutions while bringing tried-and-tested products and decades of industry know-how to the table. Whether it's a new development or series production – HYDAC will help you to implement your project successfully. Tell us about your requirements.

Electrolysis & hydrogen production

Hydrogen is one of the most promising alternative energy sources to replace fossil fuels in industry and infrastructure on the way to a carbon neutral future. Hydrogen can be produced by various processes. The most sustainable method is water electrolysis with electricity from renewable energies. In this process, two water molecules (2H2O) are broken down into two hydrogen molecules (2H2) and an oxygen molecule (O2) using electrical energy.

Regardless of the technology used (AEL, AEM, PEM, SOEC), we are able to support your hydrogen production with our continually growing product range. We already offer a wide range of products to make your electrolyser more efficient, economical and safe.

Our product range

Thermal fluid management

Rely on our Balance of Plant solutions for sophisticated thermal fluid management. Our product range spans air cooling systems, e.g. for fluid flows (DI water, aqueous KOH) and compressor cooling systems for condensation drying (gas coolers) to filtration of particles from gases and fluids. We are your contact for aerosol separation, fluid handling and gas compression. We also offer a wide range of products for the Balance of Plant of your electrolyser including selected valves and sensors (pressure, temperature, conductivity, level transmitters, level switches).

Hydrogen / gas drying

High-purity hydrogen is required for some applications. But the raw gas product hydrogen is often contaminated with impurities from water and oxygen after production. DIN EN 17124 specifies that these impurities must be less than 5 ppm. With our innovative hydrogen drying, we can reach higher hydrogen qualities than the standard requires when necessary.

Separator optimisation / phase separation

Hydrogen production poses many challenges – and the same holds true for gas-liquid separation. Conventional separator tanks are large and don't offer any active separation of the mixture. With the HYDAC solution, separator tanks can be reduced to a minimum and the efficiency of the overall system is maximised by an active degassing unit. We're also happy to examine your separators for the potential for installation space optimisation – contact us!

Hydraulic stack clamping

Threaded rods or hydraulic cylinders? Many electrolyser manufacturers rely on threaded rods or belleville washers to clamp their stacks. In contrast to these methods, hydraulic stack clamping enables optimal, homogeneous force distribution on the stack during operation. This prevents leaking between the bipolar plates, simplifies maintenance work and increases the service life. We support you with active stack pretensioning in stack operation and static stack clamping during stack assembly.

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Hydrogen refuelling station

When used as an alternative energy source, hydrogen makes emission-free driving a reality. Apart from producing energy to power fuel cell vehicles, the reaction between hydrogen and oxygen only produces pure water vapour. Harmless to man and the environment.

This technology is growing in importance worldwide, leading to constant expansions in hydrogen refuelling station infrastructure. The constant development of hydrogen refuelling technology in terms of availability, energy efficiency and costs plays a major role. HYDAC is already able to support you with a wide range of products – but new developments and innovations are in the pipeline too. Please feel free to contact us.

Our product range

Particulate contamination, hydrogen quality & gas cleanliness

Whether it's particulate contamination or harmful gases – hydrogen is subject to high cleanliness standards. Particulate contamination can lead to system failure both inside the hydrogen refuelling station and in fuel cell vehicles. As a long-standing expert in technical cleanliness, we have developed the PSA-H70, a product for sampling filling stations and evaluating the particulate contamination load. The result: we are already able to provide you with a complete gas filtration range for filling stations from low pressures to high pressures (up to 1050 bar) – suitable for both particle and liquid separation.

Harmful gases can lead to defects in the fuel cell stacks (known as catalyst poisons). Unique worldwide: HYDAC is currently developing a gas quality sensor which constantly measures the gas composition within the storage banks at filling stations.

Hydrogen cooling

To cool compressor systems, we supply efficient cooling systems and heat exchangers tailored to your requirements. We manufacture custom solutions for recooling the compressed gas in hydrogen refuelling stations. Whether it's a roof structure, V shape or directly integrated into the tank – use our expertise to optimise your filling station cooling.

With the continuous expansion of our product range, we will soon be able to offer you products for cryogenic pre-cooling for tank processes in accordance with SAE J2601. This rounds off our all-inclusive package for hydrogen cooling.

Sensors / pressure transmitters

The refuelling process at hydrogen refuelling stations is pressure controlled. This means that reliable and safe sensors are required. HYDAC supplies a complete range of hydrogen sensors for your application for low pressures to high pressures (16-1050 bar). Our sensors were specially developed for hydrogen applications – special measuring cells made of stainless steel with a high nickel content protect against hydrogen embrittlement.

New to our range is our SIL 2 certified sensor which can be used in dispensers ("pumps"), among other things. Learn more about the advantages of our new solution in a one-to-one consultation.

Drive technology for compressors (compressor systems)

The goal of many hydrogen compressor operators is fail-safe, energy efficient and resource-conserving operation. The innovative hydraulic drive units from HYDAC make this possible. We check whether conventional or variable-speed systems are suitable for your application and which system offers you the greatest potential for savings. To increase system availability, we are able to equip our systems with continuous hydraulic fluid condition monitoring. In addition to remote access, oil analyses can also be carried out at the HYDAC Fluid Care Center.

Fuel cell systems and H₂engines in mobile & industrial solutions

As the technology of the future, fuel cells hold a lot of potential in mobile and industrial solutions. Hydrogen-powered trains aren't wishful thinking anymore. They are a reality. The development of zero-emission vehicles in private transport, heavy-duty transport, construction machines, agricultural machines, ships and emergency energy supply is also being driven forward. Sophisticated technology is required for fuel cell systems to be operated in a functionally safe and energy efficient way. Based on many years of industry experience and a high level of innovation, we are already able to offer you a wide product portfolio which we are constantly expanding.

Our product range

Sensors & valve technology

Fuel cells in connection with high pressure tank systems are operated with high flow speeds and temperature fluctuations. HYDAC has developed a wide range of valve technology to control material flows in the high-pressure area of hydrogen tanks and the low pressure area of fuel cells safely and precisely. Our high pressure sensors have also been helping to detect pressures and operate systems safely for more than a decade. See for yourself.

Air quality & hydrogen quality

Fuel cells react critically to small particles and harmful gases that enter the fuel cell system during production or enter the fuel cell stack during operation. To protect the fuel cell from these factors and increase the service life, a wide range of filters are required in the fuel cell system. To protect the air side and hydrogen side from this contamination, our wide range of filter technology and separator technology is at your disposal.

Thermal management

Unlike mobile and industrial applications with combustion engines, in fuel cell systems no part of the thermal energy is dissipated with the exhaust gas flow. Most of it is dissipated in the cooling water. This results in a higher cooling power requirement in fuel cell applications. The complexity of the cooling and thermal management system increases due to a number of additional electrical consumers such as electric motors, converters and even battery systems. With innovative solutions, HYDAC supports you in the development and integration of complex cooling and thermal management systems.

Control technology

To operate fuel cell systems and tank systems in a functionally safe manner, a full understanding of current flows, material flows and information flows is required. With this understanding and our ability to develop complex software systems, HYDAC is in the position to offer custom control architecture. To make the integration of electrical systems easier, we also use our own extremely powerful controllers and functionally safe software architectures as well as HYDAC function modules tested over many years.


What is an electrolyser and how does it work?

In general, an electrolyser is a device for separating, breaking down and transforming a material or molecule (redox reaction) with the help of electrical energy. In a water electrolyser, water molecules (H2O) are converted into hydrogen molecules (H2) and oxygen molecules (O2).

The actual reaction takes place in electrochemical cells at voltages of approx. 1.4 V. For practicality reasons, a number of these cells (electrical series connection) are piled up into stacks. All the peripheral equipment around the electromechanical cells comes under the term "Balance of Plant".

What is meant by Balance of Plant?

Balance of Plant (BOP) is a term that is generally used in connection with energy technology. It refers to all supporting components and auxiliary systems required for the conversion of energy – with the exception of the generation unit or transformation unit itself.

For electrolysers, this includes energy management (transformers, inverters, power controllers etc.), fluid and gas management (water conditioning, separation of fluid and gas phases, gas drying, gas compression) and thermal management (cooling systems for power electronics, stack and condensation drying).

What is a fuel cell and how does it work?

A fuel cell consists of two electrodes – the anode (hydrogen side) and cathode (air side). Both electrodes are separated by an electrolyte. In the PEM fuel cell, this is a semi-permeable membrane that is only permeable to protons.

The hydrogen is fed to the anode. It is then split into protons and electrons with the help of a catalyst (usually platinum). The protons then migrate through the membrane to the cathode. The electrons flow to the cathode via an electrical consumer and electrical energy is supplied. At the cathode, protons and electrodes combine with oxygen from the surrounding air to form water.

What does the term "electromechanical cell" mean?

The term "electrochemical cell" is an umbrella term for different types of cells such as electrolysis cells, accumulator cells, battery cells or galvanic cells. These types of cells can sometimes be reversible, such as accumulator cells. These can be charged and discharged – this means that they can convert electrical energy into chemical energy and release it again as electrical energy. In addition, some types of electrolysis cells can be operated as fuel cells. This means that the conversion of hydrogen and oxygen into water releases electrical energy and heat.

Electrolysis cells and fuel cells consist of bipolar plates, electrodes and, depending on the technology, gas diffusion layers (GDL) and membranes. When "proton / anion exchange membranes" (PEM / AEM) are used, these are often connected directly to the electrodes and referred to as a "membrane exchange assembly" (MEA).

What is meant by the term "membrane electrode assembly" (MEA)?

The membrane electrode assembly (MEA) can be interpreted in more than one way. In some cases, this is understood to only mean the membrane with the catalyst layers coated on it (on one side for the cathode reaction; on the other side for the anode reaction). Often, however, the gas diffusion layer(s) is/are included, as this/these must also be electrically conductive.

Depending on the technology, the membrane consists of different polymers or ceramics, each which can selectively transport protons, anions (e.g. hydroxide anions = OH) or oxygen. The gas diffusion layers serve to transport the gases produced (electrolysis) and in particular the gases used (fuel cells) as homogeneously as possible away from or towards the reaction sites (catalyst layers). These gases are led out of or into the electrochemical cells via channels in the bipolar plates.

What is a bipolar plate made up of?

Bipolar plates which have been installed in a multiple-cell or stack configuration are above all responsible for physically and electrically connecting the anode from one cell with the cathode of the neighbouring cell. Bipolar plates in fuel cells are also responsible for leading the reaction gases to the reaction zone. For this purpose, flow profiles (flow fields) are milled or pressed into the plates on both sides, through which hydrogen flows on one side and air is supplied on the other.

A bipolar plate consists of the two poles of a single fuel cell: the hydrogen-carrying anode plate (the negative (-) pole) and the cathode plate (the positive (+) pole) for feeding the reaction air. The plates also regulate the removal of water vapour and the output of thermal and electrical energy. In electrolysis cells, they are mainly used to cool the electrolyser, supply reaction gases to the anode side and remove the hydrogen and gases produced in the reaction.

What is a "stack"?

In electrolysis and fuel cell technology, a stack is a stack of electrochemical cells connected in series, including the housing/frame/clamping elements. The series connection makes it possible to increase the supply voltage and reduce the current with the same power consumption according to P=U*I. Independently of this, the series connection in a stack also simplifies the overall design of the system.

What is a pressure tank system?

Gaseous hydrogen can be stored in a tank after compression at high pressure. In transport, for example, a pressure level of 350 bar for commercial vehicles and 700 bar for cars has become established. At 700 bar the density is approx. 40 kg/m³ (24 kg/m³ at 350 bar). High-pressure accumulators offer a low-cost solution for small storage quantities and are therefore mainly used in mobile applications such as cars and commercial vehicles.
There are currently four different types of pressure vessels on the market:

  • Type 1: Pressure vessel consists only of a metallic (usually steel) wall. Nominal pressures are in the range of 200 bar.
  • Type 2: In addition to the metallic wall, pressure vessels have a jacket made of resin-impregnated glass or carbon fibre with a nominal pressure of up to 1000 bar.
  • Type 3: Tanks have a liner made of metal (usually aluminium) and a jacket made of carbon fibre around the whole tank. Nominal pressures are typically 350 or 700 bar.
  • Type 4: Accumulators have a liner made of plastic (typically polyamide or polyethylene) and the jacket is usually made of carbon fibre, as with the type 3 vessels. Nominal pressures are usually 350, 500 or 700 bar.

What are the advantages and disadvantages of liquid hydrogen?

Compared to gaseous hydrogen storage, liquid hydrogen as a fuel offers advantages in terms of energy density (71 kg/m³). The pressure in the tank can also be kept low. This has a positive effect on the tank system in terms of the storage tank weight and space requirements, costs (especially for large storage volumes) and safety.

The production costs of cryogenic hydrogen (-253 °C) are not insignificant, however. The hydrogen also heats up if it is not constantly cooled. This leads to an increase in pressure within the tank. This can lead to "boil off" losses. In other words, the gaseous hydrogen is vented into the environment.

What types of hydrogen engines are there?

A hydrogen engine is a gas engine that runs on gaseous hydrogen instead of liquid fuel (such as diesel and petrol). There are pure hydrogen engines which are powered with pure hydrogen. There are also bi-fuel hydrogen engines which are powered by a fuel mixture of hydrogen and other gases (such as methane and natural gas).

A hydrogen engine is considered as an alternative to a fuel cell, as existing combustion engines can be converted with relatively little technical effort. Studies show, however, that the cost advantage will considerably decrease with the ramp up in fuel cells. In addition, hydrogen engines struggle with a lower efficiency, higher maintenance requirements and the label of not being 100% carbon neutral.

How does a fuel cell electric vehicle (FCEV) work?

"Fuel cell electric vehicles“ (FCEV) are exclusively powered by an electric motor just as with "battery electric vehicles" (BEV).

Unlike BEV, the electrical energy required is not provided by a large drive battery (known as a traction battery). Instead, it is made available by converting chemical energy from the alternative energy source into electrical energy - made possible by the fuel cell.

At the moment, fuel cells are not yet designed for such rapid and long lasting load changes as combustion engines are. For this reason, a (small) drive battery is also installed which is fed when the load is low and supplies additional energy when the load is high. This allows the fuel cell to be operated at a relatively constant load when the FCEV is being driven.

How efficient are fuel cell power plants?

Fuel cell power plants (FCPP), combined heat and power (CHP) and fuel cell combined heat and power plants (FC-CHPPP) impress with their high overall level of efficiency. Depending on the fuel cell technology used, the electrical efficiency is currently around 30-60 %. The overall efficiency can be over 95% as electricity and heat are generated directly from the electromechanical reaction without any further conversion steps.

Fuel cell power plants have so far been developed primarily in the power range of 10 kw to 3 MW. In recent years, however, the development in the lower power range has increasingly gone in the direction of micro and nano fuel cell combined heat and power plants with 0.3-1.5 kW electrical output and 0.6-2.0 kW thermal output for detached and semi-detached houses. In the upper power range, power plants with around 80 MW have already been achieved, and this is to be increased further in the coming years through modular designs.

What does “Power-to-X” mean?

Power-to-X (also called PtX or P2X) refers to the use of electricity surpluses from variable renewable energies to aid all kinds of technologies. For example, these surpluses can be stored directly in batteries (power-to-power), converted into heat (power-to-heat) or used to produce chemical energy sources (power-to-gas, power-to-liquid).

If the surplus electricity is used to produce chemical energy sources, further differentiation is often made (e.g. power-to-hydrogen, power-to-syngas, power-to-ammonia, power-to-fuel).

Why does ammonia play an important role in hydrogen economy?

Ammonia (NH3) is a chemical compound of nitrogen and hydrogen, which is present in gaseous form under normal conditions. Since the development of nitrogen fertilisation by Justus Liebig (around 1840), it has been one of the most important basic chemicals. But it was not until the Haber-Bosch process was used on an industrial scale at BASF in Ludwigshafen around 1913 that a significant increase in annual production was possible. Today, ammonia is one of the most produced chemicals (146.5 million tonnes in 2021, 80 % of which for fertiliser) and the basis for the production of all other nitrogen compounds.

In view of the developing sustainable hydrogen economy, a further increase in annual ammonia production can be expected. The reason: it is better suited for transport and storage than pure hydrogen.

Due to the rather high boiling point of -33 °C, it is much easier and cheaper to liquefy ammonia compared to hydrogen (boiling point -252 °C). The higher volumetric energy value of ammonia compared to hydrogen (3.2 kWh/l compared to 2.8 kWh/l) is also highly relevant, especially for transport logistics.

Our success stories relating to hydrogen and alternative sources of energy

The world’s leading technology for measuring particles in hydrogen systems


Hydrogen for fuel cell vehicles must be clean √ Analyse particles in hydrogen pumps with a filter & measuring cell √ Extend component life → Learn more!

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Fuel cell stacks need a flexible clamping band solution


HYDAC is your partner for fuel cell mounting technology, offering an extensive portfolio of components and systems. Find out more

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