The Hydrogen Technology Expo Europe is the largest hydrogen technology event in the world. Over 10,000 industry professionals walked through the doors of the Messe Bremen in Germany recently, with over 550 exhibitors showcasing their latest innovations in hydrogen fuel cell, combustion and storage.

The largest hydrogen technology event on the trade show calendar, this year’s Hydrogen Technology Expo Europe attracted over 10,000 attendees and 550 exhibitors at the Messe Bremen in Germany

Most of the exhibitors belonged to the aerospace, marine, rail, automotive and energy sectors. Nonetheless, we set out to uncover the most relevant hydrogen technologies for the future of motorsport. And we did not have to look far. At the back of one of the halls was the Forze VIII, the predecessor to the fastest hydrogen racecar in the world, the Forze IX. It is being developed by Forze Hydrogen Racing and boasts a dual hydrogen fuel cell system. The first of its kind in a car, it features four hydrogen fuel cell tanks pressurised to 700 bar. The tanks are capable of providing a combined output power of 240 kW (327 bhp).

In addition, an onboard accumulator stores energy from regenerative braking as well as excess energy from the fuel cells, providing a total output power of 600 kW. This boost can be deployed at the exit of every corner throughout an entire endurance race.

The Forze IX outputs 327 bhp from two hydrogen fuel cells and an extra 478 bhp from regenerative braking

“The amount of energy our car can recuperate during braking into one corner is equivalent to the energy a current Formula One car regenerates over an entire lap,” Olivier Estourgie said. “We can then use this energy almost immediately to give us 805 bhp while accelerating out of the corners, which is far more boost than our petrol-powered competitors.”

This double stack of fuel cells, along with the regenerative braking and battery systems, created a significant major challenge for the Forze team. “The biggest difference between the Forze IX and our previous car was integrating the four hydrogen fuel cell tanks,” Estourgie said.

“This required us to package the Balance of Plant [BoP], which includes the fuel cells, compressors, filters and so on, in a much more efficient way. We also made the car slightly longer to accommodate the front motors, which allowed us to deploy more power without slipping and also to generate more electricity under braking.”

A hydrogen fuel cell works by supplying hydrogen to the anode and air to the cathode. At the anode, a catalyst breaks down the hydrogen molecules into a proton and an electron, which take different routes to the cathode.

The proton passes through a membrane, whereas the electron is forced through an electrical circuit and generates electricity. At the cathode, the electron combines with the proton again as well as the oxygen from the air supply to form a molecule of water, which is then exhausted from the system.

On display was the Forze VIII hydrogen fuel cell racecar from Forze Hydrogen Racing which was the first hydrogen racer to beat petrol-powered cars in an official race, scoring second place at the Supercar Challenge on the TT Circuit Assen in 2019

“Unlike combustion engines, where fuel and air are combined together and ignited, in a hydrogen fuel cell the fuel and air are much more separated,” Estourgie said. “We can achieve a lot of performance from optimising both the airside and fuel side of our systems, which is why we have also integrated a turbo-compressor to recuperate energy from the exhaust and boost the efficiency of the airside system.”

The impressive output of the powertrain is converted to traction at the wheels via a 12:1 custom gearbox and four 150 kW motors. Controlling each wheel independently enables all-wheel drive along with torque vectoring for optimum vehicle dynamic control.

“The target eventually is to compete in the 24 hours Le Mans with this car,” Estourgie said. “But the big challenge now is figuring out the refuelling, as currently hydrogen refuelling is not allowed in the regulations. So for now, we will compete in the Supercar challenge in the GT class.

EKPO’s NM5-EVO fuel stack module consists of 335 cells and can deliver a power output of 76 kW

“The coolest thing about this project though is that it is designed entirely by students from TU Delft. Every year a fresh group of students dedicate their gap year to developing the car, which not only shows how innovative students can be but also the potential of hydrogen as an energy carrier for motorsport.”

One example of a fuel cell stack was the NM5-EVO on the EKPO stand. The module contains 335 cells to produce an output power of 76 kW and a stack voltage of 201 V. The number of cells can be varied to adjust the amount of power to suit the application, with 215-cell (39 kW), 119-cell (27 kW) and 71-cell (16 kW) versions available.

“The NM5-EVO module contains a media supply assembly that optimises the interface between the stack and the system,” said Wadim Kaiser. “It connects air for the cathode side, cooling water for the coolant side and hydrogen for the anode side. On the anode side for example, the system integrator only has to supply hydrogen and the NM5-EVO Stack Module covers everything else.

“An integrated water separator removes the water droplets from the anode outlet gas, which is subsequently mixed with the hydrogen supply to the anode inlet by an optionally available passive recirculation unit. Based on the individual function safety concept, the separated water can either be exhausted into the air emissions path or to the air humidifier. “We have also integrated sensors and actuators to provide several possible ways to use the NM5-EVO module in various applications.”

Hydrogen fuel cells are extremely sensitive to contamination, because any particulate or chemical contaminants can poison the catalyst layer that sits either side of the PTFE membrane.

Inside the Donaldson air filter (bottom) and its location in the Forze IX car, together with the water separator just after the air intake (top)

“An IC engine is a thermomechanical device, so there is a lot of heat and it is made up of many moving parts,” Korneel De Rudder of Donaldson said. “Its moving parts need to be protected from dust and hard particles that can cause wear, whereas a hydrogen fuel cell is an electrochemical device, so there are very few moving parts.

“However, contaminants still need to be removed because the catalyst is extremely sensitive to chemical poisoning from sulphur compounds, hydrocarbons and nitrogen oxides. If those are not filtered out effectively, they can damage the PEM, degrading the performance of the fuel cell and its overall lifespan.”

Donaldson has therefore developed advanced filtration solutions specifically for hydrogen fuel cell vehicles, and has supplied the Forze Hydrogen Racing team with air filters and water separators.

“There is quite a lot of water liquid and vapour around the fuel cell which you need to separate out and remove,” De Rudder said. “For the Forze team, we have a water separator at the air intake that removes rain droplets before the air goes into the air filter. Also, the Forze IX has an air compressor with a turbine on one side to recuperate energy, so there is a second water separator to remove condensed water droplets from the exhaust gases before it enters the turbine.”

Whether it is a filter for a heavy-duty truck or a racecar, packaging remains a challenge owing to the size of all the necessary components, such as the stack itself but also the BoP and high-pressure fuel tanks. Consequently, Donaldson used 3D printing to manufacture the complex shapes of the casing for both the water separator and air filter.

The filtration media consists of a spun-bound top and bottom layer of fabric, with layers of activated carbon in between. It is pleated and then secured inside the casing.

“There are two ways to optimise the performance of the filtration media,” De Rudder said. “For air filters, you want to maximise the surface area to capture as many airborne particulates as possible. For water separators, you want to maximise the volume of the activated carbon.”

Gore, a division of Gore-Tex (the company behind the waterproof materials in clothing), has developed a PEM membrane called Gore-Select, which was on display at the show.

The membrane consists of an expanded PTFE material, which has a micro-porous structure. On both sides of it is a layer of fluorine-based ionomers that allow the chemical reactions that break down the hydrogen atoms to generate electricity.

At the core of a hydrogen fuel cell is the stack, which consists of hundreds of individual cells connected in series. Each cell consists of a membrane electrode assembly, essentially a proton exchange membrane (PEM), with an anode electrode on one side and a cathode electrode on the other. This is then enclosed with a gas diffusion layer on either side and then a bipolar plate.

Consequently, when several cells are connected together, the bipolar plates help to channel hydrogen to the anode on one side of the PEM, and oxygen to the cathode on its other side.

The AeC808L-8 is an oil-free turbo compressor that uses air bearings and can generate 25 to 38 kW of power

To develop an efficient fuel cell with high power density, the material and operating conditions of the PEM need to be optimised to ensure that the maximum number of protons per unit area are transferred across the PEM.

This requires using materials with high proton conductance as well as mechanical and chemical durability. “When designing a fuel cell, you have to balance durability and performance,” explained Gore’s Nathan Ross. “If you want a high power output, such as for racing, you would choose a thinner membrane which has a higher proton conductance, whereas if you want a more durable system you might go for a thicker and more robust membrane.

“The biggest drivers in achieving a high output from the fuel cell are temperature and humidity,” he said. “The power curve between voltage and current drops as humidity is added to the system. So to minimise losses and boost efficiency you ideally want to develop a drier system.

“Temperature is another characteristic that can be fine-tuned. Systems operating at higher temperatures require less thermal management and therefore avoid the need for cooling fans and circuits, which can take efficiency away from the fuel cell itself. So it’s important to have PEM materials that can operate at higher temperatures.”

Aeristech showcased its latest oil-free turbo air compressors for hydrogen fuel cells. “A hydrogen fuel cell needs to be fed hydrogen and air, and we focus on the air side,” said Maris Kurimbokus.

“Similar to a conventional turbocharger, the more air you can feed into a fuel cell, the more power it can generate and the higher its efficiency. That’s why our air compressors spin at speeds of around 160,000 rpm, so that we can achieve a high power output but using a compact and lightweight package.”

The AeC808L-8 is currently the smallest and lightest on the market and features a compressor on one side and a turbine for energy recovery on the other; this set-up improves the efficiency of the compressor. Aeristech also develops and manufactures the power electronics that help make the AeC808L-8 a plug-and- play system.

“One of the most important considerations when designing components for fuel cells is to avoid any contamination,” Kurimbokus explained. “This can cause serious damage to the materials in the cell stacks, which are expensive to repair.

“That’s why we have developed air bearings, so instead of ball bearings running against each other and generating friction, air bearings have a shaft floating on a cushion of air. The air acts like the lubrication between the shaft and the sleeve, so there is no mechanical friction.

“Oil-free bearings are also really good for continuous running, as they don’t require a stop-start characteristic which is needed in conventional systems to allow a lubricant to be distributed around the moving parts.”

The nature of air bearings means though that the surface finish, geometry and tolerances are extremely sensitive, particularly at the high temperatures experienced in such a high-power air compressor. “The compressor and turbine layout generates high thrust loads and therefore a lot of heat within the system,” Kurimbokus said.

“That means there is a lot of pressure applied to that cushion of air within the bearings. To accommodate that, we have used high-temperature coatings and materials, and also looked at other tactics for managing those extra thrust loads. So we’ve managed to overcome those technical challenges through our r&d, which other companies have not managed to solve yet.”

As well as fuel cells, hydrogen can also be used as a gaseous or liquid fuel in an IC engine, just like conventional gasoline or diesel.  “Hydrogen is a great fuel for combustion,” Ricardo’s Richard Osborne told us. “It has fast combustion and high flame speeds, which are ideal for motorsport applications, and we’re also seeing increased development of hydrogen solutions in industries such as aerospace and marine. It has a very broad flammability range as well, which means you can run a wide range of airto- fuel ratios – in some cases, we’ve run ratios of up to lambda 5.

“Even though it significantly decreases NOx emissions, you probably wouldn’t want to run so lean, because it demands more air and therefore higher mass flow and boost pressure, reducing the overall efficiency of the engine.

The H:Interface hydrogen power system interface module from Hypermotive

“On the other hand, running too rich can increase knock and lead to other combustion anomalies that hydrogen is particularly susceptible to. Hydrogen is a bit paradoxical,” Osborne said. ‘It has a very low ignition energy but also a high auto-ignition temperature.

“This means that although it is relatively robust against knock, it ignites easily from hotspots. So, if it comes into contact with hot surfaces inside the combustion chamber then that can cause issues.”

In terms of thermal efficiency, hydrogen combustion is a little lower than conventional combustion engines using hydrocarbon fuels. However, because hydrogen is carbon-free, the engine’s thermal efficiency does not affect the amount of carbon emissions in the same way as with gasoline or diesel. Therefore, although thermal efficiency will remain important, it will no longer be the main measure of the sustainability of a hydrogen engine.

“Hydrogen combustion requires slight differences with tuning the compression ratio and the compatibility of materials, but otherwise most of the mechanical, injection and emission systems are very similar to conventional IC engines,” Osborne said. “It’s the fuel storage that is currently the biggest challenge. Hydrogen per unit weight is very good, but per unit volume it is not so good, which is making storing enough fuel in a car to last a race difficult.”

Integrating a hydrogen fuel cell into a vehicle is a major challenge – much more so than integrating an electric powertrain, for example. That is because the cell effectively requires gas handling and storage systems on top of an electric powertrain.

“Battery-based technologies will typically have a battery pack, a DC-DC converter, a charger as well as motors and inverters which are all connected together via a high-voltage power distribution solution,” Jeremy Bowman from Hypermotive explained.

“When you bring a fuel cell into the equation, you need to add another high-power DC-DC converter alongside all the gas technology and handling systems such as storage tanks, management and safety systems.

“You also need advanced thermal management systems to regulate this higher number of components effectively. So suddenly there are many more systems to integrate, and it’s not just a case of electrically ‘joining the dots’ between controllers, you have to accommodate the thermal and gas aspects as well.”

To help solve this problem, Hypermotive has developed the H:Suite range of integration products, with a prototype H:Interface module revealed at the show. This module connects to Hypermotive’s H:Store and H:Control products, and receives the commands for the hydrogen power system. The H:Interface then continually captures the operational status of the hydrogen power and storage systems, which can then be used to implement status displays for the vehicle.

The H:Interface also logs power system data, and can be connected via Ethernet to onboard telemetry systems that export this data to the cloud. H:Monitor and H:Optimise software tools then monitor, analyse and optimise the performance of the power system and deploy updates to all the H:Suite controllers installed on the vehicle.

“The biggest challenge when developing this system was accommodating components from different suppliers,” Bowman said. “Often this meant there was a lack of communication between devices, so we designed a controller that could communicate in the appropriate language to each device in the system.”

There was also the problem of coordinating the various cooling and thermal management systems, as each device required slightly different pressure, flow rate and temperature specifications. This meant that if five or six modules required an active cooling loop, three separate loops would be needed to suit the variations between suppliers.

“The complexity of this integration challenge can be largely satisfied with products that are intelligent and designed specifically for the integration of hydrogen fuel cells, which is what we hope our H:Suite range achieves,” Bowman said. “We knew there were many companies developing the technology for hydrogen fuel cells, but no one was focusing on how to put all the components together.

“So, the customer wants zero-emissions powertrains, and companies are developing the technology to enable that, but without the integration piece in the middle, it won’t happen.”

Aalberts coats around 40 million engine parts for the automotive industry every year using its inline physical vapour deposition technology. The Germany-based company has also been developing coatings for bipolar plates and electrodes for hydrogen fuel cells since 1998, some of which can be found on prototypes for different applications but also on small automotive serial production.

“We use mainly cathodic arc deposition, where a high-power electric arc is discharged at a target material, which can be made from pure metals like titanium or specially designed alloys,” Dr Torsten Will said. “This effectively evaporates some of the material from the target into a vapour, which is then ionised by the arc’s electric field and accelerated onto the part being coated.

“This acceleration is faster than the speed of sound, which means the individual particles embed themselves within the surface of the part, forming a much stronger bond.”

This high-energy process produces robust coatings that can cope in high-wear environments such as engine parts or the harsh electrochemical environments of a fuel cell or electrolyser.

“We can optimise the composition of the coating to suit the specific application,” Dr Will said. “We can also incorporate different amounts of other metals and gases to create millions of coating variations to find the best solution for each scenario.”

RET found several companies involved in hydrogen fuel cell and hydrogen combustion motorsport projects at this busy show

Allengra showcased its new ultrasonic flow meter for hydrogen combustion and fuel cell applications. This required adapting its technology from measuring liquids to measuring gases, which is particularly tricky when dealing with low-density gases such as hydrogen.

“Accurately measuring gases is more difficult because they have a much lower density, compressibility and a higher speed of sound than liquids,” Magnus Manderbach explained. “Ultrasonic flow meters work by sending an ultrasonic signal from one transducer to another.

The time taken for the signal to travel through the fluid is measured, and another signal is sent back in the opposite direction. Calculating the time difference between the two signals determines the flow velocity of the fluid.

“However, the higher the speed of-sound of the fluid, the faster the ultrasonic signal travels and therefore the smaller this time difference. So you then have to fine-tune the ultrasonic frequency, the filtering process and you have to increase the sampling rate to ensure a precise measurement. Furthermore, the sensor determines the concentration of the gas mixture due to an integrated speed of sound measurement.”

Another challenge when measuring the flow rate of gases is that in many applications there is a mixture of components, each with different concentrations. This is a particular issue with hydrogen fuel cells, where the unused hydrogen gas on the anode side is typically recirculated back to the entry of the fuel cell.

“This cycle can take place several times before the concentration of hydrogen goes below a certain level, while the levels of nitrogen and water vapour are increasing and then the gas is purged out of the system,” Manderbach said.

“The target here is to recirculate the hydrogen for long enough to be able to use it all, but not too long as too much nitrogen in the stack will reduce its lifetime. So the sensor helps to find the sweet spot between durability and efficiency.”

Unlike conventional flow measurement sensors, ultrasonic flow meters have no direct contact between the sensor and the fluid being measured. This enables the sensor to be more robust to humidity and allows it to measure both high and low flows within the same device.