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INSIGHT: HYDROGEN IN RACING

Alto Ono investigates two projects using hydrogen as a fuel for 24-hour racing

As the world moves toward carbon neutrality, motorsport has also been pushed to look at alternative solutions to petrol and diesel. Hydrogen, the most abundant element in the universe, is an attractive fuel source that some are looking to as a viable alternative to petrol for racing. To create power, hydrogen can be used mainly in one of two ways: internal combustion or fuel cells. Theoretically, the only by-product from either method is water, making it a genuinely ‘green’ fuel.

 While most of the automotive industry has committed to moving towards battery-electric vehicles (BEVs), for the most part, they simply cannot compete at the current level of motorsport without a significant leap in battery technology. Though successful as a racing series, Formula E still struggles to produce performance anywhere close to Formula One even after eight seasons.

Tomorrow’s world? The business end of the first hydrogen-powered Prototype

Ultra-fast 600 kW charging will be introduced for the Gen 3 Formula E cars but that will still not be enough to significantly reduce their weight, which is holding back their performance. Furthermore, the cost of racing a BEV at a grass-roots level is simply not possible. The batteries, the maintenance of the packs, and the additional infrastructure required to provide the energy to the whole grid quickly add up. Hydrogen might be able to solve those problems, or at least bridge the gap until there is a paradigm shift in battery technology. 

 

Fuel cells

Fuel cell technology in road vehicles has been around since the early 2000s. A fuel cell is a device that converts the chemical energy of a fuel (hydrogen) and an oxidising agent (oxygen) into electricity. While both batteries and fuel cells convert chemical energy into electricity, where the fuel cell differs greatly is that, like a combustion engine, its operation requires a constant source of fuel and oxidiser.

Refuelling the Mission 24 Prototype at Le Mans 2022 (Photo: Paul Davidson/Mission H24)

The most common form of hydrogen fuel cell is the proton exchange membrane (PEM) fuel cell. In very basic terms, a special membrane strips electrons from the hydrogen atoms and passes them through the circuit to create electricity before recombining on the other side of the membrane with the proton and oxygen, creating water vapour. A constant source of hydrogen is required, but this overcomes the weight issue of a contemporary battery, and refuelling is similar to topping up with gasoline.

The Mission H24 Prototype made its race debut at May’s Michelin Le Mans Cup event at Imola, successfully completing 110 minutes of racing

 

Mission H24

At Le Mans, RET caught up with GreenGT, the team behind the Mission H24 project. Mission H24 was launched in 2018 with the aim of showcasing the viability of a hydrogen racing class in endurance racing. The concept is a hydrogen-electric car, with fuel cells generating the power and the power delivery being provided by electric motors on the rear axle.

Speaking about the new Mission H24 Prototype, launched last year, GreenGT’s motorsport technical manager Bassel Aslan says, “The hydrogen car we built, the Prototype, is an electric car at its core, it’s just that you have a fuel cell converting the hydrogen into electricity instead of using a battery. We want to highlight that we do not have the same problems as battery-electric cars.

“With hydrogen, you can refuel like a normal petrol combustion car: our target refuelling time is 3 minutes. We refuel, rejoin the race and get back to the competition. Also, our hydrogen fuel cell system is far more efficient than an IC engine and exhausts only water vapour.”

The fuel cell onboard Mission H24’s LM P3 chassis provides around 200 kW of net power. While the fuel cell is actually generating around 240 kW, about 40 kW is used to power the compressor feeding air into the fuel cells and for other auxiliary systems, but the team plans to push that further.

Aslan says, “The target now is really to arrive at 230 to 240 kW net with our current fuel cell. With the latest fuel cell technology, I would say the power could be increased by 30 or 40% with far less weight, but we started building this prototype 2 years ago.”

 What is remarkable, even with 2-year-old technology, is the efficiency these fuel cells can achieve – around 50-55% – a figure only current Formula One engines can compete with.

A major downside of a fuel cell though is the response time in transient conditions, it cannot simply ‘ramp up’ its power output very quickly. For the power output to change, both the fuel flow rate and the air being fed into the fuel cell must be rapidly increased. That involves the compressor ‘spooling’ up, which takes time. Coolant must also be ramped up to ensure that the fragile PEM does not dehydrate. It all adds up to a relatively poor transient response.

The Mission H24 therefore has a 3.3 kWh ‘buffer’ battery onboard to react to these transients. That means the fuel cell does not have to drastically change its operating point in a short time and can be tuned to be efficient in a relatively small window of operating points. The battery provides the driver with the power response required in a racecar, and also enables excess electricity produced by the fuel cell and regenerative braking to be stored.

The combined energy between the fuel cell and the battery allows the Mission H24’s driver to currently have up to 480 kW under their right foot. But the electric powertrain can handle much more power.

“The electric powertrain can handle up to 700 kW peak power,” Aslan remarks. “Each motor can also output up to 350 Nm/258 lb-ft [at the shaft]. There are two electric motors on the rear axle, one on the right and the other on the left. Each one is attached to a dual-stage fixed-ratio gearbox.”

Because the powertrain was built to handle so much more than its current peak output, the Mission H24 team’s goal is to extract every single bit of power from the fuel cell and the batteries. However, as the power output of the fuel cell increases, the cooling requirement increases quickly as well.

Unlike an IC engine, where about half of the waste heat is discarded as exhaust gases, leaving only about 33% of the combustion energy to be dissipated using a cooling system, a fuel cell must dissipate nearly all its waste energy (45-50%) through its cooling system. Not only is that a significant amount of energy (around 200 kW here) to dissipate, it is particularly tricky to do with coolant at less than 100 °C, which is the operating temperature of the fuel cells. With such a small delta between the coolant and ambient, that makes it the biggest challenge in integrating a fuel cell system.

“We have an efficient cooling system,” remarks Aslan. “A big one, but it’s efficient. There are two radiators on both sides of the car mainly to cool the fuel cell. The cooling system is filled with water, and this water circuit flows through to the smallest details inside the fuel cell stacks. That enables us to extract the maximum power from the fuel cell and keep the temperatures under control.”

This is a fine balancing act between pushing the operating temperature of the fuel cells up and regulating the flow rate of the coolant. At the current maximum operating temperature, the flow rate required to reject the waste heat of the system is in the neighbourhood of hundreds of litres per minute, far more than any cooling circuit found in any modern IC-engined racecar.

While further developments in fuel cell cooling are important for the long-term evolution and viability of the project, the Mission H24 team focused on controlling the thermals of the buffer battery to achieve a maximum speed record at Le Mans.

“Heavy modifications to the buffer battery cooling were made to get stable thermal behaviour,” Aslan says. “Previously, we were hitting the thermal limit of the pack quickly and were forced to derate.” The improved cooling allowed the Mission H24 team to sustain full power for longer, accelerating the car to a new electric speed record of 292.8 kph down the Les Hunaudieres straight.

An important point here is that the goal of the project is to highlight the viability of a hydrogen powertrain. Aslan says, “There is still a lot we can do on the chassis and aerodynamics, but that is not our focus for the moment. The focus is to show everyone that this hydrogen technology is competitive. That doesn’t mean we will not work on the chassis, weight and everything else, we will but later.”

Optimising aerodynamics to improve cooling efficiency and reduce drag will only increase the competitiveness of the Mission H24 car. As the team inches closer to the pace of GT3 cars throughout this season, the GreenGT team has its sights firmly set on creating a reserved category for hydrogen vehicles during the 24 Hours of Le Mans in 2025.

 

Toyota Hydrogen Corolla

On the other side of the planet in Japan, Toyota is taking a different approach to pursuing hydrogen as a possible solution in motorsport with its Corolla H2 Concept, the aim of which is to speed up the development of a hydrogen combustion engine race vehicle. Powered by a modified 1.6 litre I3 turbo engine out of the GR Yaris, the Corolla H2 Concept made its racing debut in 2021, competing in four rounds of the Super Taikyu series. Toyota has committed to continue running this car in 2022 for a full season in the Super Taikyu season with the ORC Rookie team.

RET discussed the project with GR Powertrain development division general manager, Masakiyo Kojima. He explains, “This project is at a very early stage of development, so we have made only small modifications to the production engine. We had to make modifications to the fuel system; the standard injectors are built for a liquid, and we are using hydrogen gas, so new ones had to be fitted. We have also removed the fuel pump. The pressurised hydrogen tank and a regulator are directly connected to the hydrogen injectors.”

While Toyota is currently the only company exploring hydrogen combustion on the racetrack, a hydrogen IC engine is far from a new concept. Research began around the 1970s, and ranged from designing new engines to using existing diesel engines with hydrogen fuel. However, hydrogen combustion has a key issue in respect of pre-ignition.

Pre-ignition occurs when the residual heat or hotspots in the cylinder causes the fuel to ignite before the spark plug fires. As Kojima-san explains, “Hydrogen is very easy to burn and needs only a small amount of ignition energy. Pre-ignition therefore occurs easily with hydrogen fuel.

Replenishing the hydrogen gas-fuelled Toyota Corolla’s tanks

“That can be a big disadvantage, but on the other hand it also means that hydrogen suits lean burn. In lean-burn conditions, it can ignite easier and have a complete burn, so that's a merit.”

Pre-ignition of hydrogen is why many of the research concepts over the years have been based on diesel engines that automatically ignite the fuel under the heat produced by compression. However, with the advance of technology, controlling pre-ignition has become possible.

One way to control it is to create an ultra-lean burn condition. The increased availability of accurate sensors and actuators that can survive harsh outdoor conditions, the widespread adoption of direct injection, advances in spark plug technology, and manufacturing methods for complex engine component geometries have all contributed to making that possible.

If pre-ignition can be controlled successfully, hydrogen is poised to become a very attractive alternative fuel. “Basically, from a thermal efficiency point of view, there is no big difference between hydrogen and petrol,” says Kojima-san.

“So, if you put in the same amount of energy in terms of fuel, you will get out the same amount of power. In the petrol version, we operate around the stoichiometric ratio, and at WOT we run richer. If the lambda is kept the same between the two fuels [petrol and hydrogen], there is no big difference in output.”

That is particularly appealing, as the stoichiometric ratio of hydrogen combustion is 34:1, far leaner than petrol. While the volumetric density of gaseous hydrogen remains a problem, hydrogen is much lighter than petrol, leading to a lower fuel mass – an attractive proposition for motorsport.

Major improvements to the Super Taikyu Corolla H2 Corolla have been made since the introduction of the project. Kojima-san says, “At Fuji [for June’s 24-hour race], we were making about 20% more [power] than the production engine, but most of this improvement was not from the fuel change, it was largely due to other improvements around the powertrain.”

Filling time has also been improved by adding additional fuel ports on both sides of the vehicle, reducing the filling time from about 3 minutes to about 2 minutes. While making the Corolla H2 Concept faster is important, like the Mission H24 Project by GreenGT, it is also not the focus of this project.

“For now, we are investigating hydrogen combustion in a motorsport environment to measure how much we can achieve with hydrogen gas to understand the challenges – that's our target,” Kojima-san says. “There is no maximum power or torque figure we are trying to achieve.”

The hydrogen-fuelled Toyota completed more than 2000 km in finishing the 2022 24-hour race at Fuji

With Toyota being one of the small handful of OEMs that produce hydrogen fuel cell vehicles for the road, it begs the question: Why go racing with a hydrogen IC engine, not with a fuel cell? But in very Toyota fashion, the answer lies in infrastructure and supply chain.

“At Toyota, we firmly believe that BEVs are not the only solution in the transition to a carbon-neutral world,” Kojima-san says. “Energy production varies greatly around the world, so we need to keep our options open to provide mobility solutions that fit each environment and market. Hydrogen is a solution, but fuel cells are still a very expensive option, and while we would like to make them more affordable, there is still a lot of work to do.

“If we could achieve a hydrogen IC engine then that would be a more affordable solution. The second reason is the supply chain. An IC engine consists of a lot of parts compared to a BEV. If we achieve hydrogen combustion, we can keep the current supply chain with very minimal re-tooling, and therefore also reduce the cost.”

The GR Team will continue to test the limits of hydrogen combustion technology in the harsh environment of motorsport, and Toyota aims to apply the lessons learned from this initiative to developing carbon-neutral production cars in the future.

 

Onboard storage of hydrogen

A challenge that both projects face is the onboard storage of hydrogen gas. While hydrogen has more released energy per kilo of fuel compared to petrol – 142 MJ/kg versus 46 MJ/kg – its volumetric density as a gas is poor. The density of hydrogen gas is 0.08375 kg/m³, a magnitude lower than the 0.7-0.8 kg/m³ of petrol.

That is the dilemma of using hydrogen gas as a fuel. It is the lightest element on the Periodic Table, making it the lightest fuel possible, but the volume required to store it as a gas is massive. And as you increase the pressure to reduce the volume, the storage tanks become heavier to withstand the higher pressures.

To put it into perspective, both these projects are filling their tanks at 700 bar. The Mission H24 concept has 8.6 kg of fuel (a little over 200 litres) while the Corolla H24 repurposed two storage tanks from Toyota’s Mirai model and two additional tanks that are slightly shorter to provide a total onboard capacity of 180 litres, around 7 kg of fuel. One kilo of petrol would take up only about 1.3 litres of volume at atmospheric pressure.

The only real solution to this problem is to switch to liquid hydrogen. While it is a cryogenic liquid and that presents its own challenges, its energy density is 8 MJ/litre, bringing it closer to petrol's 32 MJ/litre. But creating, storing and using liquid hydrogen brings a whole new set of challenges that have to be solved.

Toyota detailed its plans for the Corolla H2 Concept earlier this year, including moving toward a liquid-hydrogen-based IC engine. That will greatly increase the range of the Corolla H2 Concept and will allow for better packaging.

 

Hydrogen production

A key issue in using hydrogen as a ‘carbon-neutral’ fuel is that the carbon footprint of the hydrogen greatly depends on how it was produced in the first place. While the same could be said about BEVs and electricity, it is particularly contentious given that creating hydrogen via electrolysis is an energy-intense process with low efficiency.

Even if the electricity to conduct the electrolysis comes from a renewable source, overall it is less efficient than a BEV from a ‘well-to-wheel’ point of view. Even worse, the currently dominant form of hydrogen production comes from steam reforming of methane or natural gas, a process that is definitely not carbon-neutral.

In motorsport though, it is important to look at the bigger picture; the carbon footprint to consider for motorsport is not just the fuel being burned. BEV battery packs are replaced often, as the high discharge and recharge rates wear them down, resulting in lower capacity and performance.

Also, the batteries are packed with rare earth metals, and lithium is often strip-mined in various parts of the world. Re-tooling factories and building brand new facilities is required for BEV r&d as well, while hydrogen combustion could be achieved with minimal re-tooling. Building new electrical infrastructure at racetracks requires considerable effort and resources, while hydrogen could potentially be transported in.

Overall, while hydrogen might not be the cleanest alternative fuel solution, what is important is to make progress. It allows us to maintain the speed, excitement and racing format of current petrol-based racecars with a ‘cleaner’ alternative fuel. And perhaps most important, hydrogen provides us with an opportunity to go racing in parts of the world that may not have renewable electricity and the infrastructure required to run a BEV series.

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