Between a Formula 1 that decisively turns towards the development of alternative fuels and a Formula E that with the announcement of the Gen4 aims at a new evolutionary leap for electric technology, the world of endurance chooses a third path. The debut of a hydrogen class at the 24 Hours of Le Mans is set for 2026, with the intention of joining the current Hypercars and possibly taking their place. If in the past fuel-cell propulsion was the only option on the table of the FIA and ACO, the organizers are now also opening up to traditional heat engines fueled by hydrogen. The 2026 edition promises to be one of the most relevant ever due to the extent of the technological challenge, but several problems are still being resolved.
The thermal joins the fuel-cell
In the press conference of the centenary of the 24 Hours of Le Mans, the organizers announced the coexistence of fuel-cell and heat engine in the future hydrogen class, whose debut is now expected in 2026. The use of hydrogen in combustion engines is gaining more and more interest for large manufacturers, seen as a possible alternative to extend the life of the thermal after the ban in Europe in 2035 of fossil fuels for new registrations. Also, unlike biofuels and synthetic gasolines, hydrogen combustion is free from particulate matter and various carbon by-products, improving air quality in urban areas.
However, the car industry also has great interest in fuel-cell propulsion. In this case, the hydrogen is not burned inside a heat engine, but is compressed inside fuel cells where it recombines with the oxygen taken from the atmosphere. The chemical reaction releases water vapor, expelled from the tailpipes, and electricity which can then be used to power one or more electric motors, without the weight and costs of a large battery. However, the fuel-cell has the characteristic of delivering constant power, thus requiring the support of a small battery with high power density to satisfy the peak demand at the accelerator.
The hydrogen class
FIA and ACO have not provided much information on the new hydrogen class, except that it will debut at Le Mans in 2026. There are rumors of interest from some manufacturers, including Hyundai, and which can achieve performances in line with current Hypercars. The two classes could therefore coexist or even merge into a single category, exploiting the same BoP mechanism currently in force.
The opening up to hydrogen heat engines raises several questions as to whether the future class will see the same chassis for all the participants or whether the manufacturers will be able to independently build a large part of the car. In fact, until now the development of the hydrogen class was entrusted to the Mission H24 project, born in collaboration between the ACO and the Swiss GreenGT. The latter is working on the construction of the transmission, electric motors and battery, while the development of the tanks is entrusted to Plastic Omnium. According to the initial plans, the frame would be made in synergy between Oreca and Red Bull Advanced Technologiesleaving the builders free to design the fuel cell, the compressor and the cooling system.
The proposals
The Mission H24 platform was born in view of a hydrogen class that was supposed to accommodate only fuel-cell vehicles. The recent opening to heat engines now raises questions about how the project can deliver a variant of the chassis where to install combustion units or rather whether the organizers intend to leave the development of the whole car to the incoming manufacturers. Another option is that of coexistence, with the Mission H24 platform available to participants who wish to use it, without however preventing the development of a prototype entirely in-house. At the moment, the FIA and the ACO have not provided any clarifications.
The suspicion is that the plans of the hydrogen class are slowly changing from a standard chassis category towards a free-development one. In fact, on the occasion of the last 24 hours of Le Mans, Toyota presented its GR H2 concept, visually different from the Mission H24 platform. The technical specifications remain secret, but the Japanese house has made it known that the concept is based on a hybrid powertrainwhere an electrical system supports a hydrogen heat engine.
Finally, again on the Centenary weekend, Bosch Engineering and Ligier presented the JS2 H2. It is a fully functional prototype, equipped with 3 tanks developed by Hexagon Purus with a capacity of 2.1 kg each, in which to store hydrogen at 700 bar. The car is also powered exclusively by a heat engine, a 3-litre twin-turbo V6 with 570 horsepower and 650 Nm. Despite being development platforms, the JS2 H2, the Toyota concept and the Mission H24 proposal show how the industry’s interest in hydrogen is tangible in all its forms: fuel-cell, thermal and hybrid.
Supplies theme
The possibility that the hydrogen class can compete with the Hypercars for the overall victory will depend not only on the technological advances on board the car. Baude Hugues, technical director of Solution F, a company involved in the development of hydrogen refueling since 2019, explains to FormulaPassion how pit stops remain a major engineering challenge:”To be able to put a hydrogen station in the paddock is a nightmare from a safety point of view. Furthermore, the regulations vary from country to country and this is a further difficulty. The first goal is to install filling stations in each WEC host country. In addition to this, we want to speed up refueling to make it comparable to that with traditional fuel, around 50 seconds. It’s a real challenge.”
“From a technical point of view, we are limited by the capabilities of the machine”, continues Hughes. “We are waiting for the next generation [di Mission H24, ndr]. At the moment for refueling we are around 3 minuteswhich means that we are far from the 50 second target, but it is acceptable”. One of the solutions to speed up refueling is to lower the temperature of the hydrogen, so as to increase its flow into the filler neck. However, the challenge is not predominantly on the infrastructure side, but also on the vehicle. Hugues explains: “The challenge for the car is to be able to complete a stint without lowering the temperature in the tank too much. As the tank empties, the temperature drops, but there is an acceptability limit to that”.
“There are different types of tanks. The first two types are metallic and are impossible to install on board. The third type is aluminum, while the fourth is carbon composite. However, the hydrogen molecule is very small. The problem is a bit like the lining of a swimming pool, which breaks if heated or cooled too much. Likewise, if the hydrogen cools too much, the tank is out of order.” While normally the driver must check the quantity of fuel in the tank, on a hydrogen car the driver must also monitor the pressure and temperature: “The pilot must check how many kg of hydrogen he still has on board, but also at what temperature and what pressure. Based on these values, when the refueling station is connected, it reads the machine parameters and regulates the flow of hydrogen towards the tank”.
From a regulatory point of view however, the work of the organizers starts from Europe. The objective is first of all to make refueling possible at Le Mans, and then to extend everything to the other tracks in the championship as well. However, it is not yet clear whether the circuits involved will have to connect to a network of hydrogen pipes or if instead the tanks will be supplied by external trucks: “We can imagine having trucks off the circuit with a hydraulic connection in the pits. There we could have a compressor that increases the pressure to 700 bar. It could be a solution”, adds Hughes. The arrival of hydrogen in the most famous race in the world certainly represents a fascinating challenge, which further enriches the offer of Le Mans. At present, however, there are still many outstanding points, both from the point of view of engineering feasibility and technical freedom for the participants.
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