How the Le Mans hydrogen racer is shaping up
Around 400 meters away from the buzz of the paddock during this year’s 24 Hours of Le Mans stood a tent with two racing cars and a mobile fueling station. Every now and then, people wearing blue T-shirts bearing the logo Mission H24 would walk by the cars to attend meetings in a motor home standing next to it.
One of them was François Granet of the Franco-Swiss company GreenGT, who appeared particularly thrilled. That’s because, on the eve of the start of this year’s race, the ACO (Automobile Club de l’Ouest), which organizes 24 Hours of Le Mans, announced a new category of race cars at the Le Mans event from 2025: hydrogen-electric prototypes. Their forerunners were stationed in that tent.
Creating a category
GreenGT is developing the hydrogen fuel cell powertrain for these cars, which will be designed around a chassis built by Oreca and Red Bull Technologies. “In partnership with ACO, we are helping define the sporting and technical regulations for the new category,” Granet says.
The H24 car, the latest of the two prototypes, is being tested at different circuits across Europe. It ran some tests at Le Mans on the days leading up to this year’s race and did a demonstration lap of the 13.6 km (8.5 mile) circuit just before the start on Saturday afternoon. “The data from these tests help us to understand and improve the car’s performance which forms the basis of creating the regulations for the new category,” he says.
One of the drivers who tested the H24 during the weekend was Stéphane Richelmi, a past winner at Le Mans. Richelmi, who won the 24 hour race in the LMP2 class in 2016, says he was most impressed with the hydrogen engine’s power. “Since it’s a new technology and doesn’t use either petrol or diesel, I was expecting the car to have low torque and low top speed. But it delivered more torque than a petrol engine, and even without pushing too hard, the car easily reached 280 km/hr [174 mph] on the straights,” he says.
The 32-year-old from Monaco says driving the car for the first time felt a bit strange. “It reminded me of my karting days,” he says. “There is the engine, brakes, acceleration pedal, steering wheel but no gearbox, which normally is a big part of a racing car.”
The H24 is powered purely by electricity. The fuel cell stacks use hydrogen and oxygen to produce electricity, most of which is directly fed into the motor. But a part is fed into the battery, which is used for faster acceleration, such as when exiting a corner.
According to Richelmi, his role is to “feel” the car on the track and give this information to the engineers. “The engineers see many things with data and simulation. But as a driver, you get a real feel of the car. My role is to tell engineers that, in certain cases, while things may look good on the computers, it may not be good on the track.”
The powertrain makes a high-pitched buzz, and Richelmi says drivers can hear more of the car. During the tests, the car was filled with high-pressure hydrogen at a fueling station developed by TotalEnergies. “While we kept the pressure at 400 bars for the tests, the tanks can hold hydrogen up to 700 bars. The higher the pressure means there is more hydrogen volume, which means more autonomy,” Granet explains. For a single lap of the Le Mans circuit, the car used 800 g of hydrogen.
Although the tests have been encouraging, there are many hurdles to clear before the car becomes race fit in terms of speed and endurance. The first of these challenges is weight reduction. “At 1,400 kg, the H24 still weighs 450 kg more than a LMP3 car and 155 kg more than a GT3 car. But since it’s a raw prototype, we can work on every single part to try and reduce weight,” he says.
For GreenGT, the H24 project has a symbiotic relationship with the hydrogen trucks it has developed for heavy industry. The 44-tonne (48.5 ton) trucks will be able to travel 450 km (280 miles) on a single fill-up. “We bring technologies from trucks to the racing car and vice versa. Though the objectives of a racing car and a truck are different, there are many similarities, starting with the powertrain technology. Interestingly, the power output of the engines for H24 and our trucks is somewhat similar.”
According to Granet, optimizing power and consuming less hydrogen are key, and they might benefit from things like optimizing humidification of air when oxygen enters the fuel cell. This sort of adjustment is common to both the projects.
Granet also argues for the benefits of using hydrogen powertrains. “An electric engine is far more efficient than a normal aspirated four-stroke engine. More importantly, it is clean energy as it emits just water vapor. Moreover, we are also targeting the use of only green hydrogen that is produced from nonpolluting sources,” he says.
Dhananjay Khadilkar is a journalist based in Paris.
via Ars Technica https://arstechnica.com
September 15, 2021 at 02:25PM