Daimler Truck and Linde Engineering recently announced sLH2, a jointly developed refueling technology for subcooled liquid hydrogen. The companies claim that subcooled liquid hydrogen allows for higher storage density compared to gaseous hydrogen, enabling greater range, faster refueling and improved energy efficiency.

“Zero-emission transport needs three factors: the right battery-electric and hydrogen-powered vehicles, the required infrastructure network and cost parity for ZEVs compared to diesel trucks,” said Andreas Gorbach, board of management for Daimler Truck AG. “With sLH2, hydrogen refueling becomes as convenient as today’s refueling with diesel. It takes about 10 to 15 minutes to fuel our GenH2 Truck for a range of more than 1,000 kilometers.”

“Subcooled liquid hydrogen considerably increases the efficiency of hydrogen refueling systems,” Juergen Nowicki, CEO of Linde Engineering. “The required investment is reduced by a factor of two to three and operational costs are five to six times lower. The technology we have developed with Daimler Truck will help pave the way for the development of a robust refueling network, which is essential to keep vehicles moving and supply chains intact.”

Fast fueling
According to the announcement, Daimler and Linde intend to homologate sLH2 as a common refueling standard for hydrogen-powered trucks. The first public sLH2 fuel station has already been christened in Wörth am Rhein, Germany. The station will be utilized for customer trials using Mercedes-Benz GenH2 trucks.

Refueling at the station reportedly takes ten to fifteen minutes for a 40-ton (36,000 kg) truck carrying 80 kg (176 lbs.) of liquid hydrogen for a range of 1,000 kilometers (621 miles). Daimler states that the sLH2 system lowers the required investment and operational costs for a hydrogen refueling station and that liquid hydrogen can be supplied reliably throughout Europe. The system uses a pump to increase the pressure of the liquid hydrogen, which sub-cools it to a temperature of -253° C (-423° F) and transforms it into a liquid (sLH2).

According to Daimler, the process reduces energy losses and increases refueling capacity. The refueling station has a capacity of 400 kg (882 lb.) of liquid hydrogen per hour. The station’s storage tank has a capacity of four tons, sufficient for approximately ten hours of non-stop refueling.

Daimler states that thanks to the lower pressure required for liquid hydrogen, the truck storage tanks are significantly lighter. This enables greater payload capacity as well as increased storage and range. An additional benefit of this process, according to Daimler, is that it mitigates boil-off effects and “return gas” (gas from the vehicle’s tank returning to the filling station). The payoff is that only one nozzle is needed to fill the tanks.

Trucking along
Daimler first introduced a prototype of the GenH2 Truck in 2021 which underwent tests in various environments. Starting in mid-2024, the company will release a total of five GenH2 trucks for customer trials. Amazon, Air Products, INEOS, Holcim and Wiedmann & Winz are the firms taking part in the initial trials. The five trucks will be deployed with their respective companies in Germany and will be under the direct supervision of Mercedes-Benz Trucks.

The Mercedes-Benz GenH2 Trucks offer a payload of approximately 25 tons and a GCW of 40 tons. The powertrain of the GenH2 truck is rated at 300 kW and the battery provides an additional 400 kW of temporary energy. A 70-kWh battery also is onboard for situational power support for the fuel cell during peak loads while accelerating or while driving uphill fully loaded.

A core element of the fuel-cell and battery system is a thermal-management layout that keeps all components at a suitable operating temperature to ensure maximum durability. In a pre-series version, the two electric motors are designed for a total of 2 x 230 kW continuous power and 2 x 330 kW maximum power.

The truck’s fuel system consists of two liquid hydrogen tanks and a cellcentric fuel-cell system. The stainless-steel liquid-hydrogen tanks have a storage capacity of 44 kg each. The tank system consists of two tubes, one within the other, that are connected and vacuum insulated.

In September of 2023, Daimler demonstrated the capabilities of its truck with a public road-approved prototype that completed a 1,047-kilometer (650-mile) route without refueling. The company aims to introduce the series version of the Mercedes-Benz GenH2 Truck in the second half of the decade.