Hydrogen fuel storage system for buses​

The Italian city of Bolzano in South Tyrol is well ahead of its time. Since 2019, 13 hydrogen buses have been making their environmentally friendly and sustainable rounds on its streets. Experts assume that by 2030, throughout Europe, 20% to 30% of all newly registered buses could be powered by green hydrogen, which is a full one-third of the entire bus market.

The lightweight fully composite hydrogen storage system is provided by global market leader in that field: Hexagon Purus, subdivision of Hexagon Composites ASA (HEX.OL). “Our systems provide lowest weight and exceptional performance and safety. Mainly due to these features, we have been able to introduce our product to many OEMS in Europe, reaching 80% market share”, says Milosz Szymaniak, Senior Business Development Manager at Hexagon Purus.

This is no accident, considering that Hexagon Purus offers customers one-stop shopping. Concretely speaking, this means that everything involved in hydrogen storage comes from a single source. „We offer customers the optimal system according to the storage capacity they‘re looking for and the space they have available – as a complete system,“ says Szymaniak. This includes not only the cylinders, but also the high-pressure system, the electrical system that monitors the storage unit, the tank panel that communicates with the tank system during the fueling process, ensuring that fueling is done in compliance with SAG standards and preventing overfilling. All necessary pressure stages are also considered in the solution. „The integration into the bus and the complete solution are our most important success criteria,“ says Szymaniak confidently.

Another advantage is that Type 4 cylinders are the safest products currently on the market for storing hydrogen because they show great resistance against corrosion and material fatigue through the entire 20 years of the product lifetime. Their operating costs are also significantly lower than those of steel tanks. “There are only four or five companies in the world that manufacture Type 4 cylinders. Because Hexagon Purus brought the first Type 4 cylinder to market back in 1993, we have the longest history, the greatest expertise, and the best knowledge of how to manufacture these cylinders – not only on the design side, but also in terms of production,” says Szymaniak. Thus, the world’s largest Type 4 cylinder is also made by Hexagon Purus. Called Titan, the storage system is manufactured in the US and consists of four cylinders, each of which is one meter in diameter and twelve meters long. Hundreds of them have already been shipped to customers, particularly in North and South America.

“There are now 150 hydrogen buses – each 12 meters long – that run on our storage system. In 2023, we will also produce storage systems that are designed for 18-meter-long buses,” says Szymaniak, offering a glimpse into future plans.

Generally speaking, the storage systems are usually installed on the roof of the buses – freeing up the rear area of the bus that usually houses the diesel engine. The current storage system operates under a pressure of 350 bar. However, 2024 will bring a revision to the approval standard, called R134. “Rather than simply adapting the storage systems to the new standard, we will optimize and simplify the system concept at the same time: maximum capacity with minimum weight in a system that is as simple as possible,” explains Szymaniak. The system is to be built according to the Lego principle: Depending on requirements, three, four or five cylinders can be installed on the bus. While 12-meter-long buses can usually make it with a hydrogen storage capacity of 25 to 36 kilograms, the 18-meter-long vehicles need 50 kilograms. The driving distance can also be extended by adding more cylinders. For example, the range can be boosted from 350 to 400 kilometers for a 35-kilogram system with three cylinders to 500 to 600 kilometers by simply adding a fourth or fifth cylinder.

In response to the expected growth in hydrogen technologies, Hexagon Purus is expanding its capacities significantly. While the US remains the market with the strongest sales due to its truck industry, Hexagon Purus has also had a presence on the European market since 1996. The major growth regions are China, India, and South America. In short: Hexagon Purus is already working globally. A new production line for hydrogen cylinders is now being added – with Wystrach GmbH also contributing its expertise.