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Bosch’s fuel-cell power module was designed to fit the envelope previously occupied by the truck’s diesel engine. (SAE/Ryan Gehm)

Bosch begins production of fuel-cell power modules for Nikola

The supplier is committed to all facets of the hydrogen economy as volume production of the module kicks off for Nikola’s Class 8 fuel-cell truck.

At its oldest and largest location – a site long accustomed to manufacturing parts for combustion engines – Bosch is now producing what it calls the most complex system it has ever developed: a fuel-cell power module (FCPM). Production at the Stuttgart-Feuerbach site in Germany officially kicked off in July during a Bosch Tech Day event attended by global media. The pilot customer for the FCPMs is Nikola with its Tre hydrogen fuel-cell electric truck, which is expected to launch in North America in the third quarter of 2023.

Bosch is committed to all facets of the hydrogen value chain, from developing an electrolysis stack and components for electrolyzers for H2 production, to engineering a drive solution for hydrogen compressors in filling stations. The supplier plans to invest nearly $2.6 billion between 2021 to 2026 in the development and manufacturing of hydrogen technologies – with nearly two-thirds of that amount devoted to the fuel-cell powertrain, Dr. Markus Heyn, chairman of the Mobility Solutions business sector, said during the Tech Day presentation.

“Bosch is entering the hydrogen economy in earnest,” Heyn said. By 2030, the supplier expects sales in the area to reach roughly $5.3 billion. One in five new trucks weighing six tons or more could feature a fuel-cell powertrain by 2030, he said. “In addition, we are working on a hydrogen engine that will be suitable above all for agricultural and construction machinery, but also for heavy long-haul trucks.”

Bosch’s plant in Bamberg, Germany, is supplying the Feuerbach factory with the fuel-cell stacks, and system components such as the electric air compressor and the recirculation blower come from its Homburg, Germany, site. Feuerbach then assembles and tests the complete system.

FCPM production also has started in Chongqing, China. The necessary components are supplied by Bosch’s plant in Wuxi. “Bosch is the first company to produce these systems in both China and Germany,” Dr. Stefan Hartung, chairman of the board of management, Robert Bosch GmbH, said at the event.

Bosch also plans to manufacture stacks for mobile applications in its U.S. plant in Anderson, South Carolina, possibly as soon as 2026, according to Dr. Alexander Klonczynski, VP manufacturing for fuel-cell power modules. Also in the U.S., Nikola will receive modules from Feuerbach, but it also expects to begin Bosch FCPM assembly itself in Coolidge, Arizona, by the end of this year. “This is a new business model for us,” Klonczynski said, which could be used with other customers in the future.

FC module details
Bosch can deliver the complete FCPM or individual components such as a hydrogen metering valve and an electric air compressor that supply the fuel cells with hydrogen and oxygen. “We have four production orders for the complete system, and further orders for our components,” Heyn said. “We are supplying truck makers in China, the U.S. and Europe. Our system has already clocked more than 2 million kilometers in pilot operation at our customers.”

In the initial stages, the Stuttgart-Feuerbach site will produce up to 5,000 modules per year at full capacity. “In the years thereafter, hopefully we will add another digit to that,” Heyn said. Bosch expects that China initially will show the strongest growth potential.

The Iveco Heavy Duty FCEV for the European market was on display at the Bosch Tech Day. With a payload of roughly 154 pounds (70 kg) of hydrogen from five tanks, the truck reportedly can travel up to 497 miles (800 km) without refueling. It takes about 20 minutes to refuel.

The fuel-cell power module comprises several hundred individual parts, weighs more than 1,102 pounds (500 kg) and has a surface area of roughly 161 square feet (15 square meters). The current module was designed to fit the envelope previously occupied by the truck’s combustion engine.

“The idea behind this [current system] was time to market. This is the ideal solution for existing new trucks, but we also are working on our next generation already,” said Hans-Joachim Schulz, director in product management. “Our second generation will be shorter in height – it will be flatter – and it will have the flexibility to put the modules side by side like here [on the current truck] or on top of each other, or to separate them even.”

The heart of the FCPM is the stack, specifically designed for commercial-vehicle applications. Several hundred PEM (polymer exchange membrane) fuel cells – 455, to be exact – are combined to form a stack, providing more than 100-kW net output (130-kW gross). Two such stacks comprise the FCPM, thus delivering more than 200-kW net (260-kW gross).

Peak efficiency of the stack is about 63%, according to Jan Buechner, product manager for the fuel-cell power module. “But you would not usually run the stack in that power area because that would be at relatively low power output,” he explained to SAE Media. “Usually, this system is run at about 40% power, if cruising on a highway – that’s the sweet spot. Then you get roughly 52% system-level efficiency.” For the next generation, Bosch’s target is to increase the efficiency by 3-5%, he said.

“Of course, in the future we see even higher power demand,” Buechner shared. “The question is how we want to achieve higher power output. We could increase the number of cells, increase the size of the actual cells, we could go higher with the current and so on. So, we are now investigating different possibilities.”

He added that Bosch already has received feedback, particularly from the North American market, to go up to 300 kW net with a twin system. “So, the stack would have to increase the [gross] power output to about 200 kW – it’s at 130 kW now – that’s the target,” Buechner said.

Smaller stack sizes also will be available for light commercial vehicle (LCV) applications, with 275, 335 or 419 cells. Each PEM fuel cell is roughly the size of an envelope and weighs less than 3.5 ounces (99 grams).

Age-defying developments
Bosch researchers are developing solutions that will help prolong the lifetime of PEM fuel cells, from its current 20,000 operating hours to as many as 30,000 hours in the future. “A lot of the aging is related to the catalyst particles,” said Thilo Lehre, project manager for fuel-cell research activities. “A lot of it is reversible. Some aging effect can be healed, so we are investigating specific healing conditions that we implement in our operation strategy.”

Electrochemical surface area is lost during operation because platinum particles and carbon supports oxidize and degrade. Platinum particles grow and catalyst layers become thinner, Lehre explained. Bosch researchers are working on homogeneous mixing of oxidation-stable catalysts with ionomers and defect-free coating of catalyst layers to combat the degradation. Healing can occur by removing oxide layers and adsorbed sulfonates from catalyst surfaces, he said.

System-level measures involve avoiding voltage fluctuations to enable steadier operation of the fuel cell at around 700-800 mV, Lehre told SAE Media. This is accomplished by using a small lithium-ion “buffer battery” to level out load cycling. “Hybridization of the powertrain helps to extend the lifetime of the fuel cell quite a bit,” he said. “And if you can operate the fuel cell at medium power, then the efficiency gets better, too.”

Lehre expects the anti-aging measures necessary to achieve a 30,000-hour lifetime to be implemented in the next generation, in the 2026-27 timeframe.

Keeping it in-house
Transferring technology and expertise from its established powertrain business gives Bosch a competitive advantage in the hydrogen market, according to Heyn. He specifically referred to Bosch’s systems know-how – the ability to control many components with sensor technology and complex electronics – and the ability to scale up new developments quickly into volume production.

“This is why we are also in demand in H2 production, where we are new to the market,” he said. “Plenty of companies can build electrolysis stacks in the laboratory. But only very few are capable of mass producing such stacks.”

Bosch intends to make 1.25-megawatt prototypes using proton exchange membranes available for electrolysis pilot applications starting this fall. The units, which can produce 23 kg (50 lbs.) of H2 per hour, are expected to be market-ready in 2025.

Bosch has modified processes from the manufacture of diesel and gasoline systems to produce fuel cells. “For example, laser welding is something we are familiar with from injector production. And whether in coating technology or leak testing, technology transfer is possible,” Heyn said. High-speed laser welding is used to make 1,200 meters (3,940 feet) of welds in each fuel-cell stack hydrogen-tight.

Maintaining in-house expertise in the hydrogen business is vital, according to Heyn. “Over the long term as well, we want more than half of the fuel-cell powertrain by value to be created internally,” he said.

The same standard applies for fuel-cell manufacturing and testing. Bosch Manufacturing Solutions supplies more than 50% of the required manufacturing equipment. The test benches in Feuerbach were developed by the Homburg-based Bosch subsidiary Moehwald.

H2 ICE innovation
Bosch engineers also are working on the hydrogen combustion engine, developing systems for both port and direct injection. This solution is particularly suitable for heavy-duty vehicles on long hauls with especially heavy loads.

“A hydrogen engine can do everything a diesel engine does, but on top of that, it is carbon neutral. This is a quick and cost-efficient way into the mobile use of hydrogen,” Heyn said, adding that more than 90% of the engineering and manufacturing technologies needed for it already exist.

Many of the systems components in existing powertrain solutions can be transferred to the fundamental structure of the fuel, air-supply and exhaust systems. While the H2 ICE still emits NOx, proven exhaust-gas treatment systems work to allow “no appreciable effect on air quality,” according to Bosch.

“The biggest technological challenge is the injector for direct injection,” Heyn explained. “Unlike in a diesel engine, it has to work without any lubrication from the fuel, and yet, just like in a diesel engine, still be capable of opening and closing billions of times over. Our engineers are in the process of solving this problem without any additional oil being emitted. Nobody else in the world has managed this so far.”

The first production vehicles equipped with these engines are expected in 2024. Bosch currently has four orders for production projects from various regions and expects six-figure unit volumes by the end of the decade.

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