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Hyundai KEFICO’s Air Cut-off Valve, the Next-generation Technology for More Powerful and Efficient FCEV


Introducing Hyundai KEFICO’s air cut-off valve, a technology for higher power of FCEV.

As all major automakers accelerate their transition to green vehicles such as EVs and FCEVs, Hyundai Motor Group announced ”FCEV Vision 2030” and has developed a variety of advanced FCEV technologies. The Air Cut-off Valve is one of the FCEV technologies that Hyundai KEFICO is currently focusing its development efforts on.

What does the Air Cut-off Valve do in a hydrogen FCEV system?

The valve shuts off the air intake and the exhaust of the fuel cell stack when the FCEV is turned off, preventing corrosion due to a chemical reaction between the fuel cell and air left within the stack. It is designed to enhance the longevity of the fuel cell stack. Hyundai KEFICO’s Air Cut-off Valve, which is used in the Hyundai Motor’s FCEV NEXO, has a bypass* which works to reduce the hydrogen concentration to meet regulatory standards.
*Bypass: A system of pipes designed to divert the flow around the main pipe

Why the bypass was added?

FCEVs need to be supplied with high purity hydrogen, yet it is common for impurities such as nitrogen to be found in the hydrogen supply. ”Impure hydrogen” needs to be discharged from the vehicle for energy efficiency at a concentration below the regulatory level of 4%, which requires supply of a high volume of air at a high speed. However, this can cause the fuel cell stack become overly dry. The bypass allows the release of impure hydrogen without contact with the fuel cell stack, thereby preventing it from drying out.

When did Hyundai KEFICO start the development of the Air Cut-off Valve?

The Air Cut-off Valve is one of the important components that determines the durability of the fuel cell stack.

It began in early 2016 when we were developing the Air Pressure Control Valve for FCEVs. During our detailed analysis of the FCEV system, we realized the need for a valve that cuts off the air in order to enhance the longevity of fuel cell stack. The key to ensuring durability of the fuel cell stack is to improve the sealing efficiency of the Air Cut-off Valve. We thought we were capable of doing so using the experience and knowledge we have gained from previous valve development.

What makes Hyundai KEFICO’s Air Cut-off Valve stand out from the competition?

Sealing ability, which is how completely the air is sealed off, is the core technology of the valve. There are two factors that are important in determining the sealing ability, the “optimized rubber sealing shape” and the “high-precision pressure control,” both of which Hyundai KEFICO has significant expertise in. So, we have made a remarkable improvement in sealing and further, developed the technology to control both the intake and exhaust channels using a single motor.

The Air Cut-off Valve is employed in NEXO. What was the biggest challenge during the NEXO project?

We did make progress in sealing, yet the rubber part was not as durable as it needed to be, showing wear and tear after repeated use. There were ways to make the rubber part more durable but applying these technologies meant reduced sealing ability. Fortunately, we were able to develop optimized rubber sealing shape technology which made it possible to achieve both an excellent sealing ability and to meet our durability target.

I was told that KEFICO is working on components for the next-generation high-power FCEV system. What is the idea behind the development and goals? Can you share the current progress of the project?

We are currently involved in the development of a more powerful next-generation FCEV system. Improving the sealing ability of the Air Cut-off Disc and developing a locking mechanism to increase the security of the seal is the main development goals. We have already achieved our target in sealing ability and plan to begin running durability tests at the end of this year. We have begun a design concept review of the locking structure with the goal of completing development until next year.

Interview. Senior Research Engineer Ung-rae Cho, Product Design Team 2 at Hyundai KEFICO