(From left) Sung-Chul Jung, senior engineer - Fuel Cell Management Development Team, Duk-Hwan Kim, team leader - Fuel Cell System Engineering Team, Guk-Il Han, team leader - MEA Engineering Team

A Fuel Cell system generates electricity through the electrochemical reaction of oxygen and hydrogen, just as an engine generates power in a conventional car. Is there any risk associated with a Fuel Cell such as electric shock? The engineers at the Mabuk Technical Institute responsible for Fuel Cell development say “It is very safe.”

Q. The Fuel Cell system is at the heart of the clean operation of FCEVs. How is it kept safe?

Unlike, an engine a Fuel Cell system generates voltage electricity as high as several hundred volts, which makes electrical safety very important.

Fuel Cell structure

“Insulation has to be kept high in all areas so that electrical currents are kept within the circuit. The whole system also needs to be designed so that electrical currents flow through and out of the vehicle system without harming the people inside and outside. It is also equally important to make sure that no hydrogen is leaked.” In summary, ensuring electrical and hydrogen safety are both equally important. At the Institute, a comprehensive set of tests to check the basic performance, electrical insulation, airtightness to prevent hydrogen leakage, vibration, shock, water and dust, corrosion, extreme environment (low and high temperature, heat cycle) are conducted to ensure safety.

The Fuel Cell system is also tested repeatedly in extreme cold (-35℃) and extreme high (95℃) and humid conditions to ensure durability. NEXO’s Fuel Cell system warranty is 10 years or 160,000km whichever comes first. However, Hyundai Motor engineers are working to ensure that the Fuel Cell system lasts significantly longer.

Q How is Fuel Cell system safety testing done?

First, various standard tests for safety and durability are performed. Then additional tests for airtightness, insulation, and performance are conducted to ensure it meets the desired standards. The goal is to ensure protection and control of the Fuel Cell in all possible situations.

In reality, there could be hundreds of situations where the controller diagnoses and responds to a system malfunction detected by the sensors, such as an unexpected hydrogen leak or an unexpected high voltage current flow. The engineers must fully address all of these possible situations.

“A lot of complicated and detailed work is required, but we know that this is essential to ensure the safety of FCEVs. We are working towards making a hydrogen FCEV which exceeds the regulatory standards for conventional cars.”

Q. In the event of an external collision, how safe is it?

Providing the best possible protection for the driver and pedestrians, is the highest priority in the event of a collision. NEXO made significant improvements through various tests to minimize the risk of injury to both the driver and pedestrians and was able to receive the highest ？EURO NCAP？ safety rating, which was a first for a hydrogen FCEV.

Engineered to meet all general and hydrogen specific safety standards and regulations, the Fuel Cell system is designed to prevent harm to the driver, pedestrians, and rescue workers, even if it is damaged during a collision. “To improve safety, we have changed the material of the support brackets to prevent the Fuel Cell system from bouncing out of the car body during a collision. In addition, we have developed a lighter and safer Fuel Cell stack mount system made using both plastic and metal. A new structure (impact beam) was incorporated within the Fuel Cell stack to prevent deformation and electrical short-circuiting in the event of a collision. The Fuel Cell stack is also designed to lose high voltage charge quickly in the case of a serious accident.”

NEXO alerts driver with a warning light when there is any problem with the car.

Q. A Fuel Cell stack generates a lot of heat, how does this affect its durability?

Fuel Cells require stronger cooling than internal combustion engines because the performance of its electrolyte membrane is reduced at high temperatures. Therefore, the use of high durability materials resistant to high-voltage environments in the Fuel Cell stack is very important.

NEXO has a cooling system designed to maintain the internal temperature of the Fuel Cell stack below 85℃. The size of the radiator and fan were also increased to meet the high-voltage design specifications. Cooling performance was tested in places such as the Mojave Desert, where temperatures regularly exceed 40℃.

“Maintaining an optimal temperature is crucial to ensure performance. NEXO has been engineered to operate reliably in even the most extreme conditions, for example a cold start at -30℃ and places such as the Mojave Desert where ambient temperature reaches 45~50℃. While typical Fuel Cell systems often reduce their output when overheated beyond 85℃, NEXO’s Fuel Cell does not.”

Q. How was NEXO？s cold start performance improved from -25℃ to -30℃?

The outstanding cold start performance of NEXO was achieved thanks to a strategic control method which focuses on overall system efficiency while allowing rapid increase of the Fuel Cell stack to an optimal level. A separate bypass was added to avoid cold cooling water from passing through the stack. The waste heat from the stack is also used to charge the high voltage battery. This not only makes it possible to quickly start up in extreme conditions, but also increases energy efficiency. As a result, NEXO can be started within 30 to 40 seconds even if it is left for more than 24 hours in a - 30℃ environment.

The Fuel Cell stack consists of hundreds of cells, each consisting of an electrolyte membrane and catalyst, a fuel electrode (hydrogen), and an air electrode (oxygen). The performance of the cell in NEXO has been improved by 12.5%.

“First, the new cell has improved catalyst and electrolyte membranes. The separator and gas diffusion layer, through which hydrogen and oxygen pass, were redesigned as well. The gases can also be supplied at variable pressure levels as well unlike the old system which had to operate at atmospheric pressure level. The improved material and operation mechanism make NEXO a true next generation green car.”