24 juin 19

Is hydrogen a safe fuel for your fleet?

Last week, a powerful explosion at a hydrogen filling station near Oslo, Norway, caused considerable damage to cars and infrastructure, but fortunately no-one was injured. Earlier this month, another explosion occurred when a hydrogen tanker truck was being fuelled in Santa Clara, California.

Two incidents in such a short timespan are raising questions about the safety of hydrogen as a fuel for fuel cell vehicles (FCEVs), which today are pretty scarce on European roads but are believed to play an essential part in future emission-free mobility.

So far, only Asian car manufacturers are truly convinced of that: Hyundai, Honda and Toyota. Other OEMs are waiting to see which way the cat jumps and prefer putting their money on battery-powered vehicles and plug-in hybrids to reach emission targets.

Still, H2 is definitely happening in China, which wants to become the world’s leading hydrogen-based economy. The Chinese government is reportedly committing resources to developing fuel cell vehicles while planning to phase out the long-time subsidy programme for the maturing EV industry next year. If things get going in the People’s Republic, there is no doubt that the hydrogen wave will spread to the rest of the world.

Hydrogen: not to be messed around with

But how safe is hydrogen really? To answer this question, let’s take a closer look at its chemical properties. Hydrogen (H2) is the smallest molecule on the planet. That means it escapes from any container more easily than oxygen (O2) and nitrogen (N2), for instance – the two main components of air. On top of that, hydrogen must be stored at high pressures, making it very difficult to avoid leaks.

Moreover, hydrogen is highly flammable. The biggest risk is static electricity – something that was probably the cause of the explosion in California – which is why earthing the container is so crucial. Static electricity is created when you transfer gas from one container to the other – basically, when you fuel a vehicle.

Another problem is that hydrogen gas heats up when it expands quickly – something that happens when you have a sizeable leak. In such a case, the heat can cause the gas to spontaneously combust. That may have been why the filling station in Norway exploded.

No such thing as an explosion

Is the future of the fuel cell vehicle at stake? “I don’t believe so. It’s not because of two probably unrelated and relatively small incidents that we should shut everything down,” says Mark Pecqueur, Automotive Research Developer at Thomas More University of Applied Sciences.

“Actually, the Oslo incident was not so much an explosion as it was a powerful and fast combustion – which is typical of hydrogen. Under atmospheric pressure, hydrogen quickly evaporates because it is much lighter than air, creating a vertical gas bubble, so to speak. When ignited, it therefore creates a vertical rather than a horizontal combustion. When something goes wrong, hydrogen is relatively safe because of this. If it was the reservoir itself that had ignited – something that is extremely unlikely to happen – then it would have been a true explosion, with an impact many times greater,” the hydrogen expert explains.

Accidents we can learn from

Hydrogen technology is still under development and like in any industry, accidents will happen. Pecqueur compares it with aviation: “Today, flying is incredibly safe, but it took a few crashes and near-misses to expose weaknesses in aircraft design, air traffic protocol and maintenance procedures, for instance. I am sure we will learn from the incidents in Norway and California and as such, these incidents will not stop fuel cell vehicle development, but indeed make the technology safer than it already is.”

People who already drive a fuel cell vehicle such as the Hyundai ix35 FCEV, Hyundai Nexo or Toyota Mirai need not be alarmed, even though both OEMs have suspended the sales of their FCEV models in Norway. It is a precautionary measure pending the results of the investigation.

Authored by: Dieter Quartier