The rise of the eMachines: Part 5: Hydrogen (H2)

By Tom Denton, Automotive Author

In this, the fifth in a series of articles, exclusive to Automechanika’s auto:resource, I will look in particular at hydrogen vehicles, and the suggestion from many, that they are the way forward rather than EVs. You may not agree with everything I say, and that’s fine, I may even be wrong – so let’s debate.

If you haven’t yet read them, parts 1-4 can be found HERE

Hydrogen is the lightest element, so this article is shorter than the others.

Figure 22 Hydrogen logo

The lightest gas

Hydrogen (H2) can be produced from fossil fuels. Or better, electricity from nuclear power or renewable resources, can be used to create hydrogen by electrolysis of water. At the moment, it is predominantly obtained by steam reformation from natural gas, but this method means that overall, the CO2 produced is about the same as conventional petrol or diesel engines. However, electrolysis from renewable sources is becoming more common.

It can be used in fuel cells to power electric motors or burned directly in internal combustion engines. Fuel cells are the much-preferred option as they are more efficient. Hydrogen is an environmentally friendly fuel, at the point of use, as it only produces water as a by-product.

Figure 23 Hydrogen filling station

Hydrogen has a very high energy density that is almost three times that of petrol. However, it does have to be compressed to between 350 and 700 bar or liquified at -253 Celsius to achieve a suitable tank volume for a normal vehicle.

Fuel cells

The key component of a fuel cell electric vehicle (FCEV) is the fuel cell! Proton-exchange membrane fuel cells, also known as polymer electrolyte membrane (PEM) fuel cells (PEMFC), are the type mainly used for transport applications. They use a special proton-conducting polymer electrolyte membrane.

Fuel cells produce electricity through the reaction of a fuel with oxygen. Hydrogen-oxygen fuels cells use hydrogen as the fuel. Water is the only waste product from this type of fuel cell. The reaction between hydrogen and oxygen is exothermic, in other words it releases energy, which can also be used.

Figure 24 Fuel cell in position on a Mirai (Source: Toyota Media)

Fuel cells use this reaction between hydrogen and oxygen to produce electrical energy. They convert a large proportion of the chemical energy into electrical energy so are very efficient.

Gas, gas, gas

For me hydrogen is not the future for cars, larger vehicles such as buses and trucks maybe, but not cars. Why I hear you ask!?

Something that I think is often forgotten, is that a hydrogen car is an EV – but with considerable added complexity. FCEVs have a lithium-ion battery and all the other components that a BEV has, but they also have to have a fuel cell stack, fuel storage tanks and associated delivery systems. This is reflected in the cost.

There has to be a specific infrastructure at fuel stations and the fuel has to be delivered and pumped. Hydrogen uses a huge amount of energy as it is being created and compressed. By comparison, delivering electricity to a charger is almost lossless.

Figure 25 Toyota Mirai electrical and hydrogen systems (Source: Toyota Media)


If the energy to create hydrogen is from nuclear or renewable sources, then the carbon footprint could be good. But remember all those arguments about BEVs creating more CO2 during their construction phase? It is the same and more for FCEVs. Long term they would still be much better then ICE but for me the technology is far better suited to larger vehicles.

Creating hydrogen when a wind or solar farm is producing more electricity than is needed, could be an ideal storage solution. Some of the truck refuelling stations could be close to where the hydrogen is created to reduce deliver costs.

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