Can hydrogen help decarbonize cars?

Hydrogen is often touted as an energy solution for the transition, and ideas for its use are multiplying, particularly in the mobility sector. In early September, for example, BMW announced that it would produce its first production model in 2028 in partnership with Toyota. But is it really appropriate to automatically turn to hydrogen for every mode of transportation?

Hydrogen may be “low-carbon,” but today it is mostly derived from fossil fuels and is therefore carbon-based

First of all, hydrogen is not a form of energy in and of itself, but an energy carrier—that is, it is produced from energy sources. And it is not necessarily low-carbon; it is currently produced from 98% fossil fuel resources, through methane steam reforming and coal gasification (accounting for 71% and 27%, respectively, of the hydrogen produced worldwide^[1]).

Low-carbon hydrogen is produced by electrolysis of water, using electricity that is itself carbon-free^[2]. In fact, To be considered low-carbon, production emissions must fall below the carbon footprint threshold set by the European Taxonomy 3 kgCO2e/kgH2, which corresponds to the carbon content of the electricity less than60 gCO2e/kWh, which is currently the case in only a few countries. France is one of the countries where direct power generation from renewable energy sources (RES) is possible.

While more and more projects using renewable electricity are being developed to produce this “green” hydrogen, the Nevertheless, production volumes remain very limited today in the face of growing demand, not to mention the existing uses that need to be decarbonized!

In the transportation sector, hydrogen is not very energy-efficient

The hydrogen car is equipped with an electric motor, such asan electric car.It is the energy storage system that distinguishes these two types of vehicles. Electric cars store electrical energy in batteries, which have low energy density, whereas hydrogen cars store energy in the form of hydrogen gas in a tank and convert it into electricity via a fuel cell to power the motor. The “conversion” of electricity into hydrogen during electrolysis, followed by its “reconversion” back into electricity on board the vehicle, results in efficiency losses that make Hydrogen-powered vehicles are less efficient than electric vehicles. That is why, to travel the same distance, you have to ~3 times more electricity for a hydrogen-powered car than for an electric car.

This implies two things: first, It costs more to drive a hydrogen-powered car than a battery-powered vehicle. (because of the higher amount of electricity); and second, The carbon footprint of a hydrogen-powered vehicle is three times more sensitive to the carbon content of the electricity. And in the case of hydrogen production above the European taxonomy threshold (e.g., electrolysis using the German electricity mix), the decarbonization benefit is effectively nullified (-9% compared to a diesel car).

Conclusion: Its use should be reserved for heavy-duty transportation.

Hydrogen-powered vehicles are therefore less economical; they only reduce carbon emissions if the electricity mix is very low-carbon, and they consume a great deal of energy—even though low-carbon electricity is, in fact, a limited resource that is already in short supply today. Therefore, its use must be restricted to certain use cases where charging and battery life constraints are very significant (for example, when the user travels more than 250 km per day) and has a limited time to recharge their vehicle (less than 1 hour available), which justifies using a vehicle that consumes much more energy. And they must be prepared to bear higher costs (both purchase and operating) (+40% compared to electric vehicles) and ensure the availability of H2 stations along their route. In practice, this applies only to niche markets for light-duty vehicles (e.g., taxis or ambulances outside urban areas), and rather, heavy-duty vehicles for long-distance travel, as the association also points out France Hydrogen. Since low-carbon hydrogen is a limited resource, it may prove particularly valuable for decarbonizing certain sectors—such as steel and fertilizer production, as well as air and maritime transportation—because hydrogen is needed to produce carbon-free synthetic fuels (or e-fuels) (see article).