Two technologies compete for zero-emission cars: on the one hand, the electric car with batteries; on the other hand, the car that uses hydrogen as fuel. But are these vehicles really ecological? Which is more virtuous?
Theoretically, the electric car and the hydrogen car are two zero technologies carboncarbon : the electric motor moves the car forward while thehydrogenhydrogen reacts with oxygen to generateenergyenergy and water in one Fuel cellFuel cell. Each technology has its advantages and disadvantages: on the one hand, the electric car is easier to maintain and entails less risk of storage, on the other hand, hydrogen provides greater autonomy and charges faster. But what about ecologically? Are the electric car and the hydrogen car really that clean?
According to the Canadian Hydrogen and Fuel Cell Association, the total carbon footprint of the hydrogen car would be much better, with a carbon footprint of 2.7. kgkg from CO2 per kilometer, compared to 20.9 kg of CO2 per km by electric car. One of the arguments put forward by the association is the weight of the batteries: the battery of a Tesla 3 therefore weighs 480 kg, compared to 88 kg for the tank of a hydrogen Toyota Mirai. The hydrogen car also requires less infrastructure (charging stations).
Energy efficiency: advantage over electric
But for Tom Baxter, a professor of chemical engineering at the University of Aberdeen, this assessment is biased because the association compares hydrogen produced from renewable sources such as wind power to an electric vehicle powered by energy. fossilsfossils. The researcher therefore calculated the energy efficiency of each technology, and the advantage is clearly in favor of the electric car.
“Hydrogen vehicle: in the end only 38 watts of the initial 100 watts are used”
” Let’s take 100 wattswatts electricity produced by a renewable source such as a wind turbinewind turbine. To power a fuel cell vehicle, this energy must be converted into hydrogen [par exemple par électrolyseélectrolyse, ndlr] During this step, about a quarter of the electricity is lost. The hydrogen produced then has to be compressed, cooled and transported to the hydrogen station. We lose another 10% of energy. Once in the vehicle, the hydrogen is converted into electricity and is further once 40% of energy is lost. Finally, 5% of energy is lost when electricity is used in the engine to move the vehicle.” In the end, only 38 watts of the starting 100 watts are used concludes the researcher.
In comparison, the electric car loses about 5 watts during transport in the network, 10 watts when charging and discharging the battery and 5 watts when moving the vehicle. The total efficiency is therefore 80%. An analysis by Horváth & Partners quoted by Volkswagen comes to similar conclusions, with an energy efficiency of between 25 and 35% for the hydrogen car versus 70 to 80% for the electric car.
Global carbon footprint: advantage over hydrogen
When the whole life cycle of the car is taken into account (manufacture, use, recyclingrecycling and end of life), Deloitte calculates that the ecological footprintecological footprint of the hydrogen car is 130 to 230 grams of CO2 per km compared to 160 to 250 g for the electric car and 180 to 270 g for a car with combustioncombustion (petrol or diesel). A difference mainly due to the production of batteries, the extraction of lithiumlithium and from metalmetal rare because it is particularly energy intensive. But again, it all depends on how the electricity is produced: Deloitte relies on the energy mixenergy mix present, which is still mainly based on the fossil fuelsfossil fuels (62% in 2019). When electricity is generated with wind, solar or nuclear energy, the balance is much more favorable for the electric car.
Costs and infrastructure: advantage of electric driving
The argument ofecologyecology is not the only advantage of the electric car. The latter would also be much more economical, with a cost of 2 to 7 euros per 100 km, compared to 9 to 12 euros per 100 km for the hydrogen car. Similarly, the electric car would be much cheaper to maintain. In addition, installing electric charging stations is cheaper than deploying a network of hydrogen stations.
According to Dietmar Voggenreiter, head of the study at Horváth & Partners, hydrogen will only be of interest in vehicles that need a very long range, such as trucks and buses, because the weight of the electric battery will then become prohibitively expensive.
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