# Could Formula E cars run on hydrogen?

*Note: I did not research hydrogen-powered racing before writing this article; I wanted to use deductive reasoning and napkin math to satisfy my curiosity*

I was curious what Formula E would be like with a fuel cell instead of batteries, so I calculated the energy storage of various cars using different fuels just for giggles.

## Energy storage of various vehicles

A 2nd generation Formula E car has a 54 kW h battery. (I prefer kW h over MJ #sorrynotsorry)

A street-legal Honda Clarity FCEV holds 5.46 kg of compressed hydrogen gas, or 214 kW h:

$$5.46~\text{kg}~\text{H}_2\cdot\frac{1000~\text{g}}{1~\text{kg}}\cdot\frac{1~\text{mol}~\text{H}_2}{2.016~\text{g}}\cdot\frac{285~\text{kJ}}{1~\text{mol}~\text{H}_2}\cdot\frac{1~\text{kW h}}{3600~\text{kJ}}\approx214~\text{kW h}$$

A 2020 F1 car holds 105 kg of premium gasoline, or 1 321 kW h:

$$105~\text{kg}~\text{gasoline}\cdot\frac{1~\text{L}}{0.75~\text{kg}}\cdot\frac{9.5~\text{kW h}}{1~\text{L}}\approx1~321~\text{kW h}$$

## Efficiency and power output

Fuel cells are only 60% efficient according to the US Dept. of Energy [1], but that’s still ~2.5x the usable amount of energy as a current Formula E car (ignoring the real battery’s internal resistance, so the actual number is even better than 2.5x).

The Clarity’s fuel cell outputs 100 kW continuous, and only weighs 52 kg. [2] It uses a 1.7 kW h buffer battery to feed the motor, which is similar to the 1 kW h accumulator F1 cars use for their MGU-K boost motor. Formula E cars use their 54 kW h battery for a 45 minute race, so the average power is 72 kW:

$$\bar{P}=\frac{54~\text{kW h}}{0.75~\text{h}}=72~\text{kW}$$

The Clarity fuel cell’s average power output should be sufficient for a race, but the Formula E car would probably need a larger supercapacitor to handle the 250 kW bursts. Luckily, the 52 kg fuel cell would be replacing a 250 kg battery, so there should be plenty of room for a capacitor energy store.

## Safety

Safety is a huge consideration with hydrogen fuel. F1 cars put their fuel tanks inside the monocoque (“safety cell”), behind the driver’s seat. The system isn’t foolproof; when Romain Grosjean crashed in 2020, his fuel system burst and there was a huge fire. Hydrogen could be a potential safety upgrade: Toyota shot their hydrogen tank with a .50 caliber round and it didn’t explode. [4] A fuel cell electric vehicle doesn’t have a hot exhaust to serve as an ignition source, and there isn’t 105kg of gasoline ready to coat the driver in case of a tank failure; hydrogen is the lightest gas/element in the universe. One safety hazard is water production: a Honda Clarity outputs roughly 50L of water per tank of hydrogen, which would need to be dumped somewhere other than the racetrack.

## Conclusion

With some modification, the hydrogen power source from a normal Honda Clarity should be sufficient to power a Formula E car. The higher available energy could lead to faster, longer, and more exciting races, and street-legal spec powertrains would further the FIA’s goal of using Formula E as a laboratory to develop more environmentally-friendly street cars. To be clear, I’m not advocating for hydrogen as a replacement for battery electric vehicles or hybrids; this is just a thought experiment about electric racing.

[1] https://www.energy.gov/sites/prod/files/2015/11/f27/fcto_fuel_cells_fact_sheet.pdf

[2] https://owners.honda.com/vehicles/information/2019/Clarity%20Fuel%20Cell/specs#mid^ZC4F8KGNW

[3] “Honda FCX platform rear Honda Collection Hall” by Morio is licensed under CC BY-SA 3.0.

[4] https://www.youtube.com/watch?v=jVeagFmmwA0

[5] “Formula E Car” by Dave Hamster is licensed with CC BY 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by/2.0/

Last modified: 03/01/2021