This article is based on information published by Hyundai about their hydrogen fuel cell vehicle, the Hyundai NEXO.
Source: https://www.hyundai.news/eu/model-news/hyundai-nexo-cleans-over-900kg-of-air-during-clean-driving-month/
Executive Summary:
- Road traffic is responsible for emitting harmful gases and particles to the environment and people. These emissions come primarily from combustion, but also from other parts of the vehicle.
- The NEXO cleans about 900 kg of air per month, the same amount of air that an adult breathes in 60 days.
Development:
Before diving into the concept of an air-purifying vehicle, it is important for the reader to know the main emitters of harmful gases and particles in a vehicle.
These are: the combustion engine, during the reaction itself. The gases and particles are a result of the combustion process and are emitted into the atmosphere through the exhaust pipe. Another emitter of particles is the braking system, where the use of brakes wears down the brake discs/pads, generating particles that end up on the road. The passage of vehicles creates currents that can lift these particles, which may then be inhaled into the lungs.
Finally, it is important to mention the tires as another emitter. It is obvious that as tires wear down, the remnants must go somewhere. Like the previous case, they end up on the asphalt and consequently in the lungs.
Hyundai conducted a study on the streets of London for 31 days with the help of University College London (UCL) to determine how much air the NEXO could clean in a month. The result was 918.75 kg, the same amount of air an adult human breathes in 2 months or 1,455 people breathe in an hour.
During those 31 days, the car travelled over 560 km and cleaned the air as it drove through London’s most polluted streets. The map was selected in collaboration with UCL, which used open-source data from a pollution study by King’s College London that focused on solid particles and nitrogen dioxide (NO2).
Hydrogen cars are electric vehicles that produce electricity within the vehicle itself by combining hydrogen and oxygen to form water. The hydrogen they use is obtained at hydrogen stations (to learn more about them, see: https://leanhydrogen.whdev.es/sobre-hidrogeneras-y-electrolineras/), while the oxygen they need is obtained from the air.
Since the vehicle operates on pure oxygen, it must filter the air very well to prevent any particles from entering the fuel cell. Thus, the NEXO incorporates advanced air purification systems that filter 99.9% of the finest dust (PM2.5). These ultrafine particles are retained by the system, preventing them from returning to the environment.
The NEXO’s air filtration system uses three stages of filtering:
- External air passes through an advanced air filter where 97% of ultrafine particles, along with harmful gases like sulfur dioxide and nitrogen dioxide, are filtered and retained.
- The remaining particles are absorbed on the surface of the humidifier in the second stage.
- Finally, the air reaches the gas diffusion layer within the fuel cell stack. This layer is made of carbon fiber paper with a microporous structure that allows for greater filtration: the resulting air is 99.9% free of ultrafine particles and toxic gases.
All hydrogen car manufacturers, like Hyundai with the NEXO, are required to use air filtration systems before passing oxygen to their fuel cells. Therefore, it can be said that all hydrogen vehicles clean and purify the air. This is a very disruptive concept as it represents a paradigm shift; with hydrogen vehicles, road traffic can potentially become beneficial for cities.
Conclusions:
The hydrogen vehicle is seen as an interesting element from the perspective of improving air quality in cities and roads in general. It remains to be seen whether the filters neutralize the emissions generated by brake and tire wear. Will there be a positive balance for the air filtration system? And finally, what type of maintenance will these systems require?
We will try to answer these questions in future entries of our blog. Follow us and lean hydrogen.
