City bus runs on formic acid

Remarkable innovation improves air quality
Research & Analysis
11 September 2017

Clean air is one of the spearheads of Air Liquide’s sustainability strategy. The company is working hard on various solutions that will improve air quality. One of these – a revolutionary city bus that runs on hydrozine – is being developed by Team FAST.

Air Liquide not only brings its own innovations in sustainability, it also sponsors promising projects of universities, such as the hydrozine city bus of Team FAST (Formic Acid Sustainable Transportation).

Team FAST is a spin-off by the Eindhoven University of Technology that consists of approximately 35 students. The team is working on a city bus that runs on hydrozine, a liquid that is 99%* formic acid (also known as methanoic acid).


Hydrozine as a power source

Hydrozine is not a fuel in itself, but it becomes one when a reformer splits the hydrozine into hydrogen and CO2. The hydrogen is then fed into a fuel cell where the conversion to electrical current takes place. The propulsion system built by Team FAST for the city bus develops 25 kW of power, which corresponds to a power output of 30 to 35 hp. This is sufficient to power a bus, albeit not with neck-snapping performance.

CO2 neutral and safe

The current version of the system consists of a hydrozine tank, the reformer and the fuel cell. It is still a little too bulky so it is placed in an integrated towed trailer known as the REX, an acronym for Range Extender. In the test project now underway, the system does indeed act as a range extender for the electric bus manufactured by the Dutch coach builders VDL. The formic acid in the REX contributes an additional 200 km of driving range.

Because the hydrozine/REX system is CO2 neutral, sustainable and safe, this technology has a genuine potential to improve air quality in cities and municipalities. It also has a number of practical advantages, among them the fact that the energy density of the liquid hydrozine is four times greater than that of a conventional storage battery.

The city bus project is still in the test phase, but the team has already used the same technology to get a one metre long scale model of a Porsche 911 sports car up and running. Team FAST opted to develop this system for a city bus since there are presently few viable and sustainable alternatives in that transport segment. Bus companies are certainly interested in a renewable energy drive systems, especially if they offer a driving range of 400 km and can be refuelled quickly.

A battery for hydrogen?

André Vredenburg, Research & Analysis Sales Representative at Air Liquide explains: “Generating green energy by cleverly using natural resources such as the sun, wind and water is a considerable challenge, especially if we want to do it in a truly sustainable and economically viable manner. Storing and transporting that energy to the right place in a timely manner is one of the major difficulties. The use of hydrozine as a hydrogen carrier can be envisioned as a kind of hydrogen battery. It is without doubt an impressive and promising innovation that makes it possible to fill a vehicle with high-density energy.”

Volgende stap: operationeel REX-prototype

“We keep an open mind and examine all relevant developments that can improve environmental air quality.

Our efforts are focused on improving efficiency, both technically and economically. We are always ready to work with universities and students since they are helping shape the future.

Our participation in this project has been very satisfying and we are looking forward to more such opportunities.

It is hoped that by the end of this year, Team FAST will have an operational REX prototype. Once we’ve reached that point, we will explore the role Air Liquide can play in the further development of this special technology.”


* The remaining 1% is an additive that allows the formic acid to be used even at low temperatures.

Learn more about hydrozine as a source of electricity

Contact our specialist André Vredenburg: ✉