Hydrogen as a pedalling aid

Hydrogen as a pedalling aid
Filling up with hydrogen instead of electricity: The e-bike relies on the fuel cell. Credit: Swiss Federal Laboratories for Materials Science and Technology

An e-bike fueled with hydrogen instead of electricity? No, this is not a utopia, but reality: industrial gas specialist Linde has developed a hydrogen pedelec equipped with a compact fuel cell instead of the usual battery. Florian Freund was inspired by the invention for his Matura thesis: He developed a prototype with which the hydrogen e-bike can be refuelled safely at the H2 filling station on the Empa mobility demonstrator move.

Florian Freund, a graduate of the Sumatra high school in Zurich, was already interested in energy as a child – from steam locomotives in museums to nuclear energy. But gradually he also developed an awareness of the disadvantages of fossil and nuclear energy technologies, especially the dangers of climate change. This motivated the young researcher to look into alternative energies for his Matura thesis. A topic was quickly found: The power-to-gas and technology should be – and at the end of the work something practical should be created.

Cycling with hydrogen

Fuel-cell vehicles are considered to be the hope of future mobility – and they are already in series production: In the Toyota Mirai, only water vapor comes from the exhaust instead of exhaust gas. At the mobility demonstrator move on the Empa, vehicles can be refuelled with produced by excess solar power. The journey can continue within minutes. A clear advantage over electric vehicles: If their batteries are empty, a longer break is required until they are sufficiently charged again. The same problem is familiar to e-bike riders: As practical as pedaling assistance is in everyday use – longer loading breaks are also required for longer distances. Could hydrogen also help out here?

Hydrogen as a pedalling aid
Credit: Swiss Federal Laboratories for Materials Science and Technology

Vienna-based gas specialist Linde Gas has developed an e-bike prototype that is equipped with a fuel cell and hydrogen tank instead of a battery. A tank filling of 33 grams of hydrogen gas should allow a range of more than 100 km. When Florian Freund heard about this concept, the practical goal for his work quickly emerged: a new refuelling concept for the hydrogen bike.

The e-bike's cylinder holds slightly more than 1.3 litres – which corresponds to around 33 grams of hydrogen at the planned cylinder pressure of 340 bar. According to the manufacturer's concept, the bike should be refueled from larger pressure bottles. Freund's idea: Instead of every bicycle owner having to store such a bottle at home, e-bikes could also be refueled at hydrogen filling stations that were actually designed for cars, such as the one at Empa's mobility demonstrator move.

However, this is not so easy: The filling stations are designed to fill the significantly larger tanks of a hydrogen vehicle – with a permanently programmed refuelling program that initially triggers a pressure surge at 440 bar pressure in order to test for possible leaks and to measure the existing pressure in the bottle. Only after this initial pressure surge does the normal refuelling process begin.

Hydrogen as a pedalling aid
A successful project: The prototype connects the filling station with the gas bottle. Credit: Swiss Federal Laboratories for Materials Science and Technology
From model to prototype

After having had to reject some concepts, Freund finally made his breakthrough during a discussion with Empa researcher Urs Cabalzar, who supported the young researcher: "We realized that the first surge of pressure was already enough to fill the bottle – provided the gas no longer flows back into the filling station afterwards," said Freund.

After some development work and with the support of the sponsor, the fluid system specialist Swagelok, this resulted in the prototype: A pressure regulator reduces the pressure surge from 440 to 275 bar. For practical reasons, this value is lower than the possible maximum cylinder pressure of 340 bar – the plug-in coupling used may only be used up to a pressure of 275 bar. A non-return valve installed in the pressure regulator ensures that the gas does not flow back to the filling station. Freund has also considered reinsurance: an overflow valve ensures that the gas is discharged at too high a pressure. Two built-in pressure gauges allow the regulator and the valve to be adjusted and the pressure to be monitored. The user can connect his bottle to the pressure regulator via a hose and a coupling.

After the graduate had completed his prototype and carefully calibrated it, the endurance test was carried out: he connected it to the Empa H2 filling station together with the bottle under the supervision of Urs Cabalzar. And the concept withstood the theory; the system started the refuelling process with the test pressure surge – and in three seconds the bottle was full.

A successful thesis—but is the principle of the hydrogen bike also suitable for everyday use? Florian Freund is – at least for the moment – still somewhat sceptical: "First, hydrogen technology would have to establish itself in regular vehicles in order for fuel cells to become cheaper and the refuelling infrastructure to be sufficiently dense. But then nothing would stand in the way of the new riding pleasure."


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Apr 18, 2018
A tank filling of 33 grams of hydrogen gas

The e-bike's pressure cylinder holds slightly more than 1.3 litres – which corresponds to around 33 grams of hydrogen at the planned cylinder pressure of 340 bar.


That much hydrogen contains 1 kWh of energy.

Meanwhile, a common 250 ml butane lighter refill bottle contains 2 kWh of energy, and the pressure in the bottle is little over 3 bars. Same thing for the camping gas containers found at every service station and general store.

With a different type of fuel cell (SOFC instead of PEM), you could go twice as far on 1/5th as much fuel in terms of volume, or with a bigger gas cylinder you wouldn't need to refill for weeks, and when you do you wouldn't need a special infrastructure because the fuel is already available everywhere.

Seriously. If 1 kWh of hydrogen gets you 100 km on an e-bike, then a simple lighter refill bottle will get you 200 km, and another one fits in your pocket. Why would you use hydrogen?

Apr 18, 2018
Because using fossil fuels is causing catastrophic climate change.

If you have a process to generate butane from non-fossil sources (say, using electricity from solar or wind to react water and CO2 from the air...), then go for it.

Otherwise, you're adding to the problem.

Apr 18, 2018

If you have a process to generate butane from non-fossil sources (say, using electricity from solar or wind to react water and CO2 from the air...), then go for it.


We do, and it doesn't need to be butane/propane as long as it's a liquid that can be easily turned to vapor. Ethanol would work even better.

And even if we use fossil fuels, bicycles consume so little energy that they hardly matter in comparison to motorcycles and cars, so the emissions would go down as people start to bike more. We're talking about machines with maximum motor output of 1/4 HP.

The main problem with e-bikes is the high price of the batteries - you may pay $200 for a basic bicycle, and $1000 for the electric version. The other thing is that you have to baby the batteries so you don't ruin the thing by leaving it out in the sun/rain. A simple gas cylinder doesn't mind.

Apr 18, 2018
If they can come up with one that would run either of my recumbent trikes both of which have 750+watt motor assist setups, I'm interested. I'm in the US. We have a bigger limit than 250 watts that is allowed in most of Europe. I would love to get away from batteries.


Apr 19, 2018
I'm in the US. We have a bigger limit than 250 watts that is allowed in most of Europe.


Assuming some realistic efficiency, the article seems to suggest the average power demand of a bicycle is on the order of 100 Watts, which isn't far from the truth unless you're in a hurry.

There's no reason why you couldn't get 750 Watts - the tank will empty faster though.

Apr 19, 2018
I ride faster than 5 mph and that's about all 100 watts would be good for with one of my trikes, if that much. Tanks can be refilled a lot faster than batteries can especially if they can make the fuel cell run on it.
I had a small gas engine on a trike that I converted to propane and I really liked that one. One small bottle held enough gas to run me all over town and the surrounding area and they are easy to refill from a 20lb or bigger tank too. A fuel cell would be nice and quiet and that would be even better.


Apr 21, 2018
I ride faster than 5 mph and that's about all 100 watts would be good for


The point of an e-bike is that you pedal too, and the motor just eases your load up the hills. You can count in another 100 Watts from your legs. With the required sensors, the motor is not on unless you pedal, and the torque it applies is proportional to the torque you apply to the wheels. Of course there are many different versions, but that's the basic one.

The 250 Watt limit in the EU countries is set around the average cyclist's 1-hour endurance limit, so an e-bike wouldn't be significantly out of pace with the average cyclist.

Apr 21, 2018
A bicycle can go fast, but it won't stop fast with the skinny tires and all, and it tends to be unstable and too flimsy for higher speeds. You're also liable to get speed-blind and get yourself into trouble among other pedestrian traffic and slower cyclists.

So it's not actually desirable to have exceedingly powerful e-bikes, unless you also upgrade the non-existent suspension and beef up the wheels for better braking and more predictable slip behaviour, or just to stop them from turning into figure-8s in a sudden pothole, which essentially makes it into an e-motorcycle.


Apr 21, 2018
Eikka, I'm disabled and have a bad leg. I can pedal about 50% of the time at best. I don't ride fast. Most of the time I ride about 12-15 mph. As a matter of fact, one of my trikes is mechanically designed so it can't go over 15 mph on motor only. The other one has a hub motor and will do about 25 mph for about 5 minutes on just the motor. At that point, the battery is generally down to 70% meaning dead so I don't do that. I haven't had any use for high-speed road bikes in the last 30 years since I was disabled. I ride a recumbent trike for all my transportation and that means being able to bring home a full grocery store cart full of food. Can't do that with a road bike. My website is https://www.packr...shop.com You can see the type of assisted trike I ride there. The point of an ebike is you can pedal or not unless it has a pedalec system where you have to pedal for the motor to work. I consider pedalec ebikes useless for me. Also, I use mag wheels. They don't taco.

Apr 21, 2018
Eikka, I don't mean to insult you but from reading both those messages of yours I would say you know very little about road bicycles and even less about electric or gas assist bicycles and trikes. I've been riding and working on bicycles for over 50 years now and I've been building custom bikes and trikes for the last 15 years. I DO know what I'm talking about.

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