Researchers in Germany may have finally solved a bottleneck that has been halting the progress of hydrogen power tech for years. Instead of storing hydrogen in cumbersome tanks, the researchers have proposed utilizing a magnesium-based paste that can store hydrogen energy at 10 times the density of a lithium battery.

The adoption of electric vehicles is growing at a breakneck pace — and I think we’re all very happy to finally see this transition away from fossil fuels. The same can’t be said about hydrogen-powered vehicles, unfortunately.

In the early 2000s, many companies and institutions, particularly in the US-backed by the Bush administration, were very optimistic about the impending “hydrogen revolution”. It soon became clear, after billions in botched investments, that hydrogen’s disruption of the transportation sector was not as straightforward as some might have hoped.

The overarching challenge is hydrogen storage within the vehicular constraints of weight, volume, efficiency, safety, and cost. While hydrogen gas itself is lightweight (it’s the lightest element in the universe) and has a phenomenal energy density — both ideal qualities you want to see in a transportation fuel — containing the gas requires expensive bulk storage.

The weight and volume of the systems required to store hydrogen are challenging to design in such a way as to enable a range greater than 300 miles. A refueling time of under 5-10 minutes is also difficult to achieve.

Just imagine that if a fuel cell car were to use atmospheric pressure to store the 1kg of hydrogen needed to drive 100km, the fuel tank would have to be 11 cubic meters in size. So today’s fuel cell cars use compressed hydrogen gas, squeezing about 5kg into a 700 bar carbon fiber reinforced tank.

Although they’re made of carbon fiber, these tanks are still hefty. If there was a way to store hydrogen more compactly, hydrogen could take off in the transportation space, perhaps even surpassing electric vehicles.

Researchers at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Dresden are proposing an alternative storage medium for hydrogen.

Although it looks like a sticky construction works material, the sludgy-like paste is in fact a high-density hydrogen fuel. The researchers combined magnesium and hydrogen at around 350 °C (662 °F) and five to six times atmospheric pressure to form magnesium hydride. They then added an ester and metal salt to form a viscous goop known as “Powerpaste”.

According to the researchers, the paste can be loaded into cartridges that can be easily and quickly replaced to restore power. The paste is stable at temperatures up to 250 °C (482 °F) and can carry much more energy than a conventional hydrogen tank of the same weight. As such, a vehicle running on Powerpaste could expect to reach an autonomy comparable to — perhaps even greater — than a gasoline-powered vehicle.

The hydrogen is released from the cartridge when the paste is placed in a chamber where it reacts with water at a controlled rate. Half of the hydrogen that eventually reaches the fuel cell comes from the water the paste reacts with, which partly explains the high energy density of this system.

“POWERPASTE thus has a huge energy storage density,” says Marcus Vogt, research associate at Fraunhofer IFAM. “It is substantially higher than that of a 700 bar high-pressure tank. And compared to batteries, it has ten times the energy storage density.”

The researchers in Germany envision the first use of Powerpaste as fuel for e-scooters, for which hydrogen tanks are totally impractical. Similarly, it could also extend the flight time of large drones, which could be able to operate for hours instead of 20 minutes as per current limitations.

Of course, the paste is an appealing option for cars as well because you don’t need dedicated hydrogen infrastructure for recharging. In places lacking hydrogen infrastructure, refilling stations could sell Powerpaste cartridges or canisters. Since the paste is fluid and pumpable, it can be supplied by a standard filling line using readily available, cheap materials.

A pilot production plant for Powerpaste is currently in development by Fraunhofer IFAM. The German research institute expects the project to commence production in 2021, with an estimated yield of four tons of Powerpaste per year.