The war in Ukraine has upended Germany's energy policy.
The nation currently buys around 25% of its oil and 40% of its gas from Russia, contributing billions of euros a year to Moscow's finances.
Germany is moving "as fast as possible" to end that relationship, but it will take time, the country's finance minister recently said.
Veronika Grimm is an economics professor at the University of Erlangen-Nuremberg, and one of Germany's three special advisors to the federal government, called Economic Sages.
"We need to diversify and decarbonise our energy sources faster than initially planned," she says. To help achieve that goal, Ms Grimm wants the nation to "ramp-up" its use of hydrogen.
Hydrogen can store vast amounts of energy, replace natural gas in industrial processes, and power fuel cells in trucks, trains, ships or planes that emit nothing but vapour of drinkable water.
Ms Grimm's enthusiasm is gaining traction, according to the International Energy Agency (IEA), an energy research group, dozens of countries have published national hydrogen strategies, or are about to.
Despite this flurry of interest, it's not clear yet that the large-scale use of hydrogen can be made viable.
After all, there has been similar excitement before: in the 1970s, after two oil crises, and in the 1990s, when climate worries arose. But both petered out. So, is today's hype any different?
The answer depends on whom you ask. Environmental groups are cautious, they point out that hydrogen cannot be harvested as a primary fuel. Firstly, it has to be made, mainly in two ways, each marked by a colour code.
Green hydrogen is produced by using electricity from renewable power to split water into hydrogen and oxygen molecules using an electrolyser. But those machines and the electricity to run them remain costly.
These costs means that, at the moment, such emission-free hydrogen makes up only 0.03% of global hydrogen production, according to the IEA.
Up to five times cheaper is so-called grey hydrogen, this is derived from natural gas, or in some cases from oil or coal. But due to losses during production, about 50% more CO2 is emitted than if natural gas were directly burned.
A related technique is known as blue hydrogen. This relies on the same process, but captures about 60-90% of the carbon emitted in production for re-use or storage. The drawback with this method is that it roughly triples the cost. So, only 0.7% of globally-produced hydrogen is blue.
So, despite its environmentally-friendly image and potential, the global production of hydrogen currently emits almost three times as much CO2 as a whole country, France, for instance.
Much then will hinges on how countries decide to produce hydrogen.
Some countries already have a clear priority - to power electrolysers most sun-baked nations bet on solar power, while France relies on nuclear energy.
The US, Canada, UK, Netherlands and Norway are leading the push for blue hydrogen, by injecting captured carbon into oil and gas fields for long-term storage, or for so-called enhanced oil recovery that boosts extraction.
In Germany, however, the picture is less clear.
Volker Quaschning, professor for renewable energy systems at Berlin's University of Applied Sciences and criticises Germany's hydrogen strategy: "Merkel's government used it as a red herring to conceal its own failures in the energy transition."
He argues that solar and wind power should have been expanded faster to facilitate future green hydrogen production.
The three parties in government, the three responsible ministries and the hydrogen council all internally argue whether to concentrate as exclusively as possible on green hydrogen, or to accept the blue alternative, to temporarily bridge the gap in limited supply.
Ms Grimm represents the majority view on the hydrogen council in favouring a multi-colour mix.
"Accepting blue hydrogen will help create the supply that we need for a budding industry," she argues. "It will foster technological breakthroughs in Germany and encourage potential suppliers to invest in green hydrogen production."