This week, the Estonian government decided to provide tens of millions of euros in financial support for several green hydrogen-based projects. There are also plans to introduce a hydrogen-powered ferry on the route connecting some of Estonia's islands.

However, according to Oliver Järvik, associate professor at Tallinn University of Technology's (TalTech) department of energy technology, hydrogen is not especially well suited for use in the transport sector. "I'm not a big fan of using hydrogen in the transport sector. I don't foresee a very bright future," he said.

Hydrogen supply chains from production to the consumer are complex and therefore expensive, Järvik explained. This is mainly because hydrogen is the smallest of the elements in terms of atomic mass, therefore making it difficult to store.

"Its boiling point is very low. It is about 20 Kelvin, or minus 253 degrees Celsius. Storing hydrogen actually involves quite significant energy costs," Järvik said. In the worst case scenario, half the hydrogen kept in storage tanks could be lost, he added.

This also means hydrogen may not provide a particularly good solution for the power sector's concerns regarding having too much renewable electricity or not enough, depending on the weather.

Hydrogen can be produced if there is a surplus of electricity, but it cannot be stored for long periods in the same way as oil or shale oil, without also leading to major energy losses. It is also true that producing hydrogen requires a lot of electricity. In the transport sector in particular, safety is also concern when it comes to the use of hydrogen, said the TalTech lecturer.

"In the fuel tank where the hydrogen is stored, the pressure is somewhere between 200 and 300 atmospheres. If there are also any kind of micro cracks, small cracks, through which this hydrogen can escape, then there can be a small amount of static electricity, which creates a high risk of an explosion," Järvik explained.

Refueling a hydrogen car is also more complicated than refueling a regular gasoline-run vehicle. "There have to be compressors, then there are intermediary coolers, after which there is compression again, or pressurization, and then cooling before that goes into the car's tank," the professor said.

Hydrogen pumps are also a lot more complex than regular gasoline pumps. It can for instance take around five minutes to fill up a hydrogen-fueled Toyota car in Estonia.

However, hydrogen may be better suited for use in trucks than the heavy batteries needed for electric motors, Järvik said. "Hydrogen cylinders, which  unlike batteries, don't weigh very much - we could add these and change the range of the mileage. That would certainly be an alternative."

Above all, green hydrogen is highly important for the chemical industry. "Certainly, it is used there a lot and will be used more and more in the future," Järvik said.

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