Batteries (except flow batteries) must be scaled linearly with the desired storage capacity. Hydrogen storage on the other hand only requires a container to be scaled with the desired capacity (square-cube law) while the conversion machinery, i.e. the power rating of the storage, can be scaled independently.

Building batteries for seasonal energy storage would require huge amounts of raw materials. Building hydrogen storage requires nothing because you can reuse salt dome caverns previously used for natural gas.

> "Building hydrogen storage requires nothing because you can reuse salt dome caverns previously used for natural gas."

Note that at atmospheric (or any) pressure, the volumetric energy density of hydrogen gas is less than 1/3 that of natural gas. You would need 3.2X more salt cavern space to store the same amount of energy.

Yes - often, if you're starting from scratch. But for replacing natural gas (for example in domestic piped domestic heating) or coal (steel production) in the short term, hydrogen may be more cost effective.

To replace natural gas you're probably much better off using that hydrogen along with some CO2 and electricity to produce methane.

They'd probably have to convert it into methane or something for domestic gas heating. It's not really safe to have in houses.

The plan in the UK IIRC is to mix hydrogen (10-20% I think) into the existing mains gas supply to lower the carbon intensity somewhat, in the long term though we're trying to replace boilers with heat pumps for domestic housing.