Hydrogen gas

Hydrogen gas (H2) is a fuel that when burned, produces no pollution and no carbon emissions - only water vapor (H2O). Just one problem: There are no natural resources of hydrogen gas.

To make hydrogen gas, you need to use some other energy source.

Production

Electrolysis

Electricity can turn water (H2O) into hydrogen gas (H2) and oxygen gas (O2).

The electricity could come from renewable sources such as solar, wind, or hydro.

Research needed

Can electrolysis be done efficiently on a medium scale, for example using the energy from a rooftop of solar panels?

Are rare minerals needed to make efficient electrolysis machines? If so, which minerals and how much of them; what are the different options?

From fossil fuels

Hydrogen gas can be made from natural gas (methane/CH4). The problem is there's currently no way to do this without also releasing CO2. It's not any greener than burning natural gas directly.

This is how most hydrogen gas is produced today.

Uses

Most hydrogen gas today is used in making fertilizer.

But in the future it could also be used for:

The general idea would be to use surplus electricity to generate hydrogen gas, and then use it as a fuel later.