6.5 Hydrogen

Hydrogen (H₂) is a clean-burning fuel, whose only combustion product is water. It is currently produced for industrial processes (particularly agricultural fertiliser manufacture) by a range of processes and they are increasingly being described in terms of their ‘colour’:

• black hydrogen is produced from coal
• grey hydrogen is produced from natural gas
• blue hydrogen is produced from natural gas but using carbon capture and storage (see section 6.10) to reduce the overall CO₂ emissions
• green hydrogen is produced using renewable energy (usually by the electrolysis of water)
• pink hydrogen is produced from nuclear electricity, again by the electrolysis of water.

Hydrogen is currently being used in transport applications using fuel cells. These can be thought of as a form of ‘gas battery’ which produces electricity when fed with a supply of hydrogen and oxygen (from the air). Fuel cell powered electric buses are currently (2024) widely in use in cities such as London. In Germany some rural train services now use hydrogen fuel cells to provide their power. Although some fuel cell cars have been produced, so far their use has been limited by the need to provide adequate hydrogen filling points at conventional petrol filling stations.

Hydrogen could potentially be used as a domestic piped heating fuel substituting for natural gas, but it is more likely that electric heating using heat pumps will dominate in the UK.

Its most important role is likely to be as a form of energy storage to cover periods when solar and wind powered electricity supplies are not adequate. A whole infrastructure will need to be developed for converting surplus renewable (and nuclear) electricity into hydrogen by the electrolysis of water. This will need to be coupled with large scale hydrogen storage and large scale electricity generation using hydrogen. This is likely to use combined cycle gas turbine (CCGT) technology, as currently used in natural gas fuelled power stations.