Hydrogen

Hydrogen is only a low-carbon fuel if it is produced in a low-carbon way. There are no significant natural stores of molecular hydrogen on Earth; it needs to be made. It can be made by using energy to ‘crack’ it out of fossil methane. This is called ‘grey’ hydrogen, and is little better from a climate change point of view than using the fossil methane in the first place, as energy is needed to do the cracking, and the carbon from the methane is released as part of the process. A better method is to perform the same process, but to fit carbon capture and storage (CCS) to the plant, capturing the emitted greenhouses gases. This is called ‘blue’ hydrogen and has a much lower (~80%), but not zero, carbon footprint. The best form of hydrogen, ‘green’ hydrogen, is that made from water by electrolysis using renewable electricity. Renewable energy is used to electrolyse water, separating the hydrogen atom within it from its molecular twin oxygen. This requires water, an electrolyser, and plentiful supplies of electricity. If this electricity comes from renewable sources, then the hydrogen is green; the only by-product being heat and pure H₂O. The separated hydrogen is pressurised and collected in hydrogen tanks that can then be stored or transported as a gas or liquid. Hydrogen produced in this way has the potential to play a key role in decarbonising industrial processes, domestic heating and transport, whilst offering an excellent method of storing excess renewable energy. Green hydrogen can be converted into 100% emission-free electricity or can be added to natural gas and burnt in thermal power or district heating plants. It can be used to replace the industrial hydrogen that gets made every year from natural gas. Using renewable energy to power electrolysis and produce hydrogen provides renewable energy generators with an additional, lucrative income stream. Wind, solar and hydroelectricity production are no longer constrained by the natural environment. If the sun is shining, wind is blowing, or water is flowing the operations can produce renewable electricity and store any additional capacity for use when needed.