Article source: IMechE
Power-to-gas is the process of using electricity to create gas, usually in the form of hydrogen.
This hydrogen is electrolysed from water, and provides energy that can be used across the power, heat, transport and industrial sectors, helping to reduce greenhouse and particulate emissions.
Power-to-gas is a technology that pulls together the different strands of our broad energy system, maximising the use of low-carbon electricity on the national grid and storing that energy in the form of hydrogen for use elsewhere.
Hydrogen as an energy vector is not a new concept. Welshman William Grove is credited with inventing the first ‘gas battery’ or fuel cell in 1839, building on the work of Christian Friedrich Schönbein. In more recent years, with increasing evidence of man-made climate change, health concerns over air pollution and the need to ensure security of energy supplies across sectors, hydrogen is re-emerging as a contender in the clean energy landscape. The appeal of hydrogen is that it offers clean, limitless energy that can fulfil the requirements of all energy sectors, as well as many heavy industries.
In the case of power-to-gas, the hydrogen produced when using low-carbon electricity is termed ‘green’ hydrogen, produced through the process of the electrolysis of water. In this process electricity is used to split water, H2O, into oxygen (O) and hydrogen (H2). Electrolysers consist of an anode and cathode separated by an electrolyte, and function slightly differently depending on the electrolyte used, such as alkaline electrolysis, polymer electrolyte membrane, and solid oxide electrolysis.
Globally, the major consumers of hydrogen are ammonia production (44%) and petroleum recovery and refinery (46%), with other sectors, such as food production, electronics and methanol production, making up the rest. This hydrogen is primarily produced through steam methane reforming and oil partial oxidation at 49% and 29% respectively, with electrolysed hydrogen making up just 4% of global hydrogen production. The main problem with the current production techniques for hydrogen is that, although they produce a zero-emissions fuel at the point of use, they generate greenhouse gases and this is not sustainable. The hydrogen produced using these methods is termed ‘brown’ hydrogen.
The use of hydrogen in industry provides engineers with a good place to initiate the use of ‘green’ hydrogen. The replacement of ‘brown’ hydrogen can provide the foundation for expanding the power-to-gas network, by utilising excess power from the grid and subsequently allowing the renewable and nuclear sectors to grow in the knowledge that all low-carbon electricity can be used effectively.
As the production of hydrogen using this method grows, we can begin to use this hydrogen across the energy system. Hydrogen is an effective fuel for large vehicles, such as HGVs, where we have seen and will continue to see increases in the use of oil.
The ultimate aim is to remove as much fossil fuel from our energy systems as possible. This can be achieved through different routes. Businesses will be able to diversify into sectors such as hydrogen production, and strengthening industrial symbiosis will see waste electricity used to power electrolysers providing feedstock for industry.
Our UK industries and existing hydrogen clusters mean that we are well placed to take advantage of this exciting opportunity and become a world leader in the production of sustainable hydrogen.