Written Evidence Submitted by The Royal Society
1.1. The Royal Society is the national academy of science for the UK. Its Fellows include many of the world’s most distinguished scientists working across a broad range of disciplines in academia, industry, charities and the public sector. The Society draws on the expertise of the Fellowship to provide independent and authoritative advice to UK, European and international decision makers.
1.2. The Society’s fundamental purpose, reflected in its founding Charters of the 1660s, is to recognise, promote, and support excellence in science and to encourage the development and use of science for the benefit of humanity. Our strategic priorities therefore are to promote excellence in science; to support international collaboration; and to demonstrate the importance of science to everyone.
1.3. The Society welcomes the opportunity to respond to the Committee’s inquiry into hydrogen. There will be no single technology that enables the UK to transition to net-zero, rather a mix of technologies will be needed. This submission provides an overview of hydrogen as one of the possible pathways that together can lead to a low carbon energy future. It also provides detail on associated technologies such as ammonia and outlines the need for a technology roadmap to net zero to deliver carbon reduction and adaptation.
1.4. To avoid confusion, it should be noted that throughout this submission, the description of hydrogen or ammonia by colour (brown, blue, green etc.) refers only to the production method. The hydrogen or ammonia produced have the same properties.
2.1. Hydrogen is the most abundant element in the Universe. On Earth, it is found in many chemical compounds, but as a gas it rarely occurs naturally. When generated as a gas it can be used as an energy carrier or vector, which at the point of use produces no carbon dioxide.
2.2. This means that the large-scale production of low-carbon hydrogen has the potential to play a significant role in decarbonising multiple parts of the energy system and ultimately the UK’s target of achieving net zero by 2050. Increased R&D investment is needed to enable the development of the technologies needed to do this. But, like all low carbon technologies, it is not a cure all and should be seen as one of the many technologies that together can help move us towards net zero.
2.3. The production of low-carbon hydrogen requires the input of energy. There are two ways in which hydrogen is currently produced at scale:
2.4. The hydrogen produced by these processes can then be stored and transported to where it will be used. At each stage, energy is lost in the transformation, for example the electrolysis of water might be 70% efficient, the burning of hydrogen to make electricity in a fuel cell might be 50% efficient, so the overall “loss” of energy can be large (65% in the above example). Minimising these losses is therefore an important R&D focus.
2.5. As an energy source, hydrogen can be burnt with air in an engine/turbine to generate power or fed into a fuel cell to produce electricity.
2.6. The cost of making low-carbon hydrogen depends upon the method used and the energy source. With steam methane reforming with carbon capture and storage (“blue” hydrogen) the price of methane is key. With the electrolysis of water using sustainable electricity (“green hydrogen”) the price of electricity is key.
2.7. Benefits of hydrogen:
2.8. Issues and limitations of hydrogen:
2.9. More detailed information on hydrogen production can be found in the following Royal Society policy briefing: Options for producing low-carbon hydrogen at scale (2018). In addition, the Royal Society policy briefing Nuclear Cogeneration: civil nuclear in a low-carbon future highlights how nuclear energy (heat) could be used to produce low carbon hydrogen more efficiently.
3. Associated technologies
3.1. Whilst the production and use of low carbon hydrogen (blue or green) has the potential to decarbonise domestic heating and heavy transport, it is also an important stage in the production of low carbon ammonia (NH3) and sustainable synthetic fuels and in the decarbonisation of many chemical and industrial processes, for example steelmaking. As highlighted in the previous section, there are also a number of associated technologies that are critical to its success such as energy storage. In the following paragraphs we briefly outline these technologies associated with hydrogen production. Given their close association, these should be viewed alongside any review of the potential contribution of hydrogen to delivering net zero.
3.2. Ammonia is commercially produced through the reaction of hydrogen with nitrogen in the Haber Bosch process. This has been used for many years to produce a range of chemicals, most notably agricultural fertilisers. The same process can be used to produce low carbon “green” ammonia using green hydrogen and nitrogen from the air. Ammonia is currently stored and transported in quantity as a liquid at much lower pressures (around 10 atmospheres) and temperatures (around –33C) than hydrogen. It can be burnt in air in engines to produce power (e.g., in ships) or used in fuel cells to generate electricity. The main disadvantage of ammonia is the energy lost in the production process. Care is also needed to ensure the safe handling and use of ammonia. More details can be found in the following Royal Society Policy Briefing: Ammonia: zero-carbon fertiliser, fuel and energy store
3.3. Sustainable synthetic fuels such as electro fuels (efuels) can be made by combining green hydrogen with carbon dioxide. The advantage of such fuels is that existing infrastructure and engines can be used, for example for aviation. In addition to the energy inefficiencies inherent in their production, the main disadvantage of efuels is the production of CO2 when they are burnt. This can at least be partly offset using direct air capture technology to capture CO2 from the air. More details can be found in the following Royal Society Policy Briefing: Sustainable synthetic carbon based fuels for transport
3.4. Alternative “direct” methods of producing ammonia and synthetic fuels, that negate the need to first produce hydrogen are being researched, however none of these are currently at a high technology readiness level.
3.5. Long term, terawatt hour scale clean energy storage will be essential to ensuring a reliable and continuous supply of electricity as more intermittent sources of electricity, wind and solar, are deployed. Whilst batteries are an excellent short-term energy storage medium, their costs and energy density currently preclude them from long term, terawatt hour storage. It is likely that bulk green hydrogen or green ammonia storage will be the most practical and cost-effective solutions, particularly if a market in the international trading of renewable energy develops.
3.6. In addition to hydrogen and the technologies directly associated with its production, there are a number of further technologies that will be crucial to successful roll-out of these to deliver net zero. These include digital technologies, from smart meters to supercomputers, weather modelling and AI, which if used effectively could deliver nearly one third of the carbon emission reductions required by 2030. Capitalising on this will require a cross-Government approach. More details can be found in the following Royal Society report: Digital technology and the planet
4. A technology roadmap to net zero to deliver carbon reduction and adaptation
4.1. As described above, there will be no single technology that enables the UK to transition to net-zero, rather a mix of technologies will be needed within the energy system. The UK should establish a body which can create and maintain an evidence based, living and investible technology roadmap to net zero to deliver carbon reduction and adaptation. This needs to sit outside short political cycles and draw on independent expertise from scientists, engineers, economists and others, across academia and industry for technology assessment (similar to the NICE process in medicine). Adequate funding that is long-term and locked-in will be critical to leveraging the scale of private sector investment that will be required for success.