Gareth Hinds, Fellow and Science Area Leader in Electrochemistry at the National Physical Laboratory (NPL) and newly appointed Fellow of the Royal Academy of Engineering, outlines some of the measurement challenges surrounding the introduction of hydrogen into the UK’s gas grid.
The UK’s heating network has a structural dependence on fossil fuels: 84% of homes are currently heated using natural gas, while in 2018 residential heating accounted for 18% of UK carbon dioxide emissions.
Innovative new technologies and policy will be key to reducing this reliance on fossil fuels in line with Britain’s 2050 net zero greenhouse gas emissions commitment and other legally binding targets.
Hydrogen gas has the potential to help decarbonise our energy and transport infrastructure. It is a clean and versatile fuel that can be used for combustion to heat homes, as well as electricity generation in fuel cells to power vehicles. However, as with any disruptive innovation, taking the integration of hydrogen into the nation’s heating network from concept to reality is a significant challenge.
The UK is already well positioned in some respects to make the transition to hydrogen. Around 10,000 GWh of natural gas is currently stored in salt caverns, meaning there is a large ready-made potential storage space for hydrogen. Before the transition to natural gas in the 1960s these substantial caverns – found in Teesside, East Yorkshire and the Cheshire Basin, for example – were originally used to store town gas, which consisted of 50% hydrogen.
Current infrastructure is also suitable for transportation of the fuel, as hydrogen can be carried through the existing natural gas network. As such, it can act as both a near and long‐term energy store to balance supply and demand for renewable energy at different scales, geographies and weather conditions. This would unlock a consistent, low-cost, ‘on-demand’ decarbonised power supply, competing with services currently only offered by power plants running on fossil fuels.
One of hydrogen’s greatest strengths is its versatility; on top of domestic heating fuel, it can also be converted directly into electricity using fuel cells, with water its only emission. Fuel cell passenger vehicles already have a range comparable to petrol and diesel vehicles: up to 400 miles. They can be refuelled in under five minutes, comparable to the time it takes to fill a petrol or diesel car, requiring little adaptation in consumer behaviour.
The vast majority of the UK’s hydrogen is currently produced by steam reforming of natural gas, but in the future it could be sourced more sustainably from electrolysis of water using electricity from excess wind and solar power that would otherwise be wasted. Capital investment will be necessary to deploy electrolyser technology at a national scale and tackle the technological and regulatory barriers that must be overcome.
The UK’s National Physical Laboratory (NPL) is working with key partners in academia and industry to address the measurement challenges associated with the transition to a hydrogen gas grid. For example, metering of hydrogen and measuring its energy content requires a completely different approach to that for natural gas. It may also be necessary to develop ways of accurately measuring the composition of blends of natural gas and hydrogen, if a staged transition to a 100% hydrogen gas grid is implemented.
If hydrogen is to be used in boilers, heaters and cookers, its combustion properties will need to be better understood and characterised. Hydrogen needs to be supplied at a faster rate to generate the same amount of heat as methane and it burns with no visible flame, which could present a safety challenge. Domestic appliances will need to conform to quality and safety standards.
Furthermore, fuel cells are sensitive to very low levels of impurities in hydrogen, which can quickly degrade their performance. If hydrogen from the grid is used for transport applications it will be necessary to establish reliable impurity thresholds, which will inform the business case for purification strategies.
Hydrogen gas is odourless and invisible, meaning that a suitable odorant needs to be identified that can be added to the gas without impacting the performance of domestic appliances and fuel cell vehicles. Hydrogen leakage and embrittlement of pipeline materials and gas network components in the presence of the gas are also a concern.
NPL is seeking answers to these questions. The growing evidence base demonstrates the near-term potential for hydrogen to make a cost-effective and scalable contribution to decarbonising the UK’s transport and heating sectors.
Gareth Hinds is Fellow and Science Area Leader in Electrochemistry at the National Physical Laboratory (NPL) and also newly appointed Fellow of the Royal Academy of Engineering. His multi-disciplinary experience combines electrochemistry with materials science for energy applications. He holds visiting academic positions at University College London, the University of Strathclyde and Harbin Institute of Technology in China. He is playing a key role in making hydrogen a realistic option for future energy infrastructure in the UK.
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