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what is hydrogen?

ENERGY DENSITY AND VISCOSITY important that an odour is added to exposure to 100 per cent hydrogen.
As the lightest known molecule, hydrogen any hydrogen distributed via pipeline
disperses into the air quicker than other to ensure leaks are detected and WHAT ROLE WILL HYDROGEN PLAY
gases due to its low molecular mass. consumers are protected. IN THE UK’S FUTURE?
On a volumetric basis, the energy The type of odorant for hydrogen It has long been recognised that
density of hydrogen is eight times smaller has not yet been finalised, however it hydrogen will play an important role in
than that of methane. So, to achieve the is anticipated that the same odorant our future energy mix if we are to stand
same energy supply, significantly greater (mercaptan NB), currently used for any realistic chance of meeting our net
volumes of hydrogen are needed. natural gas, will be applied in the initial zero carbon emissions target by 2050.
When considering the pipeline hydrogen trials. However, for a healthy hydrogen
transportation of hydrogen, it is economy to take shape with the urgency
acknowledged that greater flow rates we need to meet our 2050 goals, the
would be required to compensate for Hydrogen’s high diffusivity can industry must work collaboratively
this density difference. be advantageous from a safety and have access to the latest research
Viscosity is a measure of a gas or perspective, as hydrogen leaks knowledge across all sectors.
liquid’s resistance to flow. Hydrogen has a are likely to disperse quickly into At IGEM, we are passionate about
lower viscosity than most gases, including our leadership role to enable the UK
methane, and as it is a small molecule it the air, providing it is not near an transition to a low carbon gas network
is prone to leakage through the joints and ignition source and one of the ways we are playing our
seals of containers or pipes in which it is part is through the development of the
being stored or transported. TOXICITY Hydrogen Knowledge Centre.
However, hydrogen’s high diffusivity Hydrogen is a non-toxic gas. Pure With the backing of BEIS, we’ve created
can be advantageous from a safety hydrogen does not contain carbon and a growing and carefully curated database
perspective, as hydrogen leaks are likely as such there is no carbon dioxide (CO₂) of resources from a wide range of sources
to disperse quickly into the air, providing production, nor any carbon monoxide including gas network companies,
it is not near an ignition source. (CO), when hydrogen is burned. 10 academic institutions, research bodies,
A move to 100 per cent hydrogen supply chain organisations and industry
IGNITION AND FLAMMABILITY for heat would eliminate the risk of experts – accessible by anyone.
Like many gases, hydrogen is carbon monoxide poisoning, which kills We are working with the UK gas
flammable. The flammable range at around 60 people every year. networks and key stakeholders,
which hydrogen will burn is much including HSE, to support the safe
wider than methane (4–75.6 per cent by EFFECT ON MATERIALS transition of the network to a low
volume, compared to 5–15 per cent by Replacing natural gas with hydrogen carbon hydrogen economy.
volume for methane) and widens with has its pitfalls, starting with how it
increasing temperature or pressure. affects the pipelines it travels in and the To access to IGEM’s search engine
The minimum ignition energy of appliances that use it. of hydrogen knowledge, visit the
hydrogen is 0.02mJ, significantly lower Hydrogen embrittlement can occur Hydrogen Knowledge Centre at www.
than methane at 0.29mJ. in metals such as steel. Embrittlement h2knowledgecentre.com
The burning velocity of hydrogen takes place when a material absorbs
is around eight times greater than hydrogen atoms. As a result, it loses its
methane. This characteristic can lead to flexibility and ability to carry loads. The References
increased risk of flashback and damage material then cracks or fractures under 1. HM Government, Net Zero Strategy: Build Back
to gas appliances. pressures it would normally withstand. Greener, October 2021
Higher burning velocity, lower ignition During pipeline transportation 2. United Nations Framework Convention on
temperature and wider flammable there is risk of hydrogen causing Climate Change – www.unfccc.int/process-
range may lead to easy and undesired embrittlement and loss of ductility. and-meetings/the-paris-agreement/the-paris-
combustion if the gas is leaked. The level of degradation will depend agreement/key-aspects-of-the-paris-agreement
Whether the hydrogen ignites and on operating pressure, temperature, 3. National Grid ESO, Future Energy Scenarios
detonates will depend on concentration, concentration, type, and quality of the 2019, July 2019
leakage conditions, room ventilation, material used to transport it. 4. HM Government, UK Hydrogen Strategy,
and proximity to ignition sources. This is an area materials scientists October 2021
are trying to tackle as part of the 5. Royal Society of Chemistry, www.rsc.org/
VISIBILITY AND ODOUR UK’s hydrogen research. IGEM’s periodic-table/element/1/hydrogen
Hydrogen is a colourless, odourless Hydrogen Knowledge Centre will 6. Imperial College London; Sustainable Gas
and tasteless gas. Compounds such as continue to share the latest research Institute, A greener gas grid: What are the
mercaptans and thiophanes are used to as it emerges, supported by hydrogen options? July 2017
scent natural gas, which burns with a projects currently underway across 7. International Journal of Hydrogen Energy,
distinctive blue flame. the UK and internationally. Large-scale storage of hydrogen, March 2019
In terms of safety, flame visibility is IGEM’s reference standard for 8. Hydrogen Europe, Gas Infrastructure Europe,
an important feature. Hydrogen burns low pressure hydrogen utilisation How to transport and store hydrogen – Facts and
with a less visible flame than natural presents the effects of hydrogen on a figures, April 2021
gas and can often be difficult to see. variety of materials including metals, 9. Energy Networks Association, A System for All
There is ongoing research into methods polymers and elastomers. The standard Seasons, October 2021
to colour or otherwise indicate the identifies a number of gaps in materials 10. Institution of Gas Engineers & Managers,
presence of the flame. that require further study, to fully IGEM/H/1 Reference Standard for low pressure
As hydrogen is odourless, it will be understand the impact of long-term hydrogen utilisation, May 2021

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