12 minute read
Hydrogen
Your questions about hydrogen blending trial
Nearly 700 Gas Safe registered engineers from the Gateshead and Newcastle areas joined a webinar recently to find out more about the trial that will introduce blended hydrogen into the natural gas supply in Winlaton in early 2021. During and after the webinar, organised by Northern Gas Networks, attendees asked a number of questions, some of which are answered here by Tommy Isaac, principal engineer at Progressive Energy.
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Appliance operation Which appliances have been tested with the hydrogen blend?
Extensive appliance research has taken place at HSE and Kiwa Gastec laboratories, along with expertise from Blue Flame Associates and appliance manufacturers. Safety and performance testing has been carried out on boilers, cookers, ovens, grills, fires and heaters to assess heat outputs, temperature profiles, combustion efficiencies and flue gas analysis, as well as safety devices such flame detectors.
The overall conclusion of the appliance research has been to demonstrate that current domestic appliances operate safely and within the bounds of normal operation with a blend of hydrogen up to 20 vol%.
Will the heat output of appliances change?
The heat output of an appliance is determined by the Wobbe number of the fuel being supplied. The Wobbe number of a gaseous fuel is the amount of heat that will be provided for a given pressure drop over a gas valve. The gas characteristic takes account of both the calorific value of the fuel as well as the fluid properties that dictate its flowrate through a valve – namely its density. Therefore, gases with the same Wobbe number will provide the same heat output within an appliance.
A 20 vol% hydrogen blend remains within the current non-emergency natural gas Wobbe limits, as stipulated by the GS(M)R legislation, which is 47.2-51.4 MJ/m3. Therefore, the heat output of appliances operating in the UK won’t be changed because the range of fuel quality provided to appliances won’t be impacted.
Will I need a new flue gas analyser?
Flue emissions are of key concern with any change in gas quality, and a reduction in CO2 emissions is the principal motivation behind the adoption of hydrogen in the gas network. The appliance research has demonstrated that both CO
and CO2 production reduce when hydrogen blends are introduced: therefore, from a toxicity perspective, the combustion results in a safer emission profile.
There is also a general reduction in NOx emissions. This effect is created because of a slight cooling of the flame, which in turn is the result of a slight increase in excess air, caused by the lower volumetric air requirement of hydrogen to fully combust. Flue gas analysis research was conducted in collaboration with Worcester Bosch, Vaillant, Baxi and Ideal as well as gas detection manufacturers Kane and Crowcon (manufacturers of the Anton Sprint), using a bespoke research facility constructed through the HyDeploy programme at Keele University.
The research confirmed that current flue gas detectors (both direct and indirect CO2 measurement) can continue to be used with a hydrogen blend, without the need to know if the blend is present or not. This
research was published by Gas Safe Register in Technical Bulletin 157, published in May 2020.
Gas characteristics Could hydrogen and methane separate in the pipework?
The notion of separation within pipework is a common misconception about hydrogen blends. A great deal of research, both desk-based and experimental, has taken place in the field of gas characteristics to understand the fundamental physics of a hydrogen blend so as to inform operational procedures and technical assessments.
Hydrogen and methane are two of the most ideal gases available: therefore, they mix extremely effectively. Much like spraying deodorant in the air, the two gases will mix by themselves and stay mixed. The natural tendency of a system to maximise its entropy results in a uniform mixture of gases that stay mixed throughout the pipework.
Will a hydrogen blend leak more readily than natural gas?
Some people have pointed out that hydrogen is a very small molecule and so it might find leak paths through which natural gas can’t travel. This is a misconception: a hydrogen molecule is smaller than a methane molecule (its diameter is 84 per cent of a methane molecule), but both molecules are infinitesimally small relative to a leak path. If a leak path was a mountain tunnel, methane would be a bee and hydrogen would be a fly.
Leak rates are determined by flow regimes. Small leaks, such as those identified through drop testing, operate in the laminar flow regime: for these potential leaks there is a negligible change in leak rates of less than 1 per cent. For larger leaks, such as a full-bore rupture, the leak flow will be turbulent. In this flow regime, the leak rate could increase by up to 10 per cent: however, because the blended gas is more buoyant, the resulting ventilation rate within the room also increases. During a large gas leak, the gas will rise and escape. This draws air into the room and, over time, an equilibrium concentration of gas occurs.
Even though a large leak would increase by up to 10 per cent, the resulting ventilation caused by the escaping gas will also increase. This results in no change to the ultimate concentration of fuel in the room – it is a self-correcting system because both the leak rate and resulting ventilation rate are governed by the gas’s density.
The Boiler Research Facility at Keele University
Leakage research facility
Is the hydrogen blend more flammable than natural gas?
The lower flammable limit (LEL) of a hydrogen blend is almost identical to natural gas. Natural gas has an LEL of 4.4-5.0 vol%: the corresponding LEL of a 20 vol% hydrogen blend is 4.3-4.8 vol%.
Therefore, from a procedural perspective, the actions taken to protect against a flammable environment being created with natural gas are adequate to mitigate a flammable atmosphere of a hydrogen blend forming as well.
Will I need to add to my competencies to work with the blended gas?
A full review of all the procedures, both IGEM and BSI, that underpin ACS competencies to work on natural gas domestic applications has been undertaken to understand their potential impact due to a hydrogen blend. The review concluded that no change would be required to any domestic procedure to accommodate a blend and maintain the same level of risk management.
Therefore, natural gas competencies should be directly applicable to working on installations being supplied with up to 20 vol% hydrogen. This work is in review with the standards institutions and is due to be formalised through an upcoming Technical Bulletin that Gas Safe Register will publish before the Winlaton demonstration starts. ■
You can listen to the webinar for gas engineers, hosted by Adam Madgett, HyDeploy project manager for Northern Gas Networks, and Tommy Isaac, project manager for Progressive Energy at:
www.youtube.com/watch?v=DYiHGjhDGik
Winlaton demonstration
The HyDeploy project is on course to build on the demonstration currently under way at Keele University, where a hydrogen blend of up to 20 per cent is being supplied to 100 homes and 30 university buildings on a private gas network. The next demonstration will be conducted in Northern Gas Networks’ region in Winlaton, Gateshead, where 668 homes will receive the hydrogen blend via their public gas network from spring 2021.
The project is working with HSE to review the evidence submitted to support the safety case for the demonstration: proving that the hydrogen blend is as safe as natural gas. In parallel with this regulatory approval process, the project is designing and constructing the necessary equipment and infrastructure (‘the compound’) to enable the demonstration to take place.
The compound will consist of a hydrogen supply source provided by Air Products, along with a grid entry unit (GEU) provided by Thyson Technology. The GEU will maximise the hydrogen blend (up to 20 vol%) within process constraints while maintaining the current lower non-emergency Wobbe limit within the Gas Safety (Management) Regulations (GS(M)R) of 47.2 MJ/m3 .
Northern Gas Networks is the gas distributor for the north of England, transporting gas to 2.7 million homes and businesses across the North East, northern Cumbria and much of Yorkshire. The company has ensured that the public network that will be supplied with the hydrogen blend has been isolated from the surrounding network to create a closed network.
A service main from the compound to the isolated network has been installed, along with an associated governor to regulate the blend from the production pressure of 2 barg (medium pressure tier) to around 30 mbarg (lower pressure tier) for distribution to the end users.
The demonstration in Winlaton is due to last for 10 months until early 2022. The project team has engaged with the residents of Winlaton to provide information about the project and gather details on the appliances in use. Working with the local authority, gas safety check information has been collected from 90 per cent of the homes, with external assessments undertaken on the remaining 10 per cent where possible. The gas safety checks were carried out to ensure the integrity of the appliances due to receive the hydrogen blend and to understand the profile of the appliances.
The Winlaton demonstration area
Safety case
The safety case submitted to the HSE for review has been developed on the basis of evidence generated through technical workstreams. It details the expected effects of a hydrogen blend to all components and equipment that will interface with the blend, both during transportation and combustion, as well as post-combustion analysis.
Looking to a more efficient future
What’s the latest on energy efficiency regulations and initiatives planned for 2021, asks Baxi’s head of External Affairs Jeff House. And how will the heating industry will move towards a more sustainable future?
Last year was very challenging because of the coronavirus pandemic. Not only did COVID-19 have an impact on the way we all go about our daily lives, but it contributed to delays to expected policy announcements.
Despite this, 2020 did still see several updates from the government and independent advisors on low-carbon aims and ambitions. What we can take from this is that the pledges made by the government in 2019 to achieve its net-zero ambitions by 2050 are still central to plans for the future on how we heat our buildings.
2020: a lookback
Residential heating and hot water have long been acknowledged as key areas for action in order to meet national carbon reduction targets. As the Energy Saving Trust points out, the majority of household CO2 is the result of these two activities, roughly 31 per cent of the nation’s overall emissions. Before the net-zero target passed into law, the UK was aiming for an 80 per cent cut in emissions by 2050, which would have meant reducing the carbon generated from a home’s heating and hot water to 692kg per year.
Now, however, this figure will need to drop to 138kg per household per year.1 All new-builds will need to be low-carbon from day one to avoid adding to the 28 million existing homes that will require retrofitting in the future.
In 2020, several publications were released that aimed to show how the UK could plan to tackle these ambitious carbon emission reduction targets – the Prime Minister’s 10-Point Plan for a Green Industrial Revolution, the Energy White Paper setting out how the UK will reach net-zero emissions by 2050, and the Climate Change Committee’s (CCC) Sixth Carbon Budget recommendations.
A common theme across these publications includes a favourable view of air source heat pumps (ASHPs) and hydrogen technology.
For instance, the CCC recognises the longer-term benefit of hydrogen in decarbonising heating and recommended last year that all new boilers should be hydrogen-ready by 2025. The CCC’s path to net-zero recommendations also put forward aims to achieve an installed base of 5.5 million heat pumps by 2030.
Likewise, the 10-Point Plan’s ambitions to create a hydrogen neighbourhood in 2023, a hydrogen village by 2025, generate 5GW of hydrogen, and inject half-a-billion pounds represent a significant vote of confidence for hydrogen as a future fuel. Alongside this, a target has been set to grow the heat pump market to 600,000 installations per year by 2028.
In 2020, the government also reaffirmed its commitment to the Future Homes Standard 2025. As part of this plan, all new homes will need to incorporate low-carbon heating systems alongside high levels of energy efficiency. It is proposed that new properties will be unable to connect to the gas network, which means that other lowcarbon heating and hot water solutions will be needed.
What to expect
In 2021, we expect further publications to shape how the UK will set out to achieve net-zero carbon emissions by 2050. In particular, we should see the highly anticipated Department for Business, Energy & Industrial Strategy (BEIS) Heat and Buildings Strategy and a UK Hydrogen Strategy. Other imminent and anticipated changes include revisions to Approved Document L of the Building Regulations, which will likely mandate tighter targets for new dwelling emissions, together with implementing Standard Assessment Procedure (SAP) 10.2 as the underlying compliance calculation.
The 2021 United Nations Climate Change Conference, COP26, will be a key calendar event that will see nations come together to review their commitments and strengthen ambition for a more sustainable future.
Underpinning the low-carbon publication guidance issued in 2020, hydrogen research and development, alongside investment in air source heat pumps, will continue to thrive in 2021. Furthering the development and uptake of these technologies will be a major part of plans to achieve net-zero ambitions.
What is clear is that in order to achieve hydrogen and heat pump ambitions, investment in engineer training to install low-carbon technologies, financing and incentive payments, as well as consumer engagement, will be instrumental in achieving as a smooth a transition as possible.
With a greater reliance on electrification expected, a review of tariffs and how to offset high usage peaks will also be advantageous. In fact, work is already under way to test how smart heating systems can interact with the grid and make use of cheaper off-peak energy. n
www.baxiheating.co.uk/ the-future-of-heat
1 energysavingtrust.org.uk/significant-changesare-coming-uk-heating-market/
Baxi Heating is involved in a number of hydrogen trials and has developed a 100 per cent hydrogen boiler to help facilitate research into the viability of this fuel. In 2021, a number of high-profile hydrogen testing projects will be coming to fruition, including Hy4Heat and HyDeploy. Data should be available in the coming months to further prove the concept of hydrogen and allow for more hydrogen testing on a larger scale across more towns and cities.
The various sustainable heating projects and initiatives under way are strong indicators of how the UK is serious about investing in a low-carbon future. Baxi Heating understands the importance of helping its installer network and, along with the government, will support registered gas engineers along their sustainable heating journey.
