Hydrogen blending in the gas grid                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      

Over 200 years ago, hydrogen was a vital component of the coal gas fed into the first public gas works in the world, supplying gas to customers and street lights in London.

Today however, two centuries on, it’s natural gas that supplies homes and businesses across the UK with heat & power. And, whilst the re-introduction of hydrogen into the UK’s energy mix is possible, the use of hydrogen in the gas grid is widely questioned.

Within this article, penned by Ross Henderson, we explore how hydrogen can be re-introduced into the gas grid, why there’s so much push back on the subject, and the pros & cons of using hydrogen in this way.

UK gas industry

In 18121 Fredrick Winsor created the first public gas works company in the world which, through  a network of underground pipes, supplied gas to customers and street lights in London. By 1827 almost 70,000 street lights were in use, some of these still exist dotted around st James in London.

This process involved using coal in a coking furnace, which cooked off the volatile fraction of the coal producing, coke as a solid, and coal gas. The coal gas was a mix of carbon monoxide and hydrogen in roughly equal proportions with small amounts of other gases such as methane, carbon dioxide and Nitrogen2. This gas needed to be cleaned up before it was pumped into the grid due to hydrogen sulfide and other “smelly” contaminants, however the gas still had a bad reputation as “smelly, dirty and dangerous”.

In 1959 liquid natural gas(LNG) started to be used as a feedstock for gas reforming into what was called “town gas”. This gas was cleaner and had less smell due to the lack of sulfur in the LNG that was used to make it. The composition of natural gas is almost entirely methane with some ethane, propane, butane and pentane.

In 1965 natural gas was discovered off Grimsby UK, which kicked off the natural gas industry in the UK. Due to the indigenous nature of the natural gas in the north sea, the national gas grid, except northern Ireland, was converted from town gas to natural gas. This started in 1968 and by 1977 all gas in the national gas grid was natural gas.

During the changeover period, all gas appliances were changed over to accommodate the different gas (by changing the air/fuel mix ratio). In 1986 the national gas grid was privatized.

Hydrogen in the gas grid

Can hydrogen be safely re-introduced into the gas grid?

There are two main issues regarding the hydrogen in the gas grid. The first is safety and the second is metering.

The issue regarding safety arises from the ability of atomic hydrogen to penetrate the gas pipework and possibly weaken it. This can be avoided, however there is a cost factor to consider.

The metering issue arises from both the calorific value of the gas and the Wobbe index. The Wobbe index is a ratio between CV (calorific value) and SG (specific gravity) and is used to determine if the gas characteristics are suitable for gas consuming devices (eg is the nozzle the correct size for the gas to achieve the correct air/gas ratio for safe and efficient combustion).

The ‘end use consumer’ devices need to be designed to use gas of a specific Wobbe index range.

There is a current government proposal Hydrogen Blending into GB Gas Distribution Networks: consultation where industry is able to have a say in hydrogen blending into the gas grid.

Safety concerns

Safety concerns regarding hydrogen blending are currently being investigated by HSE who will make the final decision.

A trial study by Keele University on Winlaton, NE of England (CADENT), was completed and the results should be available in mid-2024.

The preliminary results of the trial study by Keele University were very positive, with no effect found on the safety of existing gas appliances with a 20% hydrogen blend.

The biomethane industry

The CV of natural gas with a 20% hydrogen blend is below 37 MJ/cubic meter. This would be beneficial for the Biomethane industry as it would eliminate the need for biomethane producers to inject propane to increase the CV of the gas, as the CV of biomethane is more than 37MJ/cubic meter after upgrading.

Current infrastructure plan is for a 100% hydrogen pipeline down the east coast of England from Scotland which is in pre FEED stage. The initial stage is for 20% hydrogen blend then by 2050 100% hydrogen.

Hydrogen properties

• Lower CV per NCM then natural gas

• Difficult to store. High pressure ( 700bar) and/or very low temperature (-200 deg cel). Boil off when stored or transported in liquefied form.

• Similar safety characteristics as natural gas

• Other storage possibilities include, metal hydride, Kubas interaction molecular sieve, ammonia and methanol

• Of these the molecular sieve option has the greatest advantages, giving hydrogen a better energy density than propane at 120 bar with no boil off. This is a new technology which is currently being developed for use.

Why is there pushback against hydrogen?

There is a significant lobby around heat pump use for all uk homes instead of gas boilers.

Hydrogen is seen as a “work around” for the fossil fuel industry to continue supplying fuel to the  market through “blue hydrogen”. This is where the hydrogen is produced from natural gas and the CO2 is captured.

The heat pump industry is claiming safety issues with hydrogen blending into the national grid.

This is especially pushed by the international think tank RAP (regulatory assistance project) which seeks to phase out gas infrastructure and de-carbonise the electricity grid as part of the international IPCCC Paris agreement.

RAP is the driving force behind Germany's energiewende (germanys phasing out of coal and nuclear for renewable electricity generation), which saw the closing down of nuclear power plants and the installation of wind and solar generation to replace it. This unfortunately led to an explosion in gas prices in 2022/2023 due to a wind drought in the summer of 2022, which forced Germanys electricity market to use natural gas to make up the shortfall.

RAP is lobbying the UK government to roll out heat pumps to 39 million homes, de-carbonise the electricity grid and close down the national gas network.

The Swedish market is the example RAP uses for the use case of heat pumps. However, the Swedish market uses heat pumps mostly with wood fired stoves during cold periods. This is unpopular in the UK where there is a lobby against wood stoves.

What are the pro’s and con’s of hydrogen blending into the gas grid?

Pro’s

• Reduce GHG (green house gas) emissions (using green hydrogen) from mains gas use

• Reduce the need for excessive electricity grid infrastructure investment need to deliver net zero agenda (increase in electric transport and heating will require investment into electricity grid)

• Diversify the energy mix in the UK to allow for redundancy

• Extend the working life of infrastructure without the need for significant investment

• Increase the security of the UK energy market

Con’s

• Reduce the urgency for electrifying the UK heat demand

• Reduce the calorific value of the gas delivered by the gas grid

• Increase the amount of sunken costs if the gas grid is decommissioned by 2050

• Possibly reduce the safety of the gas grid pipeline

With this is the question of cost and the widespread feeling that – at least for domestic use – hydrogen is simply too expensive, compounded by the ongoing ‘cost-of-living’ crisis currently experienced here in the UK.

Could hydrogen present opportunities to connect new renewable energy projects?

However, given the current lead times for electricity grid connection of many renewable energy projects, due to the need for increased infrastructure investment to enable these connections, the use of hydrogen as an energy carrier presents an additional opportunity to connect these renewable energy projects to the grid. Even if it is not a direct connection.

As such, hydrogen could very well bolster the UK’s commitment to the widespread adoption of renewable energy projects in efforts to achieve energy security.

In conclusion, the discussion around hydrogen blending in the gas grid is complex and multifaceted, with hydrogen projects receiving both impassioned support and push back in almost equal measure.

It’s hard to say, however, where these discussions will lead the UK as we continue to move towards a future built upon foundations of large scale renewable energy adoption and a commitment to green house gas reduction. Perhaps a look to the past will inform our future?

Appendix

1. https://wcclibraries.wordpress.com/2015/08/31/the-gas-light-and-coke-company-in-westminster

2. https://tringlocalhistory.org.uk/Tring/c_chapter%2009.htm#:~:text=Their%20work%20was%20to%20load,hot....