At present, UK gas network entry sites measure natural gas, which mostly consists of methane and a lower mix of other hydrocarbons, such as propane and butane.  Many biomethane sites are also connected to the gas network, and these must meet Gas Safety (Management) Regulations (GS(M)R) specification to inject into the national grid, often adding propane to meet the required Wobbe Number.  For hydrogen to be blended, limits embedded in the GS(M)R will have to reviewed and updated to account for the blending of hydrogen and green gases into the UK gas network.  Ofgem will also need to approve the required upgraded metering and gas quality equipment.

Where things get complicated is the accurate measurement of hydrogen as the gas presents unique challenges.  Hydrogen is molecularly small and not particularly energy dense, when compared to natural gas.  Hydrogen has approximately a third of the energy density by volume when compared to natural gas, thus the volume used and potentially the velocity, or pressure, of the gas in pipelines will also have to increase in order to achieve a comparable thermal output.

Due to the complications of the hydrogen molecule, meters and instrumentation must be designed specifically to measure the higher concentrations of hydrogen so that they can accurately identify hydrogen in the blend in order to ensure the correct thermal output is maintained.  In fact, the accurate measurement of hydrogen is key to its successful rollout, be it on a local, regional or national scale as fiscal metering and gas analysis is effectively the ‘cash register’ of the gas network companies.  If we’re unable to measure hydrogen accurately, then how are we able to assess the value of the gas going through a particular system? 

Fortunately, new coriolis and ultrasonic meters are stepping up to the challenge of measuring hydrogen.  Both types of meters are off-the-shelf products developed by Original Equipment Manufacturers (OEMs) that can currently measure up to 20% hydrogen in a blend with natural gas.  That said, a metering system does not just consist of a meter, but very importantly a gas analyser as well as secondary instrumentation such as temperature and pressure measurements designed to calculate compressibility and density.  With an increasing concentration of hydrogen selecting the correct equation of state for these calculations becomes increasingly complicated.

In addition, there also needs to be suitable ISO 17025 accredited calibration facilities, which can use hydrogen to correctly calibrate the meters.  Currently, there are very few which can provide the required concentrations, flow rates and pressures.

The role of Alderley and Kelton

As metering and measurement specialists, both Alderley and Kelton advise companies and organisations on how best to set up a hydrogen measurement system.  Our key insight is that every challenge needs a bespoke solution.  We need hydrogen to play a strong role in a decarbonised energy system but it comes with engineering challenges that many have underestimated.  For example, alongside the meters, even the piping materials, valves and certification of instruments for hydrogen metering systems need to be re-examined.  This is something that Kelton is advising companies on and developing solutions for.

Our role is to provide consultancy to organisations on what they need to install and upgrade and what they need to replace and also how to integrate and package the solutions.  Alderley is also taking the initiative in designing hydrogen-ready systems that are suitable for a future gas grid that considers the additional complexities associated with hydrogen. 

All solutions for hydrogen measurement must be digitally-focused and enabled, as there is no point in developing a technology solution that must be re-engineered several years later.  Building in predictive maintenance into hydrogen measurement systems at an early stage is also sensible given its potential to save on future costs and resource.

Delivering green hydrogen derived via electrolysis will be a particular challenge because of its current limited scale and the difficulty to integrate supplies and blend into the gas network.  The whole UK gas network will need to be reconfigured with additional injection points – in fact, there will need to be more analysers, more blending facilities and more measurement points.  This offers particular scope for Kelton to deploy its knowledge of blending and analysing hydrogen – the company remains one of only a few globally that can do this. 

We are highly optimistic about hydrogen’s potential to support the decarbonisation of the UK energy system and we believe that the supply chain is ready, as it always is, to deliver on the ambitions of industry for a more sustainable future.

Catherine Jones CEng, MIGEM is a Measurement Consultant at Kelton, the Energy Industry Consultants, which is based in Aberdeen.  Catherine can be contacted on Catherine.jones@kelton.co.uk

Mike Shepherd is Business Development Director at Alderley and has worked in the energy engineering sector for over 25 years.  Mike can be reached on mshepherd@alderley.com