Infrastructure and Distribution

M. SADRI, TÜV SÜD National Engineering Laboratory, Glasgow, Scotland

The European natural gas market is a significant contributor to energy supplies, providing approximately 24% of the total energy for domestic use (e.g., heating boilers and cookers) across Europe. Additionally, natural gas accounts for a significant proportion of global primary energy demand—representing approximately 23% of the world's energy supply—and is the source of nearly a quarter of the world's electricity generation. 

While natural gas remains a critical energy source, its environmental impact cannot be ignored. The burning of natural gas releases significant amounts of carbon dioxide (CO2), contributing to global climate change. To mitigate the environmental impact of natural gas, decarbonization of the gas grid is seen as an essential step towards achieving climate change targets by reducing CO2 emissions. 

Despite the need to reduce CO2 emissions, the complete elimination of gas networks is not considered a viable option. Even with an increase in the uptake of heat pumps and electric cooking appliances, it is expected that many homes in the future will continue to use gas for heating. Therefore, the focus is on decarbonizing the gas grid to reduce the environmental impact of natural gas consumption. The decarbonization of the gas grid involves various programs, such as blending natural gas with renewable gases like as biomethane and hydrogen (H2), which have a greatly reduced carbon footprint compared to traditional natural gas.

Many countries have set ambitious targets to reduce CO2 emissions, and decarbonizing the gas grid is an important part of these plans. For some countries, a complete substitution of natural gas with H2 is a long-term goal, but these strategies involve incremental increases in H2 amounts—as a fraction of H2-enriched natural gas (HENG)—between 20% and 100%. Some countries have already made plans to produce a 100% H2 gas grid in the near term. A fast transition to a decarbonized gas grid could support the continued operation of the natural gas market while enabling new renewable technologies. 

Introducing HENG to the gas grid is a steppingstone toward the use of pure H2. It can also reduce the carbon emissions of domestic heating, depending on the percentage of H2 used. A significant challenge, however, is that current international standards for natural gas metrology have not been adapted for HENG or pure H2, i.e., current methods used for calculating the amounts of natural gas provided to customers may not be accurate enough for HENG or H2. These calculations are based on various factors, such as the volume, temperature and pressure of the gas. For example, the volume of gas is typically measured using a gas meter (such as a common domestic diaphragm meter) that records the amount (volume per time) of gas that flows through it. The volume measurement is then adjusted for factors such as temperature and pressure to determine the actual amount of gas that is being delivered. The development of new calculation methods, measurement techniques and standards that are specifically designed for HENG and H2 is needed to ensure accurate and fair measurement and appropriate fuel pricing.  

Various techniques—such as speed of sound, gas chromatography (GC) and Roman spectroscopy—have recently been suggested as efficient ways to rapidly calculate the H2 amount fraction in HENG. Nevertheless, these methods require further development and validation to ascertain their suitability for their intended purpose.  

GC is a widely used technique for measuring the composition of gases. GC is used in analytical chemistry to separate and analyze the components of a mixture based on its physical and chemical properties. The technique is used to separate individual chemical compounds from a complex mixture based on their different boiling points, solubilities and other properties. To ensure the accuracy of GC composition measurements, it is necessary to validate GC methods against traceable primary reference materials (PRM) specifically developed for HENG. 

PRMs have a known composition and are certified by a recognized standard-setting organization. These materials provide a reference point against which the accuracy and reliability of analytical methods can be assessed. As GC methods have not yet been validated against HENG-specific PRMs, the accuracy of GC measurements for HENG is not guaranteed. Robust performance testing is needed to assess the accuracy, range and response time of GC methods for measuring HENG. Such testing would ensure that the methods are suitable for their intended purpose and help establish best practices for measurement.  

Calibration gas mixtures (gas mixtures used to calibrate gas monitoring equipment to ensure that the readings obtained are accurate and reliable) and gas standards (a reference material with a known composition used to ensure that gas measurements are traceable to internationally recognized standards) are available for measuring impurities in natural gas, as listed in ISO/TR 27921 and for fuel cell vehicles as per ISO 14687. However, these standards are not applicable to measuring natural gas for domestic appliances. Moreover, existing ISO standards for calculating thermodynamic properties of natural gas (ISO 2075-2) have limited validity under test conditions for HENG, which may lead to deviations from expected results. 

These difficulties in calibrating current flowmeter technologies with HENG mixtures create uncertainties about their accuracy when H2 is introduced to the grid. As a possibility exists that the accuracy of flowmeter measurements is affected by changes in gas composition, a strong metrological infrastructure and knowledge base for flow metering of HENG must be established.

It is important to establish standardized, accurate and reliable methods for measuring HENG and H2 to ensure their safe and efficient use as an energy source. This requires ongoing research and development efforts to address the current limitations and challenges associated with gas composition measurement and flow metering. The author’s company is a part of this joint effort in the industry, contributing to several national and international research projects on metrology for H₂ and HENG.H₂T

About the author

MAHDI SADRI is a Clean Fuels Consultant at TÜV SÜD National Engineering Laboratory, a world-class provider of technical consultancy, research, testing and program management services. Part of the TÜV SÜD Group, the organization is also a global center of excellence for flow measurement and fluid flow systems and is the UK’s Designated Institute for Flow Measurement.