Decarbonisation Technology - November 2021

of leakage. This can be difficult to detect since hydrogen is odourless. For these reasons, accurate measurement of hydrogen flow is a challenge using traditional technologies. In order to facilitate the increased adoption of hydrogen, the regulatory landscape must be robust to ensure standardisation across countries and markets. Custody

transfer across borders is a particular challenge, as differing regulations and standards may apply. Collaboration between countries, regions and organisations will be fundamental in navigating the challenges of the growing hydrogen industry. In response, the American Gas Association (AGA) standard sets out the calculations required for measurement of hydrogen in normal conditions, and calculations in the field are certified against this standard. The problem here is that ‘normal conditions’ rarely occur. The physics of pure hydrogen are well understood, however in custody transfer hydrogen is often mixed with other gases, for instance natural gas, which adds an additional layer of complexity. Operators therefore not only need to use the calculations as set out in the standard, but also need to gain an understanding of what is actually happening inside the pipe to ensure a ‘true’ reading of hydrogen quantities. Even a small error can potentially have a large financial impact. It is therefore important to ensure that measurements are as accurate as possible. Investing in advanced measurement equipment now will most likely pay off down the line through the reduced error rate. Customers must also have confidence in the measurement system, as false reports can potentially have a significant effect on the market, influencing stock and commodity prices. Measurement errors can be caused by a wide range of factors, including human error, Complexity of custody transfer arrangements

Flow computers take inputs from the flowmeter along with pressure and temperature sensors to compute a correct volume flow

incorrectly calibrated equipment, flawed or faulty measurement equipment, flow computers with incorrect algorithms, and drifting analog inputs. Inadequate maintenance of measurement systems can also lead to problems. It is important to remember that a single mistake can render an entire custody transfer worthless, so the stakes are extremely high to ensure that measurement is as accurate as it can be. New and emerging hydrogen measurement technologies This is where a flow computer can help. This, when combined with Coriolis mass flow measurement, provides a more accurate picture of the actual conditions, taking into account the presence of other gases, along with other key variables. Coriolis mass flow measurement has been used for many years in oil and gas custody transfer applications, and is widely considered to be one of the most accurate and cost-effective measurement techniques. Its advantages also make it a logical choice for the measurement of hydrogen. Coriolis meters operate on the mass flow measurement principle, and are favoured for their ability to measure multiple attributes over sustained periods with high repeatability and little maintenance requirements. The latest generation of devices from manufacturers such as ABB can measure a wide range of medium characteristics including aggregate state, conductivity and density with an accuracy to 0.1% in direct mass flow measurement.