Upgrading VSL’s high-pressure gas flow primary standard for gases of the energy transition

With the rise of Europe's sustainable economy, dedicated gas networks for carbon capture & storage and hydrogen transport are being developed. In part, they consist of repurposed natural gas grids. Gas flow primary standards that can provide directly traceable and accurate measurements at representative process conditions applicable to the gas grid are scarce due to their cost intensity, and historically developed only for natural gas. VSL's high-pressure natural gas flow primary standard was established more than two decades ago to provide traceability at pressures up to 64 bar(a) and flow rates up to 230 m 3 /h. Recently, the usage of the standard for nearly pure CO 2 -gas was assessed. This paper will present the main operational and metrological requirements set when upgrading VSL's high-pressure natural gas flow primary standard to usage with CO 2 -gas and hydrogen blends with natural gas. Practical methods for fulfilling these requirements are presented and illustrated with examples. These findings will stimulate development of primary gas flow standards and realization of direct traceability for the diverse set of energy transition gases.