Recoverable cushion gas in hydrogen storage as a national gas reserve for energy security

Abstract

<p>Large-scale storage of energy is an effective and efficient way to increase energy security. Europe is highly dependent on gas imports, but gas storage capacity has not been expanded accordingly. An increased deployment of renewable energy sources such as wind and solar will require additional energy storage to balance intermittencies, for example in the form of subsurface hydrogen storage. Hence the development of more geological storage sites is inevitable, and detailed asset planning needs to commence today.</p> <p>Cushion gas is an expensive but necessary investment in gas storage, especially in subsurface hydrogen storage as hydrogen will remain a commodity in high demand. A reduction of the cushion gas in hydrogen storage – either replacing H<sub>2</sub> cushion gas with alternative gases or reducing the cushion gas to working gas ratio – will introduce uncertainties in terms of hydrogen purity and injection and reproduction rates, and the cost-reducing effect might backfire.</p> <p>However, a certain part of the cushion gas can also be regarded as an asset, as it can be reproduced efficiently by standard production techniques. This “recoverable cushion gas” could act as a national gas reserve for times of severe energy shortages. The state could dictate to access this one-time energy backup during times of energy emergency, and therefore this particular share of the cushion gas should be paid for by the government, combining economic gas storage with national emergency gas reserves for an increase in national energy security. For this study, a North Sea gas store was used to illustrate and quantify the idea.</p> <p>As part of the cushion gas would be an investment into energy security by the government, the use of “recoverable cushion gas” could reduce implementation costs for hydrogen storage sites and set the incentive to massively expand low-carbon energy storage.  </p>