1 Introduction

Scope of this attachment is to make a high-level techno-economic review of the published information on the underground large-scale hydrogen storage facilities. Main technical characteristics of different type of underground storage reservoirs have been investigated, focusing on various topics like storage capacity, gas containment, operating pressures and possible constraints on gas delivery and injection rates. Specific investment and operating costs ranges are also provided.

The review is based on data available in the public domain, because main operators of hydrogen storage facilities have decided of not supporting this study, in order not to disclose business confidential information.