Long distance renewable-energy-sources power transmission using hydrogen-cooled MgB2 superconducting line

Renewable Energy Sources (RES) exploitation for electric energy and hydrogen production has been identified as one of the leading ways towards a future sustainable energy system. Hydrogen can be stored and transported in gaseous (GH2) or liquid form (LH2). When large hydrogen storage is required, liquefaction can be convenient with respect to compression, because of its higher storage density. LH2 can also be used as a coolant for superconducting lines, acting at the same time as energy vector and cryogen. In particular, in this paper we focus on the MgB2 material mainly due to economic considerations and working temperature match with LH2. A system for large scale RES exploitation allowing flexible and controlled delivery of electric energy and LH2 is presented. For the thermo-hydraulic design, a method is proposed which resorts to compressible fluid equations put in a convenient simplified form. A case application with 20 km distance between cooling stations is considered, and the need of taking into account LH2 compressibility for pipeline design is shown.