What is the most practical and cost efficient way to make a 10m3 gas bag for the storage of hydrogen? I am thinking of storing H2 from water electrolysis in an outdoor area, a bit like the way biodigestor gas is stored in low cost, small scale installations. My concern is the high effusing nature of the gas through membrane material. My first thought was to use reinforced PVC like that used for truck tarpaulins but I can't find any info on effusing rates verses other materials. Ideally the gas would be able to remain in the bag for a minimum 2-3 weeks until needed. Any thoughts and advice would be gratefully received! This is an experiment on the practical applications of locally produced hydrogen for home use, so I hope to be able to follow up any advice by constructing the gas bag and reporting back with the project progress.