We know Hydrogen is very light with a density 84 gm/m3 at 15 degree centg. & 1 bar (a).It is lightest from all gases & is 14 times lighter than air. Hydrogen ignition point is 585 deg. centigrade. It is higher than methane (540 deg. centg.)
Hydrogen is highly flammable where minimum auto ignition energy is 20uJ. Hydrogen flame is colorless & can’t be noticed in day light. Its explosive range is very wide from 4% volume to 77% level. So if we are looking for green hydrogen storage, transportation then safety aspects also to be considered. World is getting feared of GHG & temp. rise of earth so running behind all ways for carbon free energy but we have to see in consolidation. Type 4 composite cylinders can be used for H2 transportation as per PESO. Hydrogen being very low density gas, to be stored at high pressure ranging from 350 bar to 700 bar to get required quantity & mileage of vehicles. For passenger car, size of cylinder is in between 40 to 120 Ltr water capacity at working pressure 500 to 700 bar. The passenger car can run 600-650 KM in one filling of 5-6 KG of hydrogen.
Mr. Nitin Gadkari Toyata H2 car can store 5kg of H2 (2 cylinders of 60 Ltr water capacity) at 700 bar pressure & can travel 600 km in single filling. In India no one manufacturing type-IV composite cylinder for H2.