1. If H2 is used in internal combustion engine, there will be pollution, though minute, due to burning of cylinder lubricant;
2. Hydrogen liquefaction temp. is (-)253C, which is not practical for being used to carry good quantity of H2 for use in automobiles.
3. Rather than using electricity produced via SPV Panels, Wind Turbines etc. it can be more efficiently used to charge electrical vehicles.
4. Hydrogen can’t be liquidated at room temp. at any pressure. Therefore, enough quantity of H2 cannot be carried for use in Automobiles.
5. Until the above mentioned problems are solved, use of H2 is no more than fantasy.
6. But it is definitely highly desirable to carry on R&D towards use of H2.