why is hydrogen not used as domestic fuel even though it is has the highest calorific value?
Answers
a. It is neither cheap nor easily available/abundant.
b. It is not easy to store.
c. It is highly explosive.
d. It does not burn at a slow rate (undergoing controlled combustion).
Hydrogen can be a possible replacement for conventional gasoline and diesel fuel. But you know that each and every fuel has it's own advantages and disadvantages.
Since you have asked the reason for its disadvantages, let me discuss them briefly.
Physical Nature: First of all, hydrogen is a gaseous fuel. We know from basic physics that gases are less dense i.e. they occupy more volume. So, hydrogen requires a large fuel tank for storage.
Availability: Now, unlike other gases, hydrogen is not readily available in the atmosphere. It requires processes like electrolysis and steam reforming for production. The main challenge is, that how efficiently hydrogen can be extracted from these processes.
Storage: Though mentioned last, this point carries a lot of importance. Hydrogen storage has been a hectic process for engineers who are trying to utilize it in the form of fuel. It has to be compressed to higher pressures or stored in a cryogenic vessel for safety reasons.
Now, coming to your question, hydrogen is actually used for combustion in rockets and space shuttles were it is stored cryogenically. Even with so much difficulties, hydrogen is preferred because of it's very high energy density and tendency to produce less emissions.
So, even with this much of setbacks, with proper storage and handling methods, hydrogen can be a commercially available combustion fuel.
Hope this clarifies your question.
Thank You.