Hydrogen of Class 11
Hydrogen as fuel
Hydrogen is another proposed alternative energy source.
Some advantages of hydrogen are:
(i) Hydrogen is aboundantly available in the combined form as water.
(ii) Use of hydrogen as fuel provides pollution free atmosphere because its combination product is water.
(iii) Time required for regeneration of hydrogen is much shorter as is clear from the following diagram:
(iv) An automobile engine burning hydrogen is about 25 to 50% more efficient than an automobile engine burning gasoline.
(v) Heat of combustion per gram of hydrogen is more than twice that of jet fuel.
(vi) Hydrogen – oxygen fuel cells provide other possibilities of powering motor vehicles.
(vii) Hydrogen is excellent reducing agent and can replace coal in many industrial processes involving reduction because it produces less atmospheric pollution than carbon.
The changes in out way of life by adopting widespread uses of hydrogen listed above refer to hydrogen economy.
Obstacles of Hydrogen Economy
Although hydrogen looks as very good future fuel but some of the tough problems must be solved before we adopt hydrogen economy. The problems are as described below:
- Availability: Hydrogen is not available as much. It does not occur in free state is nature. Therefore, cheap production of Hydrogen is basic requirement of hydrogen economy. The most likely future source of hydrogen is water. Hydrogen might be generated at an appropriate site by using solar energy and then transporting it as fuel.
- Storage and Transportation: Hydrogen gas has explosive flammability which causes problem to its storage and transportation. Hydrogen can be stored in vacuum insulated cryogenic tanks (already in use for space programmes in USA) Liquid hydrogen can be transported by road and rail tankers. It can also be stored in underground tanks and transported pipelines. Another promising solution to this problem is the use of Fe-Ti alloy which act like a sponge to absorb hydrogen and results in the formation of the silvery power. Heating the power safely releases hydrogen gas. The other small storage units are alloys
- like etc. Such storage systems are safer than storage of hydrogen as gas or liquid.
- Platinum Scarcity: In oxygen-hydrogen fuel cells, a lot of platinum is required as catalyst. In each succeeding year the demand of platinum exceeds the supply. This will cause problems for fuel cells which are highly energy source for automobiles.
Uses of Liquid Hydrogen As Fuel
Liquid hydrogen has already been used as rocket fuel. The chemical reaction involved is:
Both reactions H2 and O2 are stored as liquid in separated tanks. The tank hold 1.5 x 106 L of liquid hydrogen. The oxygen tank carries 5.4 x 105 L of liquid oxygen. During the “lift off” operations, these properties power shuttle’s main engine for about 8.5 min. Here, liquid hydrogen is consumed at the rate of nearly 3000L/sec.