The suitability of hydrogen as a fuel from a practical viewpoint needs to be validated
Business Standard / New Delhi Dec 31, 2008, 00:21 IST
The proposed opening of the country's first hydrogen fuel-dispensing station in New Delhi in the next few weeks will mark a notable step towards diversifying the energy mix, and contribute to building energy security. Hydrogen is known to be the simplest and lightest element, yet also the most abundantly and freely available. The hydrogen station, being set up by the Indian Oil Corporation and the ministry of new and renewable energy, will initially dispense a 20:80 mix of hydrogen and compressed natural gas (CNG) to a group of test vehicles already running on CNG. Hydrogen is proposed to be extracted from the air, using the electroliser technique. Such a blend will not require any modification of the engine, whereas 100 per cent hydrogen may need completely new engines.
At stake is the future of the national hydrogen energy plan, drawn up in 2006 with the ambitious target of eventually running a million vehicles on hydrogen fuel. Since it is now becoming clear that the scope is limited for using ethanol and plant-based bio-fuels as alternatives to petroleum fuels, hopes rest in substantial measure on hydrogen as a clean fuel. The growing compulsions of switching over to green energy to reverse climate change have made the search for an alternative fuel all the more urgent. Unlike hydrocarbons-based fuels, which are not friendly to the environment, besides being exhaustible and subject to violent price fluctuations, hydrogen is clean (vehicles run on it emit water instead of gases), freely available and inexhaustible.
Delhi has already shifted its entire fleet of public transport vehicles to CNG, deeming it to be pollution-free. The realisation that this is not wholly so because CNG vehicles spew out noxious oxides, has prompted re-visiting of the issue. Several hundred hydrogen-powered vehicles have now been on the road in the US, Germany and other countries for the past few years. Several major auto companies, including the manufacturers of Mercedes-Benz, BMW and Mazda, have produced vehicles capable of operating on fuel cells energised by hydrogen. General Motors is reportedly planning to produce such vehicles for test running in India as well.
While the desirability of hydrogen as a future source of energy is beyond question, its suitability from a practical viewpoint needs to be validated. Hydrogen's energy content, despite being the highest among all common fuels by weight (about thrice that of petrol), is among the lowest by volume (about a fourth of petrol). This implies that it will require much bigger containers than the present petrol tanks in vehicles. Besides, many people are concerned about hydrogen's safety, it being highly combustible. These apprehensions are all the more grave in the case of liquid hydrogen which, being very cold, can freeze the air and cause accidents. On the other hand, in the event of a vehicular collision causing the rupture of a fuel tank, hydrogen may prove safer than petrol as it is one of the lightest elements, and will tend to dissipate rapidly. Hydrogen vehicles will need in-built and risk-specific safety features, as do vehicles run on other fuels.
Though it is true that hydrogen is abundant in nature and is the cleanest possible fuel, it must be remembered that making hydrogen from water actually means spending more energy than obtaining it. Anybody who understands the second law of thermodynamics will appreciate this. Even today, the most economical and practical route of manufacturing hydrogen is thorugh the break-up of naptha or natural gas. Thus the dependance on hydrocarbons will not be reduced by switching over to hydrogen as fuel.
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