The search for clean fuels is taking the political centre-stage. Recently, the Indian government announced that 2020 would be the target year to have 1 million carbon-free hydrogen vehicles on the road. So is hydrogen the favoured green technology of the future? Do we have a plan for producing hydrogen from renewable sources in cost effective ways? Or is this all a shot in the dark? R.K. Pachauri, director-general TERI, and chairman of the Intergovernmental Panel on Climate Change, has the answers

• Is hydrogen a clean source of energy?

Hydrogen is not a source of energy; it does not occur naturally. It is an energy carrier similar to electricity. The only difference is that electricity cannot be stored. But hydrogen can be stored in the form of compressed gas or liquid, and used whenever required. The product of combustion of hydrogen is water; that is why it is called a clean form of energy. However, it has to be produced from fossil fuels like petroleum, natural gas and coal, or through electrolysis of water using electricity, which is very expensive.

Further, the properties of hydrogen are unique. It is a very light gas, its density is eight times less than that of natural gas and considerable energy is required in storing it in compressed gas or liquid form. Its ignition limit (range of concentration within which the fuel will ignite if an ignition source is present) is large. Thus safety aspects involved in its storage, transportation, dispensation, and end-use are very critical.

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