In Ireland, biomass conversion and electrolysis driven by wind power currently provide the greatest potential for renewable hydrogen production, says John P Breen

Hydrogen is by far the most abundant element in the universe and one of the most common on earth. However, on Earth very little of the hydrogen is present as a gas, it is predominantly bound with other elements such as oxygen in the form of water and carbon in the form of methane and the fuels that we use to heat our homes and power our transport.

As a gas hydrogen can be used directly as a fuel to drive a vehicle, to heat water or indirectly to produce electricity for industrial, transport and domestic use.

The huge advantage that hydrogen has over other fuels is that as a fuel it is non-polluting – when you combust hydrogen the only product is water. Hydrogen is capable of producing tremendous combustion. For example, one kilogram of hydrogen could be used to power a vehicle almost three times further than the same weight of petrol.

This has been the fuel used to provide electricity for the space shuttle for almost three decades via onboard fuel cells that combine hydrogen and oxygen to generate electricity. The exhaust from the fuel cell – pure water – is used by the crew as drinking water. However on a commercial basis fuel cells can be costly, especially when used for mobile applications.

The electrodes are comprised of platinum which is very expensive and is rapidly increasing in cost. The widespread uptake of these fuel cells would drive the prices even higher.

Other disadvantages associated to the use of hydrogen include its low energy density. Although hydrogen gives much more energy when combusted than petroleum on a weight basis, it is a gas and has to be condensed either by compressing it to high pressures or liquefying it at low temperatures.

Even when compressed or liquefied, a litre of petroleum still gives a greater energy output than a litre of hydrogen. This is a particular problem for mobile applications where there are space issues and large volume tanks are a disadvantage.

This is an extract from an article featured in the Feburary edition of Construction Engineer - Click HERE to Subscribe Today!