What is Hydrogen?

What is hydrogen?
Hydrogen is an ‘energy carrier’ rather than a fuel source.  It can be produced by burning fossil fuels such as natural gas or coal, and also from renewable energy systems. Hydrogen offers the potential for low or even zero greenhouse gas emissions when burned. It also offers another important benefit; it provides a way of storing the electricity generated by renewable sources on a much larger scale than is currently possible with existing battery technology. This is important as some renewable sources are intermittent (for example, wind) which means other sources need to provide grid back up when the system is not generating. Hydrogen though offers the potential of storing the generated electrical energy as chemical energy and in a form which can be used at any time to produce power when needed.

Hydrogen can be used in two main ways:

• in a fuel cell, where it produces zero emissions at the point of use
• in normal combustion, where it produces lower emissions of pollutants than fossil fuels.
  

Fuel cells
A fuel cell is an energy conversion device that uses an electrochemical process to convert hydrogen into electricity without combustion. The fuel cell contains an anode and a cathode insulated by an electrolyte situated between them. Hydrogen is supplied to the anode while oxygen is supplied to the cathode. The two gases try to join, but because of the electrolyte, the hydrogen atom splits into a proton and an electron. The proton passes freely through the electrolyte. The electron takes a different route, creating an electric current before recombining with the hydrogen and oxygen, creating a molecule of water. This chemical process generates electrical and thermal energy and only produces pure water as a by-product.

A fuel-cell system can utilise hydrogen from any source including hydrocarbon fuels, such as natural gas and methanol, which although not emission free, emissions from the cell will be lower than the cleanest method of normal fossil fuel combustion. Hydrogen can also be made from renewable sources, by thermochemical (pyrolysis or gasification) or biological processes that break down complex organic molecules into simpler molecules including hydrogen. Hydrogen can also be produced from electricity generated by renewable sources, via electrolysis, to split water into hydrogen and oxygen.

However, fuel-cell technology is still at the pre-commercial stage and any existing installations are demonstration projects.