Stephen Tindale replies: “Hydrogen is not a separate fuel source – it is either extracted from fossil fuels or obtained by splitting water into hydrogen and oxygen, which requires electricity. However, hydrogen is a good means of storing energy from intermittent sources such as wind. The sensible way to use hydrogen is to built a gasometer near a wind farm, use electricity to split water when the wind is blowing and the power not needed, and then use the hydrogen to generate electricity when the wind isn’t blowing (or is blowing too hard) and power is needed. It is not sensible to use hydrogen to fuel vehicles, as it is difficult to transport and would require very expensive new infrastructure. Surface transport should instead run on electricity.”