Hydrogen is widely touted as the clean fuel of the future. One of the main reasons for this is that cars that run on hydrogen fuel cells emit no CO2. If the hydrogen itself is produced using renewable sources of energy, such as solar or wind power, then it does not make any direct contribution to CO2 emissions. However, one of the major criticisms levelled at hydrogen car technologies is that currently hydrogen is largely produced using fossil fuels rather than renewable energy sources.
However, a new study predicts large reductions in greenhouse gas (GHG) emissions with hydrogen technologies, even when the hydrogen is produced from fossil fuels. The researchers analysed two different modelling scenarios for the year 2060 - one in which fossil fuel energy used to produce hydrogen, and one in which renewable energy is used. From this, they were able to estimate how clean a hydrogen-powered future would be compared with a future using conventional cars (based on current projections of the future number of cars and their emissions).
The study, which was based on an urban region in California, found that using fossil fuels to generate hydrogen would result in a 59 per cent reduction in GHG emissions, while using renewable fuels would lead to a slightly larger reduction at 63 per cent. Their models also predicted significant improvements in air quality compared with a petrol-fuelled future, for example, reductions of 10 ppb (parts per billion) in peak 8 hour averaged ozone and 6 µg/m3 in 24 hour averaged particulate matter (PM) concentrations.
The researchers used an environmental tool called STREET, or 'spatially and temporally resolved energy and environment tool', to create their scenarios, and combined it with location data for existing fuel stations in their study area to predict how hydrogen fuel would be distributed in the future. Their analyses even accounted for details such as the energy required for pressurisation of hydrogen during storage.
Such tools could be used by the transport, fuels, and power industries as a means of assessing how different business decisions or scenarios might affect environmental outcomes, such as emissions. The researchers say the same tools could be adapted for use by policy makers involved in planning.