From Mark Poulter
While I support the ideals of hydrogen power there is one question that no one has yet been able to answer for me: isn’t the water vapour produced by fuel cells a more effective greenhouse gas than just about everything else? Think of Venus.
James Randerson replies:
• Water vapour does have a potent greenhouse effect, and fuel cell cars emit more water than conventional engines because oxygen is combined with hydrogen only (to make water) rather than hydrogen and carbon (to make water and CO2). However, if that hydrogen came originally from electrolysis of water then using the hydrogen as fuel will not add “new” water to the system. Even “new” water (ultimately from hydrocarbons) will not have a noticeable effect. Currently, the global energy system emits around 20 billion tonnes of water per year − 0.0038 per cent of the Earth’s annual evaporation.
Woking, Surrey, UK
