I have heard that hydrogen burns cleanly, why not replace fossil fuels with hydrogen gas?
Hydrogen, when burned in a combustion engine is a huge improvement in terms of emissions when compared to fossil fuels. Burning hydrogen does release low amounts of nitrous oxide, a component of smog, into the atmosphere. This occurs whenever high temperature combustion occurs in the presence of oxygen. Other pollutants are also released as trace amounts of lubricants are burned in the process. The main reason to employ fuel cells instead of combusting hydrogen has to do with efficiency. Anytime a fuel is ignited and burned the overall efficiency is limited by the laws of physics, especially Carnot’s Law, to around 10%. This is due to efficiency losses associated with heat and the additional steps necessary before the fuel is transformed into useable energy. A fuel cell directly converts the hydrogen fuel into electricity and is therefore inherently more efficient. A fuel cell skips the steps, associated with combustion generation, of first converting the fuel into heat, then mechanica
