Another technology that has received a lot of attention as a potential future climate gamechanger is hydrogen-derived energy. Hydrogen can produce energy in the context of a fuel cell in which the hydrogen is fed into the anode (negative electrode) and air is fed to the cathode (positive electrode) and there is an electrolyte between the anode and cathode. The electrons in the hydrogen atom will travel from anode to cathode through and external circuit, inducing an electric current and the protons travel through the electrolyte and react with oxygen and the electrons to form water vapor and heat – which can be converted to electricity.
source: https://americanhistory.si.edu/fuelcells/basics.htm
diagram of an alkali fuel cell
For more information, consult Energy.gov fuel cell basics and Energy.gov hydrogen basics.
The challenge with hydrogen is producing the hydrogen to integrate into these fuel cells. Since diatomic hydrogen is very rare in the Earth’s atmosphere, it must be produced from other source. Thus far, the most common source of hydrogen has been from methane through a process of steam reformation without capturing excess greenhouse gases made in the process. This is called “grey hydrogen”. Hydrogen produced from the same source, but with carbon capture technologies is called “blue hydrogen”. Hydrogen produced from renewable energy sources used to electrolyze water is called “green hydrogen” – but this is currently very expensive and constitutes a very small portion of the hydrogen economy. There are other “color labels” for hydrogen depending on how they are sourced. More information is available here: hydrogen color spectrum
On other linked pages, it is noted that water vapor is, itself a greenhouse gas and because of its high concentration in the atmosphere, is actually the most significant contributor to the total greenhouse effect. However, adding more water vapor to the atmosphere through using hydrogen fuel cells is not a significant climate concern for a few reasons:
1) The amount of water vapor in the atmosphere is controlled by the Clausius Clapeyron relationship and excess water vapor is likely to rain out in a short period of time. Relatedly, water vapor tends to be short lived in the atmosphere.
2) By concentration (i.e. per molecule), water vapor is not nearly as potent a greenhouse gas as carbon dioxide, let alone methane, or other anthropogenic sources.
3) The amount of additional water vapor that could be added to the atmosphere even by a massive upscaling of hydrogen technology would make a very small difference in the global concentration of atmospheric water vapor (even if all the world’s energy needs were fully satisfied by hydrogen, the amount of water vapor added to the atmosphere would be on the order of 2% of the global water vapor concentration).
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