Fuel cells combine hydrogen and air to produce electricity by running them through a chemical catalyst. The only byproducts are heat and water.

Using photovoltaic cells, the Air Tree produces a substantial amount of energy, which is then sold back to the local electric companies, the profits being used for maintenance of the structure.

But while batteries store all the chemicals needed for the necessary chemical reactions in a sealed package, fuel cells use an external fuel source and air from the atmosphere.