Hydrogen has been championed for decades as a clean alternative energy carrier to fossil fuels for transportation, as well as for other uses, because it is so “abundant,” and because when it is converted into energy, water is the only by-product, and a valuable one at that.
Of course, hydrogen in a free state is rare here on earth. Hydrogen has to be produced, either by steam reformation of natural gas, which consumes a relatively clean fuel and releases carbon into the atmosphere, or, in lesser amounts, by electrolysis of water, an energy-intensive process that also releases carbon if fossil-fueled generators produce the electricity.
Solar hydrogen generation is achieved when photovoltaic (PV) electricity is used to power proton exchange membrane (PEM) or alkaline electrolyzers for carbon-free production of hydrogen. This is being implemented in a number of fledgling projects, from hydrogen refueling stations for fuel cell cars to demonstration homes.
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