Currently the major process by which hydrogen is produced is by the steam reforming of methane. Another means of making hydrogen is by the electrolysis of water. The electricity required for electrolysis is mainly derived from the electric power grid, and the predominant source of grid electricity, combustion of fossil fuels, generates emissions, such as nitrogen oxides and particulate matter, as well as carbon dioxide. One way to eliminate such emissions is to use solar generated electricity to electrolyze water to make hydrogen. Presently, efforts are directed toward improving the efficiency, durability, and cost of the solar powered hydrogen production processes.
However, systems consisting of solar cells to make electricity together with electrolyzers to dissociate water into hydrogen and oxygen, as they exist today, cannot produce hydrogen as cheaply as the steam reforming of methane. Several projects have attempted to produce hydrogen gas to supply vehicle-fueling stations by using electricity from photovoltaic panels and commercially available electrolyzers to split water. These projects proved unsatisfactory and were usually short-lived due to the low efficiency and high cost of the combined technology, which only converted about 2%-6% of the solar energy to hydrogen fuel energy, thus, greatly increasing capital costs, the resulting hydrogen fuel cost (at least $11 per kilogram of hydrogen), and the large area covered by the system.