"The Payoff from successfull research in solar energy would be the production of very pure hydrogen that is cost-competitive with fossil fuels as an energy source. Inexpensive, high-purity hydrogen would greatly accelerate the implementation of fuel cell technology by eliminating some of the costly purification systems currently used. It would also enable the widespread use of proven technologies (such as alkaline fuel cells) that are not useful with carbon-containing fuels. Solar energy is readily available in sufficient supply to enable solar hydrogen to be the dominant global energy source if the cost/efficiency ratio of PV cells can be decreased by a factor of 10 or more." Basic Research Needs for the Hydrogen Economy page 84. (Note: This link downloads a large PDF file.)