Efficient solar thermal processes from carbon based to carbon free hydrogen production

The potential of hydrogen to be the energy carrier of the future is widely accepted. Today more than 90% of hydrogen is produced by cost effective technologies from fossil sources mainly by steam reforming of natural gas and coal gasification. But hydrogen is not important as an energy carrier yet - it is mainly a chemical. To finally benefit from hydrogen as a fuel it has to be produced greenhouse gas free in large quantities. Therefore these two tasks have to be connected by a strategy incorporating transition steps. Solar thermal processes have the potential to be the most effective alternatives for large scale hydrogen production in the future. Therefore high temperature solar technologies are under development for the different steps on the stair to renewable hydrogen. This paper discusses the strategy based on the efficiencies of the chosen solar processes incorporating carbonaceous materials as well as processes based on water splitting. And the availability of the technologies. A comparison with the most common industrial processes shall demonstrate which endeavors have to be done to establish renewable hydrogen as a fuel.