Those who are familiar with my comments here and at SmirkingChimp will know that I am a skeptic on the so called "hydrogen economy," at least under conditions in which hydrogen is proposed as a common fuel for automobiles and the like.
Leaving aside the safety and transport issues, one of my objections has always been - despite what the Bushies and others tell you - is that hydrogen is NOT a form of energy: It is an energy storage system. It requires energy to make it. Further, most of the conversions proposed to make hydrogen from other forms of energy are highly inefficient: For instance, to make hydrogen by electrolysis of salt solutions one can usually recover only about 10% of the energy. Electrolysis also requires the disposal of the chlorine side product and, at least until recently, the use of liquid metal mercury electrodes that cause huge contamination problems. The preferred and (and more efficient) way of making hydrogen is the water gas reaction, which of course consumes natural gas, a non renewable, greenhouse gas forming fuel.
Here though, is a process that goes a long way to eliminating some of the inefficiency concerns: A rather clever thermochemical process that splits water into hydrogen and oxygen via a cyclic process. The primary source of the energy for this conversion is nuclear energy, one of the cleanest options available to those of us who live in early in the 21st century. Such processes, cyclic processes, are very important in nature: Just one such example is the famous citric acid (Kreb's) cycle by which living things oxidize sugars to CO2 and water.
I still don't think that hydrogen is a desirable primary fuel. However it is an intermediate that can be used to make primary fuels. Readily available cheap hydrogen theoretically could be used to hydrogenate atmospheric CO2 to motor fuels, making such fuel use part of a "carbon cycle." It would beat the pants out of attacking foreign countries, killing their children, and stealing their oil.
Anyway, here's the link:
http://web.gat.com/hydrogen/images/pdf%20files/brown_si_cycle.pdfEnjoy.