I believe that the harnessing of solar and thermal energy to generate hydrogen means converting solar and geothermal energy into an electrical current in order to pull apart molecules of water. In doing that, no fossil fuels need to be burnt and no carbon dioxide is generated. (At least at the levels they are now).
In regards to the storage of hydrogen, yes, it does tend to leak out from its containers. But so does propane, butane, oil, gasoline, etc. etc. They all have the same propensity to escape from their ocntainers. With hydrogen, it's not really the same type of escaping. It's more of a leeching effect. The hydrogen will leech through the container walls since it is such a small molecule. However, it doesn't do this at a dangerous/flammable level. The amounts that leak out are so small that it cannot support combustion. The only problems it generates are that after a while, all of you "fuel" has dissipated away. That is why palladium storage cells are such the hot topic in terms of storing hydrogen. Palladium can store a massive amount of hydrogen and keep it in place for a good long time. If a hydrogen economy does take off, make sure to hold onto your palladium as it's price per ounce will undoubtably skyrocket.
Now what's really preventing us from moving towards an alternative fuel source? Simple; MONEY. Scientific research is not cheap, so grants need to be given in order allow the work to continue. The main sources of these grants are generally the government and private organizations. The government gets paid a lot of money by fossil fuel supporters to continue using fossil fuels, and a good deal of the private organizations which give research grants are in one form or another involved with the usage of fossil fuels. Also, any country which is a member of OPEC will in no way support the use of an alternative fuel. So without financial support, the research into using alternative fuels will be a slow, drawn-out process. We just need to hope that our governments quit being in cohorts with all these fossil fuel corporations and start looking towards the betterment of society as a whole.