I’m seeing more and more reports of studies involving the use of catalysts to generate hydrogen. This is a fascinating development, so I’ll be posting more of those here (follow this link for a description of the work CalTech is doing on this). The basic premise is to heat water to a point where an added catalysts splits the water molecules into their oxygen and hydrogen components, the hydrogen is then used as fuel. More importantly, the hydrogen can then be stored for later use. For example, imagine a solar thermal collector used to generate the heat to drive this reaction, with excess hydrogen being stored for use during night. It’s a sort of hydrogen battery, if you will.
This research is still in the laboratory stage, but is an interesting path to sustainable energy solutions which address the energy storage concerns.
Catalyst or not, it still needs energy to split the water into Hydrogen and Oxygen – 4.41 KW.h per litre of water is the thermodynamic minimum, more is required in practice. When you burn the Hydrogen, you get a maximum of 4.41 KW.h/L back, less in practice, and MUCH less if the energy is in the form of heat used to drive a heat engine.
Dave, you’re right, and something like this will never approach 100% efficient…there will be a lot of wasted energy in the process. However, I think that’s just the reality of any energy storage medium. If solar energy is used to generate the required heat, then the efficiency only matters in terms of cost per watt or unit energy produced.