Sandia Lab researcher Rich Diver has invented a new way to make hydrogen using solar energy. Using rings containing reactive ferrite material, relatively cool ferrite absorbs the oxygen out of steam. The ferrite is then heated by sunlight to drive off the oxygen prior to the next cycle. The remaining hydrogen is pumped out and compressed for use. The ferrite is heated and cooled in a regenerative cycle using counter currently rotating rings containing the ferrite.
The process is in fairly early stages of development and will require much work before it could be used in a practical system. One of the tasks that is complete is development of a ferrite material consisting of ferrite mixed with zirconia that has the right color and properties to be used as the absorbent. Rich said "We had to come up with a material that was black and absorbed heat from the sun and which had the right reaction oxidation reaction."
The next step is building a prototype of the system.
The following description from the Sandia Announcement explains the process in detail:
His invention, the Counter Rotating Ring Receiver Reactor Recuperator (CR5, for short), splits water into hydrogen and oxygen, using a simple, two-step thermochemical process. The CR5 is a stack of rings made of a reactive ferrite material, consisting of iron oxide mixed with a metal oxide such as cobalt, magnesium, or nickel oxide. Every other ring rotates in opposite directions. Concentrated solar heat is reflected through a small hole onto one side of the stack of rings. The side of the rings in the sunlit area is hot, while the other side is relatively cold. As the rotating rings pass each other in between these regions, the hot rings heat up the cooler rings, and the colder rings cool down the hot rings. This arrangement results in a conservation of heat entering the system, limiting the energy input required from the sunlight.
Steam runs by the rings on the cooler side causing a chemical reaction to take place, allowing the ferrite material to grab oxygen of of the water, leaving the hydrogen. The hydrogen is pumped out and and compressed for use.
A separate chemical reaction that drives off the oxygen occurs where the sunlight directly illuminates the ferrite material at the solar receiving end. This is needed to regenerate the rings so they can react with more water during the next cycle.
Rich Diver invents new way to make hydrogen for fuel, Sandia Lab News, Vol 58, No 3, February 3, 2006