Sun + Zinc = Clean Hydrogen
A revolutionary recipe to cook hydrogen has been elaborated by European scientists, and this might be used to drive our future hydrogen cars according to IsraCast. Take some common metal such as zinc oxide (ZnO). Put it under a heat source generated by solar energy. Don't forget to concentrate the solar rays by special mirrors to obtain a temperature of 1200°. Add a teaspoon of carbon in the form of coal. Wait until you get some pure zinc powder. Mix this powder with some water. And here is the result: pure hydrogen with almost no fossil fuels burnt! This clever recipe might be used to produce the hydrogen needed by your next car in about ten years. But this technology could also be used to produce non-toxic and non-flammable zinc-air batteries.
Iddo Genuth, the author of the article, offers a background about why we need renewable sources of energy and says that producing hydrogen from zinc by extracting oxygen from water was discovered many years ago. But the beauty of this new method is that it is a non-polluting one.
The energy cycle developed by the researchers is very efficient and relatively self-sustaining. ZnO is mined and transported to the Solzinc solar facility where it is mixed with small amounts of coal and put inside the solar furnace located on top of a high tower. A large array of heliostats (computer guided highly reflective mirrors) follows the sun around the sky and reflects the light to a hyperbolic mirror located inside the solar tower producing highly concentrated heat inside the solar furnace.
At a heat of above 1200°C (2192F) the ZnO breaks down into Zn and oxygen which in turn recombines with the carbon to create CO as a minor by-product. The Zn is then cooled down to create a fine powder which can be safely handled and transported. In order to produce hydrogen from the Zn powder a much simpler process is performed where the Zn is mixed with water at a temperature of 350°C (662F). The oxygen inside the water recombines with the Zn to produce ZnO once again and the by-product is pure hydrogen.
Below is a picture of such a solar research facility. You can see the heliostats on the ground, redirecting the sun rays towards the receivers (Credit: WIS).
And this diagram illustrates the concept of the Solzinc project (Credit: Laboratory for Solar Technology at the Paul Scherrer Institut, Switzerland).
For more information about the Solzinc project to turn ZnO into Zn, take a look at this page. And here is a link to more photographs of the Solzinc pilot plant at WIS.
This project has also been covered in August 2005 by this news release from WIS, "Solar energy project at the Weizmann Institute promises to advance the use of hydrogen fuel" and by Nature, in "Sunlight used to smelt zinc."
This research has also been published in Solar Energy under the name "Solar thermochemical production of hydrogen –– a review" (Volume 78, Issue 5, May 2005, Pages 603-615). Here are two links to the abstract and to a previous presentation (PDF format, 21 pages, 1.20 MB). The above images come from this paper.
Let's come back to the IsraCast article for the possible applications of this industrial process. First, what can we expect for our cars?
Currently there are almost no hydrogen fuel stations, let alone hydrogen-based cars. This could change within 5-10 years but it will require great investments by both countries and the industry. It will also require large amounts of inexpensive accessible hydrogen, and here enters the Solzinc process developed at the Weitzman Institute.
As Michael Epstein, head of the Solar Research Facilities Unit in the Weitzman Institute explained in an interview to IsraCast, it is now up to the industry to push the project forward into full commercialization. His assessment is that with the backing of the industry, full-scale production of hydrogen from Zn using the industrial Solzinc facility could begin within 8-10 years.
But outside cars, there are possible other usages for this technology.
In the meantime, Epstein is considering more immediate uses for Zn such as Zinc-Air batteries which are similar to existing batteries but get one of their main reactants -- oxygen -- from the outside air. These batteries are nontoxic and are neither highly reactive nor flammable.
Will we soon see these kinds of batteries? It seems that several companies are developing them, but only for our cars. Why didn't they target our computers?
Sources: Iddo Genuth, IsraCast, September 9, 2005; and various web sites
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