The research team developed a solar-thermal system through which the sun's rays can be concentrated with the help of a large array of mirrors into a single point at the top of a central tower hundreds of meters high.
![A simulation illustration of a commercial plant that utilizes the sun's rays to split a water molecule and obtain clean hydrogen fuel, a plant consisting of an array of towers and mirrors to concentrate the sun's rays [courtesy of the University of Colorado].](https://www.hayadan.org.il/images/content3/2013/08/renewalbe-hydrogen-multiplant1_0.jpg "A simulation illustration of a commercial plant that utilizes the sun's rays to split a water molecule and obtain clean hydrogen fuel, a plant consisting of an array of towers and mirrors to concentrate the sun's rays [courtesy of the University of Colorado].")
The research team developed a solar-thermal system through which the sun's rays can be concentrated with the help of a large array of mirrors into a single point at the top of a central tower hundreds of meters high. In this tower, with the help of the mirrors, it will be possible to achieve a temperature of 1350 degrees Celsius, which will be transferred to a reaction tank containing metal oxide compounds. As soon as these oxides heat up, they release the oxygen atoms stored in them and turn into various compounds searching for more oxygen atoms, explains the lead researcher. The team of researchers showed that adding steam to the system - which can be obtained from boiling water heated with the help of the concentrated beam of sunlight - causes the oxygen atoms that make up the water molecule to adhere to the surface of the metal oxide while releasing hydrogen atoms that react together to obtain clean hydrogen gas.
"We have designed a system here that is very different from all the other existing methods and, in fact, an idea that no one else had previously thought would be possible," said the lead researcher who is a professor in the Department of Chemical and Biological Engineering at the University of Colorado. "Splitting water molecules with the help of the sun's rays is the "holy grail" of a sustainable hydrogen economy." The research findings were published in the prestigious scientific journal Science.
One of the main differences between the new method and other methods developed for splitting water is its ability to hold two separate chemical reactions at the same temperature, notes one of the researchers. Although not all the details of the mechanism are known to science, the traditional theories state that the production of hydrogen with the help of the metal oxide requires heating the reaction tank to a high temperature in order to remove the oxygen atoms from the oxide and then lowering the temperature before injecting steam designed to re-oxygenate the compound while obtaining hydrogen gas emitted from the oxide itself.
"The existing approaches require control of both the lowering of the temperature in the tank from a high to a low temperature and during the flow of steam into the system," explains the researcher. "One of the great innovations of our system is that we do not make temperature changes. The entire process is controlled by turning on or off the steam valve only."
"Just as you can use a magnifying glass to start a fire, we can concentrate the sun's rays and use the heat generated from the concentrated beam to start these chemical reactions," explains the researcher. "Although we can heat the beam to a temperature higher than 1350 degrees Celsius, we heat it to the lowest possible temperature necessary to initiate the chemical reactions, this is to avoid damage to both the materials themselves and the reaction equipment."
In addition, the usual methods of splitting water using a two-step process waste both time and heat, and this despite the fact that the hours of sunlight per day are limited, notes one of the researchers. With the help of the innovative method, the amount of hydrogen produced for fuel cells or for its storage for later use depends absolutely on the amount of metal oxide - which consists of a mixture of iron, cobalt, aluminum and oxygen - and on the amount of steam injected into the system. One of the designs proposed by the researchers is to build a reaction tank in the form of tubes with a diameter of 30 cm and a length of several meters, fill them with the metal oxide and stack them one on top of the other. A commercially active system for producing a significant amount of hydrogen gas would require a number of towers to concentrate the sun's rays within an area of several thousand square meters of mirrors surrounding each of the towers.
"Despite this important discovery, the commercialization of a solar-thermal reaction vessel of this kind could take several years. "When the price of natural gas is so low, there is no incentive to utilize clean energy," explains the lead researcher. "This will only happen when heavy penalties are imposed on air pollution with carbon, or when the price of fossil fuel is too high."
The news about the research on the university website
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How is this different from what Bright Source does?
I don't know what you are trying to recall and when it is, but hydrogen storage technologies, like any technology, are developed at an exponential rate. Just do a "hydrogen" search here on the site.
Even if hydrogen production in the future will be at a negligible price, there is still a huge problem of storing it in an available form. If I remember correctly, in the experimental hydrogen car, the tank was spherical, and intended to store hydrogen and yet lost 50% of its contents within 24 hours. The hydrogen just seeped out through the tank.