A new technology would use only sunlight, air and water to supply energy

The Sun is Earth’s primary energy source and harnessing its abundant light is the Holy Grail of renewable energy
Now, a group of scientists has demonstrated a new way to use sunlight, water (H2O) and carbon dioxide (CO2)–some of the cheapest and most commonplace stuff on Earth–to make unlimited amounts of fuel to power almost anything, anywhere.
The method uses concentrated heat from the sun to convert water and carbon dioxide into hydrogen (H2) or carbon monoxide (CO). Large amounts of these two gases could be combined to make liquid fuel that fits into America’s existing energy economy.
“Alternatively, you could use the H2 and CO to make methane (natural gas) for a gas-fired electricity generator,” said Sossina Haile, professor of Materials Science and of Chemical Engineering at California Institute of Technology in Pasadena. “Or, because the fuels we produce are so pure, they could be easily used to run fuel cells, which generate power very efficiently.”
The researchers say one of the most exciting things about the discovery is its versatility. “We are not dictating to the user what the energy infrastructure should be,” Haile said. “We are making solar energy easy to use by putting it into a form that our industry is used to seeing and making it available on demand.”
Scientists have long known how to convert water and carbon dioxide into hydrogen and carbon monoxide. But to do it cheaply and efficiently enough to make the process affordable on a wide scale has been the issue. Part of the problem was the need for expensive and rare elements, such as platinum or iridium, to act as catalysts that encourage the conversion to happen.
So Haile and her team took a novel approach; they tried ceria, a material used in the walls of self-cleaning ovens. Ceria is the oxidized or “rust” form of the element cerium, which is more abundant, and therefore cheaper, than other metals that could do the same job.
The new method requires two steps, the first at high temperature using concentrated heat from the sun (about 3,000 degrees Fahrenheit), and the second at a much lower temperature.
Haile describes the process this way, “If we heat ceria up, the material ‘naturally’ releases some oxygen from its structure. If we then cool it back down, those oxygen vacancies want to be refilled. In other words, the ceria ‘exhales’ oxygen at high temperature and then ‘inhales’ it back when the temperature is lowered.”
To make fuel, the second step requires the presence of water and carbon dioxide gases. “At lower temperatures, the cerium, the hydrogen and the carbon all want the oxygen, but the cerium wants it most,” Haile said. “So the oxygen vacancies in the ceria are filled by stripping oxygen from H2O and CO2, leaving H2 and CO.”
Haile and her Caltech team, supported by an award from the National Science Foundation, recently published a paper describing the breakthrough in the journal Science. For this project, they collaborated with researchers led by Aldo Steinfeld, a renewable energy technology professor at the Swiss Federal Institute of Technology, also called ETH Zürich, in Switzerland. Steinfeld also leads the Solar Technology Laboratory at the Paul Scherrer Institute in Switzerland.

Source: www.physorg.com

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Posted by on Apr 8 2011. Filed under _featured slider, INDUSTRY, Technology. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry

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