Dec. 18, 2007 -- What if, instead of spewing carbon dioxide into the atmosphere, factories or power plants could recycle the global warming gas and turn it into fuel?
Researchers have developed a technique that does just that. The Sunshine to Petrol project at Sandia National Laboratories in Albuquerque, New Mexico, uses sunlight and steam to neutralize CO2 and ultimately turn it into a clean energy source, such as hydrogen.
"This would allow you to use CO2 one more time. You wouldn't throw it out into the atmosphere; you'd turn it into gasoline," said Rich Diver, principal member of the technical staff and lead engineer on the project.
That strategy could appeal to big CO2 emitters like factories and power plants, which could potentially increase their revenues by producing another fuel source from a gas otherwise wasted into the atmosphere.
The Sunshine to Petrol concept relies on a device developed by Diver and his team called a Counter-Rotating-Ring Receiver/Reactor/Recuperator, or CR5 for short.
At the heart of the prototype CR5 is a stack of 14 ceramic discs about 1/2-inch thick and about 12 inches in diameter. The outer ring of each disc is comprised of an inch of fairly porous material made from ferrite materials, basically iron oxide and other ingredients, including cobalt and zirconia.
The discs rotate inside a vacuum-sealed contraption that slowly turns each one in the opposite direction at about one revolution per minute. As they spin, the discs encounter two different zones where chemical reactions take place: a zone of sunlight (at the 12 o'clock position) and a zone of steam (at the 6 o'clock position).
In the zone of sunlight, solar energy concentrated by a parabolic mirror into a high-temperature beam, shines onto the porous portion of ring. The heat -- 1,400 to 1,500 degrees Centrigrade -- reduces the iron oxide material, breaking the molecular bonds and releasing oxygen molecules.
Next, the disc moves into the zone of steam. In the prototype version, the steam is simply H2O, but it could also contain CO2. The oxygen molecules in the steam glom onto the ferrite ring and replace those oxygen molecules that were previously driven away in the first step. What remains are two molecules of hydrogen that can be captured and eventually used, for example, to power a hydrogen fuel cell.
In the case of mixing CO2 with the steam, most of the oxygen molecules would glom onto the ferrite ring. The remaining molecules of hydrogen and carbon monoxide would bind to form methanol. This could be used as a fuel or synthesized into a petroleum substitute.
"The solar reactor is innovative and allows them to perform both steps of the thermo-chemical cycle in the same reactor," said professor Aldo Steinfeld, editor of the ASME Journal of Solar Energy Engineering and head of the Solar Technology Laboratory at the Swiss Federal Institute of Technology in Zurich.
The big challenges lie in the device's efficiency, he said.
"The rate of radiation heat transfer given by concentrated solar energy to the rate of the chemical reaction given by the kinetics of the process need to be matched," said Steinfeld.
Diver and his team are working to improve the efficiency, but think it could be a decade or more before such a device would be available.
Related Links:
our sites
video
mobile
shop
stay connected
corporate
