Sandia researcher Rich Diver works on the Counter Rotating Ring Receiver Reactor Recuperator (CR5) he invented.
Greener Fuels
April / May 2009
Volume 7 Number 2
Researchers at Sandia National Laboratories believe they are only weeks away from having a working device that can recycle carbon dioxide into carbon monoxide, a key building block in making combustible fuels such as methanol, gasoline, diesel and jet fuel.
"We have proven the concept in the laboratory in batch mode, but soon expect to do it in our prototype," says researcher Jim Miller, who is working with a large multi-disciplinary team to come up with an efficient and affordable way to recycle carbon dioxide and turn it back into liquid transportation fuels.
The prototype device that is on the verge of making history is the Counter Rotating Ring Receiver Reactor Recuperator (CR5, for short), invented by Rich Diver as a way to break down water into hydrogen and oxygen gases. Miller, working with Diver and Nate Siegel, saw the possibility of the CR5 also breaking down carbon dioxide, just as it would water, but into carbon monoxide and oxygen. The CR5 breaks a carbon-oxygen bond in the carbon dioxide to form carbon monoxide and oxygen in two distinct steps. Energy to break down the carbon dioxide comes from sunlight.
"People have known for a long time that theoretically it should be possible to recycle carbon dioxide, but most still think it cannot be made practical, either technically or economically," says Ellen Stechel, the program manager for the Sandia team.
Hence, only a handful of companies and scientists have pursued the process with much vigor. Not only did the Sandia team think it was possible, it has developed a prototype that has a number of unique characteristics that holds promise to move from a laboratory experiment to a technology.
Stechel named the process of effectively reversing combustion by capturing and then converting carbon dioxide and water with concentrated solar energy into liquid hydrocarbon fuels Sunshine to Petrol (S2P).
Stechel notes the invention and S2P, which is probably 15 to 20 years away from being market ready, holds a real promise of being able to reduce carbon dioxide emissions while preserving options for the domestic production of liquid fuels.
"What's exciting about this invention is that it will result in fossil fuels being used at least twice, meaning less carbon dioxide being put into the atmosphere and a reduction of the rate that fossil fuels are pulled out of the ground," she says.
As an example, coal would be burned at a clean coal power plant. The carbon dioxide from the burning of the coal would be captured and reduced to carbon monoxide in the CR5. The carbon monoxide would then be the starting point of making gasoline, jet fuel, methanol, or almost any type of liquid fuel.
The prospect of a liquid fuel is significant because it fits in with the current gasoline and oil infrastructure. After the synthesized fuel is made from the carbon monoxide, it could be transported through a pipeline or put in a truck and hauled to a gas station, just like gasoline refined from petroleum is now. Plus it would work in ordinary gasoline and diesel engine vehicles and in vehicles already on the road.
Siegel says that while the first step would be to capture the carbon dioxide from sources where it is concentrated —€”power plants, smokestacks and breweries, for example —€”the ultimate goal would be to snatch it out of the air. An S2P system that includes atmospheric carbon dioxide capture could produce carbon neutral liquid fuel liquid fuels.
"Our overall objective with this prototype is to demonstrate the practicality of the CR5 concept and to determine how test results from small-scale testing can be expanded to work in real devices," Siegel says. "The design is conservative compared to what might eventually be developed."
Diver says he hand-built the precision prototype in a shop at Sandia's National Thermal Test Facility and is now doing final calibration to get a working device. Initial tests will break down water into hydrogen and oxygen. That will be followed by tests that similarly break down carbon dioxide to carbon monoxide and oxygen.
While Diver begins tests on this first-generation prototype, other members of the full team are experimenting with the reactive materials that make the device work. They aim to better understand in detail how and why the materials work and to find materials that will work better and work longer. Other team members are working to develop models guided by the experiments and to guide future experiments. They aim to predict performance and economics of the CR5 as well as the full S2P system and to recommend changes to improve the performance and economics. The scale in the collection of models ranges from as small as atoms to as large as a chemical plant that can produce thousands of gallons of liquid fuel per day. The scale also ranges from as short a time as molecular vibrations to as long as decades.
"It is a very exciting team," Stechel says. "It has enough talent and diversity to substantially increase the odds for success in what is a very challenging endeavor."
Success will consist of continuously improved generations of prototypes and S2P systems, a new generation each three years with significant improvements in performance (measured as the amount of solar energy converted into the fuel), greater durability, and reduced cost. With that schedule of improvements, the technology should be market ready in less than two decades.
"For a concept as new as the CR5 and Sunshine to Petrol, that would be an aggressive schedule," Stechel says. "Indeed, the development of a process that can efficiently, cost effectively, and sustainably take the products of combustion, carbon-dioxide and water, and recreate liquid fuels using sunlight to put the energy back in, would be an unparalleled achievement and is the key challenge that must be surmounted to solve the intertwined problems of finding domestic substitutes for petroleum and mitigating the risk of climate change."
Chris Burroughs is an information specialist at Sandia National Laboratories.
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