Scientists are inching closer to produce ‘photosynthesising’ fuel from carbon dioxide and sunlight which they claim will help meet world’s energy needs and minimise carbon emissions. The team at Sandia National Laboratories in Albuquerque, New Mexico, is developing the technique which will produce “synthetic liquid fuels” in solar-powered reactors.
Solar-powered reactors can take carbon dioxide (CO2) and turn it into carbon monoxide. The same reactors can also be used to turn water into hydrogen and oxygen. The two can then be reacted together with a catalyst to form hydrocarbon fuels, in a technique known as the Fischer-Tropsch process.
According to the New Scientist report, fuels made in this way are sufficiently similar to those currently used in cars that major redesigns of engines and refuelling stations should not be necessary. If fuels can be made entirely from atmospheric carbon, running a car on that fuel would be carbon neutral.
One such machine, the Counter Rotating Ring Receiver Reactor Recuperator (CR5), created by a team of scientists at Sandia National Laboratories in Albuquerque captures carbon dioxide from power plant exhaust fumes.
In the future, however, they hope to extract it directly from the air, although they are not developing their own carbon-capture technique to do so. “That is a huge challenge in itself, and we opted to focus on one hard problem at a time,” says James Miller, a combustion chemist at Sandia.
The system uses a giant parabolic mirror, which concentrates sunlight on to two chambers separated by spinning rings of cerium oxide (see the picture above.) As the rings turn, the cerium oxide is heated to 1500C and releases oxygen into one of the chambers.
The oxygen is then pumped away. As the ring spins, the now de-oxidised cerium moves into the other chamber. Carbon dioxide is pumped in, and the deoxidised cerium steals one of the oxygen molecules, creating carbon monoxide and cerium oxide.
Another team from the Swiss Federal Institute of Technology, Zurich, uses a similar system, but with calcium oxide, zinc oxide and steam, which can create a stream of hydrogen and carbon monoxide. Their system can already use atmospheric carbon dioxide.
At the moment the two reactors have problems. The New Mexico team’s system currently only works for a few seconds at a time, while the Swiss model runs at a mere 10 kilowatts. But both hope to improve reliability and yield.
Ken Caldeira of the Carnegie Institution of Washington at Stanford University, California, said that creating usable fuel from solar energy is a promising way of keeping the world’s energy demands satisfied while minimising carbon emissions.
“This area holds out the promise for technologies that can produce large amounts of carbon-neutral power at affordable prices, which can be used where and when that power is needed,” he says. “It is one of the few technology areas that could truly revolutionise our energy future.” [Sandia National Laboratories via Daily Telegraph (UK) and New Scientist]