Stuart Licht's STEP (Solar Thermal Electrochemical Production) process uses solar energy to break down atmospheric CO2 and other compounds into their constituent elements. These elements would ultimately be recombined to make plastics and fuel.
At the heart of the STEP process is an electrolysis cell, a device that uses electricity to break down chemical compounds. A prototype version of the cell, about the size of a fist, consists of two electrodes—positively and negatively charged—submerged in a chemical bath containing the target compound. When electric current passes through the cell, positively charged ions from the compound are attracted to the negative coil and negatively charged ions are attracted to the positive coil, splitting the material and yielding its constituent elements along with new compounds.
The hotter the contents of the cell, the less voltage required to initiate this reaction. Using heat from an external solar array, Licht, who's based at George Washington University, can raise the temperature so high that only a minute electrical current, supplied by solar photovoltaic cells, is needed to split the compounds. When carbon dioxide is fed into the cell, electricity splits it into oxygen and solid carbon or carbon monoxide gas that could then be used to manufacture many different products and fuels.
Scientists have been watching Licht's progress closely. "It's an interesting approach to using the sun for manufacturing and fuel production," says Ellen Stechel, manager of concentrated solar technologies at Sandia National Laboratories. "But can it be cost-competitive?" Because of the cell's simplicity, Licht says, the answer is yes. If he could construct STEP solar arrays dispersed across 4 percent of the Sahara, he would be able to convert 92 billion tons of carbon dioxide into solid carbon each year. At that rate, he could eliminate one-tenth of all the carbon dioxide released since the Industrial Revolution in a single year.
