First test of cutting-edge Brayton cycle technology put power into local grid
For the first time, Sandia National Laboratories researchers delivered electricity produced by a new power-generating system to the Sandia-Kirtland Air Force Base electrical grid.
The system uses heated supercritical carbon dioxide instead of steam to generate electricity and is based on a closed-loop Brayton cycle. The Brayton cycle is named after 19th century engineer George Brayton, who developed this method of using hot, pressurized fluid to spin a turbine, much like a jet engine.
Supercritical carbon dioxide is a non-toxic, stable material that is under so much pressure it acts like both a liquid and a gas. This carbon dioxide, which stays within the system and is not released as a greenhouse gas, can get much hotter than steam — 1,290 degrees Fahrenheit or 700 Celsius. Partially because of this heat, the Brayton cycle has the potential to be much more efficient at turning heat from power plants — nuclear, natural gas or even concentrated solar — into energy than the traditional steam-based Rankine cycle. Because so much energy is lost turning steam back into water in the Rankine cycle, at most a third of the power in the steam can be converted into electricity. In comparison, the Brayton cycle has a theoretical conversion efficiency upwards of 50 percent.
“We’ve been striving to get here for a number of years, and to be able to demonstrate that we can connect our system through a commercial device to the grid is the first bridge to more efficient electricity generation,” said Rodney Keith, manager for the advanced concepts group working on the Brayton cycle technology. “Maybe it’s just a pontoon bridge, but it’s definitely a bridge. It may not sound super significant, but it was quite a path to get here. Now that we can get across the river, we can get a lot more going.”
