For the first time ever, Sandia National Laboratories have used heated supercritical carbon dioxide instead of steam to generate electricity, according to a press release by the organization. The breakthrough happened at the Sandia-Kirtland Air Force Base electrical grid.

The organization described supercritical carbon dioxide as a non-toxic, stable material that is under so much pressure that it behaves like both a liquid and a gas. Because it stays within the system and is not released as a greenhouse gas, it can get much hotter than steam (1,290 degrees Fahrenheit or 700 Celsius). These temperatures allow it to be much more efficient at turning heat from power plants into energy.

“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 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.”

On April 12, the Sandia engineering team managed to successfully heat up their supercritical CO2 system to 600 degrees Fahrenheit and use it to provide power to the grid. They generated 10 kilowatts of power which might not seem like much but is an important first step.

“We successfully started our turbine-alternator-compressor in a simple supercritical CO2 Brayton cycle three times and had three controlled shutdowns, and we injected power into the Sandia-Kirtland grid steadily for 50 minutes,” said Darryn Fleming, the lead researcher on the project.

“The most important thing about this test is that we got Sandia to agree to take the power. It took us a long time to get the data needed to let us connect to the grid. Any person who controls an electrical grid is very cautious about what you sync to their grid because you could disrupt the grid. You can operate these systems all day long and dump the power into load banks, but putting even a little power on the grid is an important step.”

In fall 2019, Fleming began experimenting with connecting Sandia’s closed-loop supercritical CO2 system to the grid. To do this, he was inspired by elevators which convert the potential energy stored in their lifted cars back into electricity for the grid.

The end result was that the Sandia team adapted the commercial-off-the-shelf power electronics from an elevator parts company to control feeding power from their test loop into the grid.

“The achievement here was coupling the system with the advanced power electronics and syncing it to the grid,” said Logan Rapp, a Sandia mechanical engineer who was involved in the test. “We have never done that before; we’d always gone to the load banks.”

Following this successful test, the team is now working on modifying the system so that it can operate at higher temperatures, 1,000 degrees Fahrenheit and above. Could this be the future of electricity?