image: Southwest Research Institute (SwRI) and 8 Rivers have patented a system that leverages fluctuations in energy demand by using liquid oxygen storage (LOX) to make power plants more cost-effective and efficient. The researchers are considering incorporating it into the Supercritical Transformational Electric Power (STEP) Demo pilot plant at SwRI’s San Antonio headquarters to make the facility even more fuel efficient.
Credit: Southwest Research Institute
SAN ANTONIO — October 15, 2025 — Southwest Research Institute (SwRI) and 8 Rivers have patented a system that leverages fluctuations in energy demand by using liquid oxygen storage (LOX) to make power plants more cost-effective and efficient. To accomplish this, the Institute modified a recently developed power cycle, the Allam-Fetvedt Cycle, which combusts fuel, like natural gas, using an oxygen and carbon dioxide mixture to allow complete carbon capture, producing minimal greenhouse gas emissions.
The Allam-Fetvedt Cycle requires high-purity oxygen separated from air, which is mostly nitrogen and trace amounts of other gases. This separation process is energy-intense and consumes 10% of a power plant’s output.
“Our idea is to generate oxygen during off-peak hours, when electricity is less expensive because demand is lower,” said SwRI Institute Engineer Dr. Jeffrey Moore, one of the new system’s inventors. “The oxygen can then be stored in liquid form and then converted back into gas for use in the plant later. This boosts plant output while lowering operating costs.”
To ensure that a power plant utilizing this technology would be profitable, SwRI conducted a techno-economic analysis, modeling both plant performance and hour-by-hour costs over a full year. Studies by Princeton University and the National Renewable Energy Laboratory showed that current price volatility for electricity will continue to increase as more forms of renewable energy come online, indicating that the economic benefits of the application will persist or grow in the future.
“The data show that in some regions prices may stay low for weeks, then spike for long periods, depending on renewable penetration. Right now, the grid is about 10–15% renewables. If that rises to 30%, the problems associated with fluctuations in wind and solar energy production will be exacerbated, making energy storage critical for overall grid reliability,” Moore said. “Currently, there’s no large-scale energy storage system on the grid, though research is underway. This oxygen storage system is one way to effectively store energy, by generating liquid oxygen when power is cheap and using it later when prices are higher.”
The researchers are also considering incorporating it into the Supercritical Transformational Electric Power (STEP) Demo pilot plant at SwRI’s San Antonio headquarters. It’s one of the largest demonstration facilities in the world for supercritical carbon dioxide power generation. Adding LOX and the Allam-Fetvedt cycle to STEP would make it even more fuel-efficient.
“The components of this system are very mature,” Moore said. “Air separation and liquid oxygen generation have been around for decades. That’s what got us to the moon. We’re putting these tested individual pieces together at larger scales, to reach greater heights in clean energy production and improving net present value of the plant.”
For more information, visit https://www.swri.org/markets/energy-environment/power-generation-utilities/advanced-power-systems.