$155M demonstration plant at Southwest Research aims to revolutionize energy industry

For 125 years, steam has been the thermal medium of choice to drive the turbines that generate electric power.

Now there’s a new thermal medium in town, one that has the potential to revolutionize how power is generated by increasing efficiency, reducing costs and decreasing planet-warming emissions.

And it really is in town — on the campus of Southwest Research Institute (SwRI) in the form of a $155 million demonstration facility that has been under construction since 2018.

Known as the Supercritical Transformational Electric Power (STEP) Demo, the pilot 10-megawatt plant is now ready to start testing to prove that carbon dioxide, when heated and pressurized to a certain point, is more efficient than steam to turn heat into energy.

“The same gas that may be hurting the planet may also be the same gas that saves it,” said Jeff Moore, a SwRI engineer who serves as project lead on STEP Demo.

Carbon dioxide is a greenhouse gas, emitted by burning fossil fuels and produced naturally by animals, causing more heat to be retained by Earth’s atmosphere. In its supercritical form, carbon dioxide has the density near that of a liquid, and is nontoxic and nonflammable.

On Thursday, officials with the industry and government consortium that have been working on STEP Demo since 2015 came together inside a nondescript 22,000-square-foot warehouse that holds the plant to celebrate its completion.

“STEP will undoubtedly change the way we think about power generation,” said SwRI President and CEO Adam Hamilton. The plant is now the largest indirectly firing supercritical CO₂ power system in the world.

Power produced using supercritical carbon dioxide, or sCO₂, instead of water is 10% more efficient. That may not sound like a lot to the lay person, said Moore, but it’s a huge increase in the world of energy.

Most power plants currently operating in the United States are more than 30 years old and operate below 35% efficiency, in addition to burning large amounts of fossil fuels that result in planet-warming greenhouse gas emissions.

The greater efficiency of sCO₂ power systems allow for its components to be approximately one-tenth the size of conventional power plants. For example, a desk-sized sCO₂ turbine can power up to 10,000 homes. That could shrink both the environmental footprint and construction cost of new power-generating facilities.

At SwRI’s demonstration facility, researchers will work to advance the technology for commercial adoption, refining the sCO₂ power cycle and demonstrating its scalability and performance ability.

The power generated by the plant will flow to CPS Energy, which will credit SwRI for what could be as much as a third of the research facility’s own power use.

The plant’s components, which are spread out over a larger area than a conventional power plant would be to allow for easier experimentation and training, also have been designed to adapt to industry changes. The SwRI team will welcome research and commercial interests looking to prove various aspects of the technology and its applications.

One application mentioned by several speakers Thursday is the potential for waste heat recovery in industrial power uses where it hasn’t been feasible previously. Waste heat recovery can improve efficiency and reduce energy bills, lower maintenance costs and improved equipment productivity.

The technology is also fuel agnostic, meaning beyond its use to make fossil fuel-burning power plants cleaner and more efficient, it can increase the efficiency and reduce the footprint of power generated from nuclear and concentrated solar, officials said, as well as long-duration storage.

STEP Demo is funded by a $124.5 million grant from the U.S. Department of Energy’s National Energy Technology Laboratory, which aims to advance technologies that will bolster the nation’s domestic energy foundation. More than a decade ago, the lab launched a comprehensive sCO₂ research and development program that culminated in STEP Demo.

GTI Energy, a technology development company dedicated to advancing technologies to decarbonize energy systems, serves as the lead partner on the project, which also includes GE Research, a division of General Electric that’s already working on commercial applications of the technology.

The state of Texas committed $4 million, and state Sen. Jose Menendez (D-San Antonio), who helped secure that funding, honed in on STEP Demo’s potential to strengthen the resilience of Texas’ power grid, better connect renewables and lower costs.

Don Stevenson, vice president of GTI Energy, called efficiency “the unsung hero of reducing carbon emissions.”

He noted that the project maintained bipartisan support through three presidential administrations and seven annual budget cycles. Getting to this point, he said, “took a monumental effort across this country and across the world.”

The team broke ground on the project in 2018, working with suppliers across the globe to source various components, slowed but not derailed by the pandemic.

SwRI has long been an industry leader in the development of sCO₂ power cycles, officials said, conducting a number of related DOE projects advancing the technology.

In February, SwRI will host the eighth International Supercritical CO₂ Power Cycles Symposium in San Antonio, bringing together industry, academia and government agencies to share their progress.