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STEP Demo supercritical CO2 pilot plant generates electricity for the first time

May 29, 2024

The Supercritical Transformational Electric Power (STEP) Demo pilot plant has generated electricity for the first time using supercritical carbon dioxide (sCO2) power cycles. The $169 million, 10-megawatt sCO2 facility at Southwest Research Institute (SwRI) in San Antonio is demonstrating next-generation power production technology in a project led by GTI Energy in collaboration with SwRI, GE Vernova, the U.S. Department of Energy/National Energy Technology Laboratory (U.S. DOE/NETL), and several industry participants.

“The impact of demonstrating that the sCO2 technology works cannot be overstated,” said SwRI Project Manager Dr. Jeff Moore. “I truly believe this project will change how we approach power generation in the near future.”

For the first time, the pilot plant’s turbine achieved its full speed of 27,000 RPM at an operating temperature of 260°C and generated a small amount of power. Over the next few weeks, the STEP team will slowly ramp up the operating temperature to 500°C and generate 5 megawatts (MWe) of power, enough to power 5,000 homes.

After completion of this first test configuration, the STEP Demo project will enter its final phase. The pilot plant will be reconfigured to boost the power plant’s efficiency and overall energy output. This modification requires the installation of new equipment, as well as a new commission and test phase that will continue into 2025 until the pilot plant is running at full power. At the end of its final phase, the pilot plant will produce 10 MWe hourly, enough to power 10,000 homes.

The STEP Demo pilot plant is one of the largest demonstration facilities in the world for sCO2 technology. Unlike conventional steam power plants, which use water as the thermal medium in power cycles, STEP uses high-temperature sCO2 to increase efficiency by as much as 10% due to its favorable thermodynamic properties. Carbon dioxide is nontoxic and nonflammable, and when CO2 is held above a critical temperature and pressure, it can act like a gas while having the density near that of a liquid.

The pilot plant’s sCO2 turbomachinery is approximately one-tenth the size of conventional power plant components, which shrinks the physical footprint and construction cost of any new facilities. Additionally, the sCO2 power cycles are compatible with many heat sources including concentrated solar power, industrial waste heat, geothermal power and advanced nuclear power plants.

SwRI, GTI Energy, and GE broke ground on the STEP Demo site in 2018. The facility achieved mechanical completion in October 2023, when major subsystems began commissioning.

Major CO2 power generator starts operations

By Zheng Xin | China Daily | Updated: 2025-12-23

The world's first commercial supercritical carbon dioxide power generator started operations in Southwest China's Guizhou province recently, a significant milestone in the global transition toward high-efficiency waste heat recovery, said its operator China National Nuclear Corp (CNNC).

Known as Chaotan One, the new generator, located at a plant in Guizhou's Liupanshui city, uses carbon dioxide instead of steam to transfer heat. Each unit of the project boasts a power generation capacity of 15 megawatts, it said.

It has been connected to the grid from a steel production plant in Guizhou to produce electricity from waste heat, addressing a long-standing technical bottleneck in the efficient utilization of small-to-medium scale thermal energy sources.

Huang Yanping, CNNC chief scientist and chief designer of Chaotan One, said the commercial operation of this project represents the first transition of this innovative technology from laboratory to commercial implementation worldwide.

The system, with simplified structural design and fewer components, makes it possible to operate and maintain more easily compared to conventional steam-cycle plants. It can generate over 70 million kilowatt-hours of electricity annually, adding about 30 million yuan ($4.26 million) in revenue.

By utilizing supercritical CO2 power generation, the project implements an innovative power cycle that is more efficient, takes up less space, requires fewer auxiliary components and reacts faster than traditional systems, he said.

According to Huang, when the working pressure of CO2 exceeds 73 atmospheres and the temperature exceeds 31 C, it enters a supercritical state, leading to increased density that approaches a liquid state, which enables it to store more energy.

Meanwhile, its viscosity remains very low, close to that of a gas, resulting in smaller flow resistance.

According to CNNC, the system offers a drastic performance leap over traditional sintering waste heat steam power technologies currently in use, with overall power generation efficiency up by more than 85 percent, net electricity generation improved by over 50 percent and required floor space reduced by 50 percent.

Beyond being an innovative technology, supercritical CO2 power generation is poised to significantly contribute to the country's dual-carbon goals by efficiently converting industrial waste heat into power, it said.

Industry experts believe the innovative thermoelectric conversion technology comes at a critical juncture for China's energy landscape, as the country's electricity consumption is expected to reach a record high in 2025, with total power use projected to surpass 10 trillion kWh nationwide.

Rising demand is driven in large part by high-tech and advanced manufacturing industries, according to the national energy work conference held recently in Beijing.

Power use in sectors such as new energy vehicle manufacturing and wind power equipment manufacturing has jumped more than 20 percent and 30 percent year-on-year, respectively, from January to November. Electricity consumption in the internet and related services sector surged more than 30 percent, it said.

Wang Hongzhi, head of the National Energy Administration, said at the conference that China is set to overfulfill its target of having nonfossil energy account for 20 percent of its total energy consumption in 2025.

Thanks to robust green investment, the leapfrog development of the new energy sector, and the accelerated construction of major hydropower and nuclear power projects, the country's green and low-carbon energy transition has accelerated this year, Wang said.

The Nuclear Power Institute of China started research into the world's cutting-edge supercritical CO2 power conversion technology as early as 2009. In 2023, construction commenced on its demonstration project in Liupanshui.

In 2024, CNNC launched a demonstration project integrating molten-salt energy storage and supercritical CO2 power generation technologies, with scheduled demonstration operations set for 2028.

Looking ahead, the supercritical CO2 power generation technology will be integrated with multiple heat sources to form power generation systems, said Huang.

This will help expand its applications to solar thermal power, waste heat recovery, energy storage and other fields, he said.

China pioneers commercial use of supercritical CO2 power generation
By Xinhua
Published: Dec 21, 2025
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Compared to conventional sintering waste-heat steam power generation technologies, Chaotan One has increased power generation efficiency by over 85 percent, net power generation by over 50 percent, and reduced the required floor space by 50 percent.
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