China Connects World's First Commercial Supercritical CO₂ Power Generator to the Grid After 77 Years of Failed Attempts
Two 15-megawatt units at a Guizhou steel plant mark the first commercial deployment of a power cycle concept proposed in 1948, claiming 50% higher efficiency than steam.
Overview
The China National Nuclear Corporation (CNNC) has connected the world’s first commercial supercritical carbon dioxide power generator to the electrical grid, marking the culmination of a power cycle concept first proposed in 1948. The facility, known as Chaotan One, comprises two 15-megawatt units installed at the Shougang Shuicheng Steel plant in Liupanshui, Guizhou province, where it converts industrial waste heat into electricity using pressurized CO₂ instead of steam, according to Interesting Engineering.
The grid connection, announced by CNNC’s Nuclear Power Institute in November 2025, comes after 17 years of dedicated research and represents the first time a technology that has eluded engineers for more than seven decades has reached commercial operation, as reported by Prototyping China.
What We Know
How Supercritical CO₂ Power Works
When carbon dioxide is heated above 31°C and pressurized beyond 7.4 megapascals, it enters a supercritical state — dense like a liquid yet flowing like a gas. In this form, it transfers heat far more efficiently than steam, according to Futura Sciences. The Chaotan One system captures waste heat from sintering processes at the steel plant, where temperatures exceed 700°C, and uses the supercritical CO₂ cycle to drive turbines and generate electricity, as detailed by the South China Morning Post.
The technology requires less energy to reach its operating state than converting water to steam, and the higher density of supercritical CO₂ enables smaller, more compact turbine designs — an advantage in confined industrial settings, according to Interesting Engineering. The system operates as a closed loop: the CO₂ is neither consumed nor burned, and the process produces zero direct emissions, as reported by Futura Sciences.
The Engineering Breakthroughs
Commercializing supercritical CO₂ power required solving several problems that had stymied engineers since 1948. The most critical was developing a dry gas sealing system capable of containing the highly pressurized fluid in megawatt-scale turbines. Engineers at the Nuclear Power Institute rebuilt the sealing approach from scratch, creating the world’s first dry gas sealing system for supercritical CO₂ turbines at this scale, according to Prototyping China.
A second major challenge involved fabricating microchannel heat exchangers — stainless steel plates containing hundreds of grooves approximately one millimeter wide that must be manufactured with exact uniformity. Traditional photochemical etching proved inadequate. After testing 218 different welding parameter combinations over 829 days across 27 optimization rounds, the team achieved successful vacuum diffusion welding, a process where metal atoms diffuse across boundaries and bond at the atomic level, as detailed by Prototyping China.
Efficiency Claims
CNNC claims the two units achieve over 50% greater net power output from the same heat source compared to conventional steam-based waste heat recovery systems. Traditional steam power plants using the Rankine cycle achieve approximately 40% efficiency with high-temperature heat sources, while the supercritical CO₂ system reportedly exceeds 50%, according to the South China Morning Post.
The Race with the United States
China is not alone in pursuing this technology. The U.S. Department of Energy funds the Supercritical Transformational Electric Power (STEP) demonstration project, a 10-megawatt pilot plant in San Antonio, Texas, led by GTI Energy. During initial testing phases, the STEP facility reached full operational speed at 500°C, generating 4 megawatts of electricity, as reported by the South China Morning Post. However, the U.S. project focuses on validation and risk reduction rather than commercial deployment, a more methodical approach that contrasts with China’s push to grid-connected operation, according to CleanTechnica.
What We Don’t Know
While the grid connection is a genuine milestone, several critical questions remain unanswered.
Long-term durability is the foremost concern. Supercritical CO₂ is known to cause carburization in steels, leading to carbide formation and embrittlement over time. The microchannel heat exchangers are particularly vulnerable, as even small surface changes can increase pressure drop and reduce efficiency, according to analysis by CleanTechnica. The same analysis estimates a 40–70% probability of noticeable seal degradation over two to five years of operation.
Operating the system in a steel plant environment introduces additional risks. Steel production exhaust contains particulates and sulfur compounds that can cause fouling, reducing heat transfer effectiveness. CleanTechnica noted that degradation in such systems rarely manifests as sudden failure — instead, operators adjust controls, maintenance intervals increase, and net output quietly declines.
Whether this technology can scale beyond niche waste heat recovery applications also remains an open question. Potential future uses include next-generation nuclear reactors, solar thermal plants, and even spacecraft power systems, according to Futura Sciences, but significant engineering work would be required to adapt the system for each application.
Looking Ahead
Chaotan One represents an unambiguous engineering achievement: a power cycle concept that languished for 77 years has now reached commercial operation. Whether it proves durable and economically viable over the years ahead will determine if supercritical CO₂ becomes a meaningful part of the global energy toolkit — or remains, as skeptics suggest, another technology that works in demonstration but struggles in sustained industrial service.