China's Tech Mosaic: China's Chaotan One turns CO2 into clean energy

Editor's note: China is not one innovation story but many – emerging from local areas across the nation. In this series, we bring you those stories as pieces of a larger mosaic that, when put together, reveal the full picture of a country on the move.

Could carbon dioxide (CO2) – one of the main greenhouse gases driving climate change – can also become a source of clean energy.

In the mountainous city of Liupanshui in southwest China's Guizhou Province, a steel plant is offering a possible answer. There, the world's first commercial-scale supercritical CO2 power-generation unit, known as Chaotan One, has begun operation, using CO2 in a new type of power system designed to improve efficiency and reduce emissions.

The project is drawing attention because it challenges one of the oldest principles in modern power generation.

For more than a century, most thermal and nuclear power plants have relied on steam to drive turbines and generate electricity. Water is heated, converted into steam and used to spin large turbine generators. Although the technology is mature and widely used, a significant amount of heat is lost during the process.

Chaotan One uses a different approach. Instead of steam, the system uses supercritical CO2, which is compressed and heated beyond its critical point of 31 degrees Celsius and 7.38 megapascals. In this state, the fluid combines some properties of both gases and liquids, allowing it to flow efficiently while maintaining high density.

Inside a closed-loop system, the supercritical CO2 moves through turbines at high speed to generate electricity more efficiently than conventional steam systems.

According to project data, the technology improves power-generation efficiency by more than 85% relative to conventional steam-based systems, while the physical footprint of the equipment is cut in half. The system also captures industrial waste heat from the steel plant that would otherwise be released into the atmosphere, converting it into more than 70 million kilowatt-hours of electricity annually.

What does this mean for the world? Researchers say the technology could help address several major challenges facing the global energy sector.

One is efficiency. Traditional steam-based systems typically operate at efficiencies of around 35%-40%, while supercritical CO2 systems could potentially increase that figure to between 50% and 60%.

Another is water consumption. Conventional steam generation requires enormous amounts of water. This new technology uses very little – or even none at all – making it especially valuable in water-stressed regions.

The technology could also improve industrial waste-heat recovery. Industries such as steel, cement and chemicals release large amounts of medium- and high-temperature waste heat each year. Supercritical CO2 systems can recover part of that energy and convert it into electricity, reducing both fuel consumption and carbon emissions.

According to estimates, if this technology were adopted across China's steel industry, the annual coal savings would equal the output of a large coal mine, while carbon emissions could be reduced by more than 12.8 million tonnes per year.

For China, Chaotan One represents not only a technological experiment, but also a broader effort to explore new pathways for cleaner industrial development.

Here, CO2 is no longer seen merely as an industrial waste product. Instead, it is becoming a potential tool for improving energy efficiency in low-carbon industrial systems.

(UpGuizhou's Chen Yitian, Tian Yinxing contributed to the story)