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30 min ago 2 min read
China has launched its first geothermal heating project using supercritical carbon dioxide (sCO2) instead of water, with the technology expected to increase heat extraction efficiency by around 20% while reducing energy consumption by 10%.
Led by China Huaneng Group in Henan Province, the project extracts underground heat by circulating supercritical CO2 through geothermal wells reaching depths of around 2.5km.
China is already the world’s fastest-growing geothermal heat market, according to policy network REN21, with growing interest in direct-use heating systems and next-generation geothermal technologies.
Once injected deep underground through pipelines, the sCO2 absorbs geothermal heat before returning to the surface through a production well.
The hot CO2 passes through a heat exchanger, which transfers the geothermal heat into a range of systems including district heating, industrial heating, or potentially power generation.
The demonstration project looks to take advantage of sCO2’s dual properties. It is dense like a liquid but flows easily like a gas, making it effective at moving through porous underground rock.
It also expands strongly when heated, which can help drive circulation naturally and reduce pumping energy.
The use of CO2 means no large volumes of water are required and there is less concern about groundwater depletion or contamination.
However, many conventional geothermal systems already operate in largely closed-loop configurations, with geothermal fluids commonly reinjected underground after heat extraction to maintain reservoir pressure and reduce water consumption.
According to the International Energy Agency, water use in geothermal operations varies depending on the technology and cooling system used.
In the US, geothermal cooling for the power sector can use between 1,700 and 4,000 gallons of water per megawatt-hour of electricity produced.
The project also points to a broader emerging role for CO2 as an industrial working fluid rather than solely a captured emission or storage medium.
There is also potential overlap with sectors specialising in compression, transport, heat exchange and high-pressure process systems.
