26/05/2026
Application of Supercritical CO ₂ Technology in Geothermal Energy: A Technological Revolution in Clean Energy
Geothermal energy, as a clean, stable, and renewable energy source, plays an increasingly important role in the global energy transition. Although traditional geothermal development technology is mature, it faces geological risks, water resource consumption, and system efficiency bottlenecks such as "water must be refilled". In recent years, breakthroughs in supercritical CO ₂ (carbon dioxide) heat extraction technology have brought new ideas for geothermal energy development. The successful operation of China's first geothermal energy supercritical CO ₂ heat extraction project marks an important leap from laboratory to commercial application of this technology.
Technical principle: How to achieve "heat extraction without water extraction" for supercritical CO ₂
Supercritical CO ₂ refers to a CO ₂ fluid that exceeds the critical point (31.1 ℃, 7.38MPa) in both temperature and pressure. At this point, it combines the low viscosity of a gas with the high density of a liquid, exhibiting excellent heat transfer performance and flow characteristics.
The working principle of the supercritical CO ₂ geothermal heat extraction system is as follows:
Pressurized carbon dioxide: Ground level storage tanks pressurize CO ₂ to a supercritical state
Inject into geothermal wells: Inject supercritical CO ₂ into mid to deep geothermal wells approximately 2500 meters underground through the wellbore
Bottom hole heat absorption: Supercritical CO ₂ comes into contact with high-temperature rock formations underground, absorbing geothermal energy
Return to the ground: High temperature CO ₂ returns to the ground along the circuit
Heat transfer: transferring heat to heating water through a heat exchanger
Recycling: The cooled CO ₂ is injected back into the well to form a fully enclosed cycle
The biggest innovation of the entire system lies in the "heat extraction without water extraction" - CO ₂ is recycled in a closed system, without the need to extract groundwater or recharge, truly achieving zero water extraction and zero pollution.
Project Practice: Zhengzhou Supercritical CO ₂ Heat Extraction Project
Project Overview
Construction location: Huiji District, Zhengzhou City, Henan Province
Construction unit: China Huaneng Group
Well depth: 2500 meters deep geothermal well
Heating capacity: capable of meeting the heating needs of over 18000 square meters of residential buildings
Investment scale: over 100 million RMB
Application scenarios
The project has constructed a complete geothermal heating chain through the organic combination of surface drilling platforms, underground heat exchange stations, and residential heating systems. The high-temperature underground strata are efficiently connected to the surface heating system through a CO ₂ circulation loop, achieving stable transfer of geothermal resources to indoor heat.
Core advantages: Triple breakthroughs in technological advancement, environmental benefits, and geological safety
Technical improvement
20% increase in heat extraction capacity: Compared to traditional water circulation systems, the heat transfer efficiency of supercritical CO ₂ is significantly improved
10% reduction in unit heating energy consumption: lower viscosity and higher density reduce energy loss during the circulation process
Environmental benefits
Replacing standard coal by approximately 288 tons/year: significantly reducing fossil energy consumption
Reducing carbon dioxide emissions by approximately 750 tons per year: making a positive contribution to mitigating climate change
Equivalent to planting about 42000 trees: significant ecological benefits
Geological safety
1. No pumping, no reinjection: avoids the geological subsidence risk that may be caused by traditional geothermal development
2. Non polluting strata: a closed loop system ensures that the underground environment is not affected
3. Wide applicability: particularly suitable for areas with scarce water resources or complex geological conditions
4. Technical Comparison: Supercritical CO ₂ vs Traditional Water Cycle
5. Comparative Dimension: Traditional Water Cycle System Supercritical CO ₂ System
6. Medium characteristics Water: high viscosity, low heat transfer coefficient CO ₂: low viscosity, high heat transfer coefficient
7. Loop mode: Open loop, requiring refilling. Closed loop, no need for refilling
Water resource consumption requires a large amount of groundwater, with high recharge pressure and zero water intake, and no need for recharge
Geological risks include subsidence, pollution, and zero geological risks
Higher system efficiency (+20%)
Widely applicable in areas with abundant water resources, especially suitable for water scarce regions
Background and significance: Promoting the upgrading of geothermal energy industry
Policy Context
Zhengzhou, as a national pilot city for clean heating, has built a geothermal heating demonstration area of tens of millions of square meters. The application of supercritical CO ₂ heat extraction technology provides a new technological path for the construction of demonstration zones.
Technical significance
The leap from laboratory to commercial application: from theoretical verification to large-scale operation, significant improvement in technological maturity
New possibilities for the development of hot dry rocks: Supercritical CO ₂ technology opens up new avenues for the development of deep geothermal resources such as hot dry rocks
Industrial Demonstration Effect: Provided a replicable and promotable technological paradigm for geothermal energy development nationwide
Development prospects
Supercritical CO ₂ geothermal heat extraction technology is not only suitable for residential heating, but can also be expanded to a wider range of fields such as industrial heat and power generation in the future. With the continuous maturity and large-scale application of technology, costs will further decrease and market competitiveness will continue to strengthen.
Challenges and Prospects
Despite the enormous potential of supercritical CO ₂ geothermal heat extraction technology, there are still some challenges in its promotion:
1. System reliability: Continuous optimization is required for the long-term stable operation of equipment in high-temperature and high-pressure environments
2. Cost control: The initial investment is relatively high, and it is necessary to reduce unit costs through large-scale application
3. Standard system: The supporting systems such as technical standards and safety regulations still need to be improved
4. Talent cultivation: Insufficient reserve of interdisciplinary professionals
In the future, with the continuous progress of materials science and thermodynamic theory, as well as increasing policy support, supercritical CO ₂ geothermal heat extraction technology is expected to occupy a more important position in the field of clean energy, contributing to the achievement of the "dual carbon" goal.
The successful application of supercritical CO ₂ geothermal heat extraction technology is a major technological innovation in the field of geothermal energy development. It adopts the core concept of "taking heat without taking water", achieving the organic unity of economic benefits, environmental benefits, and social benefits. The commissioning of the Zhengzhou project not only marks a breakthrough in this field for China, but also provides a Chinese solution for the sustainable development of global geothermal energy. With the continuous improvement of technology and the continuous expansion of application scope, supercritical CO ₂ technology will play an increasingly important role in the wave of clean energy revolution.
