Why Underground Data Centers Are the Future of Sustainable IT in 2025

The rapid growth of data volumes and the global shift to cloud services are prompting tech companies to seek innovative solutions for server deployment. One of the most promising trends for 2025 is underground data centers-engineering complexes built in mountains, mines, and bunkers. Underground data centers provide natural cooling, enhanced security, and energy efficiency, all of which are vital as energy consumption rises and climate restrictions tighten.

Why Companies Are Going Underground

Modern data centers consume vast amounts of energy and generate significant heat, requiring a stable climate and reliable power. By moving servers underground, organizations can address several strategic challenges: energy conservation, security, and resilience.

1. Stable Microclimate

   At depths of tens of meters, soil temperature remains between 8-12°C year-round, providing natural cooling for equipment. This reduces energy costs for air conditioning, which can account for up to 40% of total consumption in traditional data centers.

2. Physical Security

   Underground facilities naturally shield against storms, floods, earthquakes, and fires. Unlike above-ground data centers, they are largely immune to temperature fluctuations and external environmental impacts.

3. Cyber Resilience and Infrastructure Protection

   Housing server systems underground lowers the risk of unauthorized access and makes it easier to create isolated security zones with limited physical entry points.

4. Reusing Existing Facilities

   Many projects are based in decommissioned mines or tunnels, cutting construction costs and reducing environmental impact. For example, Sweden's Pionen underground center is housed in a former Cold War bunker.

As a result, underground data centers offer not only technological benefits but also strategic advantages, ensuring infrastructure resilience even as demand increases and risks-climate or cyber-grow.

Cooling Systems and Energy Efficiency in Underground Data Centers

One of the main advantages of underground data centers is their exceptional energy efficiency, primarily due to natural cooling. The temperature of surrounding rock and underground air remains stable throughout the year, allowing operators to minimize traditional air conditioning and ventilation needs.

1. Natural (Free) Cooling

   Many underground complexes use closed-loop air circulation, channeling server heat through heat exchangers into the surrounding rock. This approach can reduce cooling energy consumption by up to 70%.

2. Water and Geothermal Systems

   Some centers use closed water cooling loops, circulating water through natural underground sources and returning it after heat exchange. In northern countries like Norway, geothermal loops are used to recover heat for residential heating.

3. Heat Recovery

   Excess server heat is repurposed to heat nearby buildings or greenhouses, making the data center a part of the local energy ecosystem.

4. Renewable Energy Integration

   Many underground centers are connected to hydropower plants or solar farms, making them nearly carbon neutral.

These features make underground data centers a model of sustainable IT and demonstrate the potential of green data centers for the future. Read more about energy-efficient technologies and the future of green data centers.

By combining natural cooling and intelligent energy management systems, underground data centers can achieve industry-leading efficiency-PUE (Power Usage Effectiveness) below 1.1, almost twice as efficient as the industry average.

Data Security and Protection in Underground Infrastructure

Security is a key factor driving the adoption of underground data centers. These facilities deliver multi-layered protection against both physical and cyber threats.

1. Physical Isolation and Disaster Protection

   At considerable depths, equipment is well-protected from fires, storms, earthquakes, explosions, and radiation. Walls several meters thick-made of concrete or rock-make these sites resilient even to nuclear events.

2. Access Control and Cybersecurity

   Underground data centers feature advanced authorization systems, biometrics, airlocks, and strict access zones. Physical isolation simplifies connection management, reducing the risk of unauthorized entry.

3. Business Continuity (Disaster Recovery)

   With autonomous power and communication systems, underground data centers can operate during emergencies, such as power outages, network disruptions, or natural disasters.

4. Cyber-Resilient Infrastructure

   Many operators deploy hybrid storage networks, with backup nodes underground for instant data recovery.

5. Real-World Examples

   The Iron Mountain center in the U.S. is located in a former limestone mine and stores government, banking, and film archives. Its 30-meter-thick walls protect over 2,500 server rooms.

Ultimately, underground data centers provide the highest level of security, blending robust engineering with digital isolation. For organizations handling critical data-financial, medical, or governmental-this is becoming the gold standard in protection.

Notable Underground Data Centers Around the World

The trend toward underground data center construction is gaining global momentum. These projects are distinguished not only by their security but also by innovative approaches to cooling, power, and architecture.

1. Green Mountain (Norway)

   One of the world's most renowned underground data centers, located in a former military bunker by a fjord. It uses cold seawater for natural cooling and is powered by hydropower, making it entirely carbon neutral.

2. Pionen (Sweden)

   Built 30 meters beneath Stockholm in granite, this Bahnhof-operated center combines high security with sci-fi aesthetics, featuring waterfalls, vegetation, and aquariums. It can withstand a hydrogen bomb explosion and is fully power autonomous.

3. Iron Mountain (USA)

   Located in a former Pennsylvania limestone mine, it stores archives, government data, and multimedia assets. The center boasts robust climate control and backup power systems.

4. The Bunker (UK)

   A Cold War-era facility converted to a Tier 3 data center, it uses hybrid cooling and a fully autonomous security system.

5. Swiss Fort Knox (Switzerland)

   Set in the Alps, this is one of Europe's most secure data centers, capable of operating without external communications for up to six months.

These examples show that underground data centers are no longer experimental-they are proven models combining resilience, safety, and eco-friendliness. Increasingly, countries see these projects as the backbone of future IT infrastructure.

Environmental Benefits and IT Sustainability

Underground data centers play a crucial role in advancing sustainable IT by merging energy efficiency with minimal environmental impact. Their design not only reduces energy consumption but also optimizes the use of natural resources.

1. Minimizing Carbon Footprint

   Thanks to natural cooling and renewables, underground data centers can operate with zero CO₂ emissions. In some cases, server heat is reused for heating buildings, greenhouses, or water systems.

2. Efficient Land Use

   Placing infrastructure underground preserves natural landscapes, avoids land sprawl, and reduces visual impact on ecosystems.

3. Noise and Pollution Reduction

   Unlike above-ground centers, underground sites produce no noise pollution and require minimal surface ventilation, which is important for suburban and natural areas.

4. Recycling and Reuse of Equipment

   Modern centers feature programs for recycling electronic components and coolants, reducing waste. Learn more about electronic waste recycling and sustainable IT trends.

5. Integration with Green Energy Networks

   Underground data centers increasingly participate in local energy clusters, redistributing generated heat and power within urban infrastructure.

These solutions make underground data centers a model of responsible IT, blending technological progress with environmental stewardship.

The Future of Underground Data Centers and Geothermal Cooling

The future of underground data centers is closely linked to advances in geothermal and energy-efficient technologies. Companies are increasingly viewing the Earth's depths not only as protection but also as a source of natural cooling and sustainable power.

1. Next-Generation Geothermal Cooling

   Countries such as Iceland and Canada are already building data centers using closed geothermal loops, where server heat is transferred to underground aquifers. This not only enables highly efficient cooling but also repurposes excess heat for urban heating.

2. Integration with Renewable Energy

   Underground data centers are becoming part of energy ecosystems where solar, hydro, and geothermal sources work together, achieving near-zero reliance on external grids.

3. Autonomous and Modular Complexes

   Modular underground server pods are being developed for rapid deployment in mountainous or industrial areas, reducing construction time and enabling flexible scaling.

4. Geoengineering and Ground Stability

   Modern drilling and plasma treatment techniques make deep construction safe and long-lasting. Discover more about next-generation geothermal energy and deep drilling technologies.

5. AI Integration

   The underground data centers of the future will be managed by AI systems that predict demand and optimize both energy and cooling distribution in real time.

By 2035, analysts estimate that up to 15% of all global data centers will be underground, forming the backbone of a "green internet"-infrastructure that combines security, autonomy, and environmental responsibility.

Conclusion

Underground data centers are more than just an engineering solution-they embody a new philosophy of sustainable IT. They unite three key principles for future digital infrastructure: energy efficiency, security, and environmental responsibility. With their stable microclimates, protection from external threats, and use of natural cooling, these facilities are setting a new standard for efficiency in an era of growing energy demand and climate challenges.

In 2025, underground data centers are moving beyond the experimental stage to become practical, widely adopted solutions. From Norway and Switzerland to the USA and Japan, companies are building centers that can operate autonomously, recycle heat, and run on renewable energy.

The development of geothermal technologies, heat recovery systems, and green energy make underground data centers a vital part of an environmentally neutral digital ecosystem. They don't just keep the internet running-they are helping to shape the sustainable infrastructure on which the digital future will be built.