The Spark Behind the Study

Underground power cables are a vital part of modern infrastructure, ensuring reliable energy distribution while avoiding the environmental and spatial challenges of overhead lines. But have you ever wondered how soil, something so seemingly passive, actively influences their performance?

Our study was born out of a fundamental question: How does the surrounding soil affect heat dissipation from underground power cables, especially under real-world conditions?

While previous research mainly focused on theoretical models or experiments under dry conditions, we wanted to push the boundaries and investigate how cyclic heating, moisture levels, and natural convection shape the thermal performance of underground cables.

Digging Deeper: The Science of Soil and Heat

When power flows through underground cables, it generates heat. If this heat isn’t efficiently dissipated into the soil, cable performance and lifespan can be compromised.

We conducted large-scale laboratory tests using a heated cylindrical rod buried in dry and saturated sand, mimicking real-world underground power cables. Through these experiments, we explored:

• The effects of static and cyclic heating on soil behavior.
• How moisture content alters heat dissipation and cable cooling.
• The surprising emergence of convection cells in wet soil.

What we found was fascinating: soil isn't just a passive medium,  it actively interacts with heat, sometimes in unpredictable ways.

Key Discoveries: A Game-Changer for Cable Systems

Thermal Charging in Dry Sand        

When cables undergo cyclic heating and cooling, the heat isn’t always fully released between cycles. Over time, this leads to a thermal buildup,reducing heat dissipation efficiency. This could be problematic for underground power cables, especially in dry conditions where trapped heat can increase cable temperature beyond safe limits.

Moisture is a Double-Edged Sword   

While wet soil generally enhances cooling due to its higher thermal conductivity, we observed an unexpected effect: after 72 hours of continuous heating, a strong convection cell formed. This natural buoyancy-driven heat movement created a hot zone above the cable, rather than distributing heat evenly.

Implications for Green Energy and Sustainability    

As the world shifts toward renewable energy sources, high-voltage underground power cables are playing a crucial role in transmitting electricity from wind, solar, and hydro power plants. Optimizing their thermal performance can:

• Improve efficiency and lifespan of power cables.
• Reduce unnecessary energy losses due to overheating.
• Ensure safety and reliability in underground energy networks.

The Road Ahead

This research lays the groundwork for smarter underground cable systems. Future studies could explore unsaturated soil conditions, which more accurately represent field scenarios. Additionally, our findings could be used to develop advanced soil backfill materials that enhance cooling performance while minimizing environmental impact.

Final Thoughts: Science, Curiosity, and Unexpected Discoveries

One of the most exciting aspects of research is when something unexpected happens—like the formation of convection cells in our saturated soil tests. It reminds us that science isn’t just about confirming hypotheses but also about uncovering new phenomena that reshape our understanding of the world.

We hope this research contributes to building more efficient, sustainable, and resilient energy infrastructure. If you’re working in geotechnics, energy systems, or underground cable design, we’d love to hear your thoughts!

Read our full paper here: [https://doi.org/10.1038/s41598-025-91831-1]   

 
Let’s discuss! What challenges have you encountered in underground power transmission?