A recent study published in Sustainability explored new methods for enhancing building energy efficiency by utilizing the ground beneath structures for thermal energy storage.
The researchers focused on integrating geothermal systems to improve heating and cooling, providing a sustainable approach to reduce energy loss and enhance indoor climate control. They also investigated how soil temperature dynamics affect energy use, offering valuable insights for promoting more sustainable building practices.
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Advancement in Ground-Based Thermal Accumulation
The growing global energy demand, particularly in the building sector, highlights the need for sustainable solutions. Buildings account for a significant share of energy consumption, with heating alone constituting approximately 47% of global usage, more than transportation (27%) and electricity (17%) combined. This demand is particularly evident in northern Europe, where domestic hot water and space heating contribute significantly to carbon dioxide emissions.
Shallow geothermal systems are a promising renewable technology that can address these challenges. By leveraging the stable temperatures of the ground, these systems provide efficient heating and cooling, potentially reducing energy consumption by a factor of three to four and decreasing dependence on fossil fuels. However, seasonal imbalances between heat demand and supply remain a challenge.
The efficiency of geothermal systems depends significantly on soil thermal properties such as conductivity, diffusivity, density, and heat capacity. Understanding these factors is vital for optimizing soil temperature and heat flux, essential for enhancing building energy performance. This approach improves energy efficiency and supports carbon neutrality goals by allowing the ground to serve as a natural thermal reservoir.
About this Research: Leveraging Ground Under Structure
In this paper, the authors explored the potential of utilizing the soil beneath buildings as a thermal energy accumulator to enhance energy efficiency and reduce heat loss.
They combined experimental investigations and numerical simulations using COMSOL Multiphysics software to analyze heat transfer dynamics between buildings and soil.
The researchers installed a heating device at a depth of one meter, maintaining a constant temperature of 20 °C to simulate the thermal conditions of a heated building. Temperature sensors (Pt1000) were placed at various depths (between 0.25 m and 1.50 m) and monitored using a PT-104 Data Logger to track temperature changes over time.
The experiments were conducted from December to July to capture seasonal variations in thermal behavior. Key soil parameters measured included density (1460 kg/m3), moisture content (15%), thermal conductivity (0.76 W/(m·K)), and specific heat capacity (878 J/(kg·K)). The study also examined different building configurations, including structures with and without thermal insulation, and applied multiple evaluation methods to assess thermal behavior. This comprehensive approach provided insights into long-term soil heat accumulation and its impact on building energy performance.
Key Findings: Impacts of Utilizing Beneath Structure
The outcomes showed significant insights into soil thermal behavior and its interaction with building structures. The authors found that average heat flux density varied significantly throughout the year, reaching up to 679 W/m2 in winter (December and March) and decreasing to approximately 20.2 W/m2 by July. This seasonal variation, influenced by factors such as air temperature and precipitation, highlighted the importance of accounting for atmospheric conditions when designing thermal storage systems.
Notably, a new thermodynamic equilibrium in the soil was achieved within one week of continuous heating, demonstrating the soil's ability to store and release heat effectively. Temperature measurements at multiple depths revealed a time lag in heat propagation, highlighting the thermal inertia of deeper soil layers. Critical transitions in soil temperature patterns were observed in late March and early September.
The study demonstrated that using a soil-filled container beneath the building and integrating thermal insulation could reduce heat flux density by up to 21%, leading to lower heat losses and improved energy efficiency. Additionally, soil-based thermal storage systems could alleviate pressure on urban energy networks during peak demand periods. Overall, optimizing soil thermal properties can significantly reduce annual energy consumption and enhance sustainability in building design.
Practical Applications in the Construction Industry
This research has significant implications for the construction and energy sectors. It suggests that soil-based thermal accumulators can be integrated into district heating networks to help balance energy loads and reduce pressure on urban systems during peak demand. By utilizing the soil's heat storage capacity, cities can improve sustainability and support climate goals.
The study also highlights the benefits of combining ground-based thermal storage with renewable sources, such as solar panels, to manage surplus energy and reduce grid overload. Incorporating these systems into building designs can lower energy use, cut emissions, and align with global clean energy efforts.
Conclusion and Future Directions
Soil-based thermal storage systems improved building energy efficiency by reducing reliance on conventional heating. By analyzing soil temperatures from the surface to a depth of 1.5 meters, the researchers highlighted seasonal variations in heat transfer and the potential for energy savings.
Future research should investigate the long-term performance, economic viability, and integration of these systems across various climates. Integrating soil thermal storage into urban infrastructure promotes sustainable energy practices and increases resilience. As the demand for renewable solutions rises, enhancing geothermal applications will be crucial to tackling energy and climate challenges in urban settings.
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Source:
Zdankus, T.; & et al, A. Research on Increasing the Building’s Energy Efficiency by Using the Ground Beneath It for Thermo-Accumulation. Sustainability 2025, 17, 262. DOI: 10.3390/su17010262, https://www.mdpi.com/2071-1050/17/1/262