New Technologies and Applications: Materials and Equipment in Near Surface Geothermal Systems-Article

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The paper reviews emerging technologies and applications for near-surface geothermal systems, which use the ground and structural elements to store and exchange heat. By integrating heat exchangers into foundations and other infrastructure, these systems can reduce fossil-fuel use, emissions, and operating costs.<br /><br />Seasonal operation can balance summer heat rejection with winter heat extraction, but persistent imbalances may cause ground temperatures to drift and reduce performance. Thermoactive piles are the most established technology. Field tests and modeling show that temperature changes affect pile stresses and shaft resistance, so thermal loads must be considered in structural design. Other applications include diaphragm walls, tunnel linings, anchors, sewers, basement walls, and slabs. Tunnels offer substantial heat-exchange surface, while basement elements may be simpler and less costly but generally provide lower heat-exchange capacity.<br /><br />The review also considers materials and equipment that could improve performance, including alternative concrete aggregates to increase thermal conductivity, reduced or improved pipe configurations, and closed-loop carbon dioxide systems. Potential applications extend beyond building heating and cooling to bridge and runway deicing, soil improvement through thermal consolidation, grain drying, and greenhouse heating. Experimental bridge-deck results show that geothermal heating can keep a deck snow-free in moderate winter conditions, although performance may be insufficient in extreme cold without supplementary heating.<br /><br />Key priorities for future research include understanding thermally induced structural stresses, improving heat transfer in tunnel linings and basement elements, optimizing insulation, and developing better materials and heat-transfer systems. Long-term monitoring and careful system design are also needed to prevent groundwater impacts, soil freezing, and unwanted ground-temperature changes caused by unbalanced operation.

Keywords

near-surface geothermal

thermoactive piles

ground heat exchange

seasonal thermal balance

structural thermal stresses

foundation heat exchangers

tunnel linings

basement walls

thermal conductivity

geothermal heating