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Shallow geothermal energy utilises the ground at relatively shallow depths as a heat source or sink to efficiently heat and cool buildings. Geothermal pavement systems represent a novel concept where horizontal ground source heat pump systems (GSHP) are implemented in pavements instead of purpose-built trenches, thus reducing their capital costs. This paper presents a geothermal pavement system segment (20m × 10m) constructed and monitored in the city of Adelaide, Australia, as well as thermal response testing (TRT) results. Pipes have been installed in the pavement at 0.5 m depth, and several thermistors have been placed on the pipes and in the ground. A TRT has been performed with 6kW heating load to achieve an understanding of the thermal response of the system as well as to estimate the effective thermal conductivity of the ground. The results show that the conventional semi-log method may be applicable to determine the thermal conductivity for geothermal pavements. The geothermal heat exchanger at shallow depth is considerably under the influence of the ambient temperature; however, it is still acceptable for exchanging the heat within the ground. It is also concluded that the impact radius of heat exchanger in geothermal pavement during the TRT is around 0.5m in the vertical and horizontal directions for this case study.

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Geothermal pavement systems are a novel type of energy geostructure. They use sub-surface structures to exchange heat with the ground and, thereby, provide thermal energy in addition to structural support. The thermo-activation of pavements has been largely overlooked in the literature. This research focuses on the development of a detailed three-dimensional (3D) finite-element (FE) model to explore the thermal performance of geothermal pavement systems. The 3D FE model developed was successfully validated with both data measured from a full-scale experiment undertaken in Adelaide, South Australia and other published data. The validated model is further employed to evaluate the long-term performance of a geothermal pavement system under both a traditional system configuration and a hybrid system. Furthermore, a life-cycle cost analysis is performed to explore the cost implication of such pavement systems. Results show that a geothermal pavement with total pipe length of 640 m, or a hybrid system (a geothermal pavement system with a pipe length of 320 m and an auxiliary system) can provide for sufficient space heating and cooling for a typical residential building in Australia. It is found that, compared with conventional heating and cooling systems, the geothermal pavement system is indeed a cost-effective solution. This research study indicates that this pavement technology can be successfully implemented in the field and accurately modelled using FE techniques.

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