Abstract
Thermal response tests (TRT) are an essential in situ test for the sizing of ground source heat pump systems. Its application on energy piles is becoming an established practice, involving key differences in relation to testing boreholes. Recently, group TRTs emerged as an alternative to testing single short energy pile elements. This work assesses the execution and interpretation of those tests through different analytical heat transfer models implemented in a unit-response calculation methodology. To assess the suitability of the method, a comprehensive parametric analysis using a validated numerical model is undertaken, considering different energy pile sizes, thermal properties for both concrete and soil and group pile arrangements. The analytical methodology is validated against experimental and numerical results, and then tested to interpret the numerically simulated TRTs using a curve fitting algorithm. The broad parametric investigation and the evaluation of the capacity of different analytical methods on modelling each scenario provide directions to execute and interpret group TRTs. The soil effective thermal conductivity and energy pile thermal resistance are obtained with less than 5% precision error for most scenarios and less than 10% considering all scenarios. These results can be further improved with specific individual G-functions for the pile elements, that can be implemented on the proposed methodology.