Numerical sensitivity analysis of thermal response tests (TRT) in energy piles

Abstract

In recent years, energy pile systems have been developed as a cost effective alternative to traditional systems. An optimal design requires good characterization of the effective thermal properties of the soil and the system, through analysis of the results of thermal response tests (TRT). However, due to the size of foundation piles, accurate estimations require tests which are excessively long for practical applications. Hence, in most situations the analysis is carried out using the results of relatively short tests, which depend upon several factors, such as pile and ground thermal properties, pile geometry, pipe configuration, etc.In this article we use detailed numerical simulations to reproduce the results of thermal response tests for synthetic energy pile systems with different material properties, dimensions and pipe configurations. We used the standard line heat source model to evaluate the results of the numerical simulations and to highlight the magnitude of the errors this type of interpretation may produce. We demonstrate that even in the absence of groundwater flow and soil heterogeneity, TRT results obtained using the line heat source model can be misleading and must be treated with care.