Contributions to analytical, consistent modelling of borehole heat exchangers and ground heat collectors

Abstract

This thesis presents an overarching, consistent modelling methodology for shallow geothermal systems. The computational domain is divided into two sections using different modelling approaches. The source system, including installation effects, is described by analytical thermal resistance models and, where required, extended by capacity models. The surrounding subsurface and relevant surface influences are modelled using extensions of the instantaneous point source solution. Further relevant thermal effects are captured by approximate solutions as a complementary approach. The methodology is demonstrated by three applications. The first investigates grouted borehole heat exchangers with groundwater advection. The second analyses the thermal behaviour of a planar trench collector and its surrounding soil. The third presents a complementary solution for subsurface freezing and thawing around ground heat collectors, implemented for both a horizontal pipe system and a trench collector.