Field Study for the Determination of the Ratio of Convective to Total Energy Transport in Geothermal Systems

Abstract

Currently our Institute is performing a research program supported by the Federal Ministry of Economics and Technology (BMWi). The main objective of this research program titled “experimental investigation for the verification of a finite-element-multiphase-model for heat transport processes in the ground” is to analyze the subsoil as a three-phases-model with separated consideration of conduction, convection, and their subsequent interaction.

Therefore extensive experimental field tests are currently conducted at the Technical University Darmstadt. Geothermal Response Tests (GRT) as well as Enhanced Geothermal Response Tests (EGRT) are performed in different geological and hydro geological conditions. With help of pumping wells different surrounding hydraulic heads are set to borehole heat exchangers to monitor the performance of GRTs and EGRTs depending on the forced groundwater flow in combination with the Groundwater Flow Visualization (GFV) measurement technique that determines the groundwater flow velocities over depth. The increase of the effective thermal conductivity over depth determined with the EGRT measurement technique was correlated with the determined groundwater flow velocities. The ratio of conductive and convective energy transport to the whole transported energy was investigated.