E.ON Energy Research Center, RWTH University

Optimizing operations by fiber optics temperature monitoring


The new main office of the E.ON Energy Research Center (E.ON ERC) is targeted to test and proof innovative concepts of indoor climatisation under real user conditions. Part of the heating and cooling system is the ground heat exchanger field, consisting of 40 probes drilled in a small scale grid down to depths of 100 m. All heat exchanger probes were installed with additional fibre optics cables, allowing a continuous temperature monitoring along the probes. 


Geophysica GmbH was ordered by RWTH university to build a geothermal 3-D model for the subsurface with all ground heat exchangers implemented. First, the subsurface was characterized in terms of thermal and hydraulic properties using data from laboratory investigations, well logging and thermal response tests. Gamma ray logging proved to be an important tool for thermal property prediction. The record of natural radioactivity was transformed into synthetic thermal conductivity profiles. Comparing these profiles with the results of the enhanced geothermal response tests (EGRT) allowed to identify zones of advective heat transport triggered by groundwater flow. 


The geothermal 3-D model was then calibrated by the fiber optic records and the performed laboratory studies and well tests. It was necessary also to consider the variation of surface temperature during the last 500 years in order to fully describe the undisturbed temperature field by the model. Finally, the model was tested and delivered to the client. The model now serves as basis for ongoing temperature monitoring, carried out n the frame of a research project. The objective of the project is to use the measured data of the subsurface and the building in order to optimize the heat exchanger field operation.






Visualization: 3-D model of the subsurface with 40 probes implemented. The arrows mark the groundwater flow at the transition zone of the cretaceous soft sediments and the underlying dense shales of the paleozoic basement.








Comparison of a synthetic thermal property profile based on gamma ray data with the measured profile of the EGRT (right track). Both profiles fit in depth sections of conductive heat transport. Off-sets between the curves point to advective transport of groundwater flow.