Development of the borehole heat exchanger technology
  • Geothermal energy
  • Development
  • Research
  • Knowledge transfer
  • Public funds
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Period   08/2013 - 01/2016 (2,5 years)
Budget   approximately 800.000 EUR
Description   Borehole heat exchangers (BHE) can be used - often in combination with heat pumps - for the regenerative, weather-independet heating and cooling of e.g. residential and office buildings. Yet, there have been numerous fatal cases of damage in the last years in Baden-Württtemberg relating to the building of BHE. This shows that many questions concerning grouting quality of BHE and thus the borehole sealing are still open.

First results concerning these questions have been gained within the research project EWSplus (Examinations for the quality assurance of borehole heat exchangers). Real-scale tests performed in this project have shown mainly water-filled discontinuities in the BHE grouting that cannot be explained so far.

Taking into account the relevance of these discontinuities for a complete sealing of the BHE borehole, the main focus of the research project EWS-tech lies on gaining knowledge about the reasons for the discontinuities and on developing strategies to prevent them.
Client   Ministry of the environment, climate protection and the energy sector of Baden-Württemberg
  • Solites - Steinbeis Steinbeis Research Institute for Solar and Sustainable Thermal Energy Systems
  • Karlsruhe Institute of Technology (KIT) - Institute of Applied Geosciences (AGW)
  • Karlsruhe Institute of Technology (KIT) - Materials Testing and Research Institute (MPA Karlsruhe)
  • EIFER (European Institute for Energy Research)
Aim   EWS-tech aims at improving the grouting quality of borehole heat exchangers (BHE). Therefore a deeper understanding of the grouting process and the processes causing discontinuities in the grouting need to be gained.
Implementation   In order to reach the goals of the project the results and findings of the following three-stage approach will be correlated:

  1. Laboratory experiments: Detailled characterization of BHE grouting materials, Examinations on the hydraulic conductivity and durability of grouting materials and the complete BHE system

  2. Small-scale experiments: Visualiziation of the BHE grouting process for different parameters (different grouting materials, water/solid-ratios, mixing processes, grouting pump speed, etc.)

  3. Real-scale experiments: Verification of the results that have been determined in the laboratory and small-scale experiments

By means of working together with the relevant stakeholders (producers of grouting materials, grouting pumps, BHE pipes as well as drilling companies) the practicability and a wide acceptance of the results gained will be ensured.

Results   Selected Results of the research project EWS-tech are:
  • common laboratory test conditions and test criteria for BHE grouting materials
  • on-site test criteria for BHE grouting materials
  • proposal for the basic information that all grouting material data sheet should contain
  • Recommendations for a high-quality grouting of BHE

Within the research project EWS-tech, which aims at improving the grouting quality of borehole heat exchangers, the influence of many parameters on the grouting quality of borehole heat exchangers (BHE) is examined by experiments and evaluated.


Downloads and links
Zwischenbericht 2015

Zwischenbericht 2014

OTTI ONG Paper 2014

OTTI ONG Präsentation 2014

GtV Paper 2014

GtV Präsentation 2014



Mathieu Riegger