Damage event analysis of drilling borehole heat exchangers in Baden-Württemberg, Germany | Schadensfallanalyse von Erdwärmesondenbohrungen in Baden-Württemberg
2014
Ever since the first failure events relating to ground source heat pump (GSHP) systems, people have become increasingly skeptical of this technology and the annual number of newly installed GSHP systems in Baden-Württemberg has been declining since 2009. This study enabled relating causes and effects of GSHP failures to the local geological and hydrogeological characteristics, and has summarised these in conceptual failure models. The analyses showed that in 90 % of the cases, a direct link exists between local groundwater and incomplete, leaking grouting of borehole heat exchangers (BHE). Furthermore, in almost 70 % of all events, failure occurred at the interface between the Keuper and Muschelkalk formations. Initial assessments indicated that the probability of failure increased 40-fold, if the interface between the Keuper and Muschelkalk is reached during drilling. Although, more than 30,000 operating GSHP systems exist in Baden-Württemberg, the challenge for the future is to minimize the risk of damage using improved risk mitigation strategies.
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