On the importance of a coordinated site characterization for the sustainable intensive thermal use of the shallow subsurface in urban areas: a case study

Shallow geothermal applications have become standard solutions for heating and cooling in many newly built or redeveloped residential neighborhoods, but current urban development practices do not yet consider the new demands that result from the intensive thermal use of the shallow subsurface. A coordinated site characterization is of great importance as a sound basis for an optimized planning of geothermal systems that brings together user requirements (heating, cooling, and/or seasonal energy storage) and (hydro)geological subsurface conditions. The aim of this study is to raise awareness and to demonstrate the relevance of a coordinated site characterization. Therefore, this study quantifies the advantages of a site-specific over a desktop-based site characterization in reducing uncertainty for calculation of borehole heat exchanger length and predicted induced temperature changes in the subsurface for a newly developed residential neighborhood in the city of Taucha, Germany. Results show that savings of over EUR 1850 per house (EUR 98,050 for the entire neighborhood) can be achieved by a coordinated exploration and prediction accuracy of temperature plume development was substantially improved. Although being more cost intensive, exploration costs for this case study are <3% of the assumed individual geothermal system costs of EUR 16,000 if divided equally among geothermal users. Three different options are presented to implement coordinated exploration concepts into site development practice.