Larger geothermal heat pump plants in the central region of Germany

In recent years, several larger geothermal heat pump plants for offices or commercial areas have been designed and built in the central region of Germany, mainly in the Rhein-Main area. Systems with borehole heat exchangers (BHE; in the USA the term Vertical Loop is commonly used) as well as with shallow geothermal doublets (groundwater wells) are operational. New solutions had to be found to adapt the technology to certain site constraints, and innovative components such as thermally-enhanced grouting material have been used. This paper reviews the early development of Ground Source Heat Pumps (GSHP) for commercial buildings, gives details on a number of recent plants and discusses problems that arose during their realisation: UEG Wetzlar, a building with chemical laboratories and one of the first examples of direct cooling from BHE; DFS Langen (German Air Traffic Control Headquarters), with 154 BHE for heating and cooling, operating without antifreeze; Baseler Platz Frankfurt, a building right in the center of Frankfurt/Main, with a very limited construction site and the problem of avoiding contamination by groundwater pollution found in the neighbourhood; Arcade Hainburg, a small commercial district heated by a heat pump on a doublet more than 200 m deep; other examples and aspects. The experience gained from these plants, and the economic circumstances, will help in the successful realisation of future geothermal heat pump systems in the region. # 2003 CNR. Published by Elsevier Ltd. All rights reserved