Geothermal resource mapping - example from northern Switzerland

The increased interest in geothermal energy has led to a desire for more sophisticated analyses of available geothermal resources for heat and power production. The evaluation methods have traditionally used 1-D models, but progress in computing power has recently allowed us to achieve joint interpretations, including the large-scale effects of geological, topographical and hydrogeological features. This paper describes the steps taken in a recent integrated assessment and evaluation of the geothermal potential of the most populated areas of Switzerland. The methodology accounts for individual utilization scenarios and is based on temperature data that have been systematically collected over many years. The state-of-the-art compilation involves comprehensive 3-D regional geological and thermal models of 20-40 km extent. Zones of significant convective flow or preferential sites for borehole heat exchanger systems (BHE) can then be identified. In contrast to the results obtained from earlier geothermal resource assessments, the existing geological, hydrogeological and petrophysical data are included in the full 3-D numerical evaluation. The first results, referred to a well-documented subsurface area in Northern Switzerland, are now available. Analysis of temperature data have confirmed the importance of these factors. (C) 2003 CNR. Published by Elsevier Ltd. All rights reserved.