How Soil Moisture Variation Can Affect Horizontal Ground Heat Exchangers Performances: the Iter Project Case Study

Abstract

The performance of very shallow geothermal systems (VSGs), interesting the first 2 m of depth from ground level, is strongly correlated to the kind of sediment locally available. These systems are attractive due to their low installation costs, less legal constraints, easy maintenance and possibility for technical improvements. The Improving Thermal Efficiency of horizontal ground heat exchangers Project (ITER) aims to understand how to enhance the heat transfer of the sediments surrounding the pipes and to depict the VSGs behavior in extreme thermal situations. In detail five geothermal helical heat exchangers installed horizontally and surrounded by five different soil mixtures used as backfilling materials have been monitored under the same climatic conditions and tested under different operation modes. Changes of soil moisture content, ground temperature and running condition have been monitored in the ITER test site and the main results are here presented. The data collected highlight the relationship between VSGs performances and natural or induced ground temperature and soil moisture variations.