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Energies 2017, 10(11), 1897; https://doi.org/10.3390/en10111897

Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers

Department of Geology, GeoZentrum Nordbayern, Friedrich-Alexander University Erlangen-Nuremberg, 91054 Erlangen, Germany
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Received: 13 October 2017 / Revised: 12 November 2017 / Accepted: 14 November 2017 / Published: 18 November 2017
(This article belongs to the Special Issue Low Enthalpy Geothermal Energy)
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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 this regard, five helices were installed horizontally surrounded by five different backfilling materials under the same climatic conditions and tested under different operation modes. The field test monitoring concerned: (a) monthly measurement of thermal conductivity and moisture content on surface; (b) continuous recording of air and ground temperature (inside and outside each helix); (c) continuous climatological and ground volumetric water content (VWC) data acquisition. The interactions between soils, VSGs, environment and climate are presented here, focusing on the differences and similarities between the behavior of the helix and surrounding material, especially when the heat pump is running in heating mode for a very long time, forcing the ground temperature to drop below 0 °C. View Full-Text
Keywords: very shallow geothermal energy; horizontal collectors; thermal conductivity; volumetric water content; soil very shallow geothermal energy; horizontal collectors; thermal conductivity; volumetric water content; soil
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Di Sipio, E.; Bertermann, D. Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers. Energies 2017, 10, 1897.

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