Thermal properties variations in unconsolidated material for very shallow geothermal application (ITER project)

Sipio, Eloisa Di; Bertermann, David

doi:10.1515/intag-2017-0002

Cited by 25 publications

(16 citation statements)

References 51 publications

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“…The five soil mixtures have been selected according to the results of the laboratory measurements performed on 15 thermally enhanced backfilling material (TEBM) tested under different water content (complete dry up to complete saturation) and incremental load conditions [36]. Finally, the commercial product GeoSolid 240 HS (from now on cited as GS), kindly provided by Fischer Spezialbaustoffe Gmbh (Heilsbronn, Bavaria, Germany), is an enhanced thermal material (λ = 2.4 W m −1 K −1 ) generally used as grouting for borehole heat exchangers in agreement with the current recommendations of Verein Deutscher Ingenieure (VDI), Association of German Engineers) guideline for the thermal utilization of the substrate [48].…”

Section: Test Sitementioning

confidence: 99%

Section: Test Sitementioning

confidence: 99%

“…The heat transfer in soil is led by conduction, a process driven by temperature gradients and dependent on thermal conductivity, in turn a property strictly related to water content. Then, the heat transfer in soils tends to decrease as anhydrous conditions or decreasing temperature are detected [34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

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Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers

Sipio

Bertermann

2017

Energies

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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.

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Section: Test Sitementioning

confidence: 99%

Section: Test Sitementioning

confidence: 99%

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Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers

Sipio

Bertermann

2017

Energies

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“…SGES energy efficiency is highly dependent on the thermal energy transfer between the surface soil layers and the energy geostructure embedded within it. This heat transfer process is led by conduction due to an imposed temperature gradient occurring between soil and the geostructure (primary circuit of the GSHP) [4]. Hence, the evaluation of soil thermal properties, namely its thermal conductivity, is of major importance in analysing the heat transfer process [5].…”

Section: Introductionmentioning

confidence: 99%

Effects of temperature, test duration and heat flux in thermal conductivity measurements under transient conditions in dry and fully saturated states

et al. 2020

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In shallow geothermal energy systems (SGES) thermal conduction can be considered the dominant process in the heat transfer between the primary circuit (borehole heat exchanger or thermoactive geostructure) and the surrounding ground. Thus, a proper characterization of soil thermal properties, namely of its thermal conductivity, is mandatory for evaluating this energy exchange. There are difficulties associated to the assessment of soil thermal conductivity by laboratory methods related, among other factors, to the samples’ quality and to the measuring method itself. The purpose of this work is to analyse the effect of changing test control parameters in thermal conductivity measurements in transient conditions by means of a high accuracy thermal probe in both dry and fully saturated states. In order to eliminate potential measurements’ deviations and errors due to sample variability the same reconstituted samples were used several times. In each condition the sand samples were systematically tested under different ambient temperatures (10ºC, 20ºC, and 40ºC) controlled by means of a climatic chamber. The effects of changing the tests heating time and imposed thermal fluxes were also analysed.

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“…A substantially lower number of studies, however, have been focused on the effect of recycled organic matter on soil thermal properties although they are a significant factor influencing surface energy partitioning, temperature distribution (Chung and Horton 1987;Mady and Shein 2016), water transmission in the soil and nearby ground atmosphere system (Heitman et al 2007), and seed germination and plant growth (Wardani and Purqon 2016). Besides, thermal properties are used to assess heat migration in the soil in terms of using geothermal energy (Mondal et al 2015;Di Sipio and Bertermann 2018).…”

Section: Introductionmentioning

confidence: 99%

The effect of exogenous organic matter on the thermal properties of tilled soils in Poland and the Czech Republic

Usowicz

Lipiec

2019

J Soils Sediments

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Purpose Organic matter improves soil fertility and water and thermal properties, but its content often decreases. This decrease may be mitigated by the addition of exogenous organic matter (EOM). The aim of this study was to assess the effect of EOMs, including compost from manure, slurry, and straw (Ag); industrial organic compost from sewage sludge (Ra); animal meal from animal by-products (Mb); and digestate from a biogas fry factory (Dg) on soil thermal conductivity, heat capacity, thermal diffusivity, water content, and bulk density in the top (0-15-cm) layer of two soils in Poland and the Czech Republic. Materials and methods Irrespective of EOM type, the total yearly nitrogen application rate being 200 kg N ha −1 (100%) was from a given EOM at the rates 0, 50, 75, and 100% and the remaining parts from the mineral fertilizer. The study was conducted in 2013-2014 in Poland (Braszowice) and the Czech Republic (Pusté Jakartice) on loam silt and clay silt loam, respectively, as part of a cross-border cooperation project. The soil properties were examined using classical descriptive statistics, semivariograms, and kriging-interpolated maps. Results and discussion Analysis of linear regressions (trends) showed that the EOM application rate influenced (positively or negatively) the soil properties in most measurement occasions. The variability of all soil properties was low and medium (coefficient of variation 7.3-34%). Geostatistical analysis indicated that the spatial dependence (C 0 /(C 0 + C s)) of the soil properties on the EOM-amended plots was very strong or moderate. The maps revealed that the heterogeneity and degree of patch fragmentation were greater for thermal conductivity and heat capacity than for thermal diffusivity, water content, and bulk density. In general, all the soil properties were spatially more variable in the Braszowice than Pusté Jakartice soil and in spring than autumn in both sites. Conclusions The spatial analysis and maps enhance the comprehensive understanding of changes in soil thermal properties in response to EOM application. Suitability of the results from the field experiments in models predicting some thermal properties based on soil bulk density and water content in relation to EOM addition was indicated. Expressing the amount of EOMs added using the organic carbon content basis (% kg OC/kg of soil) instead of the nitrogen content basis allowed identifying areas on the kriging-interpolated maps where the distribution of soil thermal properties resembled that of soil organic carbon content, water content, and bulk density. Thus, the effect of EOMs on soil thermal properties is considered along with changes in soil water content and bulk density. The results will be helpful in forecasting effects of exogenous organic matter on the soil thermal properties affecting surfaceenergy partitioning, temperature distribution in soil, and plant growth.

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Thermal properties variations in unconsolidated material for very shallow geothermal application (ITER project)

Cited by 25 publications

References 51 publications

Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers

Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers

Effects of temperature, test duration and heat flux in thermal conductivity measurements under transient conditions in dry and fully saturated states

The effect of exogenous organic matter on the thermal properties of tilled soils in Poland and the Czech Republic

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