Published September 29, 2017 | Version v1
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Study of geological and climatic conditions impact on energy efficiency of surface geothermal systems

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Description

Surface geothermal systems extract energy from the ground via a fluid circulating in an exchanger at a depth not exceeding 200 m. Two typologies of exchangers are generally used: systems with vertical exchangers, mainly affected by geological conditions; and horizontal exchangers, closer to the surface of ground, impacted mainly by weather conditions. Thermal exchanges in the soil are mainly conduction heat transfers. Thus, thermo-physical properties of soil influence, mostly, energy extracted by exchangers. In order to quantify influence of geological and meteorological conditions on thermo-physical properties of soil, two experimental devices are developed, designed, instrumented and validated. The experimental results provide more appropriate scientific knowledge on hydric behavior of a soil subjected to rain events and influence of compactness on thermal properties of soil. In addition, one numerical study, based on a finite element 2D modeling of an earth-air heat exchanger, evaluates their energy performance under different soil moisture conditions and rain scenarios thus revealing the utility of water to significantly improve its performance. (author)

Abstract (French)

Les systemes geothermiques de surface extraient l'energie du sol via un fluide caloporteur circulant dans un echangeur pour une profondeur ne depassant pas 200 m. Deux typologies d'echangeurs sont generalement utilisees: les systemes avec echangeurs verticaux, principalement affectes par les conditions geologiques; et les echangeurs horizontaux, plus proches de la surface du sol, impactes essentiellement par les conditions climatiques. Dans le sol, les echanges thermiques sont majoritairement des transferts de chaleur par conduction. Ainsi, les proprietes thermo-physiques du sol influencent la quantite d'energie extraite par les echangeurs. Afin de quantifier les proprietes thermo-physiques d'un sol sous l'influence des conditions geologiques et climatiques, deux dispositifs experimentaux sont elabores, concus, instrumentes et valides au sein de notre laboratoire. Les resultats experimentaux enrichissent les connaissances scientifiques sur le comportement hydrique d'un sol soumis a des evenements pluvieux et l'impact de la contrainte verticale sur les proprietes thermo-physiques d'un sol. De plus, une etude numerique, a partir d'une modelisation 2D par elements finis d'un echangeur airsol, evalue les performances energetiques de ce dernier en fonction de differentes humidifications du sol et differents scenarios de pluie. Les resultats numeriques revelent ainsi l'interet d'utiliser un sol d'enrobage tres humide pour accroitre significativement les performances energetiques d'un echangeur air-sol. (auteur)

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Additional details

Additional titles

Original title (French)
Etude de l'impact des conditions geologiques et climatiques sur l'efficacite energetique des systemes geothermiques de surface

Publishing Information

Imprint Pagination
188 p.
Report number
FRNC-TH--13626

INIS

Country of Publication
France
Country of Input or Organization
France
INIS RN
53119498
Subject category
S42: ENGINEERING;
Resource subtype / Literary indicator
Thesis
Descriptors DEI
ALGORITHMS; CLAYS; COEFFICIENT OF PERFORMANCE; COMPUTERIZED SIMULATION; ENERGY EFFICIENCY; FINITE ELEMENT METHOD; GEOTHERMAL SYSTEMS; HEAT EXCHANGERS; MOISTURE; RAIN; SAND; TEMPERATURE DISTRIBUTION; THERMAL CONDUCTION; THERMAL CONDUCTIVITY; THERMAL DIFFUSIVITY; WATER SATURATION
Descriptors DEC
ATMOSPHERIC PRECIPITATIONS; CALCULATION METHODS; EFFICIENCY; ENERGY TRANSFER; HEAT TRANSFER; MATHEMATICAL LOGIC; MATHEMATICAL SOLUTIONS; MINERALS; NUMERICAL SOLUTION; PHYSICAL PROPERTIES; SATURATION; SILICATE MINERALS; SIMULATION; THERMODYNAMIC PROPERTIES

Optional Information

Notes
[110 refs.]; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses