Development of a Calculation Concept for Mapping Specific Heat Extraction for Very Shallow Geothermal Systems

Abstract

Horizontal shallow geothermal applications are easy to install, and their installation process is less liable to legislation than other geothermal systems. Due to a lack of planning guidance, the opportunity to implement such systems is often overlooked, although geothermal installations are urgently needed as a sustainable energy source. To give a foundation for including very shallow geothermal systems in local heat supply planning, potential maps are crucial. To enable their utilization in energy use plans or similar elaborations for municipalities, location-specific and system-specific heat extractions are required. Since applicable standards are not available, it is nearly impossible to provide aggregate propositions, which are essential for potential maps. In this study, a concept was evolved for deriving very shallow geothermal potential maps with location-specific and system-specific heat extraction values. As a basis, VDI 4640 Part 2 information regarding heat extraction and respective climate zone references was utilized. Furthermore, climate information and a soil map were needed to apply the concept to the study area. The application of the concept in an Austrian study area resulted in appropriate potential maps. Moreover, this concept is similarly applicable in other areas of interest.

Influence of Groundwater on the Very Shallow Geothermal Potential (vSGP) in the Area of a Large-Scale Geothermal Collector System (LSC)

“…At 1.5 m b.g.l., the simulated moisture contents were significantly higher than the observed data, with RMSE values of 0.33 (Figure 4a). The median of the observed moisture contents was 0.07 cm 3 /cm 3 . The low values can be explained by the increased water extraction by the conifers in this area, which has an effect at least down to 1.5 m b.g.l.…”

“…Based on the medians in both scenarios, moisture contents between 0.32 and 0.42 cm 3 /cm 3 were simulated for the fine-grained soils at the considered depths. The medians of the two scenarios differ by a maximum of 0.02 cm 3 /cm 3 . The sensors at "Reference" and "mLSC" recorded medians between 0.34 and 0.39 cm 3 /cm 3 , when periods of partially frozen soil are excluded.…”

“…The potential of very shallow geothermal applications can be described by the systemspecific heat extraction [3] or by the thermal conductivity of soils (λ) [4]. The parameter λ is determined by soil physical parameters such as moisture content (θ), bulk density and grain size distribution [4][5][6][7].…”

“…Simplified assumption that porosity corresponds to the maximum moisture content at saturation (θ s ). 2 k 0 , α and n taken from DIN 4220:2020-11[14] for slightly clayey loam according to KA5[38] based on a grain size analysis of the gravelly loam at B6 3. Maximum recorded value of moisture content at saturated state at 2.9 m b.g.l.…”

Structural Performance Assessment of Geothermal Asphalt Pavements: A Comparative Experimental Study

“…Several studies have proven the efficiency of environmentally friendly shallow geothermal systems in controlling the thermal performance of asphalt structures [18,19]. In many cases, through the heat exchange with the underlying subgrade layers, ground source heat pumps (GSHP) can successfully cool down asphalt pavements during the hot summertime and warm them up to be used for ice melting during the cold wintertime [20].…”