Page 126 - Analysis and Design of Energy Geostructures

98 Analysis and Design of Energy Geostructures

3.7.6 Typical values of volumetric heat capacity
Typical values of volumetric heat capacity for different materials involved in energy
geostructures applications are provided in Table 3.9. Distinct values of specific heat
and bulk density are reported in Table 3.10. The typical evolution of volumetric heat
capacity with water content for soils (e.g. unfrozen) is presented in Fig. 3.13.
The estimation of the volumetric heat capacity of materials is usually simpler than
that of the thermal conductivity. In such cases, in contrast to the estimation of the
effective thermal conductivity, a linear function of the capacities and volume ratios of
the phases characterising the material is sufficient to have a representative estimate of

Table 3.9 Volumetric heat capacity of materials characterising energy geostructures.
Material Volumetric heat capacity,
ρc p [MJ/(m 3 C)]
Dry Saturated

Clay 1.5 1.6 1.6 3.4
Silt 1.5 1.6 1.6 3.4
Sand 1.3 1.6 2.2 2.9
Gravel 1.4 1.6 2.4

Peat 0.5 3.8
Claystone/Siltstone 2.1 2.4
Sandstone 1.6 2.8
Quartzite 2.1 2.2
Marl 2.2 2.3
Limestone 2.1 2.4
Argillaceous schists 2.2 2.5
Micaschists 2.2
Metaquartzite 2.1
Marble 2.0
Gneiss 1.8 2.4
Rhyolithe 2.1
Peridotite 2.7
Granite 2.1 3.0
Gabbro 2.6
Diorite 2.9
Basalt 2.3 2.6
Concrete 1.8 2.0
Steel 3.12
Water 4.186
Air 0.0012
Source: Data from Pahud, D., 2002. Geothermal Energy and Heat Storage. Laboratorio di Energia,
Ecologia ed Economia, Canobbio.