Evaluation of the underground soil thermal storage properties in Libya

Transient Heat Transfer and Energy Transport in Packed Bed Thermal Storage Systems

“…The second type of two-medium heat storage system, as shown in Fig. 2(b), is such that the heat transfer fluid flows in tubes or pipes that run through thermal storage material, either solid (such as, concrete, wax, sands, soil (Nassar et al, 2006), salts, etc), or liquid (such as oil, or liquid salts, etc). Due to the smaller contact area between the fluid and thermal storage material, the heat transfer between the fluid and the thermal storage material in this case is worse compared to that of the first type.…”

“…Nevertheless, this type of thermal storage system, as in Example 2, still saves 31% of the heat transfer fluid. Thermal energy storage in soil (Nassar et al, 2006), concrete (Zhang et al, 2004;Laing at al., 2006;Reuss et al, 1997), and in sands (Wyman, 1980) has similar features to that of the Example 2. When the heat transfer performance (the multiplication of the heat transfer coefficient and the heat transfer area) between the heat transfer fluid and thermal storage material is poor, the energy delivery effectiveness can be rather low.…”

Numerical Simulation on the Continuous Operation of Aquifer Thermal Energy Storage System

“…where T: aquifer temperature C vr , C vw : rock and water heat capacity at constant volume λ T : thermal conductivity of aquifer q H : enthalpy source per unit bulk volume Q L : heat loss to overburden and underburden formations The aquifer is assumed to be continuous and its thermal conductivity and volumetric heat capacity are considered to be a function of porosity and the thermal characteristics of water and soil matrix (Nassar et al, 2006). Thermal dependence of density, viscosity, thermal conductivity, and heat capacity is not taken into consideration because these parameters vary little in the considered temperature range.…”

Simulation on the cyclic operation of an open borehole thermal energy storage system under regional groundwater flow

“…The differential equation is derived by assuming that energy is a function of temperature only and energy flux in the ground occurs by convection and conduction. The ground is assumed to be continuous and its thermal conductivity and volumetric heat capacity are considered to be a function of porosity and the thermal characteristics of water and soil matrix (Nassar et al, 2006). Thermal dependence of density, viscosity, thermal conductivity, and heat capacity is not taken into consideration because these parameters vary little in the considered temperature range of 5−25°C.…”