Investigation of soil-based heat storage system for sustainable building heating

Seasonal heat accumulation provides various advantages. The primary benefit is the ability to generate heat with maximum capacity under optimal conditions, store the thermal energy, and retain it until the highest needs are met. Natural and environmentally sustainable resources, such as soil, are promising materials for heat storage. This study investigated the feasibility of utilising the thermal energy generated by solar collectors from spring to autumn to heat a private building during the cold period. The proposed method involved storing heat in the soil beneath the building, isolating it from the surrounding ground. Heat dissipation in a limited soil volume was experimentally studied. The high inertia of the processes and changes in soil temperature fields, depending on the charge level of the thermal energy storage system, complicate the assessment of its state. Numerical studies have shown that the average soil temperature of the accumulator is more suitable for controlling the connection of solar collectors to the storage system than the outlet fluid temperature of the heating device, which is currently the primary method used in practice. Depending on the charge level, defined by the average soil temperature, the daily operating time of solar collectors for soil charging decreases, reducing the charging potential. In June, this reduction is less than one per cent, while in less favourable periods, such as September, it can reach about five per cent. This should be taken into account in design calculations. • Heat generated in the summer may be used in the cold season for building heating. • A compact sand heat storage system was experimentally and numerically researched. • The heat accumulator can be constructed under the building. • Depending on the increased charge level, the charging potential reduces. • The average soil temperature was identified as a more reliable control parameter.