EFFICIENCY OF SOLAR GROUND THERMAL STORAGE

Abstract

Non-stationary processes of heat exchange in seasonal solar ground thermal storage with a heat pump and 9 soil vertical heat exchangers, with daily cycles, storage charging in summer and discharging in winter for various regions of Ukraine are investigated. The research method is numerical. The iterative method selected the conditions for the complete autonomous heating. The possibility of increasing the efficiency of thermal storage by selecting a rational step of pipes and the temperature of the coolant in the ground heat exchanger is shown. In the cluster method of a seasonal battery organizing, recirculation of the coolant in heat exchangers in the case of solar radiation absence (in the passive phase) contributes to an increase of heat supply efficiency of the ground. The boundary velocity of the coolant at the entrance of the heat exchanger in the passive phase is 0.8 m/s. Such conditions make it possible to achieve an increase of the ground enthalpy and to reduce the required area of solar collectors. This also contributes to the rational value of the coolant temperature at the entrance of the soil heat exchangers, which can be recommended at 50 °C. The rational step of pipes in cluster is mainly a function of the thermophysical properties of the ground and can be determined from the obtained formula.