No abstract

No abstract

No abstract

No abstract

The efficiency of a solar thermal energy storage system using basaltic rock fills has been assessed using a scaled-down model. The proposed system is designed to operate without external electricity in cold areas. Solar energy is collected and stored in basalt ballasts filled in a shallow pit excavated above the groundwater table. The surrounding soil and an acrylic sheet cover serve as insulator. The stored thermal energy is released through a system of tubes to warm up housing at night. The thermal properties of ten rock types that occur widely in the north and northeast of Thailand were determined in the laboratory. A scaled-down model, simulating the storage system and housing, was constructed to monitor the temperature changes of the various system components and the results were compared with the predictions of mathematical models. Buriram basalt was selected for testing as it has the highest thermal conductivity and specific heat. The results indicate that throughout the night the system can increase the housing temperature to 4-6°C more than the surroundings, depending on the packing density, tube size, and surrounding temperature. The efficiency of this storage system is about 35%. The gained heat energy in the housing is equivalent to the electrical energy of 203 kJ. The mathematical models developed here agree well with the measured results.