Heat storage and release in binary paraffin-hexadecyl amine composites for solar greenhouses in cold climates

Abstract

Traditional solar greenhouses in cold regions of China often suffer from poor thermal insulation and storage capacity, resulting in inefficient use of solar energy resources and reduced crop production efficiency. Therefore, it is crucial to explore methods to enhance the thermal conditions within these greenhouses. This paper proposes incorporating a “binary paraffin hexadecyl amine” phase change material into concrete, creating a novel composite material for use in a phase change thermal storage concrete slab. This approach can effectively address the previously mentioned issues. Two solar greenhouses were constructed to directly observe the material's impact on the thermal environment within a greenhouse. One greenhouse was equipped with the phase-change thermal storage slab, while the other served as a control greenhouse without the slab. Temperature field test was conducted on both greenhouses, and the obtained test data demonstrated the temperature regulation advantages of the phase-change greenhouses. Tomatoes were concurrently cultivated in both structures, and a temperature test was conducted to assess the phase-change heat-storage slab's influence on temperature regulation. The results indicate that, compared to similar studies, the phase-change heat-storage slab employed in this study demonstrates superior temperature regulation capabilities. It raises the average greenhouse temperature by 4.2 °C during winter, storing 8.85 × 104 kJ/m3 of heat per unit volume, which is 1.5 to 2.8 times higher than existing materials in the same category. In sunny conditions, the phase-change greenhouse exhibited a 4.9 °C reduction in maximum indoor temperature during the day and a 3.5 °C increase in minimum indoor temperature at night compared to the control greenhouse. This indicated that the phase-change heat storage slab acted as a heat buffer, effectively regulating the temperature inside the solar greenhouse. Tomatoes experienced a 26.6 % increase in effective accumulated temperature, resulting in maturation period occurring 13.04 % earlier compared to the control greenhouse.