Economical fast growth worldwide has led to an increase in energy demand. Energy improvement in buildings has not only reduced our dependence on fossil fuels, but also has a significant effect on emission of greenhouse gases. The application of phase change materials in construction of buliding materials and building elements is one of the newest and the most effective methods for thermal energy storage in buildings. In this study, at first, different materials were tested and silica fume was selected as the best stabilizer. Shapestabilized phase change material (CM) was produced without any leakage in alternating thermal cycles, using PEG-600 and silica fume. Then, thermal performance and thermal energy storage capability of the filled and hollowcore specimens with thickness of 10 and 15 cm including CMs with 10 and 18 percents and macroencapsulated PCMs were investigated. The specimens were tested under the weather temperature condition of a summer day of Ardabil and Isfahan. Maximum reduction of inner side temperature and the reduction of ultimate inner side temperature and time delay to reach to the maximum temperature were measured as the thermal performance criteria. Moreover, compressive and tensile strengths of the specimens including shape-stabilized phase change materials (CMs) were measured. Results stated that the application of phase change materials in the specimens would reduce the inner side temperature of the concrete walls up to 7.2 ? and up to 9.5 hour shift in peak load with respect to the type of specimen. The specimens with macroencapsulated PEG showed the most reduction in the inner side temperature and the specimens with less thickness had a better thermal performance. Furthermore, the presence of silica fume in shape-stabilized phase change materials compensates the reduction of 122 compressive and tensile strengths of the specimens limitedly and also causes an increase in compressive strength compared to controlled ones in higher ages. Keywords: Lightweight concrete, Shape-stabilized phase change material (CM), Thermal performance, Thermal energy storage.
