بررسي عملكرد سيستم مواد تغيير فاز‌دهنده در ساختمان به‌لحاظ آسايش حرارتي و مصرف انرژي در اقليم كويري ايران

Study of Energy and Thermal Comfort Performance of PCM Systems for Building in the Desert Climate of Iran

كاربرد مواد تغيير فازدهنده (PCM) در ساختمان، به‌دليل ظرفيت بالاي اين مواد در ذخيره‌ي انرژي گرمايي، به بهبود شرايط آسايش حرارتي و نيز كاهش مصرف انرژي مي‌انجامد. با توجه به وابستگي زياد عملكرد اين مواد به نوسانات دمايي محيط، كاربرد آنها در اقليم كويري ــ كه داراي نوسانات شديد دمايي در شبانه‌روز است ــ بر شرايط آسايش حرارتي و كاهش مصرف انرژي ساختمان هاي اين نوع اقليم بسيار اثرگذار باشد. در تحقيق حاضر عملكرد يك سيستم تك‌لايه از اين مواد در اتاقي نمونه و در آب و هواي زمستاني شهر يزد بررسي مي‌شود. در اين تحقيق از قابليت‌هاي نرم‌افزار انرژي‌پلاس براي شبيه‌سازي استفاده شده است. نتايج نشان مي‌دهد كه PCM با دماي ذوب ?C20، بيشترين تاثير را بر بهبود شرايط آسايش حرارتي اتاق و PCM با دماي ذوب ?C22، بيشترين تاثير را بر كاهش مصرف انرژي اتاق دارند.

Solar energy has an enormous potential for space heating buildings in winter. However, solar radiation is a time-dependent energy source with an intermittent and variable character. Thermal energy storage provides a reservoir of stored energy to adapt to the fluctuations in solar energy. Solar energy may be stored in the Phase Change Material (PCM) panels. As the temperature increases during the daytime, the phase of the material changes from solid to liquid and, thus, the PCM absorbs heat. Similarly, when the temperature decreases during the night, the phase of the material changes from liquid to solid, and the PCM desorbs heat. This process could have a significant impact on thermal comfort and energy consumption in rooms. By considering the high dependency of these materials on environmental temperature fluctuations, employment of these materials in a desert climate with extensive daily temperature fluctuations may have a considerable effect on thermal comfort and energy consumption in buildings. In the present paper, the energy and thermal comfort performance of a south-facing direct-gain room in a desert climate, with phase change material plates as inner linings (single layer) on all interior surfaces, except the floor, has been studied. The simulation has been carried out for two cases. In the first case, simulation is done by applying ordinary plaster as the inner lining, and, in the second case, the simulation is done by applying single layer PCM as an inner lining. Effects of the main factors on room air temperature are investigated. These factors include the thermophysical properties of the PCM such as: melting temperature, thermal conductivity, and thickness of PCM plates. In the present study, EnergyPlus software has been used in the analysis. Performance of the PCMs has been modeled using the Conduction Finite Difference solution algorithm. This algorithm uses an implicit finite difference scheme coupled with an enthalpy-temperature function to account for the phase change energy accurately. The results show that the PCM, with a melting point of 20?C, has the greatest impact on improving thermal comfort conditions in the room, and the PCM with a melting point of 22?C has the greatest impact on reducing energy consumption in the room.