One of the most important applications of solar energy is its utilization in solar dryers to maintain agricultural products for long-term storage. These dryers work based on passing warm air through fresh materials by natural or forced convection. So, they have a direct dependence on the intensity of the sun's irradiance to their collector, which it disrupts the drying process in the absence of a thermal energy source in the hours when the sun is not available. In order to solve this problem, the phase change material (PCM) as thermal energy storage is used. The materials that have the capacity to absorb the thermal energy (charge phase) and, they release the absorbed energy (discharge phase) when the intensity of the solar radiation is low or during the night and cause the uniformity of the outlet temperature solar collector, and inside the drying chamber. As well as they provide the necessary thermal energy for hours when the sun is not available and increase the duration of use of the dryer. In the present research, the experimental studies have been carried out through designing and construction of an indirect cabin type solar dryer equipped with a heat pipe evacuated tube collector and using PCM material as energy storage in the expansion tank. In the present research, the experimental studies have been carried out through designing and construction of an indirect cabin type solar dryer equipped with a heat pipe evacuated tube collector and use of PCM material as energy storage in the expansion tank. The effect of various parameters such as inlet and outlet temperatures of the collector, temperature, and humidity of the drying chamber and ambient, the intensity of the solar irradiance on the drying process is investigated, with and without PCM and at two different speed of forced convection through the drying chamber. The results show that the effectiveness of forced convection on the drying process is more than the effect of PCM.

In the current study, natural solar ventilation has been investigated aiming at reducing the consumption of fossil and thus, reducing greenhouse gas emissions in a hot and dry climate in which the behavior of various fluid variables (temperature, velocity, and flow rate) is considered in different conditions. Since solar radiation is not uniform throughout the day, passive solar ventilation is unstable. In this regard, the natural displacement flow in a solar ventilator with copper thermal absorber, double-glazed glass compartment to prevent thermal energy loss, as well as phase change materials for the storage of thermal energy has been investigated, experimentally. In the case of no phase change material, due to the creation of a suitable temperature difference, the panel has made the chimney effect possible for natural ventilation in some hours of the day, but in the early hours of the night, the temperature of the panel will be the same as the ambient temperature, and the chimney effect will not be available for proper ventilation. In a panel equipped with phase change materials, the system has acceptably been able to play an important role in reducing the temperature drop in the hours of the day with no solar radiation leading to a reliable air flow rate. In fact, the main purpose of using phase change materials in passive solar ventilation is the same effect, the use of excess energy in cases of energy shortages.