Study on Carnauba wax as Phase Change Material Integrated in Evacuated Tube Collector for Solar Thermal Heat Production

Evacuated tube collector (ETC) for solar heat production is one of the most efficient systems to convert sun energy into usable energy. Unfortunately, some technological barriers are still present in solar thermal heat systems that limit the use of these technologies to decarbonize processes. An important obstacle is the requirement of heat at stable temperatures, which are not always achievable by solar fields, e.g. variable sky. For that reason, in this work, we studied the phase change materials embedded in the evacuated tube collector to keep stable the water temperature for a short period (min, hours). In this study, carnauba wax was used as a sustainable phase change material (PCM), to avoid the use of PCM based on hydrocarbon waxes. The phase - change material has been packaged using a polyethylene bag inserted in an evacuated tube collector with heat pipe technologies and tested. The collector has been tested outdoor under solar irradiation and in the shading condition. The experimental results show that is possible to detect a sensible effect of PCM on the temperature using 4 kg of carnauba wax while important effect on the temperature stabilization using 9kg of PCM. Using 9kg of the PCM we observed a stability of the outlet water temperature at 65°C for 30 minutes in shading condition.