| Work Detail |
Scientists have used different levels of Al2O3 and ZnO paraffin to improve the electrical and thermal performance of a photovoltaic-thermal (PVT) system. They have also developed a prediction model for this specific combination of hybrid phase-change nanomaterials.
Researchers from Bangladesh and Australia have studied hybrid phase change nanomaterials (HNPCMs) for PVT applications. They used paraffin wax as a phase change material (PCM), incorporating various levels of aluminum oxide (Al2O3) and zinc oxide (ZnO) nanoparticles. They also developed a prediction model.
“In this research, Al2 O3 and ZnO are incorporated at different concentrations with PCM to enhance its thermal conductivity and then used in the PVT system to examine the impact on its performance (electrical and thermal),” the group said. “The hybrid-nano/PCM samples are prepared and their morphology, structure, thermal stability, thermal conductivity and phase change behavior are carried out.”
They incorporated the Al2O3-ZnO mixture into the wax at loadings of 0.5%, 1%, and 2%. They added the mixture to the wax at 70 °C and stirred it for two hours, using an ultrasonic vibration machine to keep the beaker above the melting point. Finally, they cooled the samples to room temperature.
“Scanning electron microscope (SEM) tests were performed for morphological analysis of the samples, and the test results show that the 2% hybrid nanoparticles mixed with PCM exhibited better connection with the base paraffin without having any agglomeration… The 2% hybrid nano-PCM shows a higher thermal conductivity of 2.18 W/mK than pure paraffin (1.54 W/mK),” the group said. “The result shows the gradual increase of thermal conductivity by adding hybrid nanoparticles with mass fractions of 0.5, 1, and 2%.”
The researchers built an experimental setup combining HNPCMs with a PVT system. They attached a 20 W polycrystalline photovoltaic module to a serpentine copper tube containing the HNPCMs at the back, with copper tubes underneath carrying water at 0.0021 kg/s. The hot water was stored in a thermal energy reservoir.
The system was installed on the rooftop of the Rajshahi University of Engineering and Technology in Bangladesh. They also installed two reference systems with the same 20 W PV module: one with only the PV panel and the other with only paraffin wax PCM. Measurements were performed in late April 2022, with irradiance ranging from 400 W/m² to 900 W/m² and ambient temperature of about 26 °C.
“The experimental results showed that compared with PCM alone, the thermal conductivity of HNPCM increased by 24.68%, 28.57%, and 41.56% for the inclusion of 0.5%, 1%, and 2% hybrid nanomaterial, respectively,” the researchers said. “The electrical efficiency of the PVT/HNPCM and PVT/PCM system was improved by 31.46% and 28.70%, respectively, compared with the conventional PV system in this study.”
The group has also developed a response surface methodology (RSM) model to “predict and optimize the interaction of operational factors (independent variable) with response factors (dependent variable).” RSM uses statistics and mathematical models, typically, to improve and optimize experimental systems.
“After completing the comparisons from the experimental results, the error rate for electrical, thermal and overall efficiency is estimated to be around -1.95% and -0.57%, -4.81% and -1.66%, and -3.83% and -1.24%, respectively, for both PVT/PCM and PVT/HNPCM systems,” the academics say.
They presented their results in “ Characterization, optimization, and performance evaluation of PCM with Al2 O3 and ZnO hybrid nanoparticles for photovoltaic thermal energy storage ,” recently published in Energy and Built Environment . The study was conducted by scientists from the Rajshahi University of Engineering and Technology in Bangladesh and Edith Cowan University in Australia. |
