Yonmo Sung

With the growing demand for photovoltaic (PV) systems as a source of energy generation that produces no greenhouse gas emissions, effective strategies are needed to address the inherent inefficiencies of PV systems. These systems typically absorb only approximately 15% of solar energy and experience performance degradation due to temperature increases during operation. To address these issues, PV–thermal (PVT) technology, which combines PV with a thermal absorber to dissipate excess heat and convert it into additional thermal energy, is being rapidly developed. This review presents an overview of various PVT technologies designed to prevent overheating in operational systems and to enhance heat transfer from the solar cells to the absorber. The methods explored include innovative absorber designs that focus on increasing the heat transfer contact surface, using mini/microchannels for improved heat transfer contiguity, and substituting traditional metal materials with polymers to reduce construction costs while utilizing polymer flexibility. The review also discusses incorporating phase change materials for latent heat absorption and using nanofluids as coolant mediums, which offer higher thermal conductivity than pure water. This review highlights significant observations and challenges associated with absorber design, mini/microchannels, polymer materials, phase change materials, and nanofluids in terms of PV waste heat dissipation. It includes a summary of relevant numerical and experimental studies to facilitate comparisons of each development approach.

In this work, the effects of carbon nanotubes and an amphoteric surfactant, namely lauryl betaine, on the absorbance, contact angle, surface tension, and thermal conductivity of DW were experimentally investigated. The concentration of the carbon nanotubes was 0.5 wt% and that of lauryl betaine was 100, 500, and 1000 ppm in distilled water. From the absorbance measurement results, the addition of lauryl betaine could increase the absorbance in the wavelength range of UV and visible rays (200~1000 nm). In addition, the higher the surfactant concentration, the higher the dispersibility. The contact angle of the distilled water showed a monotonic decreasing trend with an increase in the surfactant blending ratio, while there were no significant changes in that of the carbon nanotube nanofluid. Analogous behaviors were observed in the surface tension measurements. The surface tension of the distilled water dramatically decreased with an increase in the surfactant blending ratio. The highest decrement was 46.05% at the surfactant concentration of 1000 ppm. In contrast, there were no significant changes in the case of the carbon nanotube nanofluid. Adding 0.5 wt% of the carbon nanotubes to distilled water could substantially enhance the thermal conductivity up to approximately 3%. The degradation effect of the amphoteric surfactant on the thermal conductivity of the fluids was observed in both distilled water and nanofluids.