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.

Capillary-driven action is an important phenomenon which aids the development of high-performance heat transfer devices, such as microscale heat pipes. This study examines the capillary rise dynamics of n-butanol/water mixture in a single vertical capillary tube with different radii (0.4, 0.6, and 0.85 mm). For liquids, distilled water, n-butanol, and their blends with varying concentrations of butanol (0.3, 0.5, and 0.7 wt.%) were used. The results show that the height and velocity of the capillary rise were dependent on the tube radius and liquid surface tension. The larger the radius and the higher the surface tension, the lower was the equilibrium height (h_e) and the velocity of rise. The process of capillary rise was segregated into three characteristic regions: purely inertial, inertial + viscous, and purely viscous regions. The early stages (purely inertial and inertial + viscous) represented the characteristic heights h₁ and h₂, which were dominant in the capillary rise process. There were linear correlations between the characteristic heights (h₁, h₂, and h_e), tube radius, and surface tension. Based on these correlations, a linear function was established between each of the three characteristic heights and the consolidated value of tube radius and surface tension (σL/2πr²).