Photovoltaic-thermal (PVT) solar collector technologies are considered a highly efficient solution for sustainable energy generation, capable of producing electricity and heat simultaneously. This paper reviews and discusses different aspects of PVT collectors, including fundamental principles, materials, diverse classifications, such as air-type and water-type, and different cooling mechanisms to boost their performance, such as nano-fluids, Phase Change Materials (PCMs), and Thermoelectric Generators (TEGs). At the system level, this paper analyses PVT technologies’ integration in buildings and industrial applications and gives a comprehensive market overview. The methodology focused on evaluating advancements in design, thermal management, and overall system efficiency based on existing literature published from 2010 to 2025. From the findings of various studies, water-based PVT systems provide electrical efficiencies ranging from 8% to 22% and thermal efficiencies between 30% and 70%, which are almost always higher than air-based alternatives. Innovations, including nanofluids, phase change materials, and hybrid topologies, have improved energy conversion and storage. Market data indicates growing adoption in Europe and Asia, stressing significant investments led by Sunmaxx, Abora Solar, Naked Energy, and DualSun. Nonetheless, obstacles to PVT arise regarding aspects such as cost, design complexity, lack of awareness, and economic incentives. According to the findings of this study, additional research is required to reduce the operational expenses of such systems, improve system integration, and build supportive policy frameworks. This paper offers guidance on PVT technologies and how they can be integrated into different setups based on current normativity and regulatory frameworks.

A novel and effective hybrid technique, which involves active surface heating strategies in conjunction with the use of passive splitter plates in the wake of the cylinder, is proposed. In this report, we present the results of a numerical investigation on the two-dimensional, laminar mixed convection flow over a circular cylinder with a hot rigid splitter plate attached to it on the wake side. A projection algorithm-based finite volume method is employed to obtain the solution of the coupled, nonlinear governing partial differential equations subjected to Courant–Friedrichs–Lewy conditions. The isothermal heating of the splitter plate under the influence of the gravity field generates an upward buoyancy force in the wake of the cylinder. For different length-to-diameter (L/D) ratios, the effect of heating on aerodynamic, wake, and heat transfer characteristics has been studied for a wide range of parameters; 75 ≤Re≤ 150, 0 ≤Ri≤ 1, and 0.5 ≤L/D≤ 1 at Pr = 0.7. It is observed that the hot splitter plate would bring about conspicuous changes such as asymmetry in the vortex shedding behind the cylinder at low Reynolds numbers. The outcomes demonstrate a notable improvement in convective heat transfer and drag, with gains of up to 7% and 15%, respectively. It is found that the rate of heat transfer and vortex shedding frequency decrease with an increase in L/D ratio. Correlations for the estimation of Strouhal number and Nusselt number have also been proposed which helps provide a more thorough understanding of thermal and aerodynamic features of the hybrid approach.

Numerical simulations are performed to investigate the effect of the Reynolds number (Re) on flow over curved plates. Concave and convex plates, obtained by introducing curvature on a flat plate, are analyzed in the Reynolds number range 0.1 ≤Re≤ 120. It is observed that for a concave plate, the separation point is dependent on Re, while for a convex plate, the flow separates from the outermost tips for all Reynolds numbers. The analysis of time-averaged quantities reveals that concave and convex plates behave differently for the same Reynolds number. In the steady flow regime, visualization of streamlines reveals the presence of a recirculation bubble on the front side of the concave plate, even for the lowest Reynolds number (Re = 0.1). However, at higher Reynolds numbers (Re = 110, 120), the near wake of concave plate witnesses secondary and tertiary recirculating entities. The present simulations also report the unique phenomenon of vortex realignment and divergence of vortex street in the wake of a concave plate. For a convex plate, the vortex realignment is followed by the movement of upper and lower vortices as two parallel vortex streets. The existence of multiple instabilities is another highlight in the near and far wakes of the concave plate, some of which arise due to the secondary vortex interactions. A comprehensive analysis further reveals a handful of novel phenomenal occurrences in the wake of concave surfaces.

Numerical simulations are performed to deduce the effects of slip wall and orientation on entropy generation due to natural convection (NC) in a square cavity for Rayleigh number (Ra) = 105. The laterally insulated square cavity, heated at the bottom wall and cooled at the top wall, is subjected to various orientation angles (ϕ) and slip velocities characterized by the Knudsen number (Kn). The two components of entropy generation, i.e., entropy generation due to heat transfer (SΘ) and entropy generation due to fluid friction (SΨ), are separately investigated by varying the orientation from 0 deg to 120 deg in steps of 15 deg and Knudsen number from 0 (no-slip) to 1.5 in steps of 0.5. Evidence indicates that, for most cases considered, entropy generation due to fluid friction (SΨ) dominates the one due to heat transfer (SΘ). It is observed that the slip velocity on the isothermal walls (us,iso) has a strong influence on SΘ whereas the variations in SΨ are closely connected to the change in the rate of shear strain. Interestingly, the presence of corner vortices and the secondary circulations near the core of the cavity are also found to affect the variation in entropy generation. The existence of active zones of SΘ in the vicinity of isothermal walls and their elongation and migration while changing the orientation is another unique characteristic noticed in this study. A new parameter called maximum velocity ratio (MVR) is also proposed to highlight the variation in velocity components within the enclosure.

Visualization experiments are conducted in a water channel to investigate the wake vortex characteristics of a flat plate and convex and concave curved plates. Three parameters—vortex size ($S_v$ ), vortex length ($L_v$ ), and Strouhal number ($St$ )—are investigated in this study to deduce the effect of plate curvature and orientation. These parameters are estimated for both the upper and lower vortices by keeping the chord length ($L_c$ ) fixed and changing the plate diameter (D). Various plate configurations are demonstrated by altering the $L_c/\mathrm{D}$ ratio from 0 to 1; $L_c/\mathrm{D}=0$ , 6/13, 3/4, and 1. The Reynolds number (Re) based on chord length remains unchanged at 5,878 throughout the analysis. For each case of the $L_c/\mathrm{D}$ ratio, the angle of flow incidence of the plate ($\alpha$ ) is varied from 0° to 30° in steps of 5°. For the convex plate, the combined effect of curvature and orientation is found to enhance the vortex shedding frequency by 70.7%, whereas vortices shrink by 26.71%, and the vortex length is reduced by 25.38%. The manipulations achieved for concave plates reveal comparatively lesser enhancement in shedding frequency; however, concave surfaces are observed to be more suitable for stretching the vortices toward the downstream. The modifications thus achieved have significant practical relevance in various applications. A shedding mechanism that partially interrupts Gerrard’s mechanism is also found to operate with concave plate configurations.