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Abstract Using nanofluids in photovoltaic‐thermal systems enhances the overall efficiency; however, increasing the pressure drop and pumping power, because of the higher viscosity of nanofluids, is a challenging factor for the nanofluid‐based systems. In the present study, the thermohydraulic performance of the photovoltaic‐thermal system is compared using two water‐based nanofluids including hybrid Ag‐MgO and carbon nanotubes (CNT) nanofluids, as the working fluids. The effect of type and flow rate of the working fluid, nanoparticle concentration, and channel height on the friction factor and Nusselt number is studied using the numerical model. The model is validated using the experimental and numerical results and found that the relative errors of the results are less than 3.8% and 5.2%, respectively, which confirmed the model accuracy. The results showed that at a flow rate of 8 L/h, the volume fraction of 2%, and channel height of 10 mm, the system electrical efficiency, thermal efficiency, and friction factor using CNT nanofluid are, respectively, 0.04%, 1.31%, and 62% higher than those using base fluid and 0.03%, 0.89%, and 53% higher than those using Ag‐MgO nanofluid. It is also found that although increasing the nanoparticle concentration and decreasing the channel height improves the system efficiency, it increases the friction factor and pressure drop. Comparing the results using the mono and hybrid nanofluids showed that the thermal performance of the photovoltaic‐thermal system using CNT nanofluid is slightly better; however, the hydraulic system performance using hybrid Ag‐MgO nanofluid is improved.

With the growing utilization of solar power for electricity and heat generation, photovoltaic-thermal (PVT) systems possess tremendous potential as sustainable energy solutions. This review covers recent advances in concentrated photovoltaic-thermal and photovoltaic-thermal technologies, providing insights into improving system performance. Our review concludes that recent innovations in materials, operating configurations, and integration with other technologies have largely optimized PVT designs. Moving forward, PVT systems present a promising pathway for clean, renewable energy generation through effective utilization of the full spectrum of solar energy. Further advancements in cost-competitiveness may facilitate widespread adoption. [ABSTRACT FROM AUTHOR]

Using nanofluids in photovoltaic‐thermal systems enhances the overall efficiency; however, increasing the pressure drop and pumping power, because of the higher viscosity of nanofluids, is a challenging factor for the nanofluid‐based systems. In the present study, the thermohydraulic performance of the photovoltaic‐thermal system is compared using two water‐based nanofluids including hybrid Ag‐MgO and carbon nanotubes (CNT) nanofluids, as the working fluids. The effect of type and flow rate of the working fluid, nanoparticle concentration, and channel height on the friction factor and Nusselt number is studied using the numerical model. The model is validated using the experimental and numerical results and found that the relative errors of the results are less than 3.8% and 5.2%, respectively, which confirmed the model accuracy. The results showed that at a flow rate of 8 L/h, the volume fraction of 2%, and channel height of 10 mm, the system electrical efficiency, thermal efficiency, and friction factor using CNT nanofluid are, respectively, 0.04%, 1.31%, and 62% higher than those using base fluid and 0.03%, 0.89%, and 53% higher than those using Ag‐MgO nanofluid. It is also found that although increasing the nanoparticle concentration and decreasing the channel height improves the system efficiency, it increases the friction factor and pressure drop. Comparing the results using the mono and hybrid nanofluids showed that the thermal performance of the photovoltaic‐thermal system using CNT nanofluid is slightly better; however, the hydraulic system performance using hybrid Ag‐MgO nanofluid is improved. [ABSTRACT FROM AUTHOR]

Abstract The commercial solar cells are currently less efficient in converting solar radiation into electricity. During electric power convention, most of the absorbed energy is dissipated to the surroundings. In order to improve energy efficiency, many efforts have been made to investigate and develop hybrid photovoltaic and thermal collector systems. A photovoltaic–thermal (PV/T) system does both the generation of electric power and collection of thermal energy at the same time. Thus, the overall efficiency of the photovoltaic–thermal (PV/T) system can increase accordingly. In this work, we attempt to summarize various research works on technologies like flat–plate PV/T systems and concentrator type PV/T systems, using different kinds of working fluids under a variety of environmental conditions. The purpose of this review is to define the appropriate environmental conditions and applications for different kinds of PV/T systems. Besides, it is also presented that the applications and developments of the PV/T systems. In order to develop novel PV/T systems, more effort is needed in accurate modeling, exploration of novel materials, enhancement of PV/T system stability and the design of a supporting energy storage system. Highlights • The performances of flat–plate photovoltaic–thermal systems are analyzed and compared. • Developments of concentrator type photovoltaic–thermal systems are discussed. • Applications of photovoltaic–thermal systems are summarized in detail. • A view on the future of PV/T developments and the future work is presented. [ABSTRACT FROM AUTHOR]

Combined solar photovoltaic-thermal systems (PVT) facilitate conversion of solar radiations into electricity and heat simultaneously. A significant amount of work has been carried out on these systems since 1970. Different PVT systems have been invented in the last thirty years. Several theoretical, mathematical, numerical and experimental models are introduced by many investigators across the world. The present article gives a broad classification and review of published research work on these systems. The article mostly covers the experimental work carried out on the different types of PVT systems in the last decade. The latest technology of liquid spectrum filters for PVT systems are also explored in depth. [ABSTRACT FROM AUTHOR]

Solar energy can play a leading role in reducing the current reliance on fossil fuels and in increasing renewable energy integration in the built environment, and its affordable deployment is widely recognised as an important global engineering grand challenge. Of particular interest are solar energy systems based on hybrid photovoltaic-thermal (PV-T) collectors, which can reach overall efficiencies of 70% or higher, with electrical efficiencies up to 15–20% and thermal efficiencies in excess of 50%, depending on the conditions. In most applications, the electrical output of a hybrid PV-T system is the priority, hence the contacting fluid is used to cool the PV cells and to maximise their electrical performance, which imposes a limit on the fluid’s downstream use. When optimising the overall output of PV-T systems for combined heating and/or cooling provision, this solution can cover more than 60% of the heating and about 50% of the cooling demands of households in the urban environment. To achieve this, PV-T systems can be coupled to heat pumps, or absorption refrigeration systems as viable alternatives to vapour-compression systems. This work considers the techno-economic challenges of such systems, when aiming at a low cost per kW h of combined energy generation (co- or tri-generation) in the housing sector. First, the technical viability and affordability of the proposed systems are studied in ten European locations, with local weather profiles, using annually and monthly averaged solar-irradiance and energy-demand data relating to homes with a total floor area of 100 m 2 (4–5 persons) and a rooftop area of 50 m 2 . Based on annual simulations, Seville, Rome, Madrid and Bucharest emerge as the most promising locations from those examined, and the most efficient system configuration involves coupling PV-T panels to water-to-water heat pumps that use the PV-T thermal output to maximise the system’s COP. Hourly resolved transient models are then defined in TRNSYS, including thermal energy storage, in order to provide detailed estimates of system performance, since it is found that the temporal resolution (e.g. hourly, daily, yearly) of the simulations strongly affects their predicted performance. The TRNSYS results indicate that PV-T systems have the potential to cover 60% of the combined (space and hot water) heating and almost 100% of the cooling demands of homes (annually integrated) at all four aforementioned locations. Finally, when accounting for all useful energy outputs from the PV-T systems, the overall levelised cost of energy of these systems is found to be in the range of 0.06–0.12 €/kW h, which is 30–40% lower than that of equivalent PV-only systems. [ABSTRACT FROM AUTHOR]

Abstract: Steady RANS CFD simulations were used to evaluate convective heat transfer from the roof of a low-rise building immersed in an atmospheric boundary layer for different terrain, with relevance to photovoltaic-thermal (PV/T) systems. Dimensionless correlations for the exterior convective heat transfer coefficient (CHTC), expressed as Nusselt number (Nu), were developed for the windward roof, based on Reynolds number and incident turbulence intensity at eaves height, thereby quantifying the strong influence of incident turbulence on the CHTC. Simulations were also performed for a generic flat plate of the same streamwise length so as to provide further insight into the effects of incident turbulence on the windward roof boundary layer. The CHTC values for the windward roof and, hence, the correlations presented here, for a given terrain, are largely insensitive (less than 5% change) to variations in roof slope (from 20 to 45°) or small changes in wind direction (up to 20° from the normal to the eaves). Mixed convection simulations for conditions with significant buoyancy forces (Richardson numbers from 0.9 to 7) show that the CHTC values can be up to 14% higher than those based on forced convection only. [Copyright &y& Elsevier]

As the scaling of silicon PV cells and module manufacturing has driven solar energy penetration up and costs down, concentrator photovoltaic technologies, originally conceived as a cost-saving measure, have largely been left behind. The loss of market share by CPV is being locked in even as solar energy development encounters significant obstacles related to space constraints in many parts of the world. The inherently higher collection efficiency enabled by the use of concentrators could substantially alleviate these challenges, but the revival of CPV for this purpose requires substantial reinvention of the technology to actually capture the theoretically possible efficiency gains, and to do so at market-friendly costs. This article will discuss recent progress in key areas central to this reinvention, including miniaturization of cells and optics to produce compact, lightweight "micro-CPV" systems; hybridization of CPV with thermal, illumination and other applications to make use of unused energy streams such as diffuse light and waste heat; and the integration of sun-tracking into the CPV module architecture to enable greater light collection and more flexible deployment, including integration into built structures. Applications showing particular promise include thermal applications such as water heating, industrial processes and desalination; agricultural photovoltaics; building-integrated photovoltaics with dynamic daylighting capabilities; and chemical processes including photocatalysis and hydrogen production. By appropriately tailoring systems to the available solar resource and local energy demand, we demonstrate how CPV can finally achieve real-world efficiencies, or solar resource utilization factors, far higher than those of standard silicon-based PV systems. This makes the argument for sustained development of novel CPV designs that can be applied to the real-world settings where this efficiency boost will be most beneficial. [ABSTRACT FROM AUTHOR]

In this study, the performance of a new configuration of the solar-based desiccant air conditioning system integrated with a humidification-dehumidification desalination unit was assessed thoroughly. The main novelty of the study stemmed from the fact that the regeneration air was preheated by a photovoltaic/thermal solar collector unit before it entered the desiccant wheel and the considered solar system was improved by the phase change material to satisfy the heating demands of air conditioning system at nighttime. The effects of the regeneration air flow rate and temperature on the cooling COP of the air conditioning system, freshwater production, and thermal and electrical efficiencies of the photovoltaic/thermal system were examined for a typical day in August. Results showed that the maximum COP of the air cooling system and the best value of distillate water, for an air mass flow rate of 0.78 kg/s were about 0.411and 4.9 l/h, respectively. The maximum electrical power generation capacity and electrical efficiency of the photovoltaic collector were obtained 0.72 kWh, and 13.7%, respectively, at 13 : 00. The heat capacity and efficiency were approximately 3.39 kWh and 65%, respectively at 12 : 00. Finally, the maximum thermal energy, which was delivered to the air conditioning system by the phase change material was about 0.89 kWh. • A hybrid system of desiccant air conditioning and HDH desalination units is proposed. • Effect of PCM-based solar regeneration on the performance of system was studied. • COP and freshwater production obtained 0.411 and 4.91 l / h , respectively. • Thermal energy capacity and efficiency are obtained 3.39 kWh and 65%, respectively. [ABSTRACT FROM AUTHOR]