Concentrator Photovoltaic Systems Research Articles

Reliable planning of isolated Building Integrated Photovoltaic systems

Abstract In this paper, two probabilistic reliability indices are presented to define the effect of clouds on different types of Building Integrated Photovoltaic (BIPV) systems. Existing indices do not match the main features of photovoltaic (PV) sources, such as variability, uncertainty and dependency on weather conditions. In addition, they are time indicators that describe the percentage of total failure time per year without any indication about power or energy mismatch. By using the available Geographic Information System solar-irradiation database, the proposed indices consider a similar pattern of expected daily solar irradiation as a model of PV systems. Two different models are studied for diverse building loads: an energy model for flexible loads and a constant-power model for critical loads. A comparative study is implemented for six different locations: Cairo, London, Berlin, Beijing, Madrid and Riyadh. Moreover, three types of BIPV systems are studied: fixed, double-axis-tracking and concentrated PV systems. The presented results show the effects of clouds, PV type and locations on the system performance.

Hydrogen production costs of a polymer electrolyte membrane electrolysis powered by a renewable hybrid system

In this work, a novel approach related to the production of hydrogen using a polymer electrolyte membrane electrolysis powered by a renewable hybrid system is proposed. The investigation is carried out by establishing energy balances in the different components constituting the combined renewable system. A mathematical model to predict the production of electricity and hydrogen is proposed. The discrepancies between the numerical results and those from the literature review do not exceed 7%. The results show that the overall efficiency and the capacity factor of the combined renewable system without thermal storage are 20 and 34%, respectively. The levelized cost of hydrogen also is 6.86 US$/kg. The effect of certain physical parameters such as optical efficiency, water electrolysis temperature, unit electrolysis capital cost and solar multiple on the performance of the combined system is investigated. The results show that the performance of hydrogen production is optimal when the solar installation is three times oversized. The results also show that the levelized cost of hydrogen for the optimal sized is 4.07 US$/kg. Finally, the proposed combined system can produce low cost hydrogen and compete with hybrid sulfur thermochemical cycles, conventional photovoltaic installations, concentrated photovoltaic thermal systems and wind farms developed in all regions of the world.

Analytical model for the prediction of solar cell temperature for a high-concentration photovoltaic system

This study presents a simple analytical model for the prediction of solar cell temperature for a high concentration photovoltaic system. The model is based on a heat transfer approach through the system's backplate. The results show that the solar cell temperature is governed by the incident light, material characteristics, ambient conditions, and cell size. The parameters that have a crucial impact on reducing the solar cell temperature were the backplate emissivity, wind velocity, backplate thickness, and backplate length. The backplate coating was found to be of paramount importance due to the considerable reduction of the solar cell temperature with emissivity. Higher wind speeds ventilated the HCPV system and helped lower the cell temperature through convective heat transfer. The thicker the backplate, the lower the cell temperature is due to thermal diffusion on the plate. But this finding prevailed only up to a certain thickness, after which its feasibility is neither maintained nor guaranteed. The study recommends using smaller cell sizes in harsh environments of ambient temperature higher than 40 °C to help manage the reduction of the cell temperature below a critical value of 80 °C.

Exergo-economic optimization of concentrated solar photovoltaic and thermoelectric hybrid generator

Exergo-economic analysis of a concentrated photovoltaic–thermoelectric generator (CPV-TEG) hybrid system is investigated. The specific exergy costing is employed to study the cost effectiveness of the CPV-TEG system. A multi-dimensional single-objective optimization is carried out to optimize the CPV-TEG hybrid system. The performance of the CPV-TEG system is found to be better than that of the concentrated photovoltaic (CPV) system alone in terms of overall energy and exergy efficiencies. From an exergo-economic standpoint, the CPV-TEG system is more cost effective as compared to the CPV system alone. The low value of the exergo-economic factor of the system indicated that the associated cost was mostly due to irreversibilities in the system. A compromise is made by optimizing the CPV-TEG system for maximum exergy efficiency using an optimum thermal resistance of the thermoelectric generator (TEG). For the operating conditions and the geometry considered, integration of CPV and TEG is not found to be feasible (in terms of exegetic performance) below certain values of heat transfer coefficients (< 2500 Wm−2 K−1). A minimum value of heat transfer coefficient of 5266 Wm−2 K−1 is determined for a water-cooled heat sink to limit the cell temperature to 100 °C under the studied set of operating conditions and the geometric configuration. Optimization results yielded exergy efficiencies of 42.22% and 43.48% for the stand-alone CPV system and CPV-TEG system, respectively. The minimum costs of electricity under the optimum conditions were obtained as $$0.57\;\$ \; {\text{kW}}\,{\text{h}}^{ - 1}$$ and $$0.53\;\$ \; {\text{kW}}\,{\text{h}}^{ - 1}$$ for the stand-alone CPV system and CPV-TEG system, respectively.

Characterization and Design of Photovoltaic Solar Cells That Absorb Ultraviolet, Visible and Infrared Light.

The world is witnessing a tide of change in the photovoltaic industry like never before; we are far from the solar cells of ten years ago that only had 15–18% efficiency. More and more, multi-junction technologies seem to be the future for photovoltaics, with these technologies already hitting the mark of 30% under 1-sun. This work focuses especially on a state-of-the-art triple-junction solar cell, the GaInP/GaInAs/Ge lattice-matched, that is currently being used in most satellites and concentrator photovoltaic systems. The three subcells are first analyzed individually and then the whole cell is put together and simulated. The typical figures-of-merit are extracted; all the curves obtained are presented, along with the external quantum efficiencies. A study on how temperature affects the cell was done, given its relevance when talking about space applications. An overall optimization of the cell is also elaborated; the cell’s thickness and doping are changed so that maximum efficiency can be reached. For a better understanding of how varying both these properties affect efficiency, graphic 3D plots were computed based on the obtained results. Considering this optimization, an improvement of 0.2343% on the cell’s efficiency is obtained.

A Hybrid CPV and SiPV System – Experimental Assessment of Systems Performance at a Subtropical Location

Data from two photovoltaic systems, a tracking concentrating photovoltaic (CPV) and a single-axis silicon photovoltaic (SiPV) installed at a sub-tropical location in Australia, were analysed to compare individual and combined power output performance. Metrics describing global power outputs as well as specific patterns of output are derived from the data gathered over a two-year period. At the site, CPV has the highest rate of conversion of sun energy into electrical output with a ratio of 1.9 compared to SiPV. However, the recorded annual energy per rated power for the CPV is only higher than the SiPV by a ratio of 1.07, highlighting how environmental and operational conditions influence power output. Yearly and daily data patterns for each photovoltaic system show complementarity in power output which can be exploited by optimisation of output proportions, so that the combined profile matches best use requirements. For this case study, the optimal ratio is 0.33CPV : 0.67SiPV, resulting in high annual yield and, importantly, a better match between supply and demand. Despite obvious simplicity, this approach is not commonly used when designing and deploying solar photovoltaic farms. Nevertheless, this approach could benefit investors, manufacturers and society at large through optimum use of natural resources.

Efficiency Improvement in polycrystalline solar panel using thermal control water spraying cooling

Abstract The increasing demand for electricity generated from main grids has necessitated the use of multiple microgrids, which serve as subsystems of the utility power. More recently, solar farms are being utilized for electricity generation, since solar irradiation is a green and sustainable renewable energy source. This energy source has witnessed high global growth figures, as more countries explore this alternative power source in the fourth industrial revolution. Solar panels are exposed to high temperatures due to the heat absorbed from the sun and this heat negatively impact its thermal control that lags its power generation. The excessive heat absorbed from the sun limits energy generated by the solar cells. Colling of solar panels is essential, especially on concentrated Photovoltaic (PV) systems. The paper focuses on an optimization option of an automated water spraying method that has effectively addressed a major gap experienced by the solar panel under hot weather conditions. The Introduction of a microcontroller-based thermal control water spraying system using an Arduino board was found to improve the efficiency of the solar cells. In the study, a solar collector cooling algorithm was designed and developed using a thermal control feedback system, which increased the efficiency of the solar panel array by 16.65%.

A novel heat sink for cooling concentrator photovoltaic system using PCM-porous system

A novel heat sink composed of phase change material (PCM) and metal foam (porous) is investigated in this study, which is used to cool the concentrator photovoltaic (CPV) at a solar concentration ratio (CR) of 20. The effects of the PCM-porous systems with different porosities (ε = 80%, 90%, 100%) and heights (H = 0.5x, 1.0x, 2.0x, 3.0x) on improving the electric efficiency of CPV modules are numerically studied. The results show that the metal foam with high thermal conductivity embedded in PCM with high latent heat can significantly enhance the cooling effect of CPV compared to the pure PCM as the heat sink. When the CPV is cooled by the PCM-porous, the electric efficiency of the solar cell increases with the decrease of the porosity. However, the duration time which could maintain the CPV in a constant temperature decreases with the decrease of the porosity. The height of PCM-porous is another factor to influence the cooling effect and electric efficiency of the solar cell. When the porosity is the same, increasing the height (H) of the cavity of PCM-porous from 0.5x to 1.0x could increase the electric efficiency and power productivity around to 50%. But increasing the height from 1.0x to 2.0x has little effect on improving the electric efficiency. When the porosity is less than 100%, increasing the height from 2.0x to 3.0x would slightly decrease the electric efficiency.

Optimal design of the reflective curved surface on the high concentration photovoltaic system

Optimal design of the reflective curved surface on the high concentration photovoltaic system

A Combined Thermal and Electrical Performance Evaluation of Low Concentration Photovoltaic Systems

A Combined Thermal and Electrical Performance Evaluation of Low Concentration Photovoltaic Systems

Energy and economic analysis of a point-focus concentrating photovoltaic system when its installation site varies

The concentrating photovoltaic (CPV) systems are a promising technology to obtain clean energy. However, these systems are not equally convenient worldwide due to different climatic conditions. The main aim of this paper is to analyze energy and economic performances of a point-focus CPV system for a residential user when its installation site varies. Three locations, Riyadh, Copenhagen, and Palermo, characterized by very different weather conditions are chosen. A model that links the electrical power of a triple-junction (TJ) cell with its temperature and concentrated radiation incident on it is experimentally developed to evaluate the energy performance of the CPV system. A comparison of the three localities for typical winter and summer sunny days indicates that the higher values of the TJ cell temperature are reached in summer, over 70°C at Riyadh, and its electrical power is reduced compared to a winter day. In winter, a TJ cell in Riyadh supplies an electric power of about 20% higher than that in other two cities, while in summer, the maximum power is observed at Copenhagen. On the contrary, the electrical producibility also depends on the sunlight daily hours number during the year. Hence, considering the real distribution of direct normal irradiance (DNI) and the environmental temperature for each locality, a CPV system composed of modules of 90 cells adopted for a residential user is sized. The electric producibility of the CPV system, by varying its module number, is evaluated for different localities together with the optimal number of the modules which is able to maximize the investment profitability.

Experimental and simulation investigations of CPV/TEG hybrid system

Concentrator photovoltaic (CPV) technology is a leading approach for increasing the utilization and deployment of PV systems. A major disadvantage is the need for cooling to maintain the performance of the solar cell. Active cooling is power-consuming and complex. A proposed passive cooling subsystem, uses a thermoelectric generator (TEG), besides cooling the solar cell, it generates power from waste heat. Three TEG modules with different sizes and numbers of junctions were tested. The performance of the TEGs was simulated using the finite element method and heat transfer analysis. The simulated model was validated for each TEG against the manufacturer datasheet and demonstrated good agreement between the simulated and measured performances. A CPV/TEG hybrid system was investigated experimentally and compared with the obtained simulation results. The proposed system was proven to deliver a net electrical power higher than obtained using the CPV system only. Compared to only a CPV cell on top of a heat sink, the generated power of the CPV/TEG hybrid system increased by 7.4%, 5.8%, and 3% corresponding to using the 30×30mm2, 40×40mm2 and the 62×62mm2 TEG modules, for which the number of junctions are 31, 127 and 49, respectively.

Graphene as a pre-illumination cooling approach for a concentrator photovoltaic (CPV) system

The concentrator photovoltaic (CPV) system has a high potential in increasing the power output, propelling further the concentration ratio generating excessive heat that significantly deteriorates the solar cell efficiency and reliability. To thoroughly exploit graphene as a pre-illumination cooling technique for a solar cell, we experimentally characterized screen printed graphene coating (GC) physicochemical characterizations to observe the attenuation of light across a wide wavelength range with different GC thicknesses on a low iron-glass. The thermal and electrical characterizations were further executed to observe the performance of GC on a concentrated CPV system. Based on these comprehensive experimental characterizations, the concept of utilizing graphene as a neutral density (ND) filter for focal spot CPV system is shown to reduce the device temperature significantly by 20% and 12% for GC6.3 (6.3 μm thickness) and GC2.2 (2.2 μm thickness) in comparison with the infrared filter, respectively. It has been observed that GC6.3 increased the cell efficiency by about 12% at 8 suns compared to the base case at 400 W/m2 producing 7 suns. It has been ascertained that the introduction of graphene as the ND filter component improved the solar cell efficiency instead of just reducing the geometrical concentration ratio. Further, even the most susceptible single-junction solar cell under a concentration ratio of ≈20 suns with no cooling aid has shown an excellent cell efficiency. Therefore, our approach envisages its application for non-CPV and high and ultrahigh CPV system incorporated with a triple-junction solar cell eliminate the use of external heat sinks or other cooling arrangements.

Impact of microchannel heat sink configuration on the performance of high concentrator photovoltaic solar module

Concentrating photovoltaic technology is growing rapidly among other solar energy technologies, as it reaches an electrical conversion efficiency up to 46%. The solar cell temperature increases during the conversion process, which in turn negatively affects the system’s performance by decreasing its efficiency. Thus, for safe and efficient operation, low and uniform temperature should be achieved. In this work, numerical simulations were completed to study and compare two microchannel heat sink designs as cooling devices for a high concentration photovoltaic (HCPV) system. ANSYS Fluent software was employed to solve three-dimensional conjugate heat transfer equations. The comparison was conducted under uniform solar radiation with a concentration ratio of 1000 suns (1 sun = 1000 W/m2) and a wide range of coolant inlet flowrate. The impact of heat sink design and coolant inlet flowrate variation were studied and highlighted regarding average cell temperature, electrical efficiency, temperature non-uniformity, and local temperature distribution. The results showed that heat sink design has a remarkable impact on the cooling performance of the HCPV/Thermal system. Whereas, configuration 1 achieved a lower average cell temperature by 11% than configuration 2, while the electrical efficiency was increased by 1.4%, at the minimum studied flowrate.

Ultra‐efficient intrinsic‐vertical‐tunnel‐junction structures for next‐generation concentrator solar cells

AbstractThe efficiency of solar cells can be enhanced by increasing the light intensity and/or the number of bandgaps of the structure. However, current solar cells cannot fully exploit these two factors because of various critical drawbacks. Here, we show a novel microscale, that is, side ≈ 0.5 mm, vertical solar cell structure that does not suffer the series resistance and bandgap limitations issues of current devices. The preliminary structures investigated show extreme efficiencies, &gt;40%, at ultrahigh concentration factors of 15 000 suns. In addition, future designs with a better bandgap configuration are expected to deliver cells with efficiencies far above 50% at extreme light intensities. This early design offers a fast and reliable route to push the efficiency towards the maximum solar conversion limit and represents a promising way to develop new‐generation ultraefficient and low‐cost concentrator photovoltaic systems.

Rectangular Glass Optical Fiber for Transmitting Sunlight in a Hybrid Concentrator Photovoltaic and Daylighting System

In this paper, we propose to use glass optical fibers with a rectangular cross-section for the application in a concentrator photovoltaic and daylighting system (CPVD) due to the unique characteristics of rectangular fibers with the capability to provide a uniform rectangular beam shape and a top-hat profile at the output. A mathematical model of rectangular optical fibers has been formulated in this study for different incident angles, and the results are compared with those of round optical fibers. Furthermore, the performance of the bundle of RGOFs is compared with that of the bundle of round optical fibers via simulation by using the ray-tracing method. The mathematical modelling and numerical simulation have demonstrated that the RGOF has advantages in terms of the improvement in relative transmission and reduction in energy leakage for the transmission through the optical fiber. The simulation result also shows that a higher flux of sunlight can be transmitted via the bundle of RGOFs as compared to the bundle of round optical fibers due to the higher coupling efficiency. The experiment results on the relative transmission in different incident angles for both round optical fibers and RGOFs have validated both the simulation and the mathematical modelling. The beam profile of our fabricated RGOF has also been measured via our laboratory facility. The flexibility test on the fabricated RGOF has been carried out to bend at a radius of 150 mm and twist at 90° at a fiber length of 2.2 m.

Lightweight, Passive Radiative Cooling to Enhance Concentrating Photovoltaics

Summary Radiative cooling can reject significantly more waste heat than convection and conduction at high temperatures by sending it directly into space. As a passive and compact cooling mechanism, radiative cooling is lightweight and does not consume energy. These qualities are promising for thermal management in outdoor systems generating low grade heat, such as concentrating photovoltaics (CPV) and thermophotovoltaics (TPV). In this work, we first simulate radiative cooling for a wide range of working conditions, including heat loads from 6 to 100 W with different CPV cooling designs. We then demonstrate a CPV system integrated with radiative coolers, achieving a 5°C to 36°C temperature drop and an 8% to 27% relative increase of open-circuit voltage for a GaSb solar cell, under a heat load of above 6 W with different cooling designs. We show that the temperature drops from radiative cooling may significantly improve CPV system lifetimes.

Photovoltaic Concentration: Research and Development

Concentrator Photovoltaic (CPV) technology, by using efficient optical elements, small sizes and high efficiency multi-junction solar cells, can be seen as a bright energy source to produce more cost-effective electricity. The main and basic idea is to replace the use of expensive solar cells with less expensive optical elements made from different materials. This paper aims to give to the readers a rapid and concise overview of CPV and the main characteristics to be considered when designing a CPV system. It reviews the main optical configurations presented in the literature, their advantages and drawbacks, as well as the recent progress in the concentration ratio and the major performances achieved in the field. The paper considers the more recent works, their optical designs, as well as their optical and electrical performances. It also relates the major achievements on the industrial side with the major milestones in CPV developments.

A comprehensive study of pin fins cooling channel for a single‐cell concentration photovoltaic system under ultra‐high concentration ratios

Analysis of the single-cell concentration photovoltaic (CPV) system is challenging due to the high thermal stress across the solar cell surface area inducing extreme degradation of the electro-mechanical behavior. Although the good thermal performance shown by the passive cooling using heat sinks and the different optical configurations based on Cassegrain and Fresnel lens designs, the experimentally achieved concentration ratio (CR) is still below 5800 suns. The actively cooled heat sink integrating millimeter-scale pin-fin array inside a cooling channel can be promising toward minimum heat sink weight and maximum discharge of the generated heat. The current study presents a comprehensive analysis of a pin-fins cooling channel for a single-cell CPV system under ultra-high CRs. The thermal performance and the hydraulic resistance of five pin-fin heat-sink configurations were performed at different CRs and low Reynolds number for an Aluminum substrate material. The inline pin-fins heat sink (PFHS) displayed the minimum average cell temperature for all Reynolds numbers with thermal performance higher than its closest successor by 9.07%. The thermal performance and the pressure drop showed more dependence on streamwise spacing rather than spanwise spacing for all tested staggered pin-fin heat sinks. Pressure drop drastically increased at higher Reynolds number, Re = 726, for the inline pin-fin heat sink reaching a value of 288.20 Pa due to higher disturbance in the streamwise direction. The results demonstrate that the inline pins-fin heat sink with a constant distribution of circular axial grooves (plugs) along each pin can keep the solar cell within a safe operating temperature, that is, 80°C, for CR up to 15 000 suns at an ambient temperature below or equal to 35°C.

Experimental modeling of the optical and energy performances of a point-focus CPV system applied to a residential user

There is not a standard configuration of Concentrating Photovoltaic (CPV) systems on the market because it must be defined according the user characteristics. Hence, it is important to evaluate the real optical and energy performances of CPV system to satisfy accurately the user energy demands. An experimental model able to calculate energy and optical performances of CPV system with Triple-Junction (TJ) cells, is presented in this paper. First, optical performances influencing the CPV system electrical producibility, are evaluated. Optical concentration factor (Copt) and optical efficiency are experimentally determined in terms of distance between TJ cell and optics. Successively, a black-box model able to link simultaneously TJ cell electrical power with Direct Normal Irradiation (DNI) and TJ cell temperature when Copt varies, is adopted; it is difficult to link these variables by means of a white-box model. This link is basic to evaluate the real CPV system performances when it is sized to match the user energy loads. Hence, the CPV system feasibility applied to 120 m2 residential user, is evaluated. The modules optimal number is defined to maximize the investment profitability. The modules optimal number is five with a Net Present Value equal to 7.2 k€.