Concentrator Photovoltaic Systems Research Articles

Design, Modeling, and Experimental Investigation of Active Water Cooling Concentrating Photovoltaic System

This work presents performance study of a concentrating photovoltaic/thermal (CPV/T) collector and its efficiency to produce electric and thermal power under different operating conditions. The study covers a detailed description of flat photovoltaic/thermal (PV/T) and CPV/T systems using water as a cooling working fluid, numerical model analysis, and qualitative evaluation of thermal and electrical output. The aim of this study was to achieve higher efficiency of the photovoltaic (PV) system while reducing the cost of generating power. Concentrating photovoltaic (CPV) cells with low-cost reflectors were used to enhance the efficiency of the PV system and simultaneously reduce the cost of electricity generation. For this purpose, a linear Fresnel flat mirror (LFFM) integrated with a PV system was used for low-concentration PV cells (LCPV). To achieve the maximum benefit, water as a coolant fluid was used to study the ability of actively cooling PV cells, since the electrical power of the CPV system is significantly affected by the temperature of the PV cells. This system was characterized over the traditional PV systems via producing more electrical energy due to concentrating the solar radiation as well as cooling the PV modules and at the same time producing thermal energy that can be used in domestic applications. During the analysis of the results of the proposed system, it was found that the maximum electrical and thermal energy obtained were 170 W and 580 W, respectively, under solar concentration ratio 3 and the flow rate of the cooling water 1 kg/min. A good agreement between the theoretical and experimental results was confirmed.

Performance evaluation of self-cooling concentrating photovoltaics systems using nucleate boiling heat transfer

Abstract In this study, nucleate boiling heat transfer (NBHT) based self-cooling thermal management system is designed and thermodynamically analyzed for high concentrating photovoltaics (CPV). The overall self-cooling system, consisting of two rows of CPV i.e. CPV 1 and CPV 2, iscoupled with the absorption cooling (AbC) system. Thermal energy from CPV 1 is supplied to AbC system to produce cooling, which is then used to reduce the temperature of CPV 2. Both CPV systems work simultaneously under the same solar energy conditions, hence, the demand and supply of energy are continuously in phase. Under the designed conditions, CPV 1, with an installed capacity of 66.4 kW, an operating temperature of 375.3 K and electrical efficiency of 35.5%, has the ability to cool down about 50.6 kW of CPV 2 system with an operating temperature of 335.8 K and 37.5% of electrical efficiency. A parametric study is performed to analyze the performance of the overall system at various working conditions and installed capacities. Furthermore, the designed system is analyzed for two different types of multi-junction solar cells and three different types of coolants: water, ethanol, and n-pentane. Due to higher latent heat, water has been proven to perform better working fluid with higher ability of concentration ratio. The optimum NBHT operating temperatures for CPV1 and CPV2 were found to be about 353 K and 349 K with maximum overall system efficiency of 36.64%.

Theoretical and Experimental Evaluation of the Working Fluid Temperature Levels in a CPV/T System

A linear focus Concentrator Photovoltaic and Thermal (CPV/T) system can match the thermal demands of a user. The evaluation of the cooling fluid temperature levels of a CPV/T system is fundamental to understand if this system is capable of satisfying the typical thermal requirements of a residential user (heating, cooling and domestic hot water). First, an experimental line-focus CPV/T system, realized in the Laboratory of Applied Thermodynamics of the University of Salerno (Italy), has allowed to determine the cooling fluid temperature at the CPV/T system outlet. Successively, the cooling fluid temperatures, experimentally obtained, have been compared with the same temperatures calculated by means of a theoretical model under the same operation conditions. A deviation in terms of the percentage relative error between theoretical and experimental results included between about 0.5% and 5%, has been found. The goodness of the theoretical–experimental comparison in terms of the temperature of the operation fluid at the CPV/T system outlet has represented a fundamental point to evaluate theoretically, by means of the TRNSYS software, the other levels of temperature of an integrated system, constituted by CPV/T system, thermal tank and user, for different temporal scenarios (hourly, weekly, monthly and yearly). The input data of the TRNSYS model are: Direct Normal Irradiance (DNI), Triple-Junction (TJ) cell temperature and environmental conditions. A tank model is also adopted to satisfy the thermal energy demand peaks, and the temperature stratification in the tank linked to the CPV/T system, as function of the height, is obtained in winter and summer. It is important to define these thermal levels to verify if a CPV/T system is capable to satisfy the residential user energy demands or a thermal energy integration is necessary in some periods of the year. A good stratification has been noted in the summer season, with temperature values that are variable between about 40 and 90 °C. From April to October, the tank average temperature is generally resulted about 10 °C higher than the temperature required by the fluid sent to the residential user, and a very low integration is then necessary. It has been verified that the CPV/T system covers a large part of the thermal energy needs of the residential user during the year; the coverage is limited only in the winter months.

Modeling of water cooled concentrated photovoltaic (CPV) system fed a small campus in Mansoura University – Egypt

Modeling of water cooled concentrated photovoltaic (CPV) system fed a small campus in Mansoura University – Egypt

Long-term thermophysical behavior of paraffin wax and paraffin wax/polyaniline (PANI) composite phase change materials

Abstract Phase change Material (PCM) has immense potential in the field of energy storage due to its latent heat capacity. In this study, accelerated thermal cycling is performed on Paraffin wax (PW) and Paraffin Wax/Polyaniline (PWP-1) composite up to 3000 cycles to evaluate its durability. The latent heat of PW reduced by 6.7% at the end of 3000 cycles, whereas the composite PWP-1 reduced by 9.8% but PWP-1 had higher latent heat values compared to PW. The melting temperature showed an increment with the number of thermal cycles with 11.7% and 23% increment for PW and PWP-1 composite respectively. Thermogravimetric analysis showed very little change in the weight degradation after thermal cycling, but the Fourier Transform Infrared Spectrometry showed a new absorption peak for PW and PWP-1, which may be due to the formation of carbon/char. Visual and microscopic images of the samples are analyzed. From the study it can be concluded that PWP-1 composite has better thermal reliability in terms of latent heat as compared to PW and can be used in the field of solar application like flat plate solar collector, photovoltaic thermal system and low concentrated photovoltaic thermal systems for the production of domestic hot water application.

Performance and Design Optimization of Two-Mirror Composite Concentrating PV Systems

The reflectors of a linear solar concentrator investigated in this work consisted of two plane mirrors (2MCC), and they were designed in such a way that made all radiation within the acceptance angle (θa) arrive on flat-plate absorber, after less than two reflections. To investigate the performance of an east–west aligned 2MCC-based photovoltaic (PV) system (2MCPV), a mathematical procedure was suggested based on the three-dimensional radiation transfer and was validated by the ray-tracing analysis. Analysis indicated that the performance of 2MCPV was dependent on the geometry of 2MCC, the reflectivity of mirrors (ρ), and solar resources in a site, thus, given θa, an optimal geometry of 2MCC for maximizing the annual collectible radiation (ACR) and annual electricity generation (AEG) of 2MCPV in a site could be respectively found through iterative calculations. Calculation results showed that when the ρ was high, the optimal design of 2MCC for maximizing its geometric concentration (Cg) could be utilized for maximizing the ACR and AEG of 2MCPV. As compared to similar compound parabolic concentrator (CPC)-based PV systems, the 2MCPV with the tilt-angle of the aperture yearly fixed (1T-2MCPV), annually generated more electricity when the ρ was high; and the one with the tilt-angle adjusted yearly four times at three tilts (3T-2MCPV), performed better when θa < 25° and ρ > 0.7, even in sites with poor solar resources.

Design and experimental study of a solar CPV system using CLFR concentrator

A solar concentration photovoltaic (CPV) system with compact linear Fresnel reflector (CLFR) concentrator is described in this paper. The design approach of the CPV system is introduced. Four different CLFRs are designed and compared, including one complete type and three hybrid type CLFRs. In order to evaluate the optical performance of the CPV system, solar concentration processes of the four CLFRs are simulated by using the MCRT method. The results indicate that the complete type CLFR (CLFR-c) has the highest concentrated solar radiation uniformity. An experimental set-up is built to carry out the evaluation of actual optical performance of the CLFR-c and a good agreement between the simulation and measurement results is demonstrated. The optical parameter analysis results of the CPV system reveal that the optimal solar panel height exists, which can result in the maximum ground utilization and concentration ratios. The influence of sun-tracking accuracy on the optical efficiency of the CPV system is analyzed. The results indicate that the normalized optical efficiency of the CLFR-c concentrator is 0.89 when the tracking error is 0.2°. The preliminary PV performance test results reveal a photoelectric conversion efficiency of 15.9% for the PV cell module installed on the solar CPV system.

Strategies for high performance perovskite/c-Si tandem solar cells: Effects of bandgap engineering, solar concentration and device temperature

Concentrating photovoltaic systems combined with tandem solar cells have been successfully investigated to generate high power conversion efficiencies. Nevertheless, this attractive concept has not yet been sufficiently implemented for solar cells based on perovskite. In this paper, we assess the feasibility of utilizing perovskite semiconductor with varied bandgap for tandem concentrator solar cell applications in combination with traditional crystalline silicon. We evaluate the device performance of tandem perovskite concentrator solar cell (TPCSC) under different sunlight concentrations. We derive the temperature sensitivity of our proposed TPCSC under various operating conditions. In this context, we developed a combined opto-electronic model to optimize TPCSC and reach the highest possible power conversion efficiencies (PCEs). Our simulation findings highlight that appropriate bandgap engineering of formamidinium-based mixed-halide perovskite top cell lead to higher PCE over 30% for tandem perovskite/c-Si solar cell. Of critical importance, under a wide range of solar concentrations, perovskite/c-Si tandem solar cell can exhibit appreciably higher PCE, and achieves a peak efficiency of 34.62% under 70 Suns, as compared to 30.52% under 1 Sun. Interestingly, the temperature sensitivity of TPCSC PCE decreases with increasing concentrated solar irradiances. Thus, our study shows that concentrating photovoltaic can be the possible new development direction for tandem perovskite/c-Si solar cell to achieve greater efficiencies under various conditions.

Non-uniform sizing of PV cells in the dense-array module to match the non-uniform illumination in dish-type CPV systems

Abstract To reduce the efficiency reduction caused by non-uniformity of illumination, a dense-array module with non-uniform sizing of photovoltaic (PV) cells is proposed for dish-type concentrating PV systems. The non-uniform-sized dense-array module has been designed and analyzed theoretically at the ideal irradiance of Gaussian distribution, which consists of 48 silicone solar cells. Using the ZEMAX optical simulation software, the realistic distribution of the Gaussian-like facula on the PV module has been modelled in a dish-type concentrator system. The experiments are done under the conditions of different alignments to imitate the different two-axis tracking accuracy with or without a homogenizer. Besides, the performances of dense-array modules with the classical uniform-sized and the proposed non-uniform-sized PV cells are analyzed under various illumination distributions using ZEMAX, respectively. Results show that when the deviation angle of tracking is 0, 0.02, 0.2, the photoelectric conversion efficiency and output power of the proposed non-uniform size dense-array module considerably exceeds the traditional uniform size module. Furthermore, when the tracking deviation angle is no more than 0.02°, it is a very definite possibility that the dish-type concentrator system with non-uniform-sized dense-array module need not a homogenizer as a secondary optical element, which may hence simplify the system structure.

Optimization study of solar farm layout for concentrator photovoltaic system on azimuth-elevation sun-tracker

Inappropriate space allocation for concentrator photovoltaic (CPV) systems in the solar farm causes optical losses via shadowing between adjacent CPV systems, which leads to the deterioration of the overall electrical generation of solar power plant (SPP). The deterioration of the overall electrical generation can be reduced by increasing the separation distance between adjacent CPV systems. However, it causes an increase in land-related costs due to ineffectiveness in land utilization. Therefore, it is important to focus on the layout design optimization in the SPP to attain the best trade-off between land usage and energy generation. In order to captivate the interest of investors in the future development of solar energy, levelized cost of electricity (LCOE) of the SPP needs to be competitive. A newly developed computational algorithm has been introduced to perform the optimization of the CPV field layout system by utilizing the local weather data with the consideration of shadowing effect, edge effect, land aspect ratio (LAR) and land cost. A case study has been conducted in Kota Kinabalu, Malaysia to evaluate the performance of CPV system in the SPP based on different conditions such as Dew/L ratio, Dns/L ratio, spacing angle, LAR and land cost for both square array and staggered array configuration. From the case study, the results show that the optimized field layout for the CPV systems for LAR of 1 is a staggered array layout configuration with Dew/L ratio of 2.50 at spacing angle of 45°, which accommodates the lowest value of LCOE.

Performance assessment of a V-trough photovoltaic system and prediction of power output with different machine learning algorithms

This study carried out in two stages. In the first stage, four different-sized layers were designed and manufactured for a concentrated photovoltaic system. These layers were used to change the concentration ratio and area ratio of the system. Furthermore, a new power coefficient equation with this paper is proposed to the literature for the determination of the system performance. In the second stage of the study, the power outputs measured in the study were predicted with four machine-learning algorithms, namely support vector machine, artificial neural network, kernel and nearest-neighbor, and deep learning. To evaluate the success of these machine learning algorithms, coefficient of determination (R2), root mean squared error (RMSE), mean bias error (MBE), t-statistics (t-stat) and mean absolute bias error (MABE) have been discussed in the paper. The experimental results demonstrated that the double-layer application for the concentrator has ensured better results and enhanced the power by 16%. The average concentration ratio for the double-layer was calculated to be 1.8. Based on these data, the optimum area ratio was determined to be 9 for this V-trough concentrator. Furthermore, the power coefficient was calculated to be 1.35 for optimum area ratio value. R2 of all algorithms is bigger than 0.96. Support vector machine algorithm has generally presented better prediction results particularly with very satisfying R2, RMSE, MBE, and MABE of 0.9921, 0.7082 W, 0.3357 W, and 0.6238 W, respectively. Then it is closely followed by kernel-nearest neighbor, artificial neural network, and deep learning algorithms, respectively. In conclusion, this paper is reporting that the proposed new power coefficient approach is giving more reliable results than efficiency data and the power output data of concentrated photovoltaic systems can be highly predicted with the machine learning algorithms.

The effect of using nanofluid flow into a porous channel in the CPVT under transient solar heat flux based on energy and exergy analysis

Concentrator photovoltaic thermal system is one of the heat and power generation systems that have received special attention in recent decades. In this paper, concentrator photovoltaic thermal cell with the effect of Al2O3 nanofluid flow in porous channel has been investigated under transient heat flux. The system is analyzed from energy and exergy viewpoint, and also the first and second laws of thermodynamics efficiencies are calculated. The governing equations are continuity, Brinkman momentum and energy conservation equations considering the transient solar flux using parabolic dish concentrator over a day in Mashhad city. The numerical modeling is based on the finite element method. The numerical results show that the Nusselt number, normalized temperature and electrical efficiency of the presented model have an acceptable agreement with experimental data. Efficiency of the photovoltaic cell increases with increasing the Reynolds number as the difference between the highest and the lowest efficiency value is 5% at 12 p.m. In addition, with increasing Reynolds number, the first law of thermodynamics efficiency increases due to porosity and permeability effects of the porous channel cooling. The maximum difference between highest and the lowest value for first law efficiency is 49.4% at Re = 110. The second law of thermodynamics efficiency decrease as Reynolds number increases as the highest value is 4.2% and the lowest is 2.8% at Re = 20 and Re = 10, respectively.

Enhanced Heat Transfer of Carbon Nanotube Nanofluid Microchannels Applied on Cooling Gallium Arsenide Cell

Carbon nanotube nanofluids have wide application prospects due to their unique structure and excellent properties. In this study, the thermal conductivity properties of carbon nanotube nanofluids and SiO2/water nanofluids were compared and analyzed experimentally using different preparation methods. The physical properties of nanofluids were tested using a Malvern Zetasizer Nano Instrument and a Hot Disk Thermal Constant Analyzer. Combined with field synergy theory analysis of the heat transfer performance of nanofluids, results show that the thermal conductivity of carbon nanotube nanofluids is higher than that of SiO2/water nanofluids, and the thermal conductivity of nanofluid rises with the increase of mass fraction and temperature. Moreover, the synergistic performance of carbon nanotube nanofluids is also superior to that of SiO2/water nanofluids. When the mass fraction of the carbon nanotube nanofluids is 10% and the SiO2/water nanofluids is 8%, their field synergy numbers and heat transfer enhancement factors both reach maximum. From the perspective of the preparation method, the thermal conductivity of nanofluids dispersed by high shear microfluidizer is higher than that by ultrasonic dispersion. This result provides some reference for the selection and use of working substance in a microchannel cooling concentrated photovoltaic and thermal (CPV/T) system.

Thermal management of concentrator photovoltaic systems using nano‐enhanced phase change materials‐based heat sink

Thermal management of concentrator photovoltaic systems using nano‐enhanced phase change materials‐based heat sink

Large Scale Spectral Splitting Concentrator Photovoltaic System Based on Double Flat Waveguides

In this research, we present a novel design for a large scale spectral splitting concentrator photovoltaic system based on double flat waveguides. The sunlight concentrator consists of a Fresnel lens array and double waveguides. Sunlight is firstly concentrated by Fresnel lenses then reaches an upper flat waveguide (UFW). The dichroic mirror-coated prisms are positioned at each focused area to divide the sunlight spectrum into two bands. The mid-energy (mid E) band is reflected at the prism surface and coupled to the UFW. The GaInP/GaAs dual-junction solar cell is attached at the exit port of the UFW to maximize the electrical conversion efficiency of the mid E band. The low-energy (low E) band is transmitted and reaches a bottom flat waveguide (BFW). The mirror coated prisms are utilized to redirect the mid E band sunlight for coupling with the BFW. The GaInAsP/GaInAs dual-junction solar cell is applied to convert the low E band to electricity. The system was modeled using the commercial optic simulation software LightTools™. The results show that the proposed system can achieve optical efficiencies of 84.02% and 80.01% for the mid E band and low E band, respectively, and a 46.1% electrical conversion efficiency for the total system. The simulation of the system performance and comparison with other PV systems prove that our proposed design is a new approach for a highly efficient photovoltaic system.

Misalignments measurement of CPV optical components through image acquisition.

Concentrator Photovoltaics (CPV) technology relies on optical systems that concentrate sunlight on solar cells in exchange for a reduction of the permitted angular tolerance when pointing at the sun. A proper alignment between optics and photovoltaic receivers is crucial for the performance of this technology, particularly point focus CPV systems with concentration ratios above 100X that have narrow angular tolerances. This study presents the theoretical fundamentals of a method for evaluating misalignments in a CPV module. The method is based on the acquisition and analysis of images, taken by a camera, of the photovoltaic receivers magnified through the primary optics. The method has been successfully validated by empirical measurements and ray tracing simulations of a single lens-receiver unit.

Numerical optimisation and recombination effects on the vertical-tunnel-junction (VTJ) GaAs solar cell up to 10,000 suns

Ultra-high concentrator photovoltaic systems (UHCPV), usually referred to CPV systems exceeding 1000 suns, are signalled as one of the most promising research avenues to produce a new generation of high-efficiency and low-cost CPV systems. However, the structure of current concentrator solar cells prevents their development due to the unavoidable series resistance losses at such elevated concentration ratios. In this work, we investigate the performance of the so-called vertical-tunnel-junction (VTJ), recently introduced by the authors, by using advance TCAD. In particular, we carry out an optimisation procedure of the key parameters that affect its performance and conduct a deep investigation of the impact of the main recombination mechanisms and of sun concentration up to 10,000 suns. The results indicate that the performance of the novel structure is not significantly affected by these two factors. A record efficiency of 32.2% at 10,000 suns has been found. This represents a promising way to obtain state-of-the-art efficiencies above 30% for single-band-gap cells, and offers a new route towards the development of competitive CPV systems operating at ultra-high concentration fluxes.

Estimation of the performance limits of a concentrator solar cell coupled with a micro heat sink based on a finite element simulation

Concentrated photovoltaic (CPV) technology makes use of cheap optical elements to amplify the irradiance and focus it on small-sized solar cells enabling the extraction of higher amounts of electricity. However, increasing the solar concentration raises the temperature of the PV cell which can deter its performance and can also cause its failure. To combat this issue both active and passive cooling mechanisms are utilized for different types of CPV systems. In this study, we determine the limits of passive cooling systems and establish when an active cooling system is needed based on the recommended operating temperature of the solar cell. We investigate the temperature characteristics of the solar cells bonded to three different substrate materials under different solar concentrations. Results showed that cell temperature is linearly dependent on the concentration ratio and ambient temperature independent of the substrate material. Further, the integration of a micro-finned heatsink results in higher heat dissipation by 25.32%, 23.13%, and 22.24% in comparison with a flat plate heatsink for Direct Bonded Copper (DBC), Insulated Metal Substrate (IMS), and Silicon Wafer (Si wafer) substrates respectively. The low thermal resistance of the IMS substrate compared to the DBC and the Si wafer substrates result in the best thermal performance in terms of maintaining the cell temperature < 80 °C and allowing a wider range of high concentration ratio.

Theoretical Investigation of the Temperature Limits of an Actively Cooled High Concentration Photovoltaic System

Concentrator photovoltaics have several advantages over flat plate systems. However, the increase in solar concentration usually leads to an increase in the solar cell temperature, which decreases the performance of the system. Therefore, in this paper, we investigate the performance and temperature limits of a high concentration photovoltaic Thermal system (HCPVT) based on a 1 cm2 multi-junction solar cell subjected to a concentration ratio from 500× to 2000× by using three different types of cooling fluids (water, ethylene glycol and water mixture (60:40), and syltherm oil 800). The results show that, for this configuration, the maximum volumetric temperature of the solar cell did not exceed the manufacturer’s recommended limit for the tested fluids. At 2000× the lowest solar cell temperature obtained by using water was 93.5 °C, while it reached as high as 109 °C by using syltherm oil 800, which is almost equal to the maximum operating limit provided by the manufacturer (110 °C). Overall, the best performance in terms of temperature distribution, thermal, and electrical efficiency was achieved by using water, while the highest outlet temperature was obtained by using syltherm oil 800.

Computational design and development of high-performance polymer-composites as new encapsulant material for concentrated PV modules

A computational design methodology is reported to propose a high-performance composite for backside encapsulation of concentrated photovoltaic (CPV) systems for enhanced module life and electrical power. Initially, potential polymer composite systems that are expected to provide the target properties, such as thermal conductivity, coefficient of thermal expansion, and long-term shear modulus are proposed using in-house built design codes. These codes are based on differential effective medium theory and mean-field homogenization, which lead to the selection of matrix, filler, volume fractions, and type of particulates. Thermoplastic polyurethane (TPU) loaded with ceramics fillers of a minimum spherical diameter of 6 μm are found potential composites. Some representative samples are synthesized through the melt-mixing and compression-molding route and characterized. The target properties including thermal conductivity, coefficient of thermal expansion, viscoelastic parameters, and long-term shear modulus are measured and used to evaluate the performance of CPV modules using previously published finite element model. The proposed composite can drag the cell temperature down by 5.8 °C when compared with neat TPU which leads to a 4.3% increase in electrical power along with a reasonable module life. It is expected that this approach will make a baseline for the effective production of polymer composites in various industrial applications.