High Concentration Photovoltaic Modules Research Articles

Predicting entropy generation of a hybrid nanofluid in microchannel heat sink with porous fins integrated with high concentration photovoltaic module using artificial neural networks

This paper evaluates the characteristic of second law of thermodynamic, including Bejan number and entropy generation for hybrid nanofluid containing graphene-silver nanofluid through a MCHS whit porous fins. Finite-volume technique is utilized to solve the governing equations. To simulate the problem, different porous medium thicknesses, nanoparticle concentrations, and inlet mass flow rates are used while the heat flux remains constant. The minimum values of the frictional and thermal entropy generation are 5 × 10−4 and 6.25 × 10−2, while the maximum values are 3.2 × 10−4 and 9.75 × 10−2. With increasing nanoparticle concentration up to 0.06% wt at constant porous thickness tp=200 µm, frictional entropy generation rises up by 3 × 10−5 and heat transfer rate go up while, thermal entropy generation decreases by 1.5 × 10−2. In addition, by doubling the input mass flow rate and reaching 0.02% at constant nanoparticle concentration (0.06%), thermal entropy generation decreases by 2 × 10−2 while the frictional entropy generation increases by 2.4 × 10−4. The minimum magnitude of Bejan number is 0.994. This show that the irreversibility is derived significantly from thermal entropy generation rate. Finally, an artificial neural network is employed to obtain a model for entropy generation.

Thermal analysis of high concentrator photovoltaic module using convergent-divergent microchannel heat sink design

The dense-packed high concentrator photovoltaic module (DP-HCPVM) is normally exposed to a very high heat flux concentrated from sunlight. The resultant high module operation temperature drops the overall performance and reduces the module life expectancy. Consequently, the provision of powerful cooling is compulsory for such structures. In this study, a complete three-dimensional (3D) model was developed to investigate the performance of a DP-HCPVM under the active cooling scheme to figure out its ability to attain effective heat dissipations. A new cooling convergent-divergent microchannel heat sink cases were numerically investigated and compared in terms of temperature distribution and electrical efficiency of a DP-HCPVM. The influence of heat sink design and inlet mass flowrate on the cooling performance of the heat sink device were examined. The same external dimensions are considered, and the flow was laminar with the inlet temperature of 25 °C for all designs for a reasonable comparison. The concept of variation flow direction by changing the inlet and outlet arrangement is adopted. The comparison between all studied designs was highlighted concerning surface average temperature, surface temperature uniformity, and pressure drop across the heat sink. The results indicated that the new convergent-divergent microchannel heat sink design achieved better effectiveness and heat transfer rate compared to the conventional straight microchannel heat sink design for DP-HCPVM thermal management, as it decreased the average cells temperature and temperature non-uniformity by 11.4% and 37.8%. Moreover, it was found that the electrical efficiency and Nusselt number were improved by 0.35% and 21.9% at the maximum studied inlet mass flowrate.

Temperature uniformity enhancement of densely packed high concentrator photovoltaic module using four quadrants microchannel heat sink

The dense solar radiation received by a high concentration photovoltaic module (HCPVM) causes a high cell temperature. In this module, multiple solar cells were electrically connected in both series and parallel. The higher temperature of the solar cell in the series string limits the generated power for the whole string. Therefore, it is crucial to employ a uniform cooling mechanism for higher electrical performance along with a longer lifespan. The uniform cooling is required to attain safe operating temperature and prevent the hot spot formation. Hence, in the current work, a four-compartment microchannel heat sink is proposed for the thermal management of HCPVM under high solar concentration of 1000 suns (1 sun = 1000 W/m2). A three-dimensional (3D) conjugate heat transfer model with exergy analysis is developed and validated. This model was used to investigate the effect of inlet and outlet orientation of four quadrants microchannel heat sink as a cooling method for HCPVM. Eight different orientations of parallel-flow and counter-flow conditions were investigated and compared in terms of temperature non-uniformity, module power, and exergy performance. The results showed that the inlet and outlet orientation was a key role affecting the module temperature non-uniformity. For the counter-flow operated heat sinks, the HCPVM can be operated under a temperature non-uniformity of 3.1 °C at total inlet module mass flowrate of 350 g/min and solar concentration ratio of 1000 suns. In addition, the attained HCPVM electrical, thermal, and overall exergy efficiency were 37.2%, 8.2%, and 45.4% respectively at the same conditions.

Auto-calibration method for high concentration sun trackers

High concentration photovoltaic modules allow a significant increase in the electric power produced per unit area. Nevertheless, in order to reach the maximum possible increase in performance, the sun tracker must meet severe specifications regarding sun-pointing accuracy, because the lens-cell sets of the solar modules only work in a very small angle. For the sun tracker to meet these requirements, a precise procedure of installation is necessary in order to minimize errors from different sources such as misalignment of the structure with respect to geographical North, misalignment of the solar modules with respect to the wing of the sun tracker and other structural tolerances. This paper presents an auto-calibration algorithm which allows to work with higher tolerances in the installation process by estimating some sources of error instead of spending installation time trying to minimize them. Simulation and experimental results with a testing sun tracker are exposed showing the benefits of the proposed method with respect to a manual calibration in terms of power performance.

Maximum power output prediction of HCPV FLATCON® module using an ANN approach

The estimation of the electrical power output and energy yield of high concentration photovoltaic (HCPV) modules is a hard task because of the many parameters involved. In this work, we propose the usage of an Artificial Neural Networks (ANN) method to estimate the maximum power output of a FLATCON® CPV-module manufactured by Fraunhofer ISE. The advantage of the ANN is that it is a part of the Artificial Intelligence Deep Learning domain, which makes it easy to model complex systems. A detailed knowledge about the underlying module technology is not necessary. In this work, various meteorological parameters are tested as inputs of the ANN including spectral matching ratios for considering the spectral variation of the solar irradiance to evaluate the maximum power output of the HCPV module under study. Eleven scenarios considering different combinations of input parameters have been investigated. It is demonstrated that the ANN gives excellent results and allows for an accurate prediction of the HCPV module’s instantaneous power output with only a few amount of data used on training the ANN. The model has been tested using the measured data set of a FLATCON® CPV-module located on the rooftop of the Fraunhofer ISE in Freiburg, Germany. The module has been electrically characterized outdoors in the period from April 2013 to April 2014. The accuracy of the proposed ANN approach was analyzed using this measurement data in combination with error metrics. It was found that the best agreement between the measured and the predicted maximum power output was achieved when using direct normal irradiance, wind speed, ambient temperature and spectral matching ratios as input. The normalized root mean square error for the maximum power output over one year is found to be between 2.2 and 4.6%. The deviation of the modelled energy yield to the measured one is in the range of 0.2–2.2%.

Высокоэффективные фотоэлектрические модули с концентраторами солнечного излучения

High efficiency concentrator photovoltaic modules have been designed and manufactured. Each module consists of a lens panel with 32 Fresnel lenses 12x12 cm2 each, 32 multijunction solar cells with focons as secondary concentrators and electro insulated heatsinks made of alumina ceramics mounted on aluminum sheet. The module with a total area of 0.46 m2 measured under solar simulator with a spectrum AM 1.5D and irradiance 1000 W/m2 demonstrated an efficiency of 32.2%. Meanwhile, a single submodule with an area of 144 cm2 demonstrated an efficiency equal to 33.9%.

Implementation of a modified circuit reconfiguration strategy in high concentration photovoltaic modules under partial shading conditions

A modified circuit reconfiguration (MCR) technique for high concentration photovoltaic (HCPV) modules under partial shading conditions (PSCs) is proposed. Although HCPV modules have high conversion efficiency, they are sensitive to changing environments, especially PSCs. In response, the MCR strategy exploits the reconfigurable wiring of HCPV modules to implement the dynamic circuit reconfiguration (DCR) technique. In doing so, the hardware switches and complex control algorithms of the conventional DCR are simplified to reduce cost. Moreover, an irradiation estimation method is proposed for string current equalization using existing switches and connections. Two circuit-model prototypes, one square and one rectangular, were simulated to evaluate the proposed MCR strategy. Evaluation results demonstrate that the average output-power and conversion-efficiency improvements of the square and rectangular modules were around 31.07% and 5.00%, and 32.79% and 5.23%, respectively, when compared with the original Series connection topology. In addition, after reconfiguration by MCR, the module’s GMPP power was improved and the number of LMPPs reduced, which simplified the P-V curves. Furthermore, reliability tests demonstrated that with a small reconfiguration processing time ratio (0.06–0.28%), the daily energy harvested from the rectangular module was improved around 15%. The proposed MCR strategy has the advantages of reducing the hardware/software costs and lowering circuit losses. Additionally, the MCR method can increase the output power and efficiency of an HCPV module with high dispersion ability. The proposed method and prototypes can also be extended to larger scale arrays or implemented with other PV systems.

Life Cycle Assessment of New High Concentration Photovoltaic (HCPV) Modules and Multi-Junction Cells

Worldwide electricity consumption increases by 2.6% each year. Greenhouse gas emissions due to electricity production raise by 2.1% per year on average. The development of efficient low-carbon-footprint renewable energy systems is urgently needed. CPVMatch investigates the feasibility of mirror or lens-based High Concentration Photovoltaic (HCPV) systems. Thanks to innovative four junction solar cells, new glass coatings, Position Sensitive Detectors (PSD), and DC/DC converters, it is possible to reach concentration levels higher than 800× and a module efficiency between 36.7% and 41.6%. From a circular economy’s standpoint, the use of concentration technologies lowers the need in active material, increases recyclability, and reduces the risk of material contamination. By using the Life Cycle Assessment method, it is demonstrated that HCPV presents a carbon footprint ranking between 16.4 and 18.4 g CO2-eq/kWh. A comparison with other energy means for 16 impact categories including primary energy demand and particle emissions points out that the environmental footprint of HCPV is typically 50 to 100 times lower than fossil fuels footprint. HCPV’s footprint is also three times lower than that of crystalline photovoltaic solutions and is close to the environmental performance of wind power and hydropower.

Methanol Production By H2 Generated from Water Using Integrated Ultra High Concentrated Solar Cells-Electrolysis and Captured CO2: A Process Development and Techno-Economy Analysis

A novel hybrid process based on an ultra-high concentrated solar module and water electrolysis for the production of methanol is presented. This process utilizes captured CO2 and H2 produced by electro-catalytic water splitting. The electrocatalytic system is powered by high concentration photovoltaic modules during the day and from an electrical grid during the night. The system is called the Hybrid High Concentration Solar and Electrolyzer system (HHCSE). Aside from the highly concentrated photovoltaic (UHC-PV) water splitting unit, which is currently under development, the full system is based on well-established industrial processes and component designs. Here, we present an initial assessment of energy efficiency and economic viability of a 233 tonne/day industrial-scale methanol plant. The breakeven price of the methanol produced using the base case is 0.62 $/kg. A levelized selling price of methanol of less than 0.50 $/kg can be achieved using the integrated system with a solar to hydrogen efficiency (STH) of 30% which is comparable to the current market price (0.510 $/kg). For the base case with STH (20%), the price of electricity (0.05 $/kWh) and location in Tabuk, Saudi Arabia, the gross energy efficiency of the process is 18%. Importantly, the primary economic driver is the high capital cost of the H2 production plant associated with the solar concentrator unit. The electrocatalytic system and solar concentrators account for more than 83% of the hydrogen section capital expenditure. Moreover, the electricity price also has a significant effect on the final price of methanol. The analysis indicates that an alternate pathway of concentrated solar and electrolysis to fuels has significant potential. The sensitivity study points towards future research opportunities to increase STH of the solar modules, reduce the balance of system (BOS), and reduce the electricity cost to achieve lower priced methanol. As a final element, we compared the proposed process with other renewable methanol production routes from the literature to highlight the differences in electrochemical, photoelectrochemical and thermochemical approaches. Figure 1

Modeling a High Concentrator Photovoltaic Module Using Fuzzy Rule-Based Systems

Currently, there is growing interest in the modeling of high concentrator photovoltaic modules, due to the importance of achieving an accurate model, to improve the knowledge and understanding of this technology and to promote its expansion. In recent years, some techniques of artificial intelligence, such as the Artificial Neural Network, have been used with the goal of obtaining an electrical model of these modules. However, little attention has been paid to applying Fuzzy Rule-Based Systems for this purpose. This work presents two new models of high concentrator photovoltaics that use two types of Fuzzy Systems: the Takagi-Sugeno-Kang, characterized by the achievement of high accuracy in the model, and the Mamdani, characterized by high accuracy and the ease of interpreting the linguistic rules that control the behavior of the fuzzy system. To obtain a good knowledge base, two learning methods have been proposed: the “Adaptive neuro-fuzzy inference system” and the “Ad Hoc data-driven generation”. These combinations of fuzzy systems and learning methods have allowed us to obtain two models of high concentrator photovoltaic modules, which include two improvements over previous models: an increase in the model accuracy and the possibility of deducing the relationship between the main meteorological parameters and the maximum power output of a module.

On the Thermal Performance of a Microparallel Channels Heat Exchanger

Abstract This paper presents the experimental and theoretical analysis of a micro heat exchanger designed for the waste heat recovery from a high concentration photovoltaic (HCPV) system. A test bench was built to analyze the thermal behavior of a heat exchanger targeted to work in a similar condition of an existing HCPV panel. A high power heater was encapsulated inside a copper cartridge, covered by thermal insulation, leading to dissipated heat fluxes around 0.6 MW/m2, representative of the heat flux over the solar cell within the HCPV module. The experimental campaign employed water as the coolant fluid and was performed for three different mass flow rates. An infrared camera was used to nonintrusively measure the temperature field over the micro heat exchanger external surface, while thermocouples were placed at the contact between the heat exchanger and the heater, and at the water inlet and outlet ports. In the theoretical analysis, a hybrid numerical–analytical treatment is implemented, combining the numerical simulation through the comsolmultiphysics finite elements code for the micro heat exchanger, and the analytical solution of a lumped-differential formulation for the electrical heater cartridge, offering a substantial computational cost reduction. Such computational simulations of the three-dimensional conjugated heat transfer problem were critically compared to the experimental results and also permitted to inspect the adequacy of a theoretical correlation based on a simplified prescribed heat flux model without conjugation effects. It has been concluded that the conjugated heat transfer problem modeling should be adopted in future design and optimization tasks. The analysis demonstrates the enhanced heat transfer achieved by the microthermal system and confirms the potential in reusing the recovered heat from HCPV systems in a secondary process.

Ray Tracing Comparison between Triple-Junction and Four-Junction Solar Cells in PMMA Fresnel-Based High-CPV Units

The recent development of wafer bonded four-junction concentrator solar cells (FJSCs) with record efficiency among all the existent photovoltaic (PV) cells offers new possibilities for improving the High Concentrator PV (HCPV) technology. However, the concentrator optical systems utilized in HCPV modules may have to be adapted to the new requirements of FJSC in order to properly take advantage of the increased number of p-n junctions. This research theoretically compares two identical optical concentrator systems, a Frensel lens plus a kind of refractive SILO (SIngle-Lens-Optical element) secondary (both made of PMMA, poly(methyl methacrylate)), which are equipped with a typical triple-junction concentrator solar cell (TJSC) in the one case, and with an FJSC in the other case. Both HCPV units are analyzed through ray tracing optical simulations applying an exhaustive optical modelling that takes into account the spectral responses of the different subcells within the multi-junction cells. The HCPV unit with the FJSC and PMMA SOE (secondary optical element) shows much less efficiency than that with the TJSC due to the light absorption through the PMMA SOE in the wavelength range of the bottom subcell. Therefore, PMMA SOEs may be not appropriate for FJSC in general.

Optimum sizing of the inverter for maximizing the energy yield in state-of-the-art high-concentrator photovoltaic systems

The sizing of the inverter in comparison to the rated capacity of the photovoltaic generator is investigated for high-concentrator photovoltaic (HCPV) systems. An HCPV module of typical characteristics is modelled and parameterized, taking into account direct normal irradiance (DNI), ambient temperature, air mass and aerosol optical depth as atmospheric inputs, while the DC losses of the HCPV generator are allowed to vary in the ranges reported in the literature. A set of 80 commercial inverters are analysed to obtain the typical efficiency curves of state-of-the-art low-, medium-, and high-efficiency inverters. Four locations worldwide with high annual DNI levels and different average values of the weather variables influencing HCPV performance are studied. Results show that the inverter can be sized between 84% and 112% of the rated capacity of the HCPV generator at Concentrator Standard Test Conditions depending on the scenario considered for maximizing the final energy yield of the system. The proposed methodology uses analytical equations, all the model parameters are provided and justified and atmospheric inputs are obtained from meteorological databases in order to make the application easy regarding its use in other locations where the climate data is available.

A method for the outdoor thermal characterisation of high-concentrator photovoltaic modules alternative to the IEC 62670-3 standard

The IEC 62670-3 standard recommends the open-circuit voltage method to calculate the cell temperature inside high-concentrator photovoltaic (HCPV) modules. This method requires knowledge of the temperature coefficient of open-circuit voltage (β), and the same standard provides a procedure to get this parameter. In this paper, an alternative method for the thermal characterisation of HCPV modules is proposed. As an advantage, it allows obtaining both the β parameter and the internal thermal resistance (ρ) of the device from outdoor measurements. No internal sensor for measuring the cell temperature is required as in the case of the IEC 62670-3 standard. Knowing the ρ parameter allows a more accurate characterisation of the cell temperature. The proposed procedure is applied to a real HCPV module. An outdoor experimental campaign of two months in Jaén (Southern Spain) was carried out. The β value was underestimated in a 0.50% and the ρ value was overestimated in a 4.18%. When applying the estimated parameters for the prediction of the cell temperature, the open-circuit voltage method gave a root mean square error (RMSE) of 1.41 °C, while the internal thermal resistance method gave a RMSE of 0.62 °C.

Multiphysics modelling and experimental validation of high concentration photovoltaic modules

High concentration photovoltaics, equipped with high efficiency multijunction solar cells, have great potential in achieving cost-effective and clean electricity generation at utility scale. Such systems are more complex compared to conventional photovoltaics because of the multiphysics effect that is present. Modelling the power output of such systems is therefore crucial for their further market penetration. Following this line, a multiphysics modelling procedure for high concentration photovoltaics is presented in this work. It combines an open source spectral model, a single diode electrical model and a three-dimensional finite element thermal model. In order to validate the models and the multiphysics modelling procedure against actual data, an outdoor experimental campaign was conducted in Albuquerque, New Mexico using a high concentration photovoltaic monomodule that is thoroughly described in terms of its geometry and materials. The experimental results were in good agreement (within 2.7%) with the predicted maximum power point. This multiphysics approach is relatively more complex when compared to empirical models, but besides the overall performance prediction it can also provide better understanding of the physics involved in the conversion of solar irradiance into electricity. It can therefore be used for the design and optimisation of high concentration photovoltaic modules.

Ultrahigh Efficiency HCPV Modules and Systems

Semprius manufactures high-concentration photovoltaic (HCPV) modules and systems. Module characterization and quality control methods are described in this paper. Module efficiency distribution for thousands of modules is presented, currently showing an increase in average efficiency from 33% in 2013 to 35%. Data from modules and systems in the field are presented showing consistent performance over all seasons and no apparent degradation after 3 years. Finally, the effect of ambient temperature and wind speed on performance was studied.

Comparative study of methods for the extraction of concentrator photovoltaic module parameters

The modelling and outdoor evaluation of high concentrator photovoltaic (HCPV) systems is complex due to the use of multi-junction solar cells and optical devices. At the same time, the single exponential model (SEM) is widely used for predicting the IV characteristics of PV systems. In this paper, several conventional analytical methods for extracting the five parameters of the SEM model of non-concentrating PV devices are applied and evaluated for the electrical characterization of a HCPV module for the first time. Among the different approaches, three simple analytical methods have been selected with the aim of offering rapid and easy solutions for the characterization of HCPV systems. The selected methods are: the method of Phang et al., the method of Blas et al. and the method of Khan et al. In addition, these methods are compared with a numerical extraction method previously introduced by the authors. Results show that all the methods investigated can be valid for predicting the IV curve of a HCPV module except the method of Khan et al., which tends to underestimate the IV curve and maximum power of the module. The dependence of the extracted SEM model parameters with the input irradiance is also discussed.

The environmental impact of lightweight HCPV modules: efficient design and effective deployment

AbstractWe present a life cycle analysis of a lightweight design of high concentration photovoltaic module. The materials and processes used in construction are considered to assess the total environmental impact of the module construction in terms of the cumulative energy demand and embodied greenhouse gas emissions, which were found to be 355.3 MJ and 27.9 kgCO2eq respectively. We consider six potential deployment locations and the system energy payback times are calculated to be 0.22–0.33 years whilst the greenhouse gas payback times are 0.29–0.88 years. The emission intensities over the lifetimes of the systems are found to be 6.5–9.8 g CO2eq/kWh, lower than those of other HCPV, PV and CSP technologies in similar locations. Copyright © 2016 John Wiley & Sons, Ltd.

Cascade closed-loop control of solar trackers applied to HCPV systems

High concentration photovoltaic (HCPV) modules require a high precision tracking system for reaching their highest conversion efficiency. One way to accomplish this goal is by using a closed-loop mechanism and a sun sensor to track the sunlight. This paper proposes a cascade control algorithm capable of achieving a sun tracking error of 1′ for its application in high concentration photovoltaic systems. The algorithm follows an inner loop-outer loop topology. The inner loop employs a Nonlinear Proportional-Proportional Integral (NP-PI) controller and the outer loop resorts on a Proportional Integral (PI) controller. A tuning procedure for setting up the cascade controller is also described. Experiments on a laboratory prototype compare the performance of the proposed cascade controller with a PI controller not resorting on an inner loop. These outcomes show that the proposed control law provides improved tracking accuracy with less actuator wear.

Analysis of electrical mismatches in high-concentrator photovoltaic power plants with distributed inverter configurations

Electrical mismatches have a larger impact in high-concentrator photovoltaic power plants than in conventional photovoltaic systems because of the narrow acceptance angles and the unavoidable self-shading between sun trackers. In this paper, a commercial point-focus Fresnel lens-based high-concentrator photovoltaic module is characterized outdoors and results of this characterization are used to develop a power plant model which allows electrical mismatch energy losses to be investigated. Different inverter configurations (micro, string and tracker-oriented inverters) are analyzed with it. This research offers an approach based on energy loss calculation rather than instantaneous power loss calculation as was done in the reviewed literature. Moreover, realistic 28.5 kWp trackers are analyzed rather than small trackers and a novel procedure for obtaining direct normal irradiance daily profiles is presented. From the simulations, it is concluded that micro and string inverters are very useful to minimize mismatch energy losses, reinforcing the conclusions previously published by Kim and Winston (2014). The coefficients obtained in this paper are expected to help in energy yield calculations without the need of using advanced electrical modeling, although it was found that the bigger the capacity of the inverters, the higher the uncertainty to establish electrical mismatch loss coefficients due to shading.