Photovoltaic Conversion Process Research Articles

Thermodynamic analysis of a spectrum splitting photovoltaic-thermoelectric system with a multi-physics coupling process

Quantifying the losses in the various energy transfer and conversion processes is essential for the study and application of the spectrum splitting photovoltaic-thermoelectric system because of the complex system structure. This paper develops a novel optical-electrical-thermal multi-physics coupling model for the spectrum splitting photovoltaic-thermoelectric system that correlates microstructure and macroscopic properties. Based on the multi-physics coupled model, a thermodynamic analysis method is employed to reveal the distributions of energy and exergy losses in the system, and the effect of the concentration ratio on the losses is investigated. The results show that the optical loss caused by the concentrating and splitting processes accounts for 33.3% of the total input energy. The losses in the energy conversion process are the largest of all the subsystem losses. The energy and exergy losses in the photovoltaic conversion process are 51.5% and 45.9%, while those for the thermoelectric conversion process are 87.8% and 74.5%, respectively. Raising the concentration ratio is an effective way to reduce the exergy loss in the energy conversion process, but it will also partially raise the exergy losses in the heat dissipation and cooling processes. The exergy efficiency of the SSPV-TE system can reach 21.75% at a concentration ratio of 500. The results are important for better understanding the operating principles, optimizing the performance, and advancing the application of the spectrum splitting photovoltaic-thermoelectric system.

Design and Development of a Biomimetic Solar Tree for Sustainable Cogeneration: An Energy and Exergy Assessment

Solar energy is becoming an increasingly popular and important source of renewable energy. Solar trees have emerged as a novel and innovative approach to harvesting solar energy. Solar trees are artificial structures that mimic the shape and function of trees, with branches or leaves that contain photovoltaic cells to convert sunlight into electricity. The solar tree generates both electrical and thermal energy from solar radiation. The present study tested the thermal (module temperature, heat loss coefficient), electrical (power output), and operating parameters of a solar tree at Universiti Malaysia Pahang, Pekan, Malaysia, on a typical sunny day. First-law analysis and second-law analysis were carried out to determine exergy losses during the photovoltaic conversion process of solar trees. The data obtained from the experiment is utilized to determine the energy and exergy efficiencies of the solar tree. The energy efficiency ranges from 16.8% to 8.3% throughout the day, displaying some variability. However, as for the exergy efficiency of the photovoltaic solar tree under consideration, it is observed to be lower, ranging from 16.1% to 6.6% for electricity generation. It is observed that the exergy losses increased with increasing module temperature and a drop in exergy efficiency.

Research on cleaning scheme of photovoltaic power plant based on pollutant composition analysis

Solar photovoltaic (PV) modules, as an important component of the photovoltaic conversion process within a PV system, are closely related to the efficiency and service life of the PV system’s overall work performance. Dust in the atmosphere is affected by rainfall, electrostatic forces, van der Waals forces and gravity, and will gather together and settle on the surface of the PV module to form dust accumulation, which reduces the amount of radiation and light energy absorption. Therefore, it is really necessary to carry out the research on the pollutant composition and treatment measures program of the surface pollution index of PV modules.

Spontaneous-Symmetry-Breaking Charge Separation Induced by Pseudo-Jahn-Teller Distortion in Organic Photovoltaic Material.

The driving force of charge separation in the initial photovoltaic conversion process is theoretically investigated using ITIC, a nonfullerene acceptor material for organic photovoltaic devices. The density functional theory calculations show that the pseudo-Jahn-Teller (PJT) distortion of the S1 excimer state induces spontaneous symmetry-breaking charge separation between the identical ITIC molecules even without the asymmetry of the surrounding environment. The strong PJT effect arises from the vibronic coupling between the pseudodegenerate S1 and S2 excited states with different irreducible representations (irreps), i.e., Au for S1 and Ag for S2, via the asymmetric vibrational mode with the Au irrep. The vibrational mode responsible for the spontaneous polarization, which is opposite in one ITIC monomer and the other, is the intramolecular C-C stretching vibration between the core IT and terminal IC units. These results suggest that controlling the PJT effect can improve the charge separation efficiency of the initial photovoltaic conversion process.

Passive Cooling Module to Improve the Solar Photovoltaic (PV) Performance

Solar energy is a renewable clean energy. Photovoltaic (PV) cells or solar panels use the sun light as the main source to produce electricity. However, the operating temperature has a significant impact on the PV conversion process and its performance. PV cell technology performance is sensitive to the operating temperature. Increasing cell temperature causes a significant reduction in the output voltage which in turn leads to reducing electrical efficiency. In other words, when the temperature rises, the output current rises exponentially which leads to output voltage to fall. Therefore, PV efficiency decreases. This paper aims to develop a new PV panel passive cooling system that enhances the efficiency of the panel and improves its performance. The design is based on air channels and air chimneys. Overall, cooled solar panels are efficient and cost-effective as their performance is better and their efficiency is higher than the non-cooled solar panels. Our project is designed to serve UAE’s 2021 vision (increased dependence on clean energy and green development), reduce pollution in the environment, and save energy for the next generations. The goal of this research is to lower the temperature of the PV panel., therefore, enhancing the efficiency as well as improving the performance by cooling the PV panel. So, It has the potential to alleviate the problem of overheating solar panels.

A hybrid DDAO-RBFNN strategy for fault tolerant operation in fifteen-level cascaded H-bridge (15L-CHB) inverter with solar photovoltaic (SPV) system

This paper proposes a hybrid approach for fault-tolerant operation in fifteen-level cascaded H-Bridge (15LCHB) inverter with solar photovoltaic system (SPV). Fault-tolerant operation performs two tasks: detection (classification of normal or abnormal) and identification (identification of faults). The proposed intelligent controller is the combination of Differential Annealing Dynamic Optimization (DDAO) and Radial Basis Function Neural Network (RBFNN) named DDAO-RBFNN approach. The major intention of the DDAO-RBFNN approach is separated into fault detection with lessening of complete photovoltaic solar energy conversion system. The proposed system takes into account the failure of the entire autonomous photovoltaic solar conversion process and manages the output voltage (OV) owing to the conditions of partial shading (PS). The collected data set (normal, abnormal) is stored at workstation. RBFNN is utilized to compute the CMI switching pattern that changes the PWM carrier signal. DDAO get the voltage values from RBFNN and evaluates them with the data set, if there is a rate of change of voltage. Any deviation find in the rate of voltage change, it makes a decision based on standard or fault conditions. The proposed system is activated on MATLAB/Simulink working platform, then the efficiency is compared with existing approaches.

An n–n type heterojunction enabling highly efficient carrier separation in inorganic solar cells

Carrier separation in a solar cell usually relies on the p–n junction. Here we show that an n–n type inorganic semiconductor heterojunction is also able to separate the exciton for efficient solar cell applications. The n–n type heterojunction was formed by hydrothermal deposition of Sb2(S,Se)3 and thermal evaporation of Sb2Se3. We found that the n–n junction is able to enhance the carrier separation by the formation of an electric field, reduce the interfacial recombination and generate optimized band alignment. The device based on this n–n junction shows 2.89% net efficiency improvement to 7.75% when compared with the device consisted of semiconductor absorber–metal contact. The study in the n–n type solar cell is expected to bring about more versatile materials utility, new interfacial engineering strategy and fundamental findings in the photovoltaic energy conversion process.

Discrete sources method for modeling of the influence of the non-local effect on the absorption of bimetallic core-shell non-spherical plasmonic nanoparticles

Core-shell bimetallic particles are of great interest, since their plasmonic properties can differ significantly from the properties of their constituent components. In chemistry, they are widely used to improve various photovoltaic energy conversion processes, because they have good absorption and heat transfer properties. In this paper, the generalized non-local optical response theory is used in conjunction with the discrete sources method to examine the impact of spatial nonlocality on the absorption properties of spheroidal core-shell particles composed of two plasmonic metals. It is demonstrated that variation of the core diameter and the thickness of the shell, as well as, as the particle elongation increases the absorption and shifts its maximum to longer wavelengths. Besides, it was found that accounting for spatial dispersion in both metals will reduce the absorption to 65 % of its value without including the nonlocal effect and the corresponding blue shift can exceed 15 nm.

The Effect of Solar Radiation and Temperature on Solar Cell Performance in Khartoum state

In this paper, the performance of solar cells was studied and evaluated . The role of several effects for operation condition such as temperature, sunlight intensity on the solar cells output parameters has been studied. Experimental results showed that relationship between the amount of solar cell output parameters variations such as maximum output power, open circuit voltage, short circuit current, and efficiency in terms of temperature and light intensity.
 The measurements were carried out for the intensity of solar radiation in Khartoum area in Sudan, from February month to April month which records the solar radiation in W/m2, The results were collected from 10 Am to 4 pm, three days per week, data were averaged and also illustrated in the form of graphs of solar radiation as a function of the time of the day.
 The operating temperature plays a key role in the photovoltaic conversion process. Both the electrical efficiency and the power output of the solar cell depend on the operating temperature. Solar cell performance decreases with increasing temperature.

Comprehensive energy balance analysis of photon-enhanced thermionic power generation considering concentrated solar absorption distribution

The present article reports a comprehensive energy balance analysis of a photon-enhanced thermionic emission (PETE) device when it is used for concentrated solar power (CSP) generation. To this end, we consider a realistic PETE device composed of a boron-doped silicon emitter on glass and a phosphorus-doped diamond collector on tungsten separated by the interelectrode vacuum gap. Depth-dependent spectral solar absorption and its photovoltaic and photothermal energy conversion processes are rigorously calculated to predict the PETE power output and energy conversion efficiency. Our calculation predicts that when optimized, the power output of the considered PETE device can reach 1.6 W/cm2 with the energy conversion efficiency of ~18% for 100× solar concentration, which is substantially lower than those predicted in previous works under ideal conditions. In addition, the photon-enhancement ratio is lower than 10 and decreases with the increasing solar concentration due to the photothermal heating of the emitter assembly, suggesting that PETE should be more suitable for low-to-medium CSP below ~100× concentration. These observations signify the importance of a rigorous energy balance analysis based on spectral and spatial solar absorption distribution for the accurate prediction of PETE power generation.

Performance improvement of solar PV power conversion system through low duty cycle DC‐DC converter

AbstractCharacteristics like reliability and modularity of solar photovoltaic (SPV) units makes them one of the apt options for generating electric power. However, the input intermittency is their major lacuna, and power electronic circuits are being used to nullify this effect. A solar photovoltaic power conversion process includes a DC‐DC converter in the plant side to deliver a fixed DC voltage and a DC‐AC converter in the grid side for converting DC voltage in to grid compatible AC voltage. The high duty ratio of typical DC‐DC boost converters limits the switching frequency and efficiency. In this article, a way to enhance the performance of a SPV unit using an improved quadratic boost converter (IQBC) is analysed. It can deliver a higher output voltage at lower duty ratio with Perturb and Observe (P&O) algorithm‐based Maximum Power Point Tracking (MPPT). A 250 W prototype of IQBC‐based Solar PV power conversion system (SPVPCS) is developed, and its performance is compared against conventional and quadratic boost converters and found that the IQBC‐based solar power conversion system is efficient and the results are presented.

Direct Dynamic Evidence of Charge Separation in a Dye‐Sensitized Solar Cell Obtained under Operando Conditions by Raman Spectroscopy

AbstractInterfaces play an important role in enhancing the energy conversion performance of dye‐sensitized solar cells (DSCs). The interface effects have been studied by many techniques, but most of the studies only focused on one part of a DSC, rather than on a complete solar cell. Hence, monitoring the interface evolution of a DSC is still very challenging. Here, in situ/operando resonance Raman (RR) spectroscopic analyses were carried out to monitor the dynamics of the photovoltaic conversion processes in a DSC. We observed the creation of new species (i.e., polyiodide and iodine aggregates) in the photosensitization process. We also obtained molecular‐scale dynamic evidence that the bands from the C=C and C=N bonds of 2,2′‐bipyridyl (bpy), the S=C=N bonds of the NCS ligand, and photochemical products undergo reasonably strong intensity and frequency changes, which clearly demonstrates that they are involved in charge separation. Furthermore, RR spectroscopy can also be used to quickly evaluate the performance of DSCs.

Direct Dynamic Evidence of Charge Separation in a Dye-Sensitized Solar Cell Obtained under Operando Conditions by Raman Spectroscopy.

Interfaces play an important role in enhancing the energy conversion performance of dye-sensitized solar cells (DSCs). The interface effects have been studied by many techniques, but most of the studies only focused on one part of a DSC, rather than on a complete solar cell. Hence, monitoring the interface evolution of a DSC is still very challenging. Here, in situ/operando resonance Raman (RR) spectroscopic analyses were carried out to monitor the dynamics of the photovoltaic conversion processes in a DSC. We observed the creation of new species (i.e., polyiodide and iodine aggregates) in the photosensitization process. We also obtained molecular-scale dynamic evidence that the bands from the C=C and C=N bonds of 2,2'-bipyridyl (bpy), the S=C=N bonds of the NCS ligand, and photochemical products undergo reasonably strong intensity and frequency changes, which clearly demonstrates that they are involved in charge separation. Furthermore, RR spectroscopy can also be used to quickly evaluate the performance of DSCs.

Dependence of PV Module Temperature on Incident Time-Dependent Solar Spectrum

The operating temperature of photovoltaic (PV) modules affects the photovoltaic conversion process. The operating temperature depends on various environmental conditions and on material-dependent properties of the PV modules. Many expressions for the operating temperature have been proposed in the literatures, some are simplified working Equation as NOCT (Nominal Operating Cell Temperature), and others are more complex, being based on a combination of the energy balance Equation and NOCT. The present study offers a new approach (model) for determining the PV module temperature based on the energy balance Equation and on the solar spectrum irradiance. While using the new model, the operating temperature has been determined for four module technologies: c-Si, a-Si/ μ c-Si, CdTe, and CIGS and it shows that the operating temperatures for the different cell types are close to the manufacturers’ NOCT data-sheet temperatures. For c-Si technology, for example, the simulation resulted in 43.2° and 46° for the spectrum and NOCT models, respectively. The proposed new model offers a new approach for determining the operating temperature of PV modules.

Thermal behavior analysis of different solar PV modules via thermographic imaging

The temperature of a photovoltaic (PV) system is a critical factor in the photovoltaic conversion process; hence, the practical performance of a PV system significantly depends on its temperature. Several different methods exist for the determination of PV module temperature. In this study, thermography was employed to investigate the thermal behavior of different solar PV modules under outdoor operating conditions. It was observed that the temperature difference across the area of a PV module could reach as high as 12.5–14.8 °C depending on the type of PV module. Hence, the trends for the lowest and highest temperature were not predictable. Glass-to-glass non-frame PV modules exhibited the highest temperature gradients compared to glass-to-Tedlar non-frame modules. The observed temperature gradients demonstrated that measuring the temperature at a single point on the module was not sufficient to accurately represent the temperature over the entirety of the PV module.

(Invited) Operando Characterization of Energy Conversion and Storage Devices Using Scanning Probe Microscopy

Energy conversion/storage devices, such as solar cells (SCs) and lithium ion batteries (LIBs), have been actively researched along with the growing interest in energy and environment issues. In order to further improve the performance of these devices, it is essential to have a deeper understanding of their working principles. To achieve this, the characterization of their physical and chemical properties under device operation conditions, so-called operando measurement, is thought to be highly effective. For example, in the case of SCs, important information related with photovoltaic conversion processes can be obtained by measuring the electrical potential, electronic states, and charge distribution in the vicinity of the excitation center under light irradiation conditions. In the case of LIBs, characterization of electrical potential and lithium ion distribution in the electrodes and electrode-electrolyte interfaces during charging and discharging processes is expected to provide strong insight into the origin of interface resistance and mechanism of cell degradation. Up to date, X-ray and electron spectroscopy techniques have led the field of operando measurement. However, the spatial resolution of those techniques is insufficient to characterize next generation devices that actively utilize nanostructure. Thus, in our group, as an operando measurement technique to evaluate the local properties at nanoscale and even down to the atomic scale, we have been working on developing scanning probe microscopy (SPM) systems that operate under various environments (under light irradiation, voltage application, inert atmospheric conditions). In this talk, we will introduce recent our works related to the characterization of perovskite SCs and all-solid-state LIBs by operando nano-scale profiling of electrical potential distribution using Kelvin probe force microscopy (KPFM). Perovskite solar cells (PSCs) have attracted great research interest owing to their advantages in high power conversion efficiency and low-cost fabrication. Although the power conversion efficiency of PSCs is very high (record is 22.7 %), the detailed photovoltaic conversion processes has not well understood yet compared with the conventional inorganic SCs. In this work, we used KPFM to measure internal electrical potential distribution of PSCs during device operation. We observed that the change of electrical potential induced by illumination occurred strongly at the interface between the perovskite film and charge transport layers, which suggests that charge separation mainly occurred at those interfaces, not in the perovskite film. Also, we found that the position of charge separation varied depending on the composition of perovskite materials and the device structure. These findings will be helpful for understanding the fundamental mechanism within PSCs and achieving high device efficiency. All-solid-state (ASS) LIBs are a promising candidate for next-generation energy storage devices. However, solid electrolytes for the current ASS-LIBs have various disadvantages, such as low power densities caused by high ionic resistivity at the interfaces between active materials and solid electrolytes. The high ionic resistivity has been attributed to the Li depleted layer or defects at the interfacial layer. For the fundamental understanding of the origin of interfacial resistivity, novel in situ techniques for measuring the distribution of the internal potential and/or Li ion concentration of LIB cells are strongly required. In this work, we combined Ar ion milling under non-atmospheric conditions with cross-sectional KPFM for direct imaging of the internal electrical potential distribution of the ASS-LIBs. We succeeded in the direct visualization of the change in the potential distribution of the cathode composite electrode arising from the battery charging (electrochemical reaction). The results obtained provided several insights into the battery operation, such as the behavior of Li ions and inhomogeneity of electrochemical reactions in the electrode.

Effect of Junction Cell Temperature and Geographical Coordinates on The Electrical Performances of a Photovoltaic Module

After the absorption of the photons, during the photovoltaic conversion process, one part of the radiation remains unabsorbed causing the cell to overheat and thus a drop in efficiency. The purpose of this study is to explore the effect of junction temperature, geographic coordinates as well as the season on the electrical performance of the photovoltaic cell. The results obtained show that the junction temperature has an effect which is not favorable on the electrical efficiency of the module for high temperatures around midday which is of 11% however it reaches 14% for low temperatures in the morning. Geographical coordinates at different altitudes, have no effect on the energy produced from the module, but the effect of the season on the efficiency confirms the previous results, that, the efficiency is good for low temperatures. The results are obtained by simulation, through a computer code in FORTRAN language, designed for this purpose. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The Analysis of Temperature Effect for mc-Si Photovoltaic Cells Performance

As a high potential renewable power source, solar energy is becoming one of the most important energies of the future. Recently, there has been an enormous increase in the understanding of the operational principle of photovoltaic devices, which has led to a rapid increase in the power conversion efficiencies of such devices. Solar cells vary under temperature changes; the change in temperature will affect the power output from the cells. This paper discusses the effect of light intensity and temperature on the performance parameters of monocrystalline and polycrystalline silicon solar devices. In this paper, the performance and overview use of solar cells is expressed. The role of temperature on the electric parameters of solar cells has been studied. The experimental results show that all electrical parameters of the solar cells, such as maximum output power, open circuit voltage, short circuit current, and fill factor, have changed with temperature variation. Solar cell performance decreases with increasing temperature, fundamentally owing to increased internal carrier recombination rates caused by increased carrier concentrations. The operating temperature plays a key role in the photovoltaic conversion process. Both the electrical efficiency and the power output of a photovoltaic (PV) module depend linearly upon the operating temperature. Solar cells vary under temperature changes; the change in temperature will affect the power output from the cells.

INFLUENCE OF SOLAR RADIATION AND MODULE TEMPERATURE ON SOLAR MODULE PERFORMANCE

Photovoltaic module (PV) performance decreases with the increase of module temperature. While, it increases with increasing solar radiation intensity. PV system is used to convert solar energy into electric power then it will be connected with a pumping system (DC motor and centrifugal pump) to run trickle irrigation system for small scale areas in Inshas. Solar panels temperature and solar radiation intensity play a big part in the photovoltaic conversion process. Since solar cells are semi-conductors, they are very sensitive to temperature. The characteristic power curve is affected significantly by the module temperature. In this paper each of voltage, module efficiency and the output power of PV module depend on solar panels temperature at different values (30o- 40o- 50oC), solar radiation intensity ranged at (900-1000)W/m2 and PV module (Polycrystalline 240 WP). During the operation of the PV, module efficiency reached to be around 14.5% which is PV conversion efficient for solar radiation to electricity. The electrical efficiency will decrease with the increase of solar panels temperature of the PV module.

Transient Absorption Spectroscopy for Polymer Solar Cells

Time-resolved spectroscopy is a powerful tool for studying fundamental photophysics in optoelectronic materials on a molecular temporal scale. In this review, we describe transient spectroscopic studies on fundamental photovoltaic conversion processes in polymer solar cells, which consist of a series of conversion processes such as photon absorption, exciton diffusion into a donor/acceptor interface, charge transfer at the interface, charge dissociation into free charge carriers, and charge collection to each electrode. These conversion processes are ultrafast phenomena and are ranging over the wide temporal scale from femtoseconds to microseconds, which can be directly observed by transient spectroscopy.