Photovoltaic Solar Energy Conversion Research Articles

Effect of spray volume on the properties of Cu2ZnSnS4 absorber thin film fabricated through nebulizer assisted spray pyrolysis technique

Copper Zinc Tin Sulfide (CZTS) is a growing semiconductor chalcogenide that has the potential to act as an alternative nontoxic absorber for commercial silicon-based devices in the sustainable photovoltaic conversion of solar energy in the near future. A debut attempt was made to economically fabricate this earth-abundant solar absorber thin film through indigenously designed cost-effective nebulizer assisted chemical spray pyrolysis technique without high-temperature annealing. The deposition was carried out at different spray volumes to modify the thickness of the absorber material directly on a bare soda-lime glass substrate and effect of CZTS film thickness on its structural, morphological, optical and electrical properties were studied by using appropriate characterization techniques. The film with a thickness of 740 nm for a precursor spray volume of 12 ml resulted in CZTS film with better energy conversion characteristics.

Unbiased Circular Leakage Centered Adaptive Filtering Control For Power Quality Improvement of Wind–Solar PV Energy Conversion System

The hybrid renewable energy conversion systems and their increased penetration into the utility grid are intensifying the power quality (PQ) issues especially in the form of increased total harmonic distortion of voltages and currents at point of common coupling. The objective of the proposed grid-tied wind–solar photovoltaic (PV) energy conversion system is to analyze PQ issues and to mitigate them by utilizing the unbiased circular leakage centered (UCLC) adaptive filtering control. An implementation of UCLC adaptive control improves the PQ indices and system performance by overcoming the intermittency issues associated with solar and wind energies. UCLC adaptive control effectively extracts the fundamental load current component and mitigates the grid current harmonics. It has simple structure, enhanced convergence rate, and better performance with noise corrupted input and output signals. It effectively resolves the weight drift problem depicted by the conventional least mean square (LMS) control and leaky LMS control algorithm by avoiding biased estimates. The averaging theory and the deterministic stability analysis provide the relying facts of the performance of UCLC adaptive control. The extraction of maximum power from solar PV array energy and wind generation is carried out by perturb and observe scheme. A prototype is made in the laboratory and verified for environmental variations of solar insolation level, wind speed, and perturbing load demand. The PQ issues are effectively alleviated. Test results confirm the effective performance of the proposed system.

The Nexus of Energy For Free and World Society

Recent price cuts made photovoltaic solar energy conversion the cheapest energy source for electricity production at least in sun-rich African countries. The price drops are achieved by traditional photovoltaic modules based on crystalline silicon wafers; and still important potential for price reduction exists for this technology. In addition a large number of alternative PV technologies have been developed to different stages of maturity promising even higher potential for price reduction. Thereby the electricity price may drop to values even lower than at times in the past when the energy price had already been basically negligible in calculating production costs. This leads to the question of the impact of basically cost-free electricity. The technological development is clear; the social and political implications are not even discussed so far. Here conceptualizations of World Society are used to highlight possible future scenarios. This paper should provide a first collection of thoughts on possible threats, chances and other consequences of this development.

A Generalized Crystallization Protocol for Scalable Deposition of High-Quality Perovskite Thin Films for Photovoltaic Applications.

Metal halide perovskite solar cells (PSCs) have raised considerable scientific interest due to their high cost‐efficiency potential for photovoltaic solar energy conversion. As PSCs already are meeting the efficiency requirements for renewable power generation, more attention is given to further technological barriers as environmental stability and reliability. However, the most major obstacle limiting commercialization of PSCs is the lack of a reliable and scalable process for thin film production. Here, a generic crystallization strategy that allows the controlled growth of highly qualitative perovskite films via a one‐step blade coating is reported. Through rational ink formulation in combination with a facile vacuum‐assisted precrystallization strategy, it is possible to produce dense and uniform perovskite films with high crystallinity on large areas. The universal application of the method is demonstrated at the hand of three typical perovskite compositions with different band gaps. P‐i‐n perovskite solar cells show fill factors up to 80%, underpinning the statement of the importance of controlling crystallization dynamics. The methodology provides important progress toward the realization of cost‐effective large‐area perovskite solar cells for practical applications.

Output Power Enhancement of Solar PV Panel Using Solar Tracking System

Solar Photovoltaic (PV) energy conversion has gained much attention nowadays. The output power of PV panel depends on the condition under which the panel is working, such as solar radiation, ambient temperature, dust, wind speed and humidity. The amount of falling sunlight on the panel surface (i.e., solar radiation) directly affects its output power. In order to maximize the amount of falling sunlight on the panel surface, a solar tracking PV panel system is introduced. This paper describes the design, development and fabrication of the solar PV panel tracking system. The designed solar tracking system is able to track the position of the sun throughout the day, which allows more sunlight falling on the panel surface. The experimental results show that there was an enhancement of up to a 64.72% in the output power of the PV panel with reference to the fixed orientation PV panel. Further, this study also demonstrates that the full load torque of the tracking system would be much higher than the obtained torque, which is required to track the position of the sun. This propounds, that the proposed tracking system can also be used for a higher capacity PV power generation system.

Residual Incremental Conductance Based Nonparametric MPPT Control for Solar Photovoltaic Energy Conversion System

Maximum power point tracking (MPPT) algorithms have become key elements in improving solar photovoltaic (PV) energy conversion systems. Numerous algorithms have been developed and implemented successfully in recent technology. This paper intended to introduce an improved incremental conductance (IC) algorithm based on the mathematical residue theorem. The major difference introduced in this paper is in considering the residual value of the IC to ensure MPPT achievement. Ensuring the minimal residue in IC improves the operation and eliminates the fluctuation around the operation points. Improved energy conversion efficiency has been achieved and the system has been proved mathematically and by simulations. One of the advantages that the system is free of parameters affect and atmospheric condition data are not required. The controller gain is based on sliding mode compensator to improve the uncertainty handling ability of the developed control approach.

Технико-экономическое обоснование разработки микро-ТЭС на органических теплоносителях с использованием солнечной энергии

Development of distributed generation is one of the modern trends in power supply, and the use of renewable energy sources (RES) has finally got real prospects in this trend. Despite the obvious progress in the development of photovoltaic solar energy conversion methods, the thermoelectric method still remains a less expensive and more accessible one for individual consumers (such as individual garden plots and peasant farms) with a sufficiently small power demands (4...6 kW). The article discusses the technical and economic matters concerned with designing thermoelectric installations using the low-temperature thermal component of solar radiation in the Rankin cycle with the use of organic coolants (OCs). These include the choice of working fluid optimal for the given thermal converter temperature level, the specific features and methods for design analysis of the thermal circuits and turbo machines operating with an OC, and assessment of the results. It is shown that micro thermal power plants of this capacity level can find their place in the distributed energy systems of Russia and around the world.

Power Loss Model and Efficiency Analysis of Three-Phase Inverter Based on SiC MOSFETs for PV Applications

This paper presents the power loss model analysis and efficiency of three-level neutral-point-clamped (3L-NPC) inverter that is widely employed in solar photovoltaic energy conversion system. A silicon carbide (SiC) 3L-NPC inverter is developed in this paper by employing wide bandgap semiconductor power devices, such as SiC MOSFET and SiC diode (SiC D). These devices are used due to their superior characteristics over silicon (Si) semiconductor devices for the reduction of inverter power losses, and as a result, an improving efficiency at the high switching frequency. Accurate and detailed power loss calculation formula and power loss distribution over switching devices of the SiC 3L-NPC inverter are derived according to the modulation technique and inverter operation. The switching energy loss of SiC MOSFET is then measured and determined experimentally via inductive clamp double pulse test (DPT) at the real working condition of the circuit. Afterward, this experimental data is used in the thermal description file of the device’s library of PLECS simulation software to determine the total power loss of SiC 3L-NPC inverter. The developed simulation model replicates the real operating conditions of the 3L-NPC inverter. This method gives results close to the practical test. Finally, the power loss of SiC 3L-NPC inverter is measured and compared with the theoretical results. Furthermore, SiC MOSFET and SiC D are employed to achieve high system efficiency at the high switching frequency. The results verify the features of SiC 3L-NPC inverter, the corresponding modulation technique used and their effects on reducing and improving power loss in solar SiC photovoltaic inverters.

Using Bulk-like Nanocrystals To Probe Intrinsic Optical Gain Characteristics of Inorganic Lead Halide Perovskites.

Following the introduction of perovskites for photovoltaic solar energy conversion, the use of these materials as a general purpose optoelectronic material for displays, lighting, and lasing has been explored. However, while reports on stimulated emission and lasing by perovskites show great promise, a comprehensive quantification of their optical gain characteristics is lacking. Here, we measure gain coefficients, clarify the gain mechanism, and explore the gain dynamics of colloidal CsPbBr3 nanocrystals by deploying a unique combination of broadband transient absorption and ultrafast fluorescence spectroscopy. Opposite from current literature, we show that optical gain in such nanocrystals is supported by stimulated emission from free carriers, and not from excitons or biexcitons. Importantly, we demonstrate that the concomitant gain coefficients and thresholds agree with literature results reported for perovksite thin films. Finally, we show that, even in the case of fully inorganic lead halide perovskites, a cooling bottleneck hampers the development of net stimulated emission at high excitation density. Based on these results, we propose that bulk-like colloidal nanocrystals in general offer a unique testbed to quantify optical gain of novel photonic materials and in particular for lead halide perovskites.

An Intelligent-Based Fault-Tolerant System for Solar-Fed Cascaded Multilevel Inverters

This paper presents an intelligent-based fault-tolerant system for a solar photovoltaic (PV) inverter. Artificial neural network based controller is used to monitor, detect, and diagnose the faults in solar PV panels, battery, semiconductor switches, and inverters. The cascaded multilevel inverter is connected across the combination of solar PV panel and battery for dc–ac conversion. The major advantage of the proposed topology is that it can deliver power from source to the load even under fault and partial shaded conditions. The paper also reviews on various faults in the solar PV energy conversion process and provides suitable solutions for each circumstance. Simulations are undertaken in MATLAB 2016a/Simulink and experimental investigation is carried out for a 3 kWp solar PV system. The results have proven that the system is capable to deliver power in spite of faulty environments. The comparison and discussion of the results were made to show the effectiveness of the proposed system.

Dual‐function PV‐ECS integrated to 3P4W distribution grid using 3M‐PLL control for active power transfer and power quality improvement

This study proposes a single-stage solar photovoltaic energy conversion system (PV-ECS) integrated to a three-phase four-wire (3P4W) distribution grid with dual-function capabilities, i.e. active power transfer and power quality (PQ) enhancement at the point of interaction (PoI). The PV-ECS system comprises of a solar photovoltaic array and a voltage source inverter (VSI), supplying active power (during daytime) to the distribution grid and connected single-phase and three-phase loads. Apart from transfer of power, the system also improves the PQ at the PoI by compensating reactive power and neutral current, attenuating harmonics, correcting power factor and balancing grid currents. During night, the VSI acts as a shunt active power filter mitigating PQ issues, thereby increasing the device utilisation factor. A three-phase magnitude-phase locked loop (3M-PLL) method is utilised to extract and estimate fundamental term of load currents and an incremental conductance algorithm is applied for maximum power point tracking. To demonstrate its effectiveness, the system is modelled and its performance is simulated on MATLAB and experiments are performed on a developed prototype in the laboratory.

Flexibility of Organic Thermoelectric Material for Photovoltaic Solar Energy Management and Conversion

Objective:The flexibility on a design maneuvering of building automation systems with the integration of organic solar cells is investigated.Methods:The energy demand load of the Engineering Lecture Theatre (ELT) at the University of Lagos is analyzed and parametric studies of the heat and charge transport within aMimosa pudicabased solar wafer are conducted, along with the modelling of a network of microchannels. A walk-through energy audit of all the devices that are installed or operated within the ELT and the thermophysical properties of the building envelope are considered, with the aim of satisfying the ASHRAE standard for thermal comfort and indoor air quality. A two-dimensional finite volume formulation of the heat and charge transfers within the boundaries of the flexible laminate and the organic extract is utilized.Result:Parametric analysis of the flow phenomenon and temperature distribution, especially across the wafer, at various operating conditions helps to determine significant design criteria, and assists in confirming the feasible power performance of the organic solar cell for building energy management.Conclusion:The results are anticipated for the design of reliable building automation systems for effective demand side monitoring, and for estimation of the economic viability of a proposed development of hybrid organic-inorganic based solar energy system for independent power generation within the Faculty of Engineering.

Improved photovoltaic performance from inorganic perovskite oxide thin films with mixed crystal phases

Inorganic ferroelectric perovskites are attracting attention for the realization of highly stable photovoltaic cells with large open-circuit voltages. However, the power conversion efficiencies of devices have been limited so far. Here, we report a power conversion efficiency of ~4.20% under 1 sun illumination from Bi–Mn–O composite thin films with mixed BiMnO3 and BiMn2O5 crystal phases. We show that the photocurrent density and photovoltage mainly develop across grain boundaries and interfaces rather than within the grains. We also experimentally demonstrate that the open-circuit voltage and short-circuit photocurrent measured in the films are tunable by varying the electrical resistance of the device, which in turn is controlled by externally applying voltage pulses. The exploitation of multifunctional properties of composite oxides provides an alternative route towards achieving highly stable, high-efficiency photovoltaic solar energy conversion. The use of mixed crystal phases is shown to enhance the power conversion efficiency of inorganic ferroelectric perovskite solar cells.

In Ukrainian

The purpose of this work is to develop a technology for the production of CdS films by chemical surface deposition on porous substrates of nanocrystalline silicon. The possibility of using the heterostructure CdS/porous-Si/p-Si as photovoltaic solar energy converters is considered. The formation of layers CdS was carried out by the method of precipitation in a chemical bath from an aqueous solution. As a template, plates of porous silicon (Si) are used. Nanoporous silicon was obtained by electrochemical etching of single-crystal plates Si (100) of p-type conductivity with a specific impedance of 6 mΩ•cm. For the chemical surface deposition of CdS films, a freshly prepared 0.015 M aqueous solution of cadmium chloride CdCl 2 , 1.5 M solution of thiourea CH 4 N 2 S, and 14.28 M solution of ammonium hydroxide NH 4 OH were used. The process of heating the plates lasted 5 min. The final temperature was 80 °C. The morphology of the porous silicon surface, the cross-section of the resulting CdS/porous-Si/p-Si structures and the chemical composition of the films obtained were investigated using a scanning electron microscope. The chemical composition of the film surface was determined using X-ray spectral microanalysis. According to the results of the conducted studies, it has been found that the thickness of the CdS layer is homogeneous and is 10–30 microns. CdS films have n-type conductivity. X-ray diffractograms of the sample exhibit pronounced peaks at 2θ ≈ 26.5° and at 2θ ≈ 43.3°, which correspond to the hexagonal modification of CdS. There are also intense peaks from the silicon substrate. A solar photocell is produced, which is a heterostructure of n-CdS/porous-Si/p-Si. The value of the efficiency of the received solar cells exceeds 5.4 % of the efficiency value for similar structures of CdS/p-Si under the same conditions for obtaining a conductive film of n-type CdS. Thus, the heterostructures CdS/porous-Si/p-Si produced by the precipitation of CdS layers in a chemical bath from an aqueous solution can be used as the basis of photovoltaic converters for solar energy.

Integrating solar photovoltaic energy conversion systems into industrial and commercial electrical energy utilization—A survey

Exploration of energy technology market and the role of innovation in solar energy form the core research hypothesis in this paper. There is a phenomenal growth experienced in solar photovoltaic (PV) energy market. Technological advancements have reduced the cost of solar PV generation and brought policy changes from governments across the globe. Among the solar energy technologies, solar PV system is becoming increasingly popular. Thus, there is a need to assess the pro-poor technology solutions, including field performance, consumer adoption, grid interconnection, energy storage and environmental impact assessment. This paper examines the technical issues and challenges of components associated with the generation of energy in solar PV plants. Emphasis is also given to solar PV modelling. Finally, the paper analyzes the important studies from the perspective of fault analysis and the need for energy storage and compiles them in a cohesive manner to highlight the research gaps. There is a possibility that highly educated consumers may misinterpret the information regarding solar energy and electricity. Hence, this paper shall provide an insight thereby making an interaction between industry-information-integration-communication with the society about new solar PV energy technology and energy management system. Furthermore, the application of Information and Communication Technology (ICT) and its benefits together with the environmental impact assessment (EIA) will be elaborated.

Engineering graphene and TMDs based van der Waals heterostructures for photovoltaic and photoelectrochemical solar energy conversion.

Graphene and two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted significant interest due to their unique properties that cannot be obtained in their bulk counterparts. These atomically thin 2D materials have demonstrated strong light-matter interactions, tunable optical bandgap structures and unique structural and electrical properties, rendering possible the high conversion efficiency of solar energy with a minimal amount of active absorber material. The isolated 2D monolayer can be stacked into arbitrary van der Waals (vdWs) heterostructures without the need to consider lattice matching. Several combinations of 2D/3D and 2D/2D materials have been assembled to create vdWs heterojunctions for photovoltaic (PV) and photoelectrochemical (PEC) energy conversion. However, the complex, less-constrained, and more environmentally vulnerable interface in a vdWs heterojunction is different from that of a conventional, epitaxially grown heterojunction, engendering new challenges for surface and interface engineering. In this review, the physics of band alignment, the chemistry of surface modification and the behavior of photoexcited charge transfer at the interface during PV and PEC processes will be discussed. We will present a survey of the recent progress and challenges of 2D/3D and 2D/2D vdWs heterojunctions, with emphasis on their applicability to PV and PEC devices. Finally, we will discuss emerging issues yet to be explored for 2D materials to achieve high solar energy conversion efficiency and possible strategies to improve their performance.

Structural and optical characterizations of Cu2SnS3 (CTS) nanoparticles synthesized by one-step green hydrothermal route

In this study, nanoparticles of Cu2SnS3 (CTS) have been synthesized by a simple one-step hydrothermal route without annealing. Metal chlorides and sodium sulphide precursors were dissolved in green solvent (water) and maintained at 230°C for 24h in a laboratory scale autoclave. Structural, morphological and optical characterization of synthesized CTS nanoparticles has been performed by Energy Dispersive Spectrometry (EDS), X-Ray Diffraction (XRD), Raman Spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) and UV–vis-NIR Spectroscopy. The results appear to confirm the formation of pure and quasi-stoichiometric cubic CTS nanoparticles. No secondary phases have been detected. The average size of the synthesized nanoparticles is estimated to be about 30nm. From the absorption measurements, the optical band gap energy of the CTS nanoparticles was estimated to be 1.4eV. This is very close to the optimal value required for an absorber material in photovoltaic (PV) solar energy conversion. In order to improve the understanding of the formation mechanism of CTS nanoparticles, the precipitate recovered prior to the hydrothermal reaction was analysed by EDS and XRD. The obtained results suggest that the formation of CTS nanoparticles takes place in two stages. Firstly, it is initiated from the formation of precipitates of Cu2S, CuS and SnS binary compounds in the starting precursors solution prior to the hydrothermal reaction and thereafter it is completed under hydrothermal conditions. This study shows the feasibility of synthesizing CTS nanoparticles with abundant elements using an environmentally-friendly and low cost process.

N-GaP/p-Si heterojunction solar cells fabricated by PE-ALD

Significant progress in photovoltaic conversion of solar energy can be achieved by new technological approaches that will improve the efficiency of solar cells and make them appropriate for mass production. A new technological approach for the growth of III-V compounds on Si substrates using low temperature plasma-enhanced atomic layer deposition (PE-ALD) is explored in the paper. This technique, which consists of alternatively changing the phosphorus and gallium atom source flows providing the growth of one monolayer by cycle, was developed for the growth of GaP films on Si substrates in a standard PECVD setup at 380 °C using PH3 and TMG (Trimethylgallium) as sources of III and V atoms. First (n)GaP/(p)c-Si anisotype heterojunction solar cell structures fabricated by PE-ALD exhibit open circuit voltage values similar to that obtained for (n)a-Si:H/(p)c-Si heterojunctions fabricated using the same (p)c-Si substrates. However (n)GaP/(p)c-Si solar cells demonstrates a potential to extend a high quantum efficiency in the short wavelength region due to lower absorption losses in the GaP emitter layer.

Single Stage Solar PV Fed Brushless DC Motor Driven Water Pump

In order to optimize the solar photovoltaic (PV) generated power using a maximum power point tracking technique, a dc–dc conversion stage is usually required in solar PV fed water pumping which is driven by a brushless dc (BLDC) motor. This power conversion stage leads to an increased cost, size, complexity, and reduced efficiency. As a unique solution, this paper addresses a single stage solar PV energy conversion system feeding a BLDC motor-pump, which eliminates the dc–dc conversion stage. A simple control technique capable of operating the solar PV array at its peak power using a common voltage source inverter is proposed for BLDC motor control. The proposed control eliminates the BLDC motor phase current sensors. No supplementary control is associated for the speed control of motor-pump and its soft start. The speed is controlled through the optimum power of solar PV array. The suitability of proposed system is manifested through its performance evaluation using MATLAB/Simulink-based simulated results and experimental validation on a developed prototype, under the practical operating conditions.

Pulse Electrodeposition Synthesis and Characterization of Sns Thin Films Obtained from Dimethyl Sulfoxide Solutions

Thin film materials for solar photovoltaic energy conversion have been considered a good option to provide a low cost power supply for a progressive increasing demand across the world. The most intensively studied and commercialized thin film solar cells are those based on (CIGS), Cu(In,Ga)Se2 and CdTe. Concerns regarding the cadmium because its toxicity and the limited abundance of indium and gallium could limit the future of these technologies. For these reasons alternative materials to develop new photovoltaic solar cells are currently investigated around the world. From the point of view of earth abundance, cost and toxicity SnS appears as a promising candidate. It has a direct optical band gap value (1.5 eV) which is within the optimum range for photovoltaic solar energy conversion. It exhibits p-type conductivity and high optical absorption coefficient meaning that only some microns of thickness could absorb most of the incident light. Theoretical calculations predict a conversion efficiency of 24% for materials with the same band gap1, however the reported efficiency for solar cells based on SnS is less than 2%2. Such low efficiencies were attributed to factors like poor quality of the films, grain boundaries, lower thickness employed, insufficient diffusion lengths in the layers and large band discontinuities. Hence, in order to obtain better efficiencies in SnS based solar cells the quality of the layers need to be substantially improved. Electrodeposition is one of the economical methods for large surface coating and has been successfully used to prepare semiconductor films. The method allows the control of the bandgap width and the doping level through the control of variables such as solution composition, applied potential, pH and working temperature. Furthermore, monitoring the circulating charge it is also possible to control the thickness of the deposited layers. Metal chalcogenides have been generally electrodeposited by the cathodic co-reduction of the metal and chalcogenide ions. However, compositional heterogeneity is usually a problem with this approach. An attractive option involves the use of aprotic deposition baths such as dimethylsulfoxide which presents a high boiling point and also allows the solubility of the chalcogene precursor in nonionized, molecularly dissolved form. In this solvent it is possible to form binary compounds starting from the electrochemical reduction of the elementary chalcogen precursor and the consecutive formation of a chalcogenide anion that further precipitates heterogeneously onto the surface of a convenient substrate for the formation of II-VI semiconductors. In current work SnS thin films were prepared on molybdenum substrates by pulsed electrodeposition at differents synthesis times. The structure, morphology and composition were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and Raman spectroscopy. The optical and electrical properties were studied by UV–vis absorption and capacitance-potential curves, respectively. The electrodeposited SnS films showed p-type semi-conductive characteristics and exhibited cathodic photocurrent under visible light illumination. Highly compact, dense, homogenous and almost stoichiometric films were obtained by properly selecting the electrodeposition parameters. These results show that the as grown films show composition and thickness compatible with the requirements of SnS based solar cell devices Acknowledgements: ToEuropean Commission, NanoCIS project FP7-PEOPLE-2010-IRSES grant 269279 and to CONICYT (Chile), FONDECYT (Fondo de Desarrollo Cientifico y Tecnológico, Chile) through Project N° 3160217.