Papers by Keyword: Photovoltaic Cell

Abstract: The manufacture of photovoltaic panels for the production of sustainable energy also involves the stage of electrical connection of the cells in the panel structure. This electrical connection is made by soldering of copper strips on the negative electrode of the cell. During the bonding process, due to the temperature of approximately 220-240°C at which the connecting strip is continuously heated, cracking processes of the upper layer of glass from the cell surface were identified. For this reason, it is necessary either to heat to lower temperatures, a solution that is not viable due to the melting temperature of the solder alloy which usually exceeds 210°C, or a different dosing of the heat flux. The solution proposed in the paper is to create a variable heat flux that allows the melting of the solder alloy, but at the same time to reduce the thermal load of the glass support layer. Through the proposed variant, the energy dosing is done with the help of a heating system consisting of two sources, an ultra-acoustic energy source and a classical resistive source. The resistive source provides an amount of energy to ensure a temperature in the range of 60-140°C, the difference to the melting point of the solder alloy being transferred locally by ultrasonic pulses. Research has highlighted the need to limit the range of values of the pressure of the circular sonotrode, which positively influences the mechanical stress of the photovoltaic cell, but also leads to a reduction in the joining speed. The dosing of the two components of the total energy, the one coming from the resistive source and the one coming from the ultra-acoustic vibration source is decisive for the efficiency of the joining process and for the quality of the soldered joint. Microscopic analyses revealed micro-cracks of the glass surface layer at forces higher than 100 N. Areas with lack of soldering for resistive heating at temperatures lower than 130oC were highlighted, the difference of 90-110°C being achieved by the contribution of ultra-acoustic energy.

Abstract: Sustainable development requires green energy and low carbon footprint in manufacturing sector of photovoltaic systems. The electrical connections of photovoltaic cells need to have low electrical resistance in order to reduce the electrical losses and therefore to improve the performance of the photovoltaic panels. This paper aims to present researches related to bonding of wires that connect solar cells by using microwave technology. The microwave bonding has the main advantage that offers fast bonding but, in the same time, this technology does not offer stability of the thermal heating. Two different unwanted phenomena like thermal runaway and plasma arc discharge often lead to the damaging of copper and aluminum wires used in electrical connection. The study presented in this paper is focused on simulation of the thermal field developed in copper wires in order to optimize the bonding process and increase the quality of products. The simulation of the thermal field has been done using Fourier equations for conducting heating in copper materials and eutectic alloys. The simulation model has been validated through experimental heating using a 6 kW water-cooled microwave generator controlled by a matching load auto-tuner for best transfer of the power from generator to copper wires. The temperature has been measured in real time using an infrared pyrometer for metals with 2.3 μm spectral range and measurement range between 0o C and 7000 C. The study is finalized with elaboration of mathematical model for microwave-injected power as function for temperature developed in copper wires that can be applied with success in further microwave bonding applications of copper wires. In addition, the electrical resistance of bonded wires was measured in order to collect feedback for improving the microwave bonding process.

Abstract: In this paper, we report on synthesis of graphene film on Cu foil by cold wall CVD and successfully transferred to a photovoltaic cell. The obtained sample was covered with an ultra-thin layer of Ni, of about 4 nm, using a sputtering technique. The optical and electrical properties of graphene/Ni-based films showed superior performance (transmittance =65%, sheet resistance=250 Ω/sq; EQE=40%) compared to films made of ITO/nickel, described in literature, of greater thickness.

Abstract: The article includes an overview of the effectiveness of different generations of photovoltaic cells, the temperature dependence of the electrical efficiency and methods of integration into the building envelope. Furthermore, the article focuses on experimental and simulation of proven methods to reduce the operating temperature of photovoltaic cells.

Abstract: The main aim of this work is to analyze the various heat transport mechanisms and their roles in efficiency enhancement of a thin-film solar cell due to embedded metallic nanoparticles at the rear of the cell, from both electrical and thermal aspects. The nanoparticles present deep inside the cell reflect incident radiation which then increases the optical path length for enhanced electricity generation. The increase in the optical path length also tends to induce additional but undesirable thermal heating which reduces the performance of the cells. The relationship between the improved conversion efficiency and the thermal effect is the crucial factor of maximizing the performance of thin-film solar cells and has yet to be explored. An accurate theoretical/numerical modeling is warranted in this case. Here, we present an analysis of combined light propagation and preliminary phonon transport in the cell to study solar-energy deposition and the associated thermal gradient.

Abstract: This paper presents the design and control of a grid-connected flyback inverter with a DC active filter for photovoltaic (PV) cells. The proposed topology consists of a flyback DC-AC inverter and a DC active filter that can operate independently. The flyback inverter, controlled in digital peak current mode, regulates the full-wave rectified sinusoidal current later, which is alternately inverted and injected into the grid. The DC active filter regulates the smooth current/power drawn from a PV module by using cascaded proportional-integral (PI) controllers. Analysis, design and control of the proposed topology are presented. A 100W/220V/50Hz prototype is developed and tested. The experimental results show that the proposed flyback inverter with a DC active filter is capable of regulating a sinusoidal current fed into the grid, actively filtering the DC current/power and achieving reasonably high energy conversion efficiency.

Abstract: Breakages of solar cells mostly depend on the stresses induced in process, handling and transportation, and rely on the presence of defect such as micro-crack. Transporting vibration typically induces solar cell has crack propagation and performance degradation. In addition, the resonance frequency generated by test package during shipping excites the external force happened on packaged cells. This work aimed to evaluate the performance and defect coherently in solar cell caused by vibration during both truck and air transportation, and analyzed the electrical data (P_mpp, R_s, R_sh) and defects in detailed. Result showed the breakage rate due to broken cell is 2 % only, but degradation rate due to abnormal cell is accumulated to 6 %, which exposed the high potential failure for transporting cells. Consequently, this paper has proposed a comprehensive test method to alleviate the reliability obstacles of solar cells, and accelerate the development of cells protection design for transportation.

Abstract: The paper firstly introduces the current status of solar energy generation and analyzes the principle,then uses Matlab/Simulink to model and simulate solar energy generation system, finally makes a performance analysis of the simulation results,which is that the influence of different temperature and solar radiation intensity to the voltage-current and power-voltage of solar energy cells.

Abstract: Effects of solar panels must be taken into account by the light intensity of its output characteristics in practical application, especially solar panels placed outdoor. So the light intensity coefficient is an important parameter to be considered. In this paper,we took the light intensity characteristics of single crystal silicon solar cell as the research object. Also,through transforming the illumination intensity which are 777.60W/m²,996.97 W/m² and 1224.88 W/m², we would finish researching the characteristics of the cell sheet, which included battery plate volt ampere characteristic, open circuit voltage, short circuit current and maximum output power. Also, we’ve got the relationship of U_oc-T, I_sc-T and P_m-T, respectively and Put forward the better intensity theory. It would lay a solid foundation of practice for the further study on how to improve the rate of light conversion.

Abstract: Based on mathematical models and output characteristics of photovoltaic cells, the simulation model for engineering application is established. By the model, the output characteristics of photovoltaic cells with different environmental factors can be analyzed. In MATLAB/SIMULINK environment, the model of the PV maximum power point tracking control is constructed. The simulation results demonstrate that PV can run at the maximum power point with the change of environment factors.