Crystalline Silicon PV Module under Effect of Shading Simulation of the Hot-Spot Condition

This paper centers on the silicon crystalline PV module technology subjected to operation conditions with some cells partially or fully shaded. A shaded cell under hot-spot condition operating at reverse bias are dissipating power instead of delivering power. A thermal model allows analyzing the temperature increase of the shaded cells of the module under hot-spot condition with or without protection by a bypass diode. A comparison of the simulation results for a crystalline PV module without shading and with partial or full shading is presented

Review of mismatch mitigation techniques for PV modules

The installation of photovoltaic (PV) systems is continuously increasing in both standalone and grid-connected applications. The energy conversion from solar PV modules is not very efficient, but it is clean and green, which makes it valuable. The energy output from the PV modules is highly affected by the operating conditions. Varying operating conditions may lead to faults in PV modules, e.g. the mismatch faults, which may occur due to shadows over the modules. Consequently, the entire PV system performance in terms of energy production and lifetime is degraded. To address this issue, mismatch mitigation techniques have been developed in the literature. In this context, this study provides a review of the state-of-the-art mismatch mitigation techniques, and operational principles of both passive and active techniques are briefed for better understanding. A comparison is presented among all the techniques in terms of component count, complexity, efficiency, cost, control, functional reliability, and appearance of local maximums. Selected techniques are also benchmarked through simulations. This review serves as a guide to select suitable techniques according to the corresponding requirements and applications. More importantly, it is expected to spark new ideas to develop advanced mismatch mitigation techniques.</p

Modeling and Detection of Hotspot in Shaded Photovoltaic Cells

In this paper, we address the problem of modeling the thermal behavior of photovoltaic (PV) cells undergoing a hotspot condition. In case of shading, PV cells may experience a dramatic temperature increase, with consequent reduction of the provided power. Our model has been validated against experimental data, and has highlighted a counter-intuitive PV cell behavior, that should be considered to improve the energy efficiency of PV arrays. Then, we propose a hotspot detection scheme, enabling to identify the PV module that is under hotspot condition. Such a scheme can be used to avoid the permanent damage of the cells under hotspot, thus their drawback on the power efficiency of the entire PV system

Efficiency analysis of PV power plants shaded by MV overhead lines

This paper deals with the occurrence of hot spot phenomena in photovoltaic (PV) systems under partial shading caused by objects on some parts of the modules. An interesting case of diffuse shadows is determined by overhead distribution lines whose path crosses or are in the proximity of the PV power plants. Investigating the impact of these shadows on reducing the power production of PV or on damaging the PV modules as the modules’ temperature is increasing, is of high interest. At the SolarTech laboratory of Politecnico di Milano, the conditions for hot spot phenomena occurrence due to the overhead lines shading the PV cells were reproduced. Two experimental campaigns were carried out to investigate the current–voltage and power–voltage characteristics, and the energy production. In each experimental campaign, the built shading structure was considered fixed and different shading conditions were created based on the natural displacement of the sun. The hot spot phenomena was revealed on a field PV installation in Italy, caused my medium voltage overhead lines shading the PV cells, using infrared imagery

HOT-SPOT PHENOMENON IN PV SYSTEMS WITH OVERHEAD LINES PARTIAL SHADING

This paper deals with the occurrence of hot-spot phenomenon in photovoltaic systems under PV partial shadowing. In an experimental campaign, the hot-spot phenomenon was revealed on a PV installation in Italy, caused my medium voltage overhead lines shadowing the PV cells. Starting from these practice case studies, at the SolarTech laboratory of Politecnico di Milano, the conditions for hot-spot phenomenon occurrence due to the overhead lines shading the PV cells were reproduced. Two experimental campaigns were carried out to investigate the current-voltage and power-voltage characteristics, and the energy production. In each experimental campaign, the built shadowing structure was considered fixed, and different shadowing conditions were created based on the natural displacement of the sun. Still, for occurring the hot- spot phenomenon during the laboratory tests, more PV modules must be connected in parallel

A review for solar panel fire accident prevention in large-scale PV applications

Due to the wide applications of solar photovoltaic (PV) technology, safe operation and maintenance of the installed solar panels become more critical as there are potential menaces such as hot spot effects and DC arcs, which may cause fire accidents to the solar panels. In order to minimize the risks of fire accidents in large scale applications of solar panels, this review focuses on the latest techniques for reducing hot spot effects and DC arcs. The risk mitigation solutions mainly focus on two aspects: structure reconfiguration and faulty diagnosis algorithm. The first is to reduce the hot spot effect by adjusting the space between two PV modules in a PV array or relocate some PV modules. The second is to detect the DC arc fault before it causes fire. There are three types of arc detection techniques, including physical analysis, neural network analysis, and wavelet detection analysis. Through these detection methods, the faulty PV cells can be found in a timely manner thereby reducing the risk of PV fire. Based on the review, some precautions to prevent solar panel related fire accidents in large-scale solar PV plants that are located adjacent to residential and commercial areas

Analysis and simulation of shading effects on photovoltaic cells

The usage of conventional energy applications generates disproportionate emissions of greenhouse gases and the consumption of part of the energy resources available in the world. It has become an important problem which has serious effects on the climatic change. Therefore, it is crucial to reduce these emissions as much as possible. To be able to achieve this, renewable energy technologies must be used instead of conventional energy applications. Solar Photovoltaic (PV) technologies do not release greenhouse gas emissions directly and can save more than 30 million tonnes of carbon per exajoule of electricity generated relative to a natural gas turbine running at 45% efficiency. Shadowing is one of the most important aspects that affects the performance of PV systems. Consequently, many investigations through this topic are being done in order to develop new technologies which mitigate the impact of shadowing during PV production. In order to minimise the impact of shadowing it is desired to be able to predict the performance of a system with PV-modules during shadowing. In this thesis a simulation program for calculating the IV-curve for series connected PV-modules during partial shadowing has been developed and experimentally validated. PV systems modelling and simulation in LTspice environment has been presented and validated by means of a comparative analysis with the experimental results obtained in a set of tests performed in the laboratory of Gävle University. Experimental measurements were carried out in two groups. The first group corresponds with the experiments done in the string of six modules with bypass diodes while the measurements of the second group have been performed on a single PV module at HIG University. The simulation results of both groups demonstrated a remarkable agreement with the experimental data, which means that the model designed at LTspice supposes a very useful tool that can be used to study the performance of PV systems. This tool contributes to the investigations in this topic and it aims to benefit future installations providing a better knowledge of the shading problem. The master’s thesis shows an in-depth description of the required method to design a PV cell, a PV module and a PV array using LTspice IV and the input parameters as well as the needed tests to adjust the models. Moreover, it has been carried out a pedagogical study describing the effect that different shadow configurations have in the performance of solar cells. This study facilitates the understanding of the performance of PV modules under different shadowing effects. Lastly, it has also been discussed the benefits of installing some newer technologies, like DC-DC optimizers or module inverters, to mitigate the shadowing effects. The main conclusion about this topic has been that although most of the times the output power will be increased with the use of optimizers sometimes the optimizer does not present any benefits

Reviewing the External Factors that Influence PV Output Performance in the Irish Climate

The literature review presented in this paper centres on the external factors that influence PV output performance in the Irish climate. Solar photovoltaic (PV) panels show long-term performance degradation, resulting in lower like-per-like efficiencies and performance ratios. Manufacturers of solar photovoltaic modules typically guarantee a life span of more than 20 years. But to meet such guarantees, it is necessary to track and mitigate PV module degradation during this period, and identify maintenance and repair requirements beyond this period. Solar PV modules degrade over time, becoming less efficient, less reliable, and, eventually, inoperable. External factors such as solar irradiance, dust deposition, shading, ambient temperature, operating cell temperature, humidity and wind velocity affect the PV output performance in the Irish climate. This is because the performance of a PV system is heavily influenced by the meteorological conditions of the site locations. Therefore, this paper reviews the external factors that influence PV output performance in the Irish climate

Experimental observations on hot-spots and derived

The hot-spot phenomenon is a relatively frequent problem occurring in current photovoltaic generators. It entails both a risk for the photovoltaic module’s lifetime and a decrease in its operational efficiency. Nevertheless, there is still a lack of widely accepted procedures for dealing with them in practice. This paper presents the IES–UPM observations on 200 affected photovoltaic modules. Visual and infrared inspection, as well as electroluminescence, peak power rating and operating voltage tests have been carried out. Thermography under steady state conditions and photovoltaic module operating voltage, both at normal photovoltaic system operating conditions, are the selected methods to deal in practice with hot-spots. The temperature difference between the hot-spot and its surroundings, and the operating voltage differences between affected and non-affected photovoltaic modules are the base for establishing defective criteria, at the lights of both lifetime and operating efficiency considerations. Hot-spots temperature gradients larger than 20 °C, in any case, and larger than 10 °C when, at the same time, voltage operating losses are larger than the allowable power losses fixed at the photovoltaic module warranties, are proposed as rejecting conditions for routine inspections under contractual frameworks. The upper threshold of 20 °C is deduced for temperate climates from the basic criterion of keeping absolute hot-spot temperatures below 20 °C