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A new topology to mitigate the effect of shading for small photovoltaic installations in rural sub-Saharan Africa

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Abstract

Many field researchers have in the past grappled with the problems of energy loss and panel damage as a result of shading and staining of PV panels after installation. A number of solutions have been proposed to try and minimize the effects of this problem in the field. The problem with all these solutions is that they address inter-panel connection topologies for very large installations. No particular attention has been paid to the topologies of individual panels. In sub-Saharan Africa most installations are single panel solar home systems and therefore small shading can result in an entire installation being disabled.This paper aims to study the effect of shading and staining on photovoltaic modules and propose a new topology that will reduce the effect of shading on the performance of individual photovoltaic modules.

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... The efficiency improvement of operating PV systems has become a research target. Abnormal operation of a PV system is often the cause of major power loss and, at worst, of zonal or total destruction of solar modules [13,16,21,23]. ...
... Table 3 Comparison between the results obtained from measurements and from the three models Eqs. (12), (23), and (26). Table 3 summarizes the results of measurements and calculations obtained using the three models. ...
... Eqs. (12), (23), and (26) with the experimental values associated to our application. The model equation with the quadratic terms (Eq. ...
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The aim of this study is to show how the Design of Experiments (DoE) Method can be put into use as a practical method to model an operating photovoltaic PV generator. Experiments were carried out and the whole current- voltage characteristics (I-V) were drawn. A mathematical model describing the variations of the Open-circuit voltage (Voc) and Short-circuit current (Isc) versus solar irradiance level and temperature was obtained with the DoE Method. This model is a predictive model. With the help of the HIDE software we can simulate the PV panel behavior and forecast, in real time, the variations of Voc and Isc anywhere in the surveyed experimental domain.
... The efficiency improvement of operating PV systems has become a research target. Abnormal operation of a PV system is often the cause of major power loss and, at worst, of zonal or total destruction of solar modules [13,16,21,23]. ...
... Table 3 Comparison between the results obtained from measurements and from the three models Eqs. (12), (23), and (26). Table 3 summarizes the results of measurements and calculations obtained using the three models. ...
... Eqs. (12), (23), and (26) with the experimental values associated to our application. The model equation with the quadratic terms (Eq. ...
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This paper presents a novel application of the Design of Experiments (DoE) method as a practical method to detect any dysfunction of an operating photovoltaic (PV) panel. Electrical field measurements data are used to evaluate the PV panel parameters once and for all. A mathematical model describing the variations of the maximum power versus solar irradiance level and temperature was obtained with the Design of Experiments method. This model is a predictive model. It assesses the value of the maximum power delivered anywhere in the experimental domain. Given a known solar irradiance level and temperature, any discrepancy between the calculated and measured maximum power values signals any dysfunctional operation so that appropriate action can be taken such as maintenance or repair. A complete analysis of the measurements is performed to optimize the method. Firstly, the basic elements of the Design of Experiments method are presented. Three models are then considered: the non-standard model with four trials, the non-standard model with 11 trials, and finally a model with 4 points recalculated to be placed at the vertices of the study area. A practical method of implementation is then proposed.
... Self shading and environment shading will reduce the electricity output. Environment shading will reduce power output from BIPV up to 25%-30% from its maximum ability [11]. Meanwhile for self-shading, the use of 6 dioda in one single panel will minimize the effect of self shading [11]. ...
... Environment shading will reduce power output from BIPV up to 25%-30% from its maximum ability [11]. Meanwhile for self-shading, the use of 6 dioda in one single panel will minimize the effect of self shading [11]. Optimal proportion between transparant materials and opaque PV moduls to total facade area is another factor that should be concerned when analyzing BIPV efficiency. ...
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BIPV is an architectural concept that related to energy contribution. The system has functions of producing electricity as well as building form giver. The effectivity of BIPV depends on solar radiation received. Meanwhile, the solar radiation received depends on numbers of solar receiving area and environmental shading. Environmental shading will decrease the effectivity of BIPV. But, integrated configuration of folding-BIPV is expected to create more numbers of solar receiving area. The integrated configuration of folding-BIPV will create optimum BIPV, both in electrical generation and building form giver. Experiment to low rise office building in tropical climate is done by giving folding treatment. The experiment also considers about environmental shading. Evaluation is done by analyzing and optimizing the numbers and uniformity of solar radiation received. Simulation with ARCHIPAK 5.1 is used as experimental research tool. The simulation is used to calculate annual radiation received (kWh/m ² ) from folding-BIPV configuration. Manual calculation is used to calculate total annual radiation received (kWh) and uniformity percentage. Gradient diagram is used to do the optimation. Result of this research is an optimation of electrical energy generation in low rise office building which use folding-BIPV concept.
... The window area should not exceed 15-20% of the total surface area [42][43][44]. • Shading: Mandate the use of exterior shading devices such as overhangs, louvers, and light shelves to reduce cooling loads [45][46][47]. • Renewable Energy: Ensure that at least 50% of the building's energy needs are met through on-site renewable energy sources, such as solar photovoltaic (PV) panels and solar hot water systems. Promote the use of battery storage where feasible. ...
... Promote the use of battery storage where feasible. Assess the solar energy generation potential based on site-specific irradiation data [45][46][47]. • Air Tightness: Implement air sealing measures and weatherproofing techniques to limit air leakage to 1-2 air changes per hour at 50 Pascals [48,49]. • Appliances: Establish minimum efficiency standards for appliances, equipment, and electronics used within the building [50]. ...
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High energy consumption has far-reaching consequences for the natural world, including the acceleration of climate change, the acceleration of environmental deterioration, and the acceleration of air pollution caused by the combustion of fossil fuels to generate electricity. However, there are still many obstacles to implementing the nZEB idea, notably in sub-Saharan Africa, where energy consumption and pollutant emissions from buildings are particularly high. To facilitate a smooth transition to nZEB in the countries of sub-Saharan Africa, this article focuses on Cameroon, Senegal, and Côte d'Ivoire. Guidelines for making a smooth transition to net-zero energy buildings in sub-Saharan Africa are provided, as are examples of strategies that might be used to minimize energy consumption in buildings. The path has been shown to consist of the following steps: conducting a baseline assessment; creating building energy codes and standards; conducting a stakeholder analysis; carrying out capacity building and awareness-raising; setting up financing mechanisms and incentives; creating a strong supply chain; setting up a monitoring and evaluation framework; piloting nZEB projects; disseminating best practices; and scaling up adoption. With this plan in place, sub-Saharan Africa can make the most of its time and resources as it makes the move to near-zero energy buildings.
... The original DIRECT algorithm divides all potential optimal to search for the GP globally and locally at the same time. But the dividing strategy is different [53], [54], thus the conditions are explained mathematically [52]. ...
... With the help of change in duty cycle (19) and (20), the tracking efficiency and speed of partially shaded conditions are 0.5% less than the STC. If number of cycles are more per second then the efficiency and tracking speed are more [54]. ...
... The unshaded cell in then forced to produce less energy. In this situation there is no risk of destruction and the MPPT will tend remain in it while the shadow is cast over the PV module [Ubisse andSebitosi, 2009, Picault et al., 2010b]. Now that the effects of the shadow have been introduced, this chapter takes a closer look at what shadow is and how it can be modeled from a PV perspective. ...
... Third, there is no consensus in the literature. Some authors only take the geometry of the shadow into consideration [Picault, 2010, Wang and Hsu, 2009, Ubisse and Sebitosi, 2009, Drif et al., 2008, Fujisawa and Ohya, 2003, Kovach and Schmid, 1996. While others focus themselves on the opacity of the shadow [Alonso-Garcia et al., 2006, Safari and Mekhilef, 2011, Ramos-Paja et al., 2010. ...
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Photovoltaic energy rates among the most mature renewable sources currently available in the market. However, its growing use in urban environment has met with an important obstacle: shadows. Their study present a two-fold challenge: understanding what they are and how they can be mitigated. While many authors have proposed different solutions for this problem, very few have tried to understand the shadow in its complexity. This thesis seeks, at the same time, a comprehensive view on the shadow itself while proposing a new solution to mitigate it. The comprehensive view of the shadow is proposed through an intermittency theory, where its optical properties and electrical consequences are taken into account. This theory provides the elements to review the current literature into a new perspective. The available solutions are, then, divided into two families: series and parallel. Series solutions employ several structures, each extracting the power of a reduced number of photovoltaic cells. As a consequence the impact of the shadow is restricted. Parallel solutions use few structures to redistribute the current between shaded and unshaded photovoltaic cells, thus sharing the impact of the shadow. The new solution proposed to mitigate the shadow is a parallel system called PV Equalizer. Inspired from its battery equivalent, it has a different topology with a high integration potential, easily scalable but seemingly difficult to control. To prove its concept, a study is conducted to determine its functions. It is found to be capable of not only mitigating but also detecting the shadow. These functions are characterized and their results used to conceive a control algorithm. Finally, this algorithm is tested and validated in a prototype under real operating conditions. The system detected the presence of the shadow, chose the best way to mitigate it and raised the power output by roughly 40 %.
... The unshaded cell in then forced to produce less energy. In this situation there is no risk of destruction and the MPPT will tend remain in it while the shadow is cast over the PV module [Ubisse andSebitosi, 2009, Picault et al., 2010b]. Now that the effects of the shadow have been introduced, this chapter takes a closer look at what shadow is and how it can be modeled from a PV perspective. ...
... Third, there is no consensus in the literature. Some authors only take the geometry of the shadow into consideration [Picault, 2010, Wang and Hsu, 2009, Ubisse and Sebitosi, 2009, Drif et al., 2008, Fujisawa and Ohya, 2003, Kovach and Schmid, 1996. While others focus themselves on the opacity of the shadow [Alonso-Garcia et al., 2006, Safari and Mekhilef, 2011, Ramos-Paja et al., 2010. ...
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Photovoltaic energy rates among the most mature renewable sources currently available in the market. However, its growing use in urban environment has met with an important obstacle: shadows. Their study present a two-fold challenge: understanding what they are and how they can be mitigated. While many authors have proposed different solutions for this problem, very few have tried to understand the shadow in its complexity. This thesis seeks, at the same time, a comprehensive view on the shadow itself while proposing a new solution to mitigate it. The comprehensive view of the shadow is proposed through an intermittency theory, where its optical properties and electrical consequences are taken into account. This theory provides the elements to review the current literature into a new perspective. The available solutions are, then, divided into two families: series and parallel. Series solutions employ several structures, each extracting the power of a reduced number of photovoltaic cells. As a consequence the impact of the shadow is restricted. Parallel solutions use few structures to redistribute the current between shaded and unshaded photovoltaic cells, thus sharing the impact of the shadow. The new solution proposed to mitigate the shadow is a parallel system called PV Equalizer. Inspired from its battery equivalent, it has a different topology with a high integration potential, easily scalable but seemingly difficult to control. To prove its concept, a study is conducted to determine its functions. It is found to be capable of not only mitigating but also detecting the shadow. These functions are characterized and their results used to conceive a control algorithm. Finally, this algorithm is tested and validated in a prototype under real operating conditions. The system detected the presence of the shadow, chose the best way to mitigate it and raised the power output by roughly 40 %.
... In other words, the current-voltage (I-V) curves of modules must be similar. For instance, if a shadowed or damaged solar cell in a string causes that the cell produces current lower than the other cells then it will block the current flow from healthy cells to the output terminal of the string [1][2][3]. The generating current of solar cell depends strongly on irradiance level. ...
... The proposed method is intended to find the global MPPs under the non-uniform operating conditions. This is very difficult for classical MPPT controllers [3,34]. In this reason, an intelligent technique is required [1]. ...
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Mismatching losses reduction of photovoltaic (PV) array has been intensively discussed through the increasing penetration of residential and commercial PV systems. Many causes of mismatching losses have been identified and plenty of proposed methods to solve this problem have been recently proposed. This paper deals with reducing method of mismatching losses due to the non-uniform irradiance conditions. It is well-known that a certain number of multiple peaks occur on the power–voltage curve as the number of PV modules in one-string increases under non-uniform operating conditions. Since the conventional control method only drives the operating points of PV system to the local maxima close to open circuit voltage, only small portion of power can be extracted from the PV system. In this study, a radial basis function neural network (RBF-ANN) based intelligent control method is utilized to map the global operating voltage and non-irradiance operating condition in string and central based MPPT systems. The proposed method has been tested on 10 × 3 (2.2 kW), 15 × 3 (2.5 kW) and 20 × 3 (3.3 kW) of series–parallel PV array configuration under random-shaded and continuous-shaded patterns. The proposed method is compared with the ideal case and conventional method through a simple power–voltage curve of PV arrays. The simulation results show that there are significant increases of about 30–60% of the extracted power in one operating condition when the proposed method is able to shift the operating voltage of modules to their optimum voltages.
... In other words, the current-voltage (I-V) curves of modules must be similar. For instance, if a shadowed or damaged solar cell in a string causes that the cell produces current lower than the other cells then it will block the current flow from healthy cells to the output terminal of the string [1][2][3]. The generating current of solar cell de- pends strongly on irradiance level. ...
... The proposed method is intended to find the global MPPs under the non-uniform operating conditions. This is very difficult for clas- sical MPPT controllers [3,34]. In this reason, an intelligent tech- nique is required [1]. ...
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) Abstract -- The paper proposes the short circuit identification method for induction motor winding. Four states of motor operation are defined as normal operation, starting of short circuit, steady state short circuit and ending of short circuit. The neural network based detection system is utilized to distinguish these defined operation states. Motor current is processed using discrete wavelet transformation to extract energy component of high frequency signal, which is latterly used for variable detection. Three different wavelet types varied by five levels of transformation are evaluated using linear discriminant analysis (LDA) in order to obtain the most appropriate wavelet filter for detection task. A laboratory experiment is performed to validate the accuracy of the proposed method.
... PV installations can experience partial or complete shading leading to a reduction in electrical energy generation. Studies have measured this reduction to be between 10 to 30 percent in soft and hard shading conditions (Feng et al. 2023;Ubisse and Sebitosi 2009;Zomer and Rüther 2017). ...
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Previous studies have found the potential of Building Integrated Photovoltaic (BIPV) implementation on vertical facades. The implementation was suggested for buildings with a minimum of 45 percent window-to-wall ratio (WWR). This number is quite challenging for tropical buildings where the suggested WWR ranges around 20 to 40 percent. Furthermore, the installation may appear less efficient due to the lower irradiance received on tropical vertical facades. Given the abundance of vertical facades in tropical high-rise buildings, there exists an opportunity to offset power reduction. Therefore, this study aims to determine the feasibility, influencing factors, and approach for installing building-integrated thin film transparent photovoltaics (BITPV) in tropical regions, focusing on energy production. The objective is achieved through a combination of literature review and simulation. Three layout configurations on three different geographical locations, which present a typical classroom module for school buildings, are observed. Treatment is applied based on orientation, WWR, and the cell coverage ratio. The feasibility is shown by at least 23 percent energy substitution promoted by several configurations. East is suggested for classrooms with 1:1 and 3:2 modules, while north is suggested for classrooms with 2:3 modules. For buildings with minimum WWR (20 percent), TPV installation with ≥40 percent cell coverage ratio (on the specified orientation) is suggested to achieve the mixenergy use target. Additionally, this study presents the influencing factors and design approach for BITPV to provide a comprehensive understanding of the subject.
... Environment shading will reduce power output from BIPV up to 40%-60% from its maximum ability [10]. Meanwhile for self-shading, previous study shows that using 6 dioda in one single panel will minimize the effect of self shading [11]. Optimal proportion between transparant materials and opaque PV moduls to total facade area is another factor that should be concerned when analyzing BIPV efficiency. ...
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Efficiency of BIPV measured by comparing electricity output and electricity demand. Electricity output generized by BIPV depends on the amount of solar radiation received by PV panel. Some factors that affect the amount of radiation received are the tilt angle and the orientation angle of PV panel. This research try to rise electricity output by collaborating this factor with orientation principle in folding concept. The collaboration results in bigger surface area to receive radiation. Meanwhile, the reducement of electricity demand will be described in relation with users behaviour, both individual behaviour and communal behaviour. As the object taken in this research is an office building, communal behaviour will take more impact to reduce energy demand. Policies and strategies related to energy efficiency made by central operational management in office building will control communal behaviour.
... This experiment also helps us analyze the effects of power output due to fast-and slowmoving shades of the vehicle moving at low speed. It is important to analyze the effects of shading on electricity production because shading over 5% of the area of the solar panel can reduce the power output as low as to 50% [96]. 2019 Toyota Camry LE car was used to conduct this experiment and its tire specification is P215/55R17. ...
Thesis
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The concurrent energy shortages of non-renewable energy resources have directed attention to the potential of harvesting renewable energy resources from roadway. Strong incentives to a sustainable solution to this problem have led to the design of innovative pavement solar panel technology. This research is based on designing and developing a solar panel for roadway application. The designed prototype consists of a thin film solar panel, a transparent cover to protect the solar panel and a wooden frame to support the whole configuration. Since the pavement is exposed to solar radiation throughout the daytime, the pavement embedded solar panel will be utilized to harvest the solar energy and store with the integration of storage system and convert into electricity. It should also provide service during power failures in remote areas without electrical utilities. The main challenge of the project is the selection of proper transparent cover since it should bear the traffic loads and should not impair the transparency at the same time. The types of transparent covers chosen for this study are polycarbonate samples of varying thicknesses, textured glass grit samples, and textured float glass with corundum skid-resistant coating on the surface. The percentage transmittance of each sample was determined using transmittance spectroscopy in the visible light range. The percentage transmittance for the 10 mm, 12 mm, and 16 mm polycarbonate samples were 87%, 84%, and 82%, and for the textured glass grit sample it was 40% at each wavelength in the visible light range. The finite element analysis was carried out to replicate the in-situ installation of the solar panels with polycarbonate shield covers to determine the structural feasibility. The prototype panel was subjected to static and dynamic loading and the stress, strain and deflection analysis was performed and compared with a typical pavement model without any transparent cover. Finite element analysis demonstrated that the panel would not fail by fatigue under the loading condition considered. Power generation data from these solar panels were collected and compared in a wide range of weather conditions and different seasons to assess the relationship of power and other environmental factors such as irradiance, illuminance, temperature, and cloud cover Since the panels were designed for pavement application, the panels were subjected to vehicular loading during the field tests to determine the decline in the power output due to shading of vehicles. Another purpose of the field test is to analyze whether the transparent covers face any disruption, damage, or failure under the wheel loading. Although polycarbonate samples and textured float glass samples can withstand traffic loads, the textured glass grit sample failed in fracture without any warning of failure under wheel loading. Experimental results also showed that 12-inch × 12-inch pavement solar panels generate an average of 2.2 W in sunny conditions but produce less power in cloudy conditions. Based on the power production data of SP10 from 12 PM to 6 PM, its feasibility was assessed for utilizing in the smart pedestrian system to lighten the crosswalk and alert the drivers of approaching vehicles.
... The research process begins with the selection of a location. The parameters used to select the site are accessible to solar irradiance and minimum environment shading conditions (Ubisse & Sebitosi, 2009). Once the site is selected, observation is done to determine the building's energy consumption and surface availability. ...
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generated from a variety of sources, both renewable and nonrenewable. Switching from nonrenewable to renewable energy sources is one of many strategies that can be used to achieve net-zero buildings. In Indonesia, this strategy is very feasible due to its abundant renewable energy resources, particularly solar energy. This research presents a school building as the proposed case. The school, SCK Citra Garden, is chosen as the pilot project due to its access to solar radiation and its minimum shading conditions. Using Helioscope software, BIPV modelling was simulated on its roof, and the electrical energy output from BIPV was calculated. The substitution percentages of BIPV energy output for conventional electrical energy consumed by the building were then measured. This percentage was compared to the National Energy Mix target and Greenhouse Gas Standard to assess its performance towards net-zero school buildings. The result shows that BIPV has a good performance. Even though the substitution percentage is still below the national energy mix target, it exceeds the greenhouse gas standard target for on-site renewable energy tools.
... External conditions, such as the effect of solar panel shading and a country's solar spectrum are vital to consider when designing solar panels, as their optimisation could improve energy generation capacity (Simon & Meyer, 2008;Ubisse & Sebitosi, 2009). For example, a higher capacity system was required in one region of South Africa compared to another, in order to generate the same amount of energy, which was attributed to solar irradiance differences (Azimoh, Klintenberg, Wallin, & Karlsson, 2015b). ...
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Solar home systems (SHSs) have seen rapid growth and have proven to be a viable source of electricity for households due to their capability to reach remote users that do not have access to grid systems. Based on a comprehensive literature review of 139 papers focussing on SHSs in Sub-Saharan Africa, this paper highlights the key trends, research gaps and policy recommendations. The literature was categorised into four themes: institutional, technology, viability and user-centric. The review finds that the current primary themes of research are technology, user-centric and viability. This highlights the need for further research into the institutional barriers of SHSs, as well as the regulatory frameworks and incentives needed to increase their adoption. The most popular topics discussed in the reviewed literature included SHS business models, SHS design, the energy demand of end-users and barriers to SHS adoption. The authors also identified paucity of research in countries with low electrification rates, highlighting new locations for SHS research.
... Several studies and research studies have evaluated the performance of photovoltaic modules in different climatic conditions, in particular the effect of sand dust accumulation and partial shading on energy loss in photovoltaic modules and arrays [14][15][16][17][18][19][20][21]. ...
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Usually, manufacturers provide PV panels, accompanied with data measured under Standard Test Conditions (STC), i.e. determined at AM1.5 with an irradiance of 1000W/m2 and a cell temperature equal to 25 C. In fact, these conditions do not reflect the reality of natural operation of PV panel conditions and these functional data associated with the real panel operating point may vary from one environment to another due to the change in weather conditions. The characterization of different types of PV panels under natural conditions of operation is, therefore, necessary in order to have a global view about the true electrical performance of different technologies at a given site. This work evaluates the influence of climatic conditions on the behavior of QS-60DGF module which has been installed at the Unit of Research in Renewable energy URERMS Adrar in the southern Algeria. The degradation evaluation of QS-60DGF module with different defects was performed, using (I-V/P-V) characteristics under daily weather conditions and the the visual inspection such as glass breakag. This study is to investigate the degradation rates of a-Si PV module after more than one year of outdoor exposure in desert conditions.
... Therefore, it is necessary to quantify the shading losses through a combination of the geometric shading factor and its electrical impact on the PV array, which leads to an effective shading factor (FES). Several methods already exist to transform the geometric shading factor into the effective shading factor (Kawamura et al., 2003;Alonso-García et al., 2006;Karatepe et al., 2007;Karatepe et al., 2008;Silvestre and Chouder, 2008;Ubisse and Sebitosi, 2009;Ishaque et al., 2011;Wang and Hsu, 2011;Rodrigo et al., 2013;Díaz-Dorado et al., 2014), many of which are based on I-V curves. ...
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Photovoltaic (PV) systems can be affected by complex shading. Software solutions have been developed over time, offering an ever-increasing set of simulation possibilities to evaluate the energy losses induced by shading on PV systems. Yet, several practical cases cannot be satisfactorily solved by means of existing tools. This study explores the possibilities offered by the powerful graphics processing units (GPUs) that have been developed for the video game industry. It is shown that complex shading problems applicable to PV systems can be satisfactorily analyzed, both visually and quantitatively, with a focus on the rasterization process for an in-depth evaluation of the shading dynamics that affect the direct component of solar irradiance. This analysis can be conducted at high spatiotemporal resolution for maximum accuracy. Its application is illustrated based on several practical cases that are typically encountered in the world of PV systems engineering, such as building-integrated PV (BIPV) on large and complex buildings, urban PV planning, or PV plants equipped with tracking systems and installed on uneven ground. Additional advantages are also presented, including the full integration of the GPU-based shading simulation tool into a Web browser, and the use of online input information.
... Many rural electrification assessment studies have been conducted. Some studies evaluate a technology to be used to promote rural electrification; examining its components, analyzing performance potential, and assessing the performance of the system in the targeted rural communities (Huacuz et al., 1995;Krauter, 2004;Mukerjee, 2007;Heal, 2009;Shaahid and El-Amin, 2009;Ubisse and Sebitosi, 2009;Pappas, 2012). Such studies address the economic and technical aspects (and viability) of the technologies used to promote rural electrification. ...
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This research is driven by the goal to develop human survivability studies, a solution oriented, trans-disciplinary academic approach for resolving multiple complex societal challenges. Given persisting poverty and inequality in rural areas of developing countries, as well as their vulnerability to the effects of climate change, there are high expectations that rural electrification using renewable energy can contribute to their sustainable development. We therefore use a sustainability framework to assess the contributions of four electrification projects in rural Kenya in ensuring the long-term well-being of local residents and future generations. Our results show that off-grid electrification projects run by the private sector were the better performers in the assessment. While more research is necessary to improve robustness, our preliminary policy recommendations are that Kenyan policy makers should provide further support to private sector-led off-grid solar electrification efforts.
... Environment shading will reduce power output from BIPV up to 40%-60% from its maximum ability (Urbanetz, Xomer, & Ruther, 2011). Meanwhile, for self-shading, Ubisse & Sebitosi (2009) has explained that using 6 diodes in one single panel will minimize the effect of self-shading. The optimal proportion of transparent materials and opaque PV modules to total facade area is another factor that should be concerned when analyzing BIPV efficiency. ...
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This research would compare optimal configurations of Folding Wall-BIPV to flat wall-BIPV (as base case model). Experiment with simulation as it tools was used as a method to get the optimal configuration of Folding Wall-BIPV. Related to second strategy towards LCB (Low Carbon Building), this research calculated how much electricity energy was produced by renewable energy resource (created by the integrated configuration of folding wall-BIPV) could substitute electricity energy produced from fossil fuel and how much was the uniformity ratio generated from both side of Folding Wall-BIPV. This research used the experimental methods. The data was collected from Badan Meteorologi dan Geofisika Surabaya and then hold the pretest, treatment, and post-test condition for its methods. The result shows that integrated configuration of folding wall-BIPV match to the second strategies adopted by LCB. It is about switching to renewable energy sources to substitute fossil fuel energy sources.
... E is the irradiance level and c 0 is a reflection coefficient [15]. When no load is connected, the current flows through the diode D determining the solar cell's open voltage V OC [17]. The amount of irradiation colliding with the PV surface determines the short circuit current (I sc ), and from the model shown above it is simply the light generated. ...
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Photovoltaic solar technology is now being widely investigated for implementation in the UAE as a possible renewable energy source. Currently the main emphasis is on the accessible areas but remote locations are now being explored for the possibility of large scale deployment. However due to the environment and location certain measures such as regular cleaning must be considered to ensure the efficient operation of the PV panels. This paper investigates the cost of current developed cleaning technologies available in the Gulf region, highlights their advantages and disadvantages and the time needed to recoup initial investment.
... Environment shading will reduce power output from BIPV up to 40%-60% from its maximum ability (Urbanetz, et al, 2011). Meanwhile for selfshading, Ubisse, et al (2009) explained that using 6 dioda in one single panel will minimize the effect of self shading. Optimal proportion between transparant materials and opaque PV moduls to total facade area is another factor that should be concerned when analyzing BIPV efficiency. ...
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BIPV (Building Integrated Photovoltaics) refers to the application of PV (photo-voltaic) in which the system as well as having the function of producing electricity, also takes the role of building form and element. Empirical facts show that PV in BIPV system is integrated as add-on element only. They didn’t take the role as form giver yet. Electricity output generized by BIPV depends on the amount of solar radiation received by PV panel. There are some factors affect the amount of radiation received. Two of them are tilt and orientation angle of PV panel, and total area prepared for PV panel installment.This research try to rise electricity output by collaborating those two factors with orientation and multiplicity principle in folding concept. Folding element can be arranged based on optimum tilt and orientation angle to reach maximum radiation supply. Also, the collaboration results in bigger surface area to receive higher solar irradiance. Experiment with simulation as it tools will be used as research method to get the optimal configuration of Folding Roof-BIPV.
... The aging and degradation of photovoltaic modules is also dependent on climatic and environmental conditions [12,13]. Several research works and studies have treated the evaluation of the performance of photovoltaic modules under different climatic conditions, in particular the effect of sand dust accumulation and partial shading on the power loss in photovoltaic modules and arrays [14][15][16][17][18][19][20][21]. The objective of this work is to study the effect of partial shading and deposition of sand dust on power loss in photovoltaic modules (ISOFOTON 100), we perform also experimental investigation of the effect of varying temperature and irradiation on PV performance parameters for one day. ...
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The main objective of this study is to investigate the impact of climatic conditions on the performance of photovoltaic modules installed in the desert region in south of Algeria. Firstly, the performance of ISOFOTON 100 module under daily weather conditions is evaluated. Next, the effects of partial shading and accumulation of sand dust for a period of two months on power loss and the current-voltage characteristics of photovoltaic modules are examined. Finally, the visual inspection of the degradation of the UDTS 50 modules such as discoloration of encapsulant and delamination show the influence of high temperature and the other climatic factors in the Saharan environment after a long time exposure of more than 10 years observed in the field at the Unit of Research in Renewable energy URERMS Adrar. The performance degradation is also assessed using (I-V and P-V) curves normalized at STC condition compared with the nominal STC data given by the manufacturer. The experimental results show that the performance parameters such as maximum output current (Imax), maximum output voltage (Vmax), maximum power output (Pmax), open-circuit voltage (Voc), short-circuit current (Isc) and fill factor (FF) of UDTS 50 modules are degraded after these years of exposition.
... The use of sophisticated controllers to enhance performance of SHS has been achieved in a study like [34]. Bypassed diodes has been used to mitigate the effect of shading, thereby maintaining the power quality of a shaded solar panels [35]. Most of these solutions concentrated on the technical design of solar panels and its paraphernalia. ...
... Shading panels greatly reduce system performance and output power presents several maxima [2], while tracking algorithms of the Maximum Power Point (MPPT) are usually based on the assumption that the power curve generated has a single peak [3,4,1,5]. In recent years, the impact of shading on the energy performance of photovoltaic systems has been discussed [6][7][8]. Before attempting to eliminate or reduce the effects of mismatch, a deep understanding of their origin and behavior is necessary. Since field tests are long term, costly, and highly dependent on climatic conditions, it is necessary to define a simulation-based model that allows proper inclusion of the shading effects. ...
... Output power changes of grid-connected PV systems due to moving clouds, inducing rapid changes in irradiance incident on the PV array, is studied in [15]- [17]. Methods have been proposed for improving PV system performance under partial shading conditions, mainly focusing on alterations of PV array configuration in terms of bypass diode number [18] and string connection patterns [19]. ...
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Photovoltaic (PV) system performance is influenced by several factors, including irradiance, temperature, shading, degradation, mismatch losses, soiling, etc. Shading of a PV array, in particular, either complete or partial, can have a significant impact on its power output and energy yield, depending on array configuration, shading pattern, and the bypass diodes incorporated in the PV modules. In this paper, the effect of partial shading on multicrystalline silicon (mc-Si) PV modules is investigated. A PV module simulation model implemented in P-Spice is first employed to quantify the effect of partial shading on the I-V curve and the maximum power point (MPP) voltage and power. Then, generalized formulae are derived, which permit accurate enough evaluation of MPP voltage and power of mc-Si PV modules, without the need to resort to detailed modeling and simulation. The equations derived are validated via experimental results.
... Each cell may have its own bypass diode to reduce the negative effect of mismatching conditions. On the other hand, this configuration is not recommended by manufacturers because of economic reasons and difficulties in the assembly of lamination PV module [6]. The multiple-local MPPs on power – voltage curve of PV arrays make much more difficult to track the global MPP for a conventional controller. ...
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The interest in improving the efficiency of photovoltaic (PV) system has emerged because of increasing the number of home-based or small-scale PV power system. However, the home-based PV system is vulnerable to the non-uniform operating conditions. Under such circumstances, multiple-local maximum power points (MPPs) occur on the power-voltage characteristics and an advanced control algorithm is required to track the global MPP. It is very difficult to provide a sophisticated control algorithm because of the non-linear characteristics of PV system. This study describes the potential to improve the efficiency of PV arrays under non-uniform operating conditions by using the conventional hill-climbing MPP tracking method in total cross tied (TCT) connected PV arrays, in which each group of series connected solar cells that belong to single bypass diode is interconnected. The various scenarios were tested and the results indicate that the efficiency of the proposed system is much higher than that of the same size of series-parallel (SP) PV array configuration.
... This voltage varies depending on the properties of each type of solar cell, but for most silicon cells, it is in the range 0.5-0.6 V (the normal forward voltage of a p-n junction diode) [8]. The series resistance (R s ) represents the ohmic losses of the cell and the shunt resistance (R sh ) represents the losses due to diode leakage currents. ...
Conference Paper
Full-text available
This paper highlights and presents a solution to reduce the effect of shading and staining on photovoltaic (PV) modules on offshore platforms. Knowledge of the negative consequences of this factor on the PV panels' output has led to recognizing the importance of regular cleaning. Due to the system's location, the research had to take into consideration several constraints such as lack of power supply, availability of distilled water, maintenance and available space. Microcontroller technology was used as the electrical basis for the design because of its many advantages especially due to its low power consumption.
... Such problems have presumably not been reported in recent literature on account of technological development in inverters and other electronic and electrical balance of systems. One of the recent studies has highlighted the impact of shading and staining on overall energy loss for single module solar home systems that are largely found in Africa and other developing countries [153] . According to this paper, the inter-panel connection topologies for very large installations are addressed to some extent by researchers world wide. ...
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The challenges of providing electricity to rural households are manifold. Ever increasing demand–supply gap, crumbling electricity transmission and distribution infrastructure, high cost of delivered electricity are a few of these. Use of renewable energy technologies for meeting basic energy needs of rural communities has been promoted by the Governments world over for many decades. Photovoltaic (PV) technology is one of the first among several renewable energy technologies that was adopted globally as well as in India for meeting basic electricity needs of rural areas that are not connected to the grid. This paper attempts at reviewing and analyzing PV literature pertaining to decentralized rural electrification into two main categories—(1) experiences from rural electrification and technology demonstration programmes covering barriers and challenges in marketing and dissemination; institutional and financing approaches; and productive and economic applications, (2) techno-economic aspects including system design methodologies and approaches; performance evaluation and monitoring; techno-economic comparison of various systems; and environmental implications and life cycle analysis. The paper discusses the emerging trends in its concluding remarks.
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Full-text available
Solar energy generated by photovoltaic (PV) technology can be supplied to standalone systems, as it combines efficiency and cost-effectiveness. However, this combination is achieved only after considering the effects of shading, which can significantly influence electrical output. The primary factor that influences the use of solar energy in electricity generation is irradiation. PV cells are significantly impacted by shading, where the output of the PV cell reduces in the presence of a shadow. In this study, the researchers have presented an experimental analysis of how shading affects two PV cells, using the series and parallel configurations. The experimental work is installed at the University of Mosul, Department of Electrical Engineering, Renewable Lab (Iraq). MATLAB was used to simulate, evaluate, and compared the results to understand the effects of shading on PV cell output. This research offers an analytical technique to determine the probable effects of Partial shadowing conditions on PV power generation. The results provide the effects of partial shadowing in an annual performance loss of ≥10-30%. The orientation of the PV panels' tilt angle has an impact on their output power. When the tilt angle deviates from its ideal value, the PV panel's output drops off substantially.
Article
Solar energy generated by photovoltaic (PV) technology can be supplied to standalone systems, as it combines efficiency and cost-effectiveness. However, this combination is achieved only after considering the effects of shading, which can significantly influence electrical output. The primary factor that influences the use of solar energy in electricity generation is irradiation. PV cells are significantly impacted by shading, where the output of the PV cell reduces in the presence of a shadow. In this study, the researchers have presented an experimental analysis of how shading affects two PV cells, using the series and parallel configurations. The experimental work is installed at the University of Mosul, Department of Electrical Engineering, Renewable Lab (Iraq). MATLAB was used to simulate, evaluate, and compared the results to understand the effects of shading on PV cell output. This research offers an analytical technique to determine the probable effects of Partial shadowing conditions on PV power generation. The results provide the effects of partial shadowing in an annual performance loss of ≥10–30%. The orientation of the PV panels' tilt angle has an impact on their output power. When the tilt angle deviates from its ideal value, the PV panel's output drops off substantially.
Article
This paper aims to analyse the effect of climate conditions on the performance of infinity PV organic solar cells in a Saharan setting in the region of Adrar (southern Algeria). The first part of this study consists of an analysis and assessment of organic photovoltaic (OPV) module degradation following a prolonged exposure to these open-air conditions (> 2 years). Inspection of the OPV module revealed various degradation modes such as solar cell deforma- tion and coating degradation. A degradation assessment was conducted on the modules via I– V/P-V characteristics together with the rate of degradation of Pmax,Imp,Vmp,Isc,Voc and FF para- meters under Standard Test Conditions (STC) to draw a comparison with the reference data provided by the photovoltaic panel manufacturer. Last, the impacts of partial shading, illumi- nation, temperature, and dust accumulation were investigated to evaluate the evolution of both I–V and P-V curves.
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Full-text available
This work aims at describing a simulation model that studies the influence of the cell string layout on the performance of solar panels taking into account the environmental conditions. Several solar cell string configurations in the photovoltaic modules are simulated using a simulation program for integrated circuits, looking for a mitigation of the effects of shading and/or non-uniform illumination of the solar panel. The simulation model is validated using data provided by Solarus, as well as results obtained experimentally in Sweden concerning outdoor tests or using a lab solar simulator with similar collectors. The model is simple and flexible enough to be easily matched to various string layout configurations and, unlike several maximum power point tracking procedures, it allows the correct assessment of the maximum power in situations presenting multiple maxima in the power versus voltage stationary characteristic of the solar panel. The simulated and experimental average electrical efficiency in December in Gavle (Sweden) for flat collectors manufactured by Solarus with strings of 38 solar cells connected in series is around 20%. Modifications in the solar modules currently manufactured in Solarus are proposed, together with the identification of the contexts in which they represent a reasonable added value. Examples of module configurations with overlapped bypass diodes show an increase of almost 100% in the short circuit current. The methodology used in this work for the design of the solar cell configuration is a valid contribution to the analysis of stationary roof/ground grid-tied or off-grid small installations and it represents undoubtedly an important tool for the enterprises in the manufacturing process.
Chapter
The objective of this chapter is to optimize the photovoltaic power plant considering the effects of variable shading on time and weather. For that purpose, an optimization scheme based on the simulator from Sanchez Reinoso, Milone, and Buitrago (2013) and on evolutionary computation techniques is proposed. Regarding the latter, the representation used and the proposed initialization mechanism are explained. Afterwards, the proposed algorithms that allow carrying out crossover and mutation operations for the problem are detailed. In addition, the designed fitness function is presented. Lastly, experiments are conducted with the proposed optimization methodology and the results obtained are discussed.
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The aim of this study is to investigate the effect of dust on the degradation of PV modules deployed in a temperate climate region, Perth, Western Australia. Results revealed that PV performance, quantified by normalised maximum power output, varied with season. For a one-year period of study, over which the only cleaning activities were due to wind and rain, the performance of PV modules deployed in Perth, decreased at the end of summer and spring, tended to increase at the end of autumn and reached their peaks at the end of the winter season. Assuming the effect of dust on Pmax output is similar among the PV modules and is linear among the consecutive seasons, economic analysis indicated that the total cost of production losses of 13 polycristalline silicone PV modules caused by dust (A$ 5.47) is lower than total cleaning cost (A$ 78). Therefore, no cleaning procedure is recommended for the grid-connected PV system simulated in the case study.
Article
The objective of this chapter is to optimize the photovoltaic power plant considering the effects of variable shading on time and weather. For that purpose, an optimization scheme based on the simulator from Sanchez Reinoso, Milone, and Buitrago (2013) and on evolutionary computation techniques is proposed. Regarding the latter, the representation used and the proposed initialization mechanism are explained. Afterwards, the proposed algorithms that allow carrying out crossover and mutation operations for the problem are detailed. In addition, the designed fitness function is presented. Lastly, experiments are conducted with the proposed optimization methodology and the results obtained are discussed.
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This paper applies a new dynamical electrical array reconfiguration strategy on photovoltaic (PV) panels arrangement based on the connection of all PV panels on two parallel groups to reach the 24 V requested by the considered load and providing a maximum output current by connecting in series the two groups. If one of the PV panels or more are shaded, dusty or faulty the connection of the others in the same group will be automatically modified to maintain the requested load output voltage. This dynamical reconfiguration allows also limiting the lost power, due to the incriminate panel, by switching off this panels and reconfiguration the topology. As a result, a real time adaptation of a switch matrix allows a self-ability to maintain a constant load voltage. Moreover, a minimum number of PV panels are switched off by isolating the effect of unhealthy panels. In addition, the proposed solution can also be applied for identifying and locating the shaded, dusty and faulty panel. Experimental setup has been built and the results validate the proposed method.
Book
This paper applies a new dynamical electrical array reconfiguration strategy on the photovoltaic (PV) panels arrangement based on the connection of all PV panels on two parallel groups to reach the 24 V requested by the considered load and providing a maximum output current by connecting in serial the two groups. If one of the PV panels or more is shaded, the connection of the other in the same group will be automatically modified to maintain the requested 24 V for each PV panel row. This dynamical reconfiguration allows also reducing the lost power, due to the shaded panel, by recovering this power from the reconfiguration of the other panels. As a result, a real time adaptation of switch matrix allows a self-ability to maintain a constant voltage at 24 V and minimum number of PV panels is switched off by isolating the effect of shaded panels. In addition, the proposed solution can also be applied for the dirty panel and identify the shaded, dusty and faulty panel.
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The operation and performance of a photovoltaic system (PV) are affected by some factors such as; solar radiation, ambient temperature, PV array configuration and shadow which may be either completely or partially. The partially shadow is caused by clouds, trees due to wind, neighboring buildings and utilities. The shadow effect causes the multiple local maximum power points in the PV module voltage-power characteristics and only one Global Maximum Power Point (GMPP); additionally the shadowing causes high power loss in the shaded cells and produces hot spot. In this paper a new optimization approach based on proposed Modified Artificial Bee Colony (MABC) algorithm is used to solve a proposed constrained objective function of PV module power loss and mitigate the shading effect. The proposed MABC is compared with GA, PSO and ABC. The obtained results proved that the MABC is the most efficient algorithm in solving the objective function that mitigating the power loss in the PV module under partially shading effect.
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A new method to track the global maximum power point (GMPP) under partially shaded conditions (PSCs), for stand-alone photovoltaic (PV) systems, is introduced. Two loads, static and dynamic, have been used to evaluate the effectiveness of the method under different PSCs. Simulation results show that the developed method guarantees convergence to the GMPP under different PSCs and provides fast convergence in rapid variation of insolation conditions. To assess the performance of the developed algorithm, a comparison between two algorithms recently published has been carried out. It is shown that the developed method outperforms other methods found in literature both in terms of efficiency (95.80% and 95% for static and dynamic load) and response time (less than 0.25 s). Negligible oscillations around the MPP and easy implementation are the main advantages of the proposed method.
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In this paper, we present a framework for the testing and evaluation of solar array performance that enables analysis of degradation effects, high density temperature monitoring, I-V curve traces under realistic operating conditions, and the analysis of hot-spot evolution during partial shading and its impact on power production. We describe details our software and hardware infrastructure and present data collected from our array under partial shading.
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ABSTRACTA process to fabricate a parallel connection dye‐sensitized solar cell (DSSC) module has been developed using commercially available materials and screen printed silver grid. The process is not only simple but also easy to manipulate and therefore facilitates researchers in evaluating new materials in a module platform. By changing the design of the silver grid pattern, it was found that the performance of DSSC modules can be controlled. With the silver grid, DSSC modules have shown that a 7% conversion efficiency can be reached. Modules fabricated by this process, but with a non‐volatile electrolyte system, passed a 60 °C, 1000 h thermal aging test. Copyright © 2012 John Wiley & Sons, Ltd.
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Photovoltaic (PV) solar energy is the solution combining economy and efficiency for the supply of stand alone systems. This combination can only be achieved by taking into account the effects of shading which have dramatic consequences on the electrical power delivered. In this paper, we present an experimental study of the effect of shading PV array on a pumping system performance. The experimental bench is installed at the Industrial Technology and Information Laboratory (LTII) in Bejaia (Algeria). In order to test the performances of the proposed system we propose different array configurations which show different behaviors against partial shading conditions. Shadow impacts fundamentally the global PV pumping system production; its influence is difficult to model because it depends on many parameters such as the configuration of the PV array, the relative rate of shadow, and the shaded area of the module. In general, it is better to have a completely shaded string than several partially shaded ones. These are ones of the most important conclusions obtained in this work.
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A general method for modeling typical photovoltaic (PV) arrays and modules is proposed to find the exact current and voltage relationship of PV arrays or modules of geometrically and electrically different configurations. Nonlinear characteristic equations of electrical devices in solar array or module systems are numerically constructed without adding any virtual electrical components. Then, a robust damped Newton method is used to find exact I–V relationship of these general nonlinear equations, where the convergence is guaranteed. The model can deal with different mismatch effects such as different configurations of bypass diodes, and partial shading. Geometry coordinates of PV components are also considered to facilitate the modeling of the actual physical configuration. Simulation of a PV array with 48 modules, partially shaded by a concrete structure, is performed to verify the effectiveness and advantages of the proposed method.
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In order to help keep readers up-to-date in the field each issue of Progress in Photovoltaics will contain a list of recently published journal articles most relevant to its aims and scope. This list is drawn from an extremely wide range of journals, including IEEE Transactions on Electron Devices, Journal of Applied Physics, Applied Physics Letters, Progress in Photovoltaics and Solar Energy Materials and Solar Cells. To assist the reader, the list is separated into broad categories, but please note that these classifications are by no means strict. Also note that inclusion in the list is not an endorsement of a paper's quality.
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This paper proposes a single-stage three-phase photovoltaic (PV) system that features enhanced maximum power point tracking capability, and an improved energy yield under partial shading conditions. Further, the proposed PV system can effectively double the maximum permissible dc voltage of a grounded conventional single-stage PV system, with no need for insulators, fuses, disconnects, and switchgear of a higher voltage class, with respect to safety/insulation standards or common system integration practices exercised for conventional grounded single-stage PV systems. The proposed PV system is realized through the parallel connection of an auxiliary half-bridge converter to the dc link of a conventional single-stage PV system and, therefore, is also an option for retrofit applications. This paper presents the mathematical model, principles of operation, and the control loops of the proposed single-stage PV system. The performance of the proposed single-stage PV system is demonstrated by time-domain simulation studies conducted on a detailed switched model in the PSCAD/EMTDC software environment.
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The electrical characteristics of array interconnection schemes are investigated, using simulation models to find a configuration that is comparatively less susceptible to shadow problems and power degradation resulting from the aging of solar cells. Three configurations have been selected for comparison: simple series-parallel (SP) array, which has zero interconnection redundancy; total-cross-tied (TCT) array, which is obtained from the simple SP array by connecting ties across each row ofjunctions and which may be characterized as the scheme with the highest possible redundancy; and bridge-linked (BL) array, in which all cells are interconnected in bridge rectifier fashion. The explicit computer simulations for the energy yield and current-voltage distributions in the array are presented, which seem to favor cross-tied configurations (TCT and BL) in coping with the effects of mismatch losses.
Article
A new method of measurement of series resistance Rs and shunt resistance Rsh of a silicon solar cell is presented. The method is based on the single exponential model and utilizes the steady state illuminated I–V characteristics in third and fourth quadrants and the Voc–Isc characteristics of the cell. It enables determination of values of Rsh and Rs with the intensity of illumination. For determination of Rs it does not require Rsh to be assumed infinite and realistic values of Rsh can be used. The method is very convenient to use and in the present study it has been applied to silicon solar cells having finite values of Rsh. We have found that Rsh is independent of intensity but the Rs decreases with both the intensity of illumination and the junction voltage.
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The authors have developed the sophisticated verification (SV) method, which can evaluate involving performance ratio, power conditioner efficiency, temperature factor, shading factor, load matching factor and other array parameter. So, we also have ensured adequacies of the evaluation of PV systems. However, the originally proposed method accepts PV installations facing the south only. In this paper, we have modified the SV method by taking into account the arbitrary orientation and inclination, because of improved the accuracy of evaluation. Therefore, the shading effect can be intelligible for each hour. The maximum value of shading losses reached 13.1%.
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The models for photovoltaic (PV) systems currently in ESP-r prove very useful in estimating the electrical and thermal impact of building-integrated photovoltaics. However, while they represent well the impact of photovoltaics on the building's thermal energy balance, they may lack in accuracy in the prediction of the system's energy production. To achieve both goals at once it is suggested to improve the PV models in ESP-r, taking into account all phenomena affecting the power output of PV modules: solar radiation intensity, cell temperature, angle of incidence, spectral distribution, uncertainty in manufacturer's ratings, ageing, mismatch, soil and dirt, snow, partial shading, diodes and wiring. This would provide a more realistic estimate of the probable output of the PV system over its lifetime. It is suggested to implement three models: a simple model based on constant efficiency, a one-diode equivalent model with explicit temperature dependency of the parameters, and the Sandia model for cases when detailed modeling is required.
Article
A simulation of shading effects in arrays with different string configurations has been done. Simulation has been performed using as the basic unit the solar cell, modelled in direct bias by the conventional one exponential model, and in reverse bias by an equation previously validated in different types of photovoltaic cells reverse characteristics. The influence of the amount of shading, the type of reverse characteristic of the cell, the string length and the number of shaded cells has been analysed, and some recommendations are extracted.
Article
In this contribution a simulation procedure is described which was developed as a working tool to calculate the energy output of building-integrated photovoltaic (PV) arrays experiencing shading or reflection effects. A three-quadrant solar cell model incorporating the reverse bias characteristics and breakdown voltage is verified by current-voltage (I–V) measurements performed on commercially manufactured mc-Si solar cells under controlled laboratory conditions. For the simulations, a point matrix giving the irradiation distribution over the PV array is calculated for each hour using a raytracing technique. With a raytracing technique, shading of both beam and diffuse irradiation as well as primary and secondary reflections can be modelled. The results of two cases studies simulated using this technique are presented and analysed. In conclusion, general guidelines based on the simulation results are drawn up. These guidelines aim to assist architects and engineers in planning an optimized layout strategy of building-integrated PV arrays to reduce energy losses caused by shading.
Article
Solar photovoltaic (PV) arrays in field conditions deliver lower power than the array rating. In this paper, the sensitivity of solar cell parameters in the variation of available power from the array is investigated. The parameters characteristic of aging and fresh cells used in prototype field systems have been used for computation of reduction in the available power. It is found that in series string the fractional power loss would increase from 2% to 12% with aging of solar cells. However, this fractional power loss may be reduced to 0.4–2.4% by an appropriate series-paralleling.
Article
Quality inspection of PV-modules includes measurement of peak-power Ppk and internal series resistance Rs. Peak-power is defined as maximum power under standard test conditions (STC). As the peak-power can decrease due to degradation effects, a continuous quality inspection has to be realized on-site under natural ambient conditions. Losses in the PV-modules can be described by an internal series resistance Rs. An increasing Rs shows internal losses as well as degrading contacts. A measuring method is presented, which can measure under natural ambient conditions and directly display the results peak-power Ppk and internal series resistance Rs. I-V-characteristics measured under ambient conditions can be corrected concerning temperature and irradiation according to IEC 60891. The description of the characteristic by the "effective solar cell characteristic" makes it possible to explicitely carry out the calculations for Ppk. IEC 60891 also describes a method for the evaluation of the internal series resistance Rs. A graphic method is used in order to determin certain points in the I-V-characteristic, which serve as input-values for the calculation of the series resistance. The accuracy of this graphic method is limited by the accuracy of the graphically determined points. Using the method of the "effective solar cell characteristic" it is possible to explicitely calculate the demanded points of the I-V-characteristic, thus beeing capable of explicit calculation of the series resistance Rs. The method of the "effective solar cell characteristic" is presented as well as some significant results concerning Ppk– and Rs–measurement under natural ambient conditions.
Article
A new method for estimating the irradiance on a partially shaded photovoltaic generator system is proposed. The basic principle of this method consists of two parts: firstly, an approximation of the obstacles’ outline or the local horizon by a set of linear functions. Here, a survey of the surroundings is based on the reading of the topographic coordinates of the only significant points of all the objects surrounding the photovoltaic generator. Secondly, the irradiance on the photovoltaic plane is estimated using an accurate model such as the Perez et al. model and assuming that the shading affects both the direct radiation and a part of the diffuse component (circumsolar component).The aim of this paper is to present the principles of the proposed method and the algorithm used for calculating the irradiance on shaded planes. In addition, the results of the comparison between the simulated and measured values of this method are presented.
Article
Partial shadowing has been identified as a main cause for reducing energy yield of grid-connected photovoltaic systems. The impact of the applied system configuration on the energy yield of partially shadowed arrays has been widely discussed. Nevertheless, there is still much confusion especially regarding the optimal grade of modularity for such systems. A 5-kWp photovoltaic system was installed at K.U. Leuven. The system consists of three independent subsystems: central inverter, string inverter, and a number of AC modules. Throughout the year, parts of the photovoltaic array are shadowed by vegetation and other surrounding obstacles. The dimensions of shadowing obstacles were recorded and the expectable shadowing losses were estimated by applying different approaches. Based on the results of almost 2 years of analytical monitoring, the photovoltaic system is assessed with regard to shadowing losses and their dependence on the chosen system configuration. The results indicate that with obstacles of irregular shape being close to the photovoltaic array, simulation estimates the shadowing losses rather imprecise. At array positions mainly suffering from a reduction of the visible horizon by obstacles far away from the photovoltaic array, a simulation returns good results. Significant differences regarding shadow tolerance of different inverter types or overproportional losses with long module strings could not be confirmed for the system under examination. The negative impact of partial shadowing on the array performance should not be underestimated, but it affects modular systems as well as central inverter systems.
Article
The aim of this study is to investigate the effects of non-uniform solar irradiation distribution on energy output of different interconnected configurations in photovoltaic (PV) arrays. In order to find which configuration is less susceptible to mismatch effects, a PV module model is developed. This model can take into consideration the effects of bypass diodes and the variation of the equivalent circuit parameters with respect to operating conditions. The proposed model can provide sufficient degree of precision as well as solar cell-based analysis in analyzing large scale PV arrays without increasing the computational effort. In order to produce more reliable and robust simulations, improved and extended algorithms are presented. Some results are discussed in detail and some recommendations are extracted by testing several shading scenarios.
Article
Partially shaded photovoltaic (PV) modules typically exhibit additional difficulties in tracking the maximum power point since their power–voltage characteristics are complex and may have multiple local maxima. For this reason, conventional techniques fail to track the maximum power point effectively if the PV array is partially shaded or some of its cells are damaged. This paper presents a novel power compensation system for PV arrays for complicated non-uniform insolation conditions. The proposed system is based on recovering the power of non-shaded PV modules into the system again completely by forward biasing a bypass diode of the shaded PV modules. For this purpose, the proposed system uses dc–dc converters equipped with each PV string in the PV array. For identifying which shaded PV modules should be deactivated, the operating voltage of the PV modules are monitored and compared. The proposed system enables the non-shaded PV modules to operate effectively at their normal maximum power point. The effectiveness of the proposed system is investigated and confirmed for complicated partially shaded PV arrays.
Review and recommendations for improving the modeling of building integrated photovoltaic systems. In: Building simulation, ninth international IBPSA conference, vols. 15-18. Montréal Canada
  • D Thevenard
Thevenard D. Review and recommendations for improving the modeling of building integrated photovoltaic systems. In: Building simulation, ninth international IBPSA conference, vols. 15-18. Montréal Canada; August 2005. p. 1221-8.