• Current Photovoltaic Research
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• v.6 no.1
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• pp.21-26
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• 2018

Beside several advantages, the PV power generation as a clean energy source, is still below the supply level due to high power generation cost. Therefore, the interest in fabricating low-cost thin film solar cells is increasing continuously. $Cu_2O$, a low cost photovoltaic material, has a wide direct band gap of ~2.1 eV has along with the high theoretical energy conversion efficiency of about 20%. On the other hand, it has other benefits such as earth-abundance, low cost, non-toxic, high carrier mobility ($100cm^2/Vs$). In spite of these various advantages, the efficiency of $Cu_2O$ based solar cells is still significantly lower than the theoretical limit as reported in several literatures. One of the reasons behind the low efficiency of $Cu_2O$ solar cells can be the formation of CuO layer due to atmospheric surface oxidation of $Cu_2O$ absorber layer. In this work, atomic layer deposition method was used to remove the CuO layer that formed on $Cu_2O$ surface. First, $Cu_2O$ absorber layer was deposited by electrodeposition. On top of it buffer (ZnO) and TCO (AZO) layers were deposited by atomic layer deposition and rf-magnetron sputtering respectively. We fabricated the cells with a change in the deposition temperature of buffer layer ranging between $80^{\circ}C$ to $140^{\circ}C$. Finally, we compared the performance of fabricated solar cells, and studied the influence of buffer layer deposition temperature on $Cu_2O$ based solar cells by J-V and XPS measurements.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.297-302
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• 2020

A coverglass pattern was designed to improve the annual electrical energy production of a building-integrated photovoltaic (BIPV) module installed in the exterior walls of buildings. The transmittance pattern was calculated using ray tracing, and the results were derived by optimizing the simulation using Taguchi's method. We obtained the optimal pattern by analyzing the conventional patterns for improving the transmittance and derived design factors by quantifying the pattern. By calculating the influence of electrical energy on each design factor, we obtained the optimal coverglass pattern that produced the maximum annual electrical energy. The annual electrical energy production improved by approximately 11.79% compared to the non-patterned coverglass.

• Current Photovoltaic Research
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• v.9 no.2
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• pp.36-44
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• 2021

To endorse the reliability and durability of the solar photovoltaic (PV) device several tests were conducted before exposing to the outdoor field in a non-ideal condition. The PV module has high probability that intend to perform adequately for 30 years under operating conditions. To evaluate the long term performance of the PV module in diversified terrestrial conditions, one should use the outdoor performance data. However, no one wants to wait for 25 years to determine the module reliability. The accelerating stress tests performing in the laboratory by mimicking different field conditions are thus important to understand the performance of a PV module. In this review, we will discuss briefly about different accelerating stress types, levels and prioritization that are used to evaluate the PV module reliability and durability before using them in real field.

• Advances in aircraft and spacecraft science
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• v.11 no.1
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• pp.23-31
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• 2024

This paper addresses the enhancement of long-endurance solar-powered aircraft through the integration of a rechargeable battery and Maximum Power Point Tracking (MPPT) controller. Traditional long-endurance aircraft often rely on non-renewable energy sourcessuch as batteries orjetfuel, contributing to carbon emissions. The proposed system aims to mitigate these environmental impacts by harnessing solar energy and efficiently managing its storage and utilization. The MPPT controller optimizes the power output of photovoltaic cells, enabling simultaneous charging and discharging of the battery for propulsion and servo control. A prototype is presented to illustrate the practical implementation and functionality of the proposed design, marking a promising step towards more sustainable and enduring solar-powered flight.

• Journal of the Korean Solar Energy Society
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• v.38 no.1
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• pp.45-55
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• 2018

Environmentally benign lead-free solder coated ribbon (e. g. SnCu, SnZn, SnBi${\cdots}$) has been intensively studied to interconnect cells without lead mixed ribbon (e. g. SnPb) in the crystalline silicon(c-Si) photovoltaic modules. However, high melting point (> $200^{\circ}C$) of non-lead based solder provokes increased thermo-mechanical stress during its soldering process, which causes early degradation of PV module with it. Hence, we proposed low-temperature conductive paste (CP) based tabbing method for lead-free ribbon. Modules, interconnected by the lead-free solder (SnCu) employing CP approach, exhibits similar output without increased resistivity losses at initial condition, in comparison with traditional high temperature soldering method. Moreover, 400 cycles (2,000 hour) of thermal cycle test reveals that the module integrated by CP approach withstands thermo-mechanical stress. Furthermore, this approach guarantees strong mechanical adhesion (peel strength of ~ 2 N) between cell and lead-free ribbons. Therefore, the CP based tabbing process for lead free ribbons enables to interconnect cells in c-Si PV module, without deteriorating its performance.

• Journal of the Korean Solar Energy Society
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• v.26 no.4
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• pp.17-23
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• 2006

This paper proposes a novel active frequency drift (AFD) method for the islanding prevention of grid-connected photovoltaic inverter. To detect the islanding phenomenon of grid-connected photovoltaic (PV) inverters concerning about the safety hazards and the damage to other electric equipments, many kinds of anti-islanding methods have been presented. Among them, AFD method using chopping fraction enables the islanding detection to drift up (or down) the frequency of the voltage during the islanding situation. In this paper, injecting the periodic zero current into the basic AFD method is proposed. This proposed method shows the analytical design value of cf to meet the test procedure of IEEE Std. 1547 with various load conditions. Detection of islanding is verified using simulation tool PSIM.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1874-1885
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• 2018

The customer side operation is getting more complex in a smart grid environment because of the adoption of renewable resources. In performing energy management planning or scheduling, it is essential to forecast non-controllable resources accurately and robustly. The PV system is one of the common renewable energy resources in customer side. Its output depends on weather and physical characteristics of the PV system. Thus, weather information is essential to predict the amount of PV system output. However, weather forecast usually does not include enough solar irradiation information. In this study, a PV system power output prediction model (PPM) under limited weather information is proposed. In the proposed model, meteorological radiation model (MRM) is used to improve cloud cover radiation model (CRM) to consider the seasonal effect of the target region. The results of the proposed model are compared to the result of the conventional CRM prediction method on the PV generation obtained from a field test site. With the PPM, root mean square error (RMSE), and mean absolute error (MAE) are improved by 23.43% and 33.76%, respectively, compared to CRM for all days; while in clear days, they are improved by 53.36% and 62.90%, respectively.

• Transactions on Electrical and Electronic Materials
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• v.15 no.2
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• pp.103-111
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• 2014

This paper investigates the output powers of PV modules by predicting three unknown parameters: reverse saturation current, and series and shunt resistances. A theoretical model using the non-uniform physical parameters of solar cells, including the temperature coefficients, voltage, current, series and shunt resistances, is proposed to obtain the I-V characteristics of PV modules. The solar irradiation effect is included in the model to improve the accuracy of the output power. Analytical and Newton methods are implemented in MATLAB to calculate a module output. Experimental data of the non-uniform solar cells for both serial and parallel connections are used to extend the implementation of the model based on the I-V equation of the equivalent circuit of the cells and to extend the application of the model to m by n modules configuration. Moreover, the theoretical model incorporates, for the first time, the variations of series and shunt resistances, reverse saturation current and irradiation for easy implementation in real power generation. Finally, this model can be useful in predicting the degradation of a PV system because of evaluating the variations of series and shunt resistances, which are critical in the reliability analysis of PV power generation.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.5
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• pp.372-378
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• 2009

With the increase in capacity of photovoltaic generation systems, studies are being actively conducted to improve system efficiency. In order to develop the high performance photovoltaic power system it is required to understand the physical characteristics of the solar cell. However, solar cell models have a non-linear form with many parameters entangled and conventional methods suggested to extract the parameters of the solar cell model require some kind of assumptions, which accompanies the calculation errors, thereby lowering the accuracy of the model. Therefore, in this paper a novel method is proposed to calculate the ideality factor and reverse saturation current of the solar cell from the I-V curve measured and announced by solar cell manufacturers, derive the ideal I-V curve, and then extract the series and shunt resistances value from the difference between the ideal and measured I-V curve. Also, validity of the proposed method is demonstrated by calculating the correlation between I-V curve based on modeling parameters and I-V curve actually measured through least squares method.

• Current Photovoltaic Research
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• v.1 no.2
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• pp.90-96
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• 2013

We report here flexible dye-sensitized solar cells (DSSC) based on Ti-mesh electrodes that show good mechanical flexibility and electrical conductivity. $TiO_2$ nanotube arrays prepared by electrochemical anodizing Ti-mesh substrate were used as photoanode. A Pt-coated Ti-mesh substrate was used as counter electrode. The photoanodes were modified by coating a $TiO_2$ porous layer onto the $TiO_2$ nanotubes in order to increase the specific surface area. To increase the long term stability of the DSSCs, a gel type electrolyte was used instead of a conventional liquid type electrolyte. The DSSC based on $33.2{\mu}m$ long porous $TiO_2$ nanotubes exhibited a better energy conversion efficiency of ~2.33%, which was higher than that of the DSSCs based on non-porous $TiO_2$ nanotubes.