International Journal of Photoenergy The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Formation of Silicon Carbide Using Volcanic Ash as Starting Material and Concentrated Sunlight as Energy Resource Mon, 30 Mar 2015 06:18:03 +0000 SiC was formed using volcanic ash as starting material and concentrated sunlight as energy resource. The solar furnace was composed of two parts: Fresnel lens and reacting furnace. The reacting furnace was composed of a cylindrical vacuum chamber and quartz glass plate functioning to guide the concentrated sunlight into the furnace and was placed at the focal point of the Fresnel lens. The sample was made from the mixture of silica formed from volcanic ash and graphite and placed in the carbon crucible inside the reacting furnace. The temperature in the carbon crucible reached more than 1500°C. After the reaction using concentrated light, β-SiC was formed. The weight % of formed SiC was 90.5%. Kensuke Nishioka, Junki Komori, Kouji Maeda, Yasuyuki Ota, Hiroshi Kaneko, and Kosei Sato Copyright © 2015 Kensuke Nishioka et al. All rights reserved. Investigation of Photovoltaic Assisted Misting System Application for Arbor Refreshment Thu, 26 Mar 2015 12:20:42 +0000 In this study, for the first time in the literature, solar assisted cooler with misting system established on an arbor with an area of 24 m2 and georeferenced in Elazig (38.6775° N, 39.1707° E), Turkey, is presented. Here, we present a system that reduces interior temperature of the arbor while increasing humidity. Also, the system generates required electricity with a solar photovoltaic module to power pressurized water pump through an inverter and stores it in a battery for use when there is no sunlight. The model of the photovoltaic module was implemented using a Matlab program. As a result of being an uncomplicated system, return on investment for the system is 3.7 years. Hikmet Esen and Omer Tuna Copyright © 2015 Hikmet Esen and Omer Tuna. All rights reserved. An Adaptive Photovoltaic Topology to Overcome Shading Effect in PV Systems Wed, 25 Mar 2015 08:37:28 +0000 Shading in photovoltaic systems can cause many undesired effects. When shading occurs, the power generated from the PV system is much less than nominal power, increasing the electrical mismatching losses between PV system components. Active research to address this power loss focuses on static and adaptive systems. This paper addresses an adaptive system solution and proposes a new method to adaptively overcome losses due to shading during low radiation conditions. In addition, a statistical analysis for choosing the most feasible and efficient configuration for the system size is presented. The proposed system has been validated under shade conditions in a simulation and prototype experiment. The experiments are conducted using a PV system consisting of 10 PV modules located at the Petroleum Institute in the United Arab Emirates. The proposed system is shown to minimize the shading losses of the PV array in real time by an average of 100% under simulated conditions and 84% in practical experiments. Mohamed Amer Chaaban, Lana El Chaar, and Mahmoud Alahmad Copyright © 2015 Mohamed Amer Chaaban et al. All rights reserved. A New Energy Management Technique for PV/Wind/Grid Renewable Energy System Wed, 25 Mar 2015 06:21:09 +0000 An intelligent energy management system (IEMS) for maintaining the energy sustainability in renewable energy systems (RES) is introduced here. It consists of wind and photovoltaic (PV) solar panels are established and used to test the proposed IEMS. Since the wind and solar sources are not reliable in terms of sustainability and power quality, a management system is required for supplying the load power demand. The power generated by RES is collected on a common DC bus as a renewable green power pool to be used for supplying power to loads. The renewable DC power bus is operated in a way that there is always a base power available for permanent loads. Then the additional power requirement is supplied from either wind or PV or both depending upon the availability of these power sources. The decision about operating these systems is given by an IEMS with fuzzy logic decision maker proposed in this study. Using the generated and required power information from the wind/PV and load sides, the fuzzy reasoning based IEMS determines the amount of power to be supplied from each or both sources. Besides, the IEMS tracks the maximum power operating point of the wind energy system. Onur Ozdal Mengi and Ismail Hakki Altas Copyright © 2015 Onur Ozdal Mengi and Ismail Hakki Altas. All rights reserved. Synergetic Enhancement of Device Efficiency in Poly(3-hexylthiophene-2,5-diyl)/[6,6]-phenyl C61 Butyric Acid Methyl Ester Bulk Heterojunction Solar Cells by Glycerol Addition in the Active Layer Tue, 24 Mar 2015 13:43:27 +0000 Poly(3-hexylthiophene-2,5-diyl)(P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PC60BM) is the widely used active layer for the bulk heterojunction solar cells. Annealing is essential for P3HT:PC60BM active layer, since it facilitates the creation of better network for the transfer of the charge carriers. However, the PC60BM in the active layer can crystallize excessively during annealing treatments and disrupt the favorable morphology by forming crystallites in micrometer ranges, thus reducing device efficiency. In this paper we used glycerol as an additive in the active layer. Due to high boiling point of glycerol, it makes slow drying of the active layer possible during the annealing. It thus gives enough time to both electron donor (P3HT) and electron acceptor (PC60BM) components of the active layer to self-organize and also restrict the crystal overgrowth of PC60BM. Further, the glycerol additive makes the active layer smoother, which may also improve adhesion between the electrode and the active layer. The devices with the pristine active layer showed a power conversion efficiency (PCE) of about 2.1% and, with the addition of 30 vol% of glycerol in the active layer, the PCE value increased to 3%. Bobins Augustine and Tapio Fabritius Copyright © 2015 Bobins Augustine and Tapio Fabritius. All rights reserved. Progress in Photovoltaic Devices and Systems Tue, 24 Mar 2015 07:28:16 +0000 Hongxing Yang, Hui Shen, Tao Xu, and Dimitrios Karamanis Copyright © 2015 Hongxing Yang et al. All rights reserved. Morphological Effect of CNT/Ti Nanocomposite Photoelectrodes Dye-Sensitized Solar Cell on Photovoltaic Performance with Various Annealing Temperatures Thu, 19 Mar 2015 13:51:26 +0000 This research focused on the fabrication of dye-sensitized solar cell based on a photoanode of carbon nanotube/titanium dioxide (CNT/TiO2) nanocomposite photoanode synthesized through acid-catalyzed sol-gel method. The results show the improvement of the chemical and electrical properties of the solar cells annealed at different temperatures. The CNT/TiO2 colloidal solution was synthesized using titanium tetraisopropoxide and CNT/2-propanol solution. The thin films were doctor-bladed on a fluorine tin oxide glass before being annealed at 550, 650, and 750°C. The field emission scanning electron microscopy morphological images show that the thin films were homogenously distributed and maintained their spherical structures. The X-ray diffraction patterns show that the films consisted of anatase and rutile phases with large crystallite sizes due to temperature increment. The atomic force microscopy analysis presents the thin film roughness in terms of root mean square roughness. The photovoltaic performance was analyzed using IV curve and electrochemical impedance spectroscopy (EIS). The thin films annealed at 750°C had the highest energy conversion efficiency at 5.23%. The EIS analysis estimated the values of the effective electron lifetime (), effective electron diffusion coefficient, effective electron diffusion (), and effective recombination rate constant (). A large , small , and longer can improve photovoltaic performance efficiency. Mohd Zikri Razali, Huda Abdullah, and Izamarlina Asaahari Copyright © 2015 Mohd Zikri Razali et al. All rights reserved. Application of Extension Theory with Chaotic Signal Synchronization on Detecting Islanding Effect of Photovoltaic Power System Tue, 17 Mar 2015 07:26:01 +0000 The detection of islanding effect is a highly important topic for photovoltaic (PV) power system. The islanding effect occurs when the distributed power source is disconnected from the main supply while the power is still supplied in partial load area, which may injure the set maintenance personnel or damage the equipment. Combining chaotic synchronization and extension theory, this research is to propose a novel detection method to distinguish the occurrence of islanding effect based on nonautonomous Chua’s circuit. To demonstrate the effectiveness of the proposed method, this paper applies PSIM to simulate the PV power system. The experimental results show that the accuracy of the proposed method achieves 98% on islanding effect. Meng-Hui Wang, Mei-Ling Huang, and Kang-Jian Liou Copyright © 2015 Meng-Hui Wang et al. All rights reserved. Effects of CdS Buffer Layers on Photoluminescence Properties of Cu2ZnSnS4 Solar Cells Thu, 12 Mar 2015 11:59:31 +0000 Cu2ZnSnS4 (CZTS) absorber layers grown by sputtering were investigated by photoluminescence before and after the chemical bath deposition of CdS in order to evaluate the possible passivation of point defects by Cd atoms at the absorber/buffer layer interface. According to the literature, a broad emission around 1.21 eV was observed at low temperature under above bandgap excitation of the as-grown CZTS samples. Broad bands at 1.075 eV and 0.85 eV were detected for the first time under below bandgap excitation of the as-grown CZTS samples at low temperature, which were explained in terms of radiative transitions involving point defect-related levels determined in the literature by first-principles calculations. The emissions observed in the as-grown samples were monitored by both above and below bandgap excitations also in standard CZTS solar cells produced on the same layers. The obtained results suggest that, as in the case of Cu(In, Ga)Se2, Cd atoms passivate point defects at the absorber/buffer layer interface also in CZTS. A. Le Donne, S. Marchionna, P. Garattini, R. A. Mereu, M. Acciarri, and S. Binetti Copyright © 2015 A. Le Donne et al. All rights reserved. Optimal Design of a Secondary Optical Element for a Noncoplanar Two-Reflector Solar Concentrator Thu, 05 Mar 2015 13:11:01 +0000 This paper presents the results of a parametric design process used to achieve an optimal secondary optical element (SOE) in a noncoplanar solar concentrator composed of two reflectors. The noncoplanar solar concentrator comprises a primary parabolic mirror (M1) and a secondary hyperbolic mirror (M2). The optical performance (i.e., acceptance angle, optical efficiency, and irradiance distribution) of concentrators with various SOEs was compared using ray-tracing simulation. The parametric design process for the SOE was divided into two phases, and an optimal SOE was obtained. The sensitivity to assembly errors of the solar concentrator when using the optimal SOE was studied and the findings are discussed. Yi-Cheng Chen and Chia-Chi You Copyright © 2015 Yi-Cheng Chen and Chia-Chi You. All rights reserved. Photodegradation of Methylene Blue by TiO2-Fe3O4-Bentonite Magnetic Nanocomposite Mon, 02 Mar 2015 08:58:24 +0000 -bentonite nanoparticles have been prepared by a coprecipitation technique under a nitrogen atmosphere. An aqueous suspension of bentonite was first modified with FeCl2 and FeCl3. TiO2 was then loaded onto the surface of the -bentonite by a sol-gel method. After sufficient drying, the colloidal solution was placed in a muffle furnace at 773 K to obtain the -bentonite composite. The material has been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and vibrating sample magnetometry (VSM). Morphological observation showed that and TiO2 nanoparticles had been adsorbed on the surface of bentonite nanoneedles. The material was then applied for the photodegradation of the azo dye methylene blue (MB). It was found that the removal efficiency of MB exceeded 90% under UV illumination, and that only a 20% mass loss was incurred after six cycles. The composite material thus showed good photocatalytic performance and recycling properties. Wei Chen, Hongyao Xiao, Hang Xu, Tonggang Ding, and Yanmei Gu Copyright © 2015 Wei Chen et al. All rights reserved. Silver Nanoparticles in PEDOT:PSS Layer for Polymer Solar Cell Application Mon, 02 Mar 2015 07:50:05 +0000 We compare the performance of polymer solar cells based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) with silver nanoparticles (Ag NPs) incorporated in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The structure of constructed solar devices was ITO/PEDOT:PSS:Ag NPs/P3HT:PCBM/Al. Typical polyol chemistry was used to synthesize silver in water solution. Ag nanoparticles were investigated by UV-vis, atomic force microscopy (AFM), and dynamic light scattering (DLS) methods. We investigated influence of amount of silver in a hole transporting layer on the performance of bulk heterojunction polymer solar cells. The value of power conversion efficiency (PCE), equal to 2.16% under simulated 100 mW/cm2 AM 1.5G irradiation, was found for device created in air with 60 µL of Ag NPs added to 1 mL of PEDOT:PSS. Along with the increase amount of Ag NPs from 60 to 150 µL, the PCE decrease was found. Stability of solar cells with Ag was also investigated. The loss in value of PCE after 8 months was found in the range 13–47% depending on the device architecture. The solar cells were additionally measured with impedance spectroscopy. Agnieszka Iwan, Bartosz Boharewicz, Igor Tazbir, Andrzej Sikora, and Beata Zboromirska-Wnukiewicz Copyright © 2015 Agnieszka Iwan et al. All rights reserved. A Multicriteria Analysis of Photovoltaic Systems: Energetic, Environmental, and Economic Assessments Mon, 02 Mar 2015 06:44:50 +0000 The development of photovoltaic (PV) energy has led to rising efficiencies, better reliability, and falling prices. A multicriteria analysis (MCA) of PV systems is proposed in this paper in order to evaluate the sustainability of alternative projects. The investigations are presented using multiple indicators: Energy Payback Time (EPBT), Energy Return on Investment (EROI), Greenhouse Gas per kilowatt-hour (GHG/kWh), Greenhouse Gas Payback Time (GPBT), Greenhouse Gas Return on Investment (GROI), Net Present Value (NPV), Discounted Payback Time (DPBT), and Discounted Aggregate Cost Benefit (). PV energy is a relevant player in global electricity market and can have a key-role in sustainable growth. Federica Cucchiella and Idiano D’Adamo Copyright © 2015 Federica Cucchiella and Idiano D’Adamo. All rights reserved. Reliability Assessment of Transformerless PV Inverters considering Mission Profiles Sun, 01 Mar 2015 13:30:57 +0000 Due to the small volume and high efficiency, transformerless inverters have gained much popularity in grid-connected PV applications, where minimizing leakage current injection is mandatory. This can be achieved by either modifying the modulation schemes or adding extra power switching devices, resulting in an uneven distribution of the power losses on the switching devices. Consequently, the device thermal loading is redistributed and thus may alter the entire inverter reliability performance, especially under a long-term operation. In this consideration, this paper assesses the device reliability of three transformerless inverters under a yearly mission profile (i.e., solar irradiance and ambient temperature). The mission profile is translated to device thermal loading, which is used for lifetime prediction. Comparison results reveal the lifetime mismatches among the power switching devices operating under the same condition, which offers new thoughts for a robust design and a reliable operation of grid-connected transformerless PV inverters with high efficiency. Yongheng Yang, Huai Wang, and Frede Blaabjerg Copyright © 2015 Yongheng Yang et al. All rights reserved. Dynamics in Photoexcited DNA Bases and Related Molecules Sun, 01 Mar 2015 07:57:42 +0000 Yusheng Dou, Zhisong Wang, Fuli Li, and Roland E. Allen Copyright © 2015 Yusheng Dou et al. All rights reserved. Corrigendum to “Expanding Thermal Plasma Chemical Vapour Deposition of ZnO:Al Layers for CIGS Solar Cells” Wed, 25 Feb 2015 14:39:09 +0000 K. Sharma, B. L. Williams, A. Mittal, H. C. M. Knoops, B. J. Kniknie, N. J. Bakker, W. M. M. Kessels, R. E. I. Schropp, and M. Creatore Copyright © 2015 K. Sharma et al. All rights reserved. Analytical Modelling of High Concentrator Photovoltaic Modules Based on Atmospheric Parameters Mon, 23 Feb 2015 10:18:45 +0000 The goal of this paper is to introduce a model to predict the maximum power of a high concentrator photovoltaic module. The model is based on simple mathematical expressions and atmospheric parameters. The maximum power of a HCPV module is estimated as a function of direct normal irradiance, cell temperature, and two spectral corrections based on air mass and aerosol optical depth. In order to check the quality of the model, a HCPV module was measured during one year at a wide range of operating conditions. The new proposed model shows an adequate match between actual and estimated data with a root mean square error (RMSE) of 2.67%, a mean absolute error (MAE) of 4.23 W, a mean bias error (MBE) of around 0%, and a determination coefficient () of 0.99. Eduardo F. Fernández, F. Almonacid, T. K. Mallick, and P. Pérez-Higueras Copyright © 2015 Eduardo F. Fernández et al. All rights reserved. Functionalized Activated Carbon Derived from Biomass for Photocatalysis Applications Perspective Mon, 23 Feb 2015 06:33:34 +0000 This review highlighted the developments of safe, effective, economic, and environmental friendly catalytic technologies to transform lignocellulosic biomass into the activated carbon (AC). In the photocatalysis applications, this AC can further be used as a support material. The limits of AC productions raised by energy assumption and product selectivity have been uplifted to develop sustainable carbon of the synthesis process, where catalytic conversion is accounted. The catalytic treatment corresponding to mild condition provided a bulk, mesoporous, and nanostructure AC materials. These characteristics of AC materials are necessary for the low energy and efficient photocatalytic system. Due to the excellent oxidizing characteristics, cheapness, and long-term stability, semiconductor materials have been used immensely in photocatalytic reactors. However, in practical, such conductors lead to problems with the separation steps and loss of photocatalytic activity. Therefore, proper attention has been given to develop supported semiconductor catalysts and certain matrixes of carbon materials such as carbon nanotubes, carbon microspheres, carbon nanofibers, carbon black, and activated carbons have been recently considered and reported. AC has been reported as a potential support in photocatalytic systems because it improves the transfer rate of the interface charge and lowers the recombination rate of holes and electrons. Samira Bagheri, Nurhidayatullaili Muhd Julkapli, and Sharifah Bee Abd Hamid Copyright © 2015 Samira Bagheri et al. All rights reserved. Optical Properties of Spin-Coated TiO2 Antireflection Films on Textured Single-Crystalline Silicon Substrates Mon, 23 Feb 2015 06:32:31 +0000 Antireflection coating (ARC) prepared by a wet process is beneficial for low cost fabrication of photovoltaic cells. In this study, we investigated optical properties and morphologies of spin-coated TiO2 ARCs on alkaline textured single-crystalline silicon wafers. Reflectance spectra of the spin-coated ARCs on alkaline textured silicon wafers exhibit no interferences and low reflectance values in the entire visible range. We modeled the structures of the spin-coated films for ray tracing numerical calculation and compared numerically calculated reflectance spectra with the experimental results. This is the first report to clarify the novel optical properties experimentally and theoretically. Optical properties of the spin-coated ARCs without interference are due to the fractional nonuniformity of the thickness of the spin-coated ARCs that cancels out the interference of the incident light. Ryosuke Watanabe, Yohei Eguchi, Takuya Yamada, and Yoji Saito Copyright © 2015 Ryosuke Watanabe et al. All rights reserved. Bonded Excimer in Stacked Cytosines: A Semiclassical Simulation Study Sun, 22 Feb 2015 13:52:38 +0000 The formation of a covalent bond between two stacked cytosines, one of which is excited by an ultrafast laser pulse, was studied by semiclassical dynamics simulations. The results show that a bonded excimer is created, which sharply lowers the energy gap between the LUMO and HOMO and consequently facilitates the deactivation of the electronically excited molecule. This is different from the case of two stacked adenines, where the formation of a covalent bond alters the nonadiabatic deactivation mechanism in two opposite ways. It lowers the energy gap and consequently leads to the coupling between the HOMO and LUMO levels, thus enhancing the deactivation of the electronically excited molecule. On the other hand, it leads to restriction of the deformation vibration of the pyrimidine in the excited molecule, because of a steric effect, and this delays the deactivation process of the excited adenine molecule with return to the electronic ground state. Weifeng Wu, Shuai Yuan, Jiajie She, Yusheng Dou, and Roland E. Allen Copyright © 2015 Weifeng Wu et al. All rights reserved. Photocatalytic Based Degradation Processes of Lignin Derivatives Sun, 22 Feb 2015 11:09:41 +0000 Photocatalysis, belonging to the advanced oxidation processes (AOPs), is a potential new transformation technology for lignin derivatives to value added products (e.g., phenol, benzene, toluene, and xylene). Moreover, lignin represents the only viable source to produce aromatic compounds as fossil fuel alternative. This review covers recent advancement made in the photochemical transformation of industrial lignins. It starts with the photochemical reaction principle followed by results obtained by varying process parameters. In this context, influences of photocatalysts, metal ions, additives, lignin concentration, and illumination intensity and the influence of pH are presented and discussed. Furthermore, an overview is given on several used process analytical methods describing the results obtained from the degradation of lignin derivatives. Finally, a promising concept by coupling photocatalysis with a consecutive biocatalytic process was briefly reviewed. Colin Awungacha Lekelefac, Nadine Busse, Michael Herrenbauer, and Peter Czermak Copyright © 2015 Colin Awungacha Lekelefac et al. All rights reserved. Hybrid Neural Network Approach Based Tool for the Modelling of Photovoltaic Panels Sun, 22 Feb 2015 09:34:02 +0000 A hybrid neural network approach based tool for identifying the photovoltaic one-diode model is presented. The generalization capabilities of neural networks are used together with the robustness of the reduced form of one-diode model. Indeed, from the studies performed by the authors and the works present in the literature, it was found that a direct computation of the five parameters via multiple inputs and multiple outputs neural network is a very difficult task. The reduced form consists in a series of explicit formulae for the support to the neural network that, in our case, is aimed at predicting just two parameters among the five ones identifying the model: the other three parameters are computed by reduced form. The present hybrid approach is efficient from the computational cost point of view and accurate in the estimation of the five parameters. It constitutes a complete and extremely easy tool suitable to be implemented in a microcontroller based architecture. Validations are made on about 10000 PV panels belonging to the California Energy Commission database. Antonino Laudani, Gabriele Maria Lozito, Francesco Riganti Fulginei, and Alessandro Salvini Copyright © 2015 Antonino Laudani et al. All rights reserved. TiO2 Photocatalytic Materials 2014 Thu, 19 Feb 2015 09:40:40 +0000 Jiaguo Yu, Mietek Jaroniec, Wei Xiao, Christos Trapalis, and Hong Liu Copyright © 2015 Jiaguo Yu et al. All rights reserved. Water Soluble Aluminum Paste Using Polyvinyl Alcohol for Silicon Solar Cells Wed, 18 Feb 2015 13:25:21 +0000 Screen-printing aluminum is still dominantly used in the solar cell fabrication process. Ethyl cellulose is one of the main contents of screen-printing pastes that require dichloromethane for its cleaning process, a substance renowned for being extremely toxic and threatening to the human body. Developing environmental friendly aluminum pastes is essential in order to provide an alternative to the commercial pastes. In this work, new, nontoxic polyvinyl alcohol-based aluminum pastes are introduced. Polyvinyl alcohol was used as a soluble polymer that can be synthesized without saponification and that is also soluble in water. Three different pastes were developed using different recipes including many aluminum particle sizes varying from 3.0 to 45 μm, aluminum oxide with particle sizes between 35 and 50 μm, and acetic acid. Evaluation of the pastes was carried out by Scanning Electron Microscope (SEM) image analysis, sheet resistance measurements, and fabricating silicon solar cells using each paste. Solar cells with 15.6% efficiency were fabricated by nonvacuum processing on CZ-Si p-type wafers using developed aluminum pastes on the back side. Abdullah Uzum, Taiki Ashikaga, Takuma Noguchi, Hiroyuki Kanda, Toshifumi Matsuoka, Toru Nakanishi, Hidehito Fukui, Tomitaro Harada, and Seigo Ito Copyright © 2015 Abdullah Uzum et al. All rights reserved. Wet-Chemical Surface Texturing of Sputter-Deposited ZnO:Al Films as Front Electrode for Thin-Film Silicon Solar Cells Tue, 10 Feb 2015 09:45:27 +0000 Transparent conductive oxides (TCOs) play a major role as the front electrodes of thin-film silicon (Si) solar cells, as they can provide optical scattering and hence improved photon absorption inside the devices. In this paper we report on the surface texturing of aluminium-doped zinc oxide (ZnO:Al or AZO) films for improved light trapping in thin-film Si solar cells. The AZO films are deposited onto soda-lime glass sheets via pulsed DC magnetron sputtering. Several promising AZO texturing methods are investigated using diluted hydrochloric (HCl) and hydrofluoric acid (HF), through a two-step etching process. The developed texturing procedure combines the advantages of the HCl-induced craters and the smaller and jagged—but laterally more uniform—features created by HF etching. In the two-step process, the second etching step further enhances the optical haze, while simultaneously improving the uniformity of the texture features created by the HCl etch. The resulting AZO films show large haze values of above 40%, good scattering into large angles, and a surface angle distribution that is centred at around 30°, which is known from the literature to provide efficient light trapping for thin-film Si solar cells. Xia Yan, Selvaraj Venkataraj, and Armin G. Aberle Copyright © 2015 Xia Yan et al. All rights reserved. Structural Dependence of Electronic Properties in A-A-D-A-A-Type Organic Solar Cell Material Tue, 10 Feb 2015 08:58:51 +0000 Small conjugated molecules (SCMs) are promising candidates for organic photovoltaic (OPV) devices because of their structural simplicity, well control over synthetic reproducibility, and low purification cost. However, industrial development of SCM-based OPV devices requires improving their performance, which in turn relies on the fundamental understanding of structural dependence of electronic properties of SCMs. Herein, we report the structural and electronic properties of the BCNDTS molecule as a model system for acceptor-acceptor-donor-acceptor-acceptor (A-A-D-A-A) type SCMs, using density functional theory (DFT) and time-dependent DFT methods. Systematic calculations of two-dimensional potential energy surfaces, molecular electrostatic potential surfaces, ground state frontier molecular orbital energies, and the vertical excitation energies are performed. We found that the lowest energy conformation of the BCNDTS molecule is planar. The planar conformation favors the lowest ground state and the excited state energies as well as the strongest oscillator strength. The present results suggest that SCMs containing central dithienosilole cores connected with 2,1,3-benzothiadiazole groups have potential to be an efficient electron donor for OPV devices. Ram S. Bhatta and Mesfin Tsige Copyright © 2015 Ram S. Bhatta and Mesfin Tsige. All rights reserved. LED Lighting System Reliability Modeling and Inference via Random Effects Gamma Process and Copula Function Thu, 05 Feb 2015 06:04:09 +0000 Light emitting diode (LED) lamp has attracted increasing interest in the field of lighting systems due to its low energy and long lifetime. For different functions (i.e., illumination and color), it may have two or more performance characteristics. When the multiple performance characteristics are dependent, it creates a challenging problem to accurately analyze the system reliability. In this paper, we assume that the system has two performance characteristics, and each performance characteristic is governed by a random effects Gamma process where the random effects can capture the unit to unit differences. The dependency of performance characteristics is described by a Frank copula function. Via the copula function, the reliability assessment model is proposed. Considering the model is so complicated and analytically intractable, the Markov chain Monte Carlo (MCMC) method is used to estimate the unknown parameters. A numerical example about actual LED lamps data is given to demonstrate the usefulness and validity of the proposed model and method. Huibing Hao, Chun Su, and Chunping Li Copyright © 2015 Huibing Hao et al. All rights reserved. Solar CPC Pilot Plant Photocatalytic Degradation of Indigo Carmine Dye in Waters and Wastewaters Using Supported-TiO2: Influence of Photodegradation Parameters Thu, 05 Feb 2015 05:59:46 +0000 The photocatalytic degradation of indigo carmine (IC) dye in the presence of titanium dioxide under different conditions was reported. Several factors which interfere with the photodegradation efficiency as catalyst concentration, pH, initial concentration of dye, presence of inorganic anions, temperature, and the addition of hydrogen peroxide were studied under artificial irradiation with a 125 W mercury vapor lamp. Additionally, the catalyst supported on glass spheres was used for the photocatalytic degradation of the dye present in several types of waters in a CPC solar pilot plant. The photocatalytic products, carboxylic acids, and and were followed during IC mineralization. Formate, acetate, and oxalate were detected in real MWWTP secondary effluent. The mineralization efficiency was of 42 and 21% using in suspension and supported TiO2, respectively. In order to evaluate biological effects, Eisenia andrei earthworms were used as a model organism. No significant difference () of weight was observed in the earthworm submitted to different concentrations of IC and its photoproducts. The photocatalytic degradation of IC on TiO2 supported on glass spheres suffered strong influence of the water matrix; nevertheless the method has the enormous advantage that it eliminates the need for the final catalyst removal step, reducing therefore the cost of treatment. Enrico Mendes Saggioro, Anabela Sousa Oliveira, Thelma Pavesi, Margarita Jiménez Tototzintle, Manuel Ignacio Maldonado, Fábio Verissimo Correia, and Josino Costa Moreira Copyright © 2015 Enrico Mendes Saggioro et al. All rights reserved. Characteristics of DSSC Panels with Silicone Encapsulant Wed, 04 Feb 2015 14:39:41 +0000 Dye-sensitized solar cells (DSSC) allow light transmission and the application of various colors that make them especially suitable for building-integrated PV (BIPV) application. In order to apply DSSC modules to windows, the module has to be panelized: a DSSC module should be protected with toughened glass on the entire surface. Up to the present, it seems to be common to use double glazing with DSSC modules, with air gaps between the glass pane and the DSSC modules. Few studies have been conducted on the characteristics of various glazing methods with DSSC modules. This paper proposes a paneling method that uses silicone encapsulant, analyzing the performance through experimentation. Compared to a multilayered DSSC panel with an air gap, the encapsulant-applied panel showed 6% higher light transmittance and 7% higher electrical efficiency. The encapsulant also prevented electrolyte leakage by strengthening the seals in the DSSC module. Jun-Gu Kang, Jin-Hee Kim, Han-Bin Jang, and Jun-Tae Kim Copyright © 2015 Jun-Gu Kang et al. All rights reserved. Comparative Study of Maximum Power Point Tracking Techniques for Photovoltaic Systems Wed, 04 Feb 2015 13:02:45 +0000 The generation of electricity from photovoltaic (PV) arrays has been increasingly considered as a prominent alternative to fossil fuels. However, the conversion efficiency is typically low and the initial cost is still appreciable. A required feature of a PV system is the ability to track the maximum power point (MPP) of the PV array. Besides, MPP tracking (MPPT) is desirable in both grid-connected and stand-alone photovoltaic systems because the solar irradiance and temperature change throughout the day, as well as along seasons and geographical conditions, also leading to the modification of the (current versus voltage) and (power versus voltage) curves of the PV module. MPPT is also justified by the relatively high cost of the energy generated by PV systems if compared with other sources. Since there are various MPPT approaches available in the literature, this work presents a comparative study among four popular techniques, which are the fixed duty cycle method, constant voltage (CV), perturb and observe (P&O), and incremental conductance (IC). It considers different operational climatic conditions (i.e., irradiance and temperature), since the MPP is nonlinear with the environment status. PSIM software is used to validate the assumptions, while relevant results are discussed in detail. Fernando Lessa Tofoli, Dênis de Castro Pereira, and Wesley Josias de Paula Copyright © 2015 Fernando Lessa Tofoli et al. All rights reserved.