Journal of Solar Energy The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Correlation of Global Solar Radiation of Eight Synoptic Stations in Burkina Faso Based on Linear and Multiple Linear Regression Methods Mon, 29 Feb 2016 14:44:43 +0000 We utilize the multiple linear regression method to analyse meteorological data for eight cities in Burkina Faso. A correlation between the monthly mean daily global solar radiation on a horizontal surface and five meteorological and geographical parameters, which are the mean daily extraterrestrial solar radiation intensity, the average daily ratio of sunshine duration, the mean daily relative humidity, the mean daily maximum air temperature, and the sine of the solar declination angle, was examined. A second correlation is established for the entire country, using, this time, the monthly mean global solar radiation on a horizontal surface and the following climatic variables: the average daily ratio of sunshine duration, the latitude, and the longitude. The results show that the coefficients of correlation vary between 0.96 and 0.99 depending on the station while the relative errors spread between −3.16% (Pô) and 3.65% (Dédougou). The maximum value of the RMSD which is 312.36 kJ/m2 is obtained at Dori, which receives the strongest radiation. For the entire cities, the values of the MBD are found to be in the acceptable margin. Ousmane Coulibaly and Abdoulaye Ouedraogo Copyright © 2016 Ousmane Coulibaly and Abdoulaye Ouedraogo. All rights reserved. Symmetric Compound Parabolic Concentrator with Indium Tin Oxide Coated Glass as Passive Cooling System for Photovoltaic Application Sun, 28 Feb 2016 13:57:09 +0000 One problem with concentrating photovoltaic systems is the increase in operating photovoltaic module temperature which results in power output reduction. Indium Tin Oxide (ITO) coated glasses exhibit both high transmittance in the visible region and high reflectance in the infrared region of the solar spectrum. Such materials can be used as selective windows in photovoltaic modules operating under concentrating system enabling passive cooling. In this paper, a Heat Reflector Window (HRW) consisting of a glass coated with 180 nm layer of ITO was experimentally tested. The ITO coated glass had a transmittance of about 85% in the visible region and over 80% reflectance in the infrared region of the solar spectrum and was placed at the exit aperture of a Compound Parabolic Concentrator (CPC). Results indicate that the temperature of a photovoltaic module under CPC with the HRW was reduced by about 50% as compared to a similar photovoltaic module with CPC but without the HRW. However, due to presence of the HRW at the exit aperture of the CPC, the photovoltaic module with the CPC and HRW received less solar irradiance compared to a similar photovoltaic module with the CPC but without HRW. Damasen Ikwaba Paul Copyright © 2016 Damasen Ikwaba Paul. All rights reserved. Dependence of the Photocurrent of a Schottky-Barrier Solar Cell on the Back Surface Recombination Velocity and Suggestion for a Structure with Improved Performance Sun, 20 Dec 2015 15:23:15 +0000 Though Schottky-barrier solar cells have been studied extensively previously, not much work has been done recently on these cells, because of the fact that conventional p-n junction silicon solar cells have much higher efficiency and have attracted the attention of most of the researchers. However, the Schottky-barrier solar cells have the advantage of simple and economical fabrication process. In this paper, the effect of back surface recombination velocity on the minority carrier distribution and the spectral response of a Schottky-barrier silicon solar cell have been investigated and, based on this study, a new design of the cell with a back surface field has been suggested, which is expected to give much improved performance. Avigyan Chatterjee, Ashim Kumar Biswas, and Amitabha Sinha Copyright © 2015 Avigyan Chatterjee et al. All rights reserved. A Modified Control Scheme of Droop-Based Converters for Power Stability Analysis in Microgrids Mon, 23 Nov 2015 08:34:29 +0000 Microgrid is principally an active distribution network since it aggregates numerous DG systems through their interface converters and different loads at distribution level. This paper discusses the power sharing in autonomous AC-microgrid infrastructure by common - and - droop control schemes on parallel-connected converters. Moreover, this research work proposes a frequency and voltage restoration mechanism through the utilization of secondary control. Experimental results are presented for a two-50 kVA parallel-connected converter-based system, demonstrating the necessity for the proper operation of the secondary control in order to monitor the system’s capability to withstand any perturbations that may occur and to ensure the system’s security. Igor Usunariz, Mikel Santamaria, Konstantina Mentesidi, and Monica Aguado Copyright © 2015 Igor Usunariz et al. All rights reserved. The Potential of Concentrated Solar Power for Remote Mine Sites in the Northern Territory, Australia Thu, 19 Nov 2015 08:57:06 +0000 The Northern Territory (NT) is among the regions in Australia and the world with the highest solar radiation intensities. The NT has many mine sites which consume significant amount of fossil fuel with consequent greenhouse gas (GHG) emissions. The environmental concern related to the fossil fuel consumption and availability of immense solar energy resource in the NT open the possibilities for considering the provision of power to the mining sites using proven solar technologies. Concentrating solar power (CSP) systems are deemed as the potential alternatives to current fossil fuel based generating systems in mining industry in the NT. The finding is based on consideration of the major factors in determining the feasibility of CSP system installation, with particular reference to the NT mine sites. These are plant design requirements, climatic, environmental, and other requirements, and capital and operating costs. Based on these factors, four mine sites have been identified as having the potential for CSP plants installation. These are McArthur River Mine, Ranger Mine, Northern Territory Gold Mines, and Tanami Operations. Each site could be served by one CSP plant to cater for the needs of mining operation and the local communities. M. H. Baig, D. Surovtseva, and E. Halawa Copyright © 2015 M. H. Baig et al. All rights reserved. A Dynamic Multinode Model for Component-Oriented Thermal Analysis of Flat-Plate Solar Collectors Thu, 05 Nov 2015 11:56:44 +0000 A mathematical model of a flat-plate solar collector was developed on the basis of the physical principles of optics and heat transfer in order to determine collector’s component temperatures as well as collector efficiency. In contrast to many available models, the targeted use of this dynamic model is the detailed, theoretical investigation of the thermal behaviour of newly developed or adjusted collector designs on component level, for example, absorber, casing, or transparent cover. The defined model is based on a multinode network (absorber, fluid, glazing, and backside insulation) containing the relevant physical equations to transfer the energy. The heat transfer network covers heat conduction, convection, and radiation. Furthermore, the collector optics is defined for the plane glazing and the absorber surface and also considers interactions between them. The model enables the variation of physical properties considering the geometric parameters and materials. Finally, the model was validated using measurement data and existing efficiency curve models. Both comparisons proved high accuracy of the developed model with deviation of up to 3% in collector efficiency and 1 K in component temperatures. Christoph N. Reiter, Christoph Trinkl, Wilfried Zörner, and Vic I. Hanby Copyright © 2015 Christoph N. Reiter et al. All rights reserved. Ray Tracing Study of Optical Characteristics of the Solar Image in the Receiver for a Thermal Solar Parabolic Dish Collector Thu, 29 Oct 2015 13:50:15 +0000 This study presents the geometric aspects of the focal image for a solar parabolic concentrator (SPC) using the ray tracing technique to establish parameters that allow the designation of the most suitable geometry for coupling the SPC to absorber-receiver. The efficient conversion of solar radiation into heat at these temperature levels requires a use of concentrating solar collectors. In this paper detailed optical design of the solar parabolic dish concentrator is presented. The system has diameter  mm and focal distance  mm. The parabolic dish of the solar system consists of 11 curvilinear trapezoidal reflective petals. For the construction of the solar collectors, mild steel-sheet and square pipe were used as the shell support for the reflecting surfaces. This paper presents optical simulations of the parabolic solar concentrator unit using the ray tracing software TracePro. The total flux on the receiver and the distribution of irradiance for absorbing flux on center and periphery receiver are given. The goal of this paper is to present the optical design of a low-tech solar concentrator that can be used as a potentially low cost tool for laboratory scale research on the medium-temperature thermal processes, cooling, industrial processes, polygeneration systems, and so forth. Saša R. Pavlovic and Velimir P. Stefanovic Copyright © 2015 Saša R. Pavlovic and Velimir P. Stefanovic. All rights reserved. Analysis of Global Solar Irradiance over Climatic Zones in Nigeria for Solar Energy Applications Mon, 12 Oct 2015 13:35:20 +0000 Satellite derived solar irradiance over 25 locations in the 5 climatic zones of Nigeria (tropical rainforest TRF, Guinea savannah GS, Sahel savannah SHS, Sudan savannah SUS, and Mangrove swamp forest MSF) was analyzed. To justify its use, the satellite data was tested for goodness of agreement with ground measured solar radiation data using 26-year mean monthly and daily data over 16 locations in the 5 climatic zones. The well-known R2, RMSE, MBE, and MPE statistical tests were used and good agreement was found. The 25 locations were grouped into the 5 climatic zones. Frequency distribution of global solar irradiance was done for each of the climatic zones. This showed that 46.88%, and 40.6% of the number of days (9794) over TRF and MSF, respectively, had irradiation within the range of 15.01–20.01 MJ/m2/day. For the GS, SHS, and SUS, 46.19%, 55.84% and 58.53% of the days had total irradiation within the range of 20.01–25.01 MJ/m2/day, respectively. Generally, in all the climatic zones, coefficients of variation of solar radiation were high and mean values were low in July and August. Contour maps showed that high and low values of global solar irradiance and clearness index were observed in the Northern and Southern locations of Nigeria, respectively. Adekunle Ayodotun Osinowo, Emmanuel Chilekwu Okogbue, Stephen Bunmi Ogungbenro, and Olugbenga Fashanu Copyright © 2015 Adekunle Ayodotun Osinowo et al. All rights reserved. Global Annual Final AC Yield Comparison between HCPV and c-Si PV Mon, 12 Oct 2015 09:03:14 +0000 A worldwide comparison of the annual yield between conventional c-Si photovoltaic (PV) technology and high concentrated photovoltaic (HCPV) technology is presented. The idea of this paper is to find the most appropriate locations for HCPV systems in terms of the annual energy produced when comparing to fixed tilt PV systems and two-axis oriented PY systems. For estimating the annual energy generation, the method of the Performance Ratio is used. For some locations with high annual direct normal irradiation values, which are distributed around the world, HCPV systems are found to be more advantageous than fixed tilt PV systems. World maps showing this comparison are presented. Juan Pablo Ferrer-Rodríguez, Pedro Pérez-Higueras, Florencia Almonacid, and Eduardo F. Fernández Copyright © 2015 Juan Pablo Ferrer-Rodríguez et al. All rights reserved. Simulations Based on Experimental Data of the Behaviour of a Monocrystalline Silicon Photovoltaic Module Mon, 31 Aug 2015 11:43:37 +0000 The performance of monocrystalline silicon cells depends widely on the parameters like the series and shunt resistances, the diode reverse saturation current, and the ideality factor. Many authors consider these parameters as constant while others determine their values based on the characteristic when the module is under illumination or in the dark. This paper presents a new method for extracting the series resistance, the diode reverse saturation current, and the ideality factor. The proposed extraction method using the least square method is based on the fitting of experimental data recorded in 2014 in Ngaoundere, Cameroon. The results show that the ideality factor can be considered as constant and equal to 1.2 for the monocrystalline silicon module. The diode reverse saturation current depends only on the temperature. And the series resistance decreases when the irradiance increases. The extracted values of these parameters contribute to the best modeling of a photovoltaic module which can help in the accurate extraction of the maximum power. Abraham Dandoussou, Martin Kamta, Laurent Bitjoka, Patrice Wira, and Alexis Kuitché Copyright © 2015 Abraham Dandoussou et al. All rights reserved. Influence of Different Types of Recombination Active Defects on the Integral Electrical Properties of Multicrystalline Silicon Solar Cells Sun, 08 Mar 2015 08:08:12 +0000 In this contribution the influence of different types of recombination-active defects on the integral electrical properties of multicrystalline Si solar cells is investigated. Based on a previous classification scheme related to the luminescence behavior of crystal defects, Type-A and Type-B defects are locally distinguished. It is shown that Type-A defects, correlated to iron contaminations, are dominating the efficiency by more than 20% relative through their impact on the short circuit current ISC and open circuit voltage VOC in standard Si material (only limited by recombination active crystal defects). Contrarily, Type-B defects show low influence on the efficiency of 3% relative. The impact of the detrimental Type-A defects on the electrical parameters is studied as a function of the block height. A clear correlation between the area fraction of Type-A defects and both the global Isc and the prebreakdown behavior (reverse current) in voltage regime-2 (−11 V) is observed. An outlier having an increased full-area recombination activity is traced back to dense inter- and intragrain nucleation of Fe precipitates. Based on these results it is concluded that Type-A defects are the most detrimental defects in Si solar cells (having efficiencies > 15%) and have to be prevented by optimized Si material quality and solar cell process conditions. Dominik Lausch and Christian Hagendorf Copyright © 2015 Dominik Lausch and Christian Hagendorf. All rights reserved. Spatial Approach of Artificial Neural Network for Solar Radiation Forecasting: Modeling Issues Wed, 18 Feb 2015 07:07:48 +0000 Design of neural networks architecture has been done on setting up the number of neurons, delays, and activation functions. The expected model was initiated and tested with Indian solar horizontal irradiation (GHI) metrological data. The results are assessed using the effect of different statistical errors. The effort is made to verify simulation capability of ANN architecture accurately, on hourly radiation data. ANN model is a well-organized technique to estimate the radiation using different meteorological database. In this paper, we have used nine spatial neighbour locations and 10 years of data for assessment of neural network. Hence, overall 90 different inputs are compared, on customized ANN model. Results show the flexibility with respect to spatial orientation of model inputs. Yashwant Kashyap, Ankit Bansal, and Anil K. Sao Copyright © 2015 Yashwant Kashyap et al. All rights reserved. A Novel Solar Tracker Based on Omnidirectional Computer Vision Sat, 31 Jan 2015 13:36:15 +0000 This paper presents a novel solar tracker system based on omnidirectional vision technology. The analysis of acquired images with a catadioptric camera allows extracting accurate information about the sun position toward both elevation and azimuth. The main advantages of this system are its wide field of tracking of 360° horizontally and 200° vertically. The system has the ability to track the sun in real time independently of the spatiotemporal coordinates of the site. The extracted information is used to control the two DC motors of the dual-axis mechanism to achieve the optimal orientation of the photovoltaic panels with the aim of increasing the power generation. Several experimental studies have been conducted and the obtained results confirm the power generation efficiency of the proposed solar tracker. Zakaria El Kadmiri, Omar El Kadmiri, Lhoussaine Masmoudi, and Mohammed Najib Bargach Copyright © 2015 Zakaria El Kadmiri et al. All rights reserved. Coordinated Collaboration between Heterogeneous Distributed Energy Resources Tue, 02 Dec 2014 12:57:21 +0000 A power distribution feeder, where a heterogeneous set of distributed energy resources is deployed, is examined by simulation. The energy resources include PV, battery storage, natural gas GenSet, fuel cells, and active thermal storage for commercial buildings. The resource scenario considered is one that may exist in a not too distant future. Two cases of interaction between different resources are examined. One interaction involves a GenSet used to partially offset the duty cycle of a smoothing battery connected to a large PV system. The other example involves the coordination of twenty thermal storage devices, each associated with a commercial building. Storage devices are intended to provide maximum benefit to the building, but it is shown that this can have a deleterious effect on the overall system, unless the action of the individual storage devices is coordinated. A network based approach is also introduced to calculate some type of effectiveness metric to all available resources which take part in coordinated operation. The main finding is that it is possible to achieve synergy between DERs on a system; however this required a unified strategy to coordinate the action of all devices in a decentralized way. Shahin Abdollahy, Olga Lavrova, and Andrea Mammoli Copyright © 2014 Shahin Abdollahy et al. All rights reserved. Interfacial Properties of CZTS Thin Film Solar Cell Wed, 26 Nov 2014 07:42:03 +0000 Cu-deficient CZTS (copper zinc tin sulfide) thin films were grown on soda lime as well as molybdenum coated soda lime glass by reactive cosputtering. Polycrystalline CZTS film with kesterite structure was produced by annealing it at 500°C in Ar atmosphere. These films were characterized for compositional, structural, surface morphological, optical, and transport properties using energy dispersive X-ray analysis, glancing incidence X-ray diffraction, Raman spectroscopy, scanning electron microscopy, atomic force microscopy, UV-Vis spectroscopy, and Hall effect measurement. A CZTS solar cell device having conversion efficiency of ~0.11% has been made by depositing CdS, ZnO, ITO, and Al layers over the CZTS thin film deposited on Mo coated soda lime glass. The series resistance of the device was very high. The interfacial properties of device were characterized by cross-sectional SEM and cross-sectional HRTEM. N. Muhunthan, Om Pal Singh, M. K. Thakur, P. Karthikeyan, Dinesh Singh, M. Saravanan, and V. N. Singh Copyright © 2014 N. Muhunthan et al. All rights reserved. Effects of Ambient Temperature and Wind Speed on Performance of Monocrystalline Solar Photovoltaic Module in Tripura, India Thu, 25 Sep 2014 05:16:37 +0000 The effects of ambient temperature and wind speed on the performance analysis of a monocrystalline silicon solar photovoltaic module have been analyzed in a particular location called Tripura, India, for the period of 2012-2013. The research work has been carried out by monitoring the variation of module efficiency with ambient temperature and wind speed. A statistical analysis has also been done and the result indicates that the values of correlation coefficient are 96% and 68% for ambient temperature and wind speed, respectively, considering confidence level of 95%.The result shows that there is a strong positive linear relationship between module efficiency and ambient temperature and a moderate positive linear relationship between module efficiency and wind speed. The deviation from the standard test condition (STC) affects the generation of output power while designing green buildings in Tripura. Tanima Bhattacharya, Ajoy K. Chakraborty, and Kaushik Pal Copyright © 2014 Tanima Bhattacharya et al. All rights reserved. Effect of Parametric Uncertainties, Variations, and Tolerances on Thermohydraulic Performance of Flat Plate Solar Air Heater Sun, 21 Sep 2014 00:00:00 +0000 The paper presents results of an analysis carried out using a mathematical model to find the effect of the uncertainties, variations, and tolerances in design and ambient parameters on the thermohydraulic performance of flat plate solar air heater. Analysis shows that, for the range of flow rates considered, a duct height of 10 mm is preferred from the thermohydraulic consideration. The thermal efficiency changes by about 2.6% on variation in the wind heat transfer coefficient, ±5 K variation in sky temperature affects the efficiency by about ±1.3%, and solar insolation variation from 500 to 1000 Wm−2 affects the efficiency by about −1.5 to 1.3% at the lowest flow rate of 0.01 kgs−1 m−2 of the absorber plate with black paint. In general, these effects reduce with increase in flow rate and are lower for collector with selective coating on the absorber plate surface. The tolerances in the duct height and absorber plate emissivity should be small while positive tolerance of 3° in the collector slope for winter operation and ±3° for year round operation, and a positive tolerance for the gap between the absorber plate and glass cover at nominal value of 40 mm are recommended. Rajendra Karwa and Shweta Baghel Copyright © 2014 Rajendra Karwa and Shweta Baghel. All rights reserved. Thermoeconomic Analysis and Multiobjective Optimization of a Solar Desalination Plant Tue, 16 Sep 2014 08:00:08 +0000 A solar desalination plant consisting of solar parabolic collectors, steam generators, and MED unit was simulated technoeconomically and optimized using multiobjective genetic algorithm. A simulation code was developed using MATLAB language programming. Indirect steam generation using different thermal oils including THERMINOL VP1, THERMINOL66, and THERMINOL59 was also investigated. Objective function consisted of 17 essential parameters such as diameter of heat collector element, collector width, steam generator pinch, approach temperatures, and MED number of effects. Simulation results showed that THERMINOL VP1 had superior properties and produced more desalinated water than other heat transfer fluids. Performance of the plant was analyzed on four characteristic days of the year to show that multiobjective optimization technique can be used to obtain an optimized solution, in which the product flow rate increased, while total investment and O&M costs decreased compared to the base case. Hamid Mokhtari, Mokhtar Bidi, and Mahdi Gholinejad Copyright © 2014 Hamid Mokhtari et al. All rights reserved. Experimental Learning of Digital Power Controller for Photovoltaic Module Using Proteus VSM Mon, 15 Sep 2014 08:07:58 +0000 The electric power supplied by photovoltaic module depends on light intensity and temperature. It is necessary to control the operating point to draw the maximum power of photovoltaic module. This paper presents the design and implementation of digital power converters using Proteus software. Its aim is to enhance student’s learning for virtual system modeling and to simulate in software for PIC microcontroller along with the hardware design. The buck and boost converters are designed to interface with the renewable energy source that is PV module. PIC microcontroller is used as a digital controller, which senses the PV electric signal for maximum power using sensors and output voltage of the dc-dc converter and according to that switching pulse is generated for the switching of MOSFET. The implementation of proposed system is based on learning platform of Proteus virtual system modeling (VSM) and the experimental results are presented. Abhijit V. Padgavhankar and Sharad W. Mohod Copyright © 2014 Abhijit V. Padgavhankar and Sharad W. Mohod. All rights reserved. High-Efficiency Glass and Printable Flexible Dye-Sensitized Solar Cells with Water-Based Electrolytes Wed, 13 Aug 2014 12:12:41 +0000 The performance of a flexible and glass dye-sensitized solar cell (DSSC) with water-based electrolyte solutions is described. High concentrations of alkylamidazoliums were used to overcome the deleterious effect of water and, based on this variable, pure water-based electrolyte DSSCs were tested displaying the highest recorded efficiency so far of 3.45% and 6% for flexible and glass cells, respectively, under a simulated air mass 1.5 solar spectrum illumination at 100 mWcm−2. An improvement in the with high water content and the positive impact of GuSCN on the enhancement of the performance of pure water-based electrolytes were also observed. Omar Moudam and Silvia Villarroya-Lidon Copyright © 2014 Omar Moudam and Silvia Villarroya-Lidon. All rights reserved. The Vertical-Tube Solar Collector: A Low-Cost Design Suitable for Temperate High-Latitude Locations Thu, 03 Jul 2014 00:00:00 +0000 A new low-cost solar collector based on thick (4.5′′) vertical tubes related to the previous design based on long 1.5′′ plastic hoses connected directly between water-grid supply and consumption is presented. This novel design could noticeably improve its performance for temperate locations mid and high latitudes, as was demonstrated by dynamic thermal modeling. This tool has been useful for understanding the particular characteristics of this kind of water-pond collector and besides, for noticeably improving its performance by optimizing its parameters, like tube diameter and number of glazing layers. By this way, the optimized design could fully satisfy the household demand up to midnight along the whole year for Buenos Aires (35°S) and during summers (remaining as a useful preheater for the whole year) for Ushuaia (55°S). Besides, its high simplicity makes it available for user’s own construction, costing down 50 dollars for a single-family unit. Luis Juanicó and Nicolás Di Lalla Copyright © 2014 Luis Juanicó and Nicolás Di Lalla. All rights reserved. Study of Cylindrical Honeycomb Solar Collector Mon, 12 May 2014 11:50:56 +0000 We present the results of our investigation on cylindrical honeycomb solar collector. The honeycomb has been fabricated with transparent cellulose triacetate polymer sheets. Insulation characteristics of the honeycomb were studied by varying the separation between the honeycomb and the absorber plate. The optimal value of the separation was found to be 3.3 mm for which the heat transfer coefficient is 3.06 W m−2 K−1. This supports result of previous similar experiments. Further we test the honeycomb through a field experiment conducted in Delhi (28.6°N, 77°E) and found that when the incident angle of the solar radiation is within 20° then the performance of the system with the honeycomb is better than the one without the honeycomb. Atish Mozumder, Anjani K. Singh, and Pragati Sharma Copyright © 2014 Atish Mozumder et al. All rights reserved. Exergoeconomic and Enviroeconomic Analysis of Photovoltaic Modules of Different Solar Cells Wed, 23 Apr 2014 15:06:33 +0000 The exergoeconomic and enviroeconomic analysis of semitransparent and opaque photovoltaic (PV) modules based on different kinds of solar cells are presented. Annual electricity and net present values have also been computed for the composite climatic conditions of New Delhi, India. Irrespective of the solar cell type, the semitransparent PV modules have shown higher net energy loss rate () and net exergy loss rate () compared to the opaque ones. Among all types of solar modules, the one based on c-Si, exhibited the minimum and . Compared to the opaque ones, the semitransparent PV modules have shown higher CO2 reduction giving higher environmental cost reduction per annum and the highest environmental cost reduction per annum was found for a-Si PV module. Ankita Gaur and G. N. Tiwari Copyright © 2014 Ankita Gaur and G. N. Tiwari. All rights reserved. About the Relation between Sunshine Duration and Cloudiness on the Basis of Data from Hamburg Thu, 10 Apr 2014 17:31:15 +0000 The aim of this paper is to relate the two meteorological parameters known as relative (bright) sunshine duration and cloudiness using the data from two stations of the city of Hamburg, Germany. We test the classic linear relationship, as well as newer polynomial extensions suggested in the literature. The results of regression are interpreted against a theoretical background recently put forward by Badescu. The suggested relations can be borne out, but we also point out difficulties due to data quality and insufficiency. Stefanie Neske Copyright © 2014 Stefanie Neske. All rights reserved. Hybrid TiO2 Solar Cells Produced from Aerosolized Nanoparticles of Water-Soluble Polythiophene Electron Donor Layer Thu, 27 Feb 2014 12:55:25 +0000 Hybrid solar cells (HSCs) with water soluble polythiophene sodium poly[2-(3-thienyl)-ethyloxy-4-butylsulfonate] (PTEBS) thin films produced using electrospray deposition (ESD) were fabricated, tested, and modeled and compared to devices produced using conventional spin coating. A single device structure of FTO/TiO2/PTEBS/Au was used to study the effects of ESD of the PTEBS layer on device performance. ESD was found to increase the short circuit current density () by a factor of 2 while decreasing the open circuit voltage () by half compared to spin coated PTEBS films. Comparable efficiencies of 0.009% were achieved from both device construction types. Current-voltage curves were modeled using the characteristic solar cell equation and showed a similar increase in generated photocurrent with an increase by two orders of magnitude in the saturation current in devices from ESD films. Increases in are attributed to an increase in the interfacial contact area between the TiO2 and PTEBS layers, while decreases in are attributed to incomplete film formation from ESD. Marshall L. Sweet, Joshua G. Clarke, Dmitry Pestov, Gary C. Tepper, and James T. McLeskey Jr. Copyright © 2014 Marshall L. Sweet et al. All rights reserved. Empirical Models for Estimating Global Solar Radiation over the Ashanti Region of Ghana Thu, 16 Jan 2014 13:05:38 +0000 The performances of both sunshine and air temperature dependent models for the estimation of global solar radiation (GSR) over Ghana and other tropical regions were evaluated and a comparison assessment of the models was carried out using measured GSR at Owabi (6°45′0′′N, 1°43′0′′W) in the Ashanti region of Ghana. Furthermore, an empirical model which also uses sunshine hours and air temperature measurements from the study site and its environs was proposed. The results showed that all the models could predict very well the pattern of the measured monthly daily mean GSR for the entire period of the study. However, most of the selected models overestimated the measured GSR, except in April and November, where the empirical model using air temperature measurements underestimated the measured GSR. Nevertheless, a very good agreement was found between the measured radiations and the proposed models with a coefficient of determination within the range 0.88–0.96. The results revealed that the proposed models using sunshine hours and air temperature had the smallest values of MBE, MPE, and RMSE of −0.0102, 0.0585, and 0.0338 and −0.2973, 1.7075, and 0.9859, respectively. Emmanuel Quansah, Leonard K. Amekudzi, Kwasi Preko, Jeffrey Aryee, Osei R. Boakye, Dziewornu Boli, and Mubarick R. Salifu Copyright © 2014 Emmanuel Quansah et al. All rights reserved. Optimum Tilt Angle for Photovoltaic Solar Panels in Zomba District, Malawi Thu, 09 Jan 2014 13:41:18 +0000 A study to determine the optimum tilt angle for installing photovoltaic solar panels in Zomba district, Malawi, has been conducted. The study determined the optimum monthly tilt angles of PV solar panels and the seasonal adjustments needed for the panels in order to collect maximum solar radiation throughout the year. In this study, global solar radiation (GSR) on four tilted surfaces was measured. The north-facing surfaces were titled at angles of 0°, 15°, 20°, and 25°. The GSR data was used to determine the daily and monthly optimum tilt angles for the PV panels. The optimum tilt angles were found to be 0° or 25° depending on the time of the year. From October to February, the optimum tilt angle has been determined to be 0° and, from March to September, the optimum tilt angle is observed to be 25°. There are only two seasonal adjustments that are needed for PV solar panels in Zomba district and these should be carried out at the end of February and at the end of September. For fixed solar panels with no seasonal adjustments, the optimum tilt angle for the PV solar panels that are northfacing has been determined to be 25°. B. Kamanga, J. S. P. Mlatho, C. Mikeka, and C. Kamunda Copyright © 2014 B. Kamanga et al. All rights reserved. Experimental Study of Thermal Performance of One-Ended Evacuated Tubes for Producing Hot Air Sun, 08 Dec 2013 13:25:35 +0000 The thermal performance of an evacuated tube solar air collector is experimentally investigated at different air flow rates. Air is used as a working fluid in experimental setup and tested in Indian climatic conditions. The evacuated tube solar air collector consists of fifteen evacuated tubes and manifold channel. The manifold channel consists of a hollow pipe (square pipe) in centre through which air flows. The temperature difference and efficiency are studied with different air flow rates. The reflectors are used to enhance the performance of evacuated tubes solar air collector. It is observed that in case of reflector evacuated tube solar air collector gives higher outlet temperature and temperature difference and has better thermal performance as compared to the case without reflector. The maximum outlet temperature and temperature difference of air are found to be 97.4°C and 74.4°C at a flow rate of 6.70 kg/hr. Ashish Kumar, Sanjeev Kumar, Utkarsh Nagar, and Avadhesh Yadav Copyright © 2013 Ashish Kumar et al. All rights reserved. Review of Ni-Cu Based Front Side Metallization for c-Si Solar Cells Thu, 21 Nov 2013 14:14:26 +0000 Given the high percentage of metal cost in cell processing and concerns due to increasing Ag prices, alternative metallization schemes are being considered. Ni-Cu based front side metallization offers potential advantages of finer grid lines, lower series resistance, and reduced costs. A brief overview of various front side patterning techniques is presented. Subsequently, working principle of various plating techniques is discussed. For electroless plated Ni seed layer, fill factor values nearing 80% and efficiencies close to 17.5% have been demonstrated, while for Light Induced Plating deposited layers, an efficiency of 19.2% has been reported. Various methods for qualifying adhesion and long term stability of metal stack are discussed. Adhesion strengths in the range of 1–2.7 N/mm have been obtained for Ni-Cu contacts tabbed with conventional soldering process. Given the significance of metallization properties, different methods for characterization are outlined. The problem of background plating for Ni-Cu based metallization along with the various methods for characterization is summarized. An economic evaluation of front side metallization indicates process cost saving of more than 50% with Ni-Cu-Sn based layers. Recent successful commercialization and demonstration of Ni-Cu based metallization on industrial scale indicate a potential major role of Ni-Cu based contacts in near future. Mehul C. Raval and Chetan S. Solanki Copyright © 2013 Mehul C. Raval and Chetan S. Solanki. All rights reserved. Nanostructured CuO Thin Films Prepared through Sputtering for Solar Selective Absorbers Tue, 01 Oct 2013 11:47:07 +0000 Nanostructured cupric oxide (CuO) thin films have been deposited on copper (Cu) substrates at different substrate temperatures and oxygen to argon gas ratios through direct current (DC) reactive magnetron sputtering. The deposited CuO thin films are characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), profilometry, and spectrophotometry techniques. The crystalline phases, morphology, optical properties, and photothermal conversion efficiency of the CuO thin films are found to be significantly influenced by the change in substrate temperature and oxygen to argon gas ratio. The variations in the substrate temperature and oxygen to argon gas ratio have induced changes in Cu+ and Cu2+ concentrations of the CuO thin films that result in corresponding changes in their optical properties. The CuO thin film prepared at a substrate temperature of 30°C and O2 to Ar gas ratio of 1 : 1 has exhibited high absorptance and low emittance; thus, it could be used as a solar selective absorber in solar thermal gadgets. Senthuran Karthick Kumar, Sepperumal Murugesan, Santhanakrishnan Suresh, and Samuel Paul Raj Copyright © 2013 Senthuran Karthick Kumar et al. All rights reserved.