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Photovoltaics
Kinds of Photovoltaics Terms modified by Photovoltaics Selected AbstractsImproved Photovoltaic Performance of Heterostructured Tetrapod-Shaped CdSe/CdTe Nanocrystals Using C60 InterlayerADVANCED MATERIALS, Issue 44 2009Yanqin Li Photovoltaic (PV) devices based on CdSe/CdTe-C60 active layers, in which the nanocrystal and fullerene (C60) layers work as electron-donor and electron-acceptor/transport layers, respectively, were fabricated. Efficiencies up to 0.62% were reached in the hybrid cells. The PV performance was greatly improved with respect to that of CdSe/CdTe-P3HT- and CdSe/CdTe-based devices, fabricated as reference. [source] Local control of photovoltaic distributed generation for voltage regulation in LV distribution networks and simulation toolsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2009Stefania Conti Abstract The increasing connection of distributed generation (DG) in distribution networks may affect the quality of power offered to customers. One of the most relevant issues is the possibility to have unacceptable voltage rise at the point of common coupling (PCC). This work focuses on the problem of voltage control in LV distribution networks in the presence of photovoltaic (PV) DG. The paper presents a local voltage control method based on PV generation curtailment as an alternative to ,on/off' operation, typically required by distribution operators to prevent overvoltage at the PCCs by means of overvoltage protections embedded in the PV unit. To show the effect of the proposed local voltage control, a simulation tool, developed in MATLAB®,Simulink® environment, is presented. Appropriate numerical models for network components and PV generators are provided in order to describe computer simulation implementation of the test system. The final results show that the control system is able to adjust the active power output of local generators to keep the voltage profile of the feeder, in which DG is installed, within the range allowed by Norm EN 50160. Copyright © 2008 John Wiley & Sons, Ltd. [source] Influence of Molecular Weight on the Performance of Organic Solar Cells Based on a Fluorene DerivativeADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Christian Müller Abstract The performance of organic photovoltaic (OPV) bulk-heterojunction blends comprising a liquid-crystalline fluorene derivative and a small-molecular fullerene is found to increase asymptotically with the degree of polymerization of the former. Similar to various thermodynamic transition temperatures as well as the light absorbance of the fluorene moiety, the photocurrent extracted from OPV devices is found to strongly vary with increasing oligomer size up to a number average molecular weight, Mn,,,10,kg,mol,1, but is rendered less chain-length dependent for higher Mn as the fluorene derivative gradually adopts polymeric behavior. [source] Solar Energy Collectors with Tunable TransmissionADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Michael G. Debije Abstract A new type of "smart" window is proposed that makes use of fluorescent dye guests in a liquid-crystal host sandwiched between glass panels. The dye absorbs a variable amount of light depending on its orientation, and re-emits this light, of which a significant fraction is trapped by total internal reflection at the glass,air interface, and becomes concentrated along the edges. Such a device could both generate electricity via an attached photovoltaic as well as allow user control of the amount of transmitted light. By applying a voltage across the cell, absorption could be varied 31%, while the usable light output only varied 11% due to the increased efficiency of light collection at homeotropic dye orientation. [source] Anode Interfacial Tuning via Electron-Blocking/Hole-Transport Layers and Indium Tin Oxide Surface Treatment in Bulk-Heterojunction Organic Photovoltaic CellsADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Alexander W. Hains Abstract The effects of anode/active layer interface modification in bulk-heterojunction organic photovoltaic (OPV) cells is investigated using poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and/or a hole-transporting/electron-blocking blend of 4,4,-bis[(p -trichlorosilylpropylphenyl)-phenylamino]biphenyl (TPDSi2) and poly[9,9-dioctylfluorene- co - N -[4-(3-methylpropyl)]-diphenylamine] (TFB) as interfacial layers (IFLs). Current,voltage data in the dark and AM1.5G light show that the TPDSi2:TFB IFL yields MDMO-PPV:PCBM OPVs with substantially increased open-circuit voltage (Voc), power conversion efficiency, and thermal stability versus devices having no IFL or PEDOT:PSS. Using PEDOT:PSS and TPDSi2:TFB together in the same cell greatly reduces dark current and produces the highest Voc (0.91,V) by combining the electron-blocking effects of both layers. ITO anode pre-treatment was investigated by X-ray photoelectron spectroscopy to understand why oxygen plasma, UV ozone, and solvent cleaning markedly affect cell response in combination with each IFL. O2 plasma and UV ozone treatment most effectively clean the ITO surface and are found most effective in preparing the surface for PEDOT:PSS deposition; UV ozone produces optimum solar cells with the TPDSi2:TFB IFL. Solvent cleaning leaves significant residual carbon contamination on the ITO and is best followed by O2 plasma or UV ozone treatment. [source] Efficiency Enhancement in Organic Photovoltaic Cells: Consequences of Optimizing Series ResistanceADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Jonathan D. Servaites Abstract Here, means to enhance power conversion efficiency (PCE or ,) in bulk-heterojunction (BHJ) organic photovoltaic (OPV) cells by optimizing the series resistance (Rs),also known as the cell internal resistance,are studied. It is shown that current state-of-the-art BHJ OPVs are approaching the limit for which efficiency can be improved via Rs reduction alone. This evaluation addresses OPVs based on a poly(3-hexylthiophene):6,6-phenyl C61 -butyric acid methyl ester (P3HT:PCBM) active layer, as well as future high-efficiency OPVs (,,>,10%). A diode-based modeling approach is used to assess changes in Rs. Given that typical published P3HT:PCBM test cells have relatively small areas (,0.1,cm2), the analysis is extended to consider efficiency losses for larger area cells and shows that the transparent anode conductivity is then the dominant materials parameter affecting Rs efficiency losses. A model is developed that uses cell sizes and anode conductivities to predict current,voltage response as a function of resistive losses. The results show that the losses due to Rs remain minimal until relatively large cell areas (>0.1,cm2) are employed. Finally, Rs effects on a projected high-efficiency OPV scenario are assessed, based on the goal of cell efficiencies >10%. Here, Rs optimization effects remain modest; however, there are now more pronounced losses due to cell size, and it is shown how these losses can be mitigated by using higher conductivity anodes. [source] Tuning Conversion Efficiency in Metallo Endohedral Fullerene-Based Organic Photovoltaic DevicesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Russel B. Ross Abstract Here the influence that 1-(3-hexoxycarbonyl)propyl-1-phenyl-[6,6]-Lu3N@C81, Lu3N@C80,PCBH, a novel acceptor material, has on active layer morphology and the performance of organic photovoltaic (OPV) devices using this material is reported. Polymer/fullerene blend films with poly(3-hexylthiophene), P3HT, donor material and Lu3N@C80,PCBH acceptor material are studied using absorption spectroscopy, grazing incident X-ray diffraction and photocurrent spectra of photovoltaic devices. Due to a smaller molecular orbital offset the OPV devices built with Lu3N@C80,PCBH display increased open circuit voltage over empty cage fullerene acceptors. The photovoltaic performance of these metallo endohedral fullerene blend films is found to be highly impacted by the fullerene loading. The results indicate that the optimized blend ratio in a P3HT matrix differs from a molecular equivalent of an optimized P3HT/[6,6]-phenyl-C61 -butyric methyl ester, C60,PCBM, active layer, and this is related to the physical differences of the C80 fullerene. The influence that active layer annealing has on the OPV performance is further evaluated. Through properly matching the film processing and the donor/acceptor ratio, devices with power conversion efficiency greater than 4% are demonstrated. [source] Bimolecular Crystals of Fullerenes in Conjugated Polymers and the Implications of Molecular Mixing for Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009A. C. Mayer The performance of polymer:fullerene bulk heterojunction solar cells is heavily influenced by the interpenetrating nanostructure formed by the two semiconductors because the size of the phases, the nature of the interface, and molecular packing affect exciton dissociation, recombination, and charge transport. Here, X-ray diffraction is used to demonstrate the formation of stable, well-ordered bimolecular crystals of fullerene intercalated between the side-chains of the semiconducting polymer poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2- b]thiophene. It is shown that fullerene intercalation is general and is likely to occur in blends with both amorphous and semicrystalline polymers when there is enough free volume between the side-chains to accommodate the fullerene molecule. These findings offer explanations for why luminescence is completely quenched in crystals much larger than exciton diffusion lengths, how the hole mobility of poly(2-methoxy-5-(3,,7,-dimethyloxy)-p-phylene vinylene) increases by over 2 orders of magnitude when blended with fullerene derivatives, and why large-scale phase separation occurs in some polymer:fullerene blend ratios while thermodynamically stable mixing on the molecular scale occurs for others. Furthermore, it is shown that intercalation of fullerenes between side chains mostly determines the optimum polymer:fullerene blending ratios. These discoveries suggest a method of intentionally designing bimolecular crystals and tuning their properties to create novel materials for photovoltaic and other applications. [source] Optimal Control of Voltage in Distribution Systems by Voltage Reference ManagementIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2009Tomonobu Senjyu Student member Abstract Recently, renewable energy technologies such as wind turbine generators and photovoltaic (PV) systems have been introduced as distributed generations (DGs). Connections of a large amount of distributed generations may cause voltage deviation beyond the statutory range in distribution systems. A reactive power control of DGs can be a solution of this problem, and it also has a possibility to reduce distribution loss. In this paper, we propose a control methodology of voltage profile in a distribution system using reactive power control of inverters interfaced with DGs and tap changing transformers. In the proposed method, a one-day schedule of voltage references for the control devices are determined by an optimization technique based on predicted values of load demand and PV power generation. Reactive power control of interfaced inverters is implemented within the inverter capacity without reducing active power output. The proposed method accomplishes voltage regulation within the acceptable range and reduction of distribution loss. The effectiveness of the proposed method is confirmed by simulations. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Analysis of PV/wind potential in the Canadian residential sector through high-resolution building energy simulationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2009Ali M. Syed Abstract Rising fuel prices and global warming are two major issues that concern people today. In this paper, the effect that the integration of the hybrid photovoltaic (PV)/wind-turbine generation can have on conservation of energy and reduction of greenhouse gases (GHGs) has been studied. Base-case energy demands were calculated using building energy simulation software and then the residential buildings were equipped with the PV/wind-turbine electricity generation devices. The results show that the integration of those equipments can reduce both cost of fuel and GHG emissions to a fair amount. Copyright © 2008 John Wiley & Sons, Ltd. [source] Coupling of thermoelectric modules with a photovoltaic panel for air pre-heating and pre-cooling application; an annual simulationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2008Nolwenn Le Pierrès Abstract Thermoelectric (TE) modules are possible reversible pre-cooling and pre-heating devices for ventilation air in buildings. In this study, the opportunity of direct coupling of TE modules with photovoltaic (PV) cells is considered. This coupling is evaluated through a numerical simulation depending on the meteorological conditions of Chambéry, Alpine region in France, and on the cooling or heating use of the TE modules, through annual energy and exergy efficiencies. For the considered conditions, TE module performances are of the same order as the ones of the vapour compression heat pumps, with a TE coefficient of performance higher than 2 for low values of input DC current. The PV,TE coupling efficiency varies between 0.096 and 0.23 over the year, with an average value of 0.157. Evolutions of the exergy effectiveness of PV and TE elements follow the same trends as the corresponding energy efficiencies but with steeper variations for the coupling exergy yield that varies between 0.004 and 0.014, with an annual average value of 0.010. The direct PV,TE coupling does not seem to be a sustainable option for the summer cooling purpose particularly. A case study with indirect coupling under a warm climate is considered and shows that the use of TE devices could be efficient in housing to ensure summer thermal comfort, but the corresponding necessary PV area would induce a high investment. Copyright © 2008 John Wiley & Sons, Ltd. [source] Economic analysis of small photovoltaic facilities and their regional differencesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2004M. Varela Abstract Small grid-connected photovoltaic (PV) facilities in Spain receive either a premium of 0.36, kWh,1 over the average price on the power market or a fixed price of 0.40, kWh,1. However, legislation on this matter (Royal Decree 2818/98) requires a periodic review of these figures. The basis of on-going revision of these prices has been their profitability. However, the economic success of such PV facilities is clearly affected by the amount of solar radiation at the site where they are located. Since Spain is between latitudes 44 and 36° in the northern hemisphere, the feasibility of these systems must be analysed for different regions. Two different models have been used to produce the required input data for such an analysis: a model that generates typical solar radiation years and temperatures taken from satellite images and an empirical model for the prediction of daily power produced by a grid-connected photovoltaic system. From the results of this regional economic analysis, it may be concluded that the existing prices are insufficient in and of themselves to make these small grid-connected systems profitable anywhere in Spain. To guarantee the economic feasibility of these PV installations in any given location, the fixed price paid for the electricity should be around 0.93, kWh,1. Nevertheless, if the Government were to double the current fixed price, in consideration of the slow increase in the PV market in recent years, this would mean that small grid-connected installations would become profitable in at least 77% of the Spanish territory. Copyright © 2004 John Wiley & Sons, Ltd. [source] Synthesis, light emission, and photovoltaic properties of perylene-containing polyacetylenesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2008Jianli Hua Abstract Perylene (Py)-containing polyacetylenes with different skeleton structures [HCC(C6H4)CO2Py]n (P1), [HCC(CH2)8CO2Py]n (P2), and {[(C6H5) CC(CH2)9NH2]co[(C6H5)CC(CH2)9Py]}n (P3) are synthesized in satisfactory yields by Rh-catalyzed polymerization (for P1 and P2) and polymer reaction (for P3). All the polymers are soluble and possess high molecular weights (Mw up to 2.8 × 105). Their structures and properties are characterized and evaluated by IR, NMR, UV, TGA, PL, and photovoltaic (PV) analyses. The polymers are thermally stable, losing little of their weights when heated to 330 °C. When their solutions are irradiated, their perylene pendants emit intense red fluorescence at 610 nm. PV cells with a configuration of ITO/PEDOT:PSS/polymer/LiF/Al are fabricated, which show maximum current density of 10.3 ,A/cm2. The external quantum efficiency is sensitive to the polymer structure, with P3 exhibiting the highest value of 0.23%. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2025,2037, 2008 [source] Photosynthetic biomass and H2 production by green algae: from bioengineering to bioreactor scale-upPHYSIOLOGIA PLANTARUM, Issue 1 2007Ben Hankamer The development of clean borderless fuels is of vital importance to human and environmental health and global prosperity. Currently, fuels make up approximately 67% of the global energy market (total market = 15 TW year,1) (Hoffert et al. 1998). In contrast, global electricity demand accounts for only 33% (Hoffert et al. 1998). Yet, despite the importance of fuels, almost all CO2 free energy production systems under development are designed to drive electricity generation (e.g. clean-coal technology, nuclear, photovoltaic, wind, geothermal, wave and hydroelectric). In contrast, and indeed almost uniquely, biofuels also target the much larger fuel market and so in the future will play an increasingly important role in maintaining energy security (Lal 2005). Currently, the main biofuels that are at varying stages of development include bio-ethanol, liquid carbohydrates [e.g. biodiesel or biomass to liquid (BTL) products], biomethane and bio-H2. This review is focused on placing bio-H2 production processes into the context of the current biofuels market and summarizing advances made both at the level of bioengineering and bioreactor design. [source] Interface-tailored and nanoengineered polymeric materials for (opto)electronic devicesPOLYMER INTERNATIONAL, Issue 6 2009Hong Ma Abstract For plastic (opto)electronic devices such as light-emitting diodes (LEDs), photovoltaic (PV) cells and field-effect transistors (FETs), the processes of charge (hole/electron) injection, charge transport, charge recombination (exciton formation), charge separation (exciton diffusion and dissociation) and charge collection are critical to enhance their performance. Most of these processes are relevant to nanoscale and interfacial phenomena. In this review, we highlight the state-of-the-art developments of interface-tailored and nanoengineered polymeric materials to optimize the performance of (opto)electronic devices. These include (1) interfacial engineering of anode and cathode for polymer LEDs; (2) nanoengineered (C60 and inorganic semiconductor nanoparticles) ,-conjugated polymeric materials for PV cells; and (3) polymer and monolayer dielectrics/interfaces for FETs and light-emitting and nano-FETs. Copyright © 2009 Society of Chemical Industry [source] Evaluation of photovoltaic modules based on sampling inspection using smoothed empirical quantiles,PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2010Ansgar Steland Abstract An important issue for end users and distributors of photovoltaic (PV) modules is the inspection of the power output specification of a shipment. The question is whether or not the modules satisfy the specifications given in the data sheet, namely the nominal power output under standard test conditions, relative to the power output tolerance. Since collecting control measurements of all modules is usually unrealistic, decisions have to be based on random samples. In many cases, one has access to flash data tables of final output power measurements (flash data) from the producer. We propose to rely on the statistical acceptance sampling approach as an objective decision framework, which takes into account both the end users and producers risk of a false decision. A practical solution to the problem is discussed which has been recently found by the authors. The solution consists of estimates of the required optimal sample size and the associated critical value where the estimation uses the information contained in the additional flash data. We propose and examine an improved solution which yields even more reliable estimated sampling plans as substantiated by a Monte Carlo study. This is achieved by employing advanced statistical estimation techniques. Copyright © 2009 John Wiley & Sons, Ltd. [source] Coupling PV and CAES power plants to transform intermittent PV electricity into a dispatchable electricity sourcePROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2008James Mason Abstract This study investigates the transformation of photovoltaic (PV) electricity production from an intermittent into a dispatchable source of electricity by coupling PV plants to compressed air energy storage (CAES) gas turbine power plants. Based on historical solar irradiation data for the United States' south western states and actual PV and CAES performance data, we show that the large-scale adoption of coupled PV,CAES power plants will likely enable peak electricity generation in 2020 at costs equal to or lower than those from natural gas power plants with or without carbon capture and storage systems. Our findings also suggest that given the societal value of reducing carbon dioxide and the sensitivity of conventional generation to rising fossil fuel prices, this competitive crossover point may occur much sooner. Copyright © 2008 John Wiley & Sons, Ltd. [source] Disconnection detection using earth capacitance measurement in photovoltaic module stringPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2008Takumi Takashima Abstract A disconnection detection method using an earth capacitance measurement in photovoltaic (PV) module string was experimentally studied. In the experiments with disconnections between PV modules in the string, the earth capacitance of the string was increased in proportion to the module number, and this feature resulted in that the disconnection position between the modules could be estimated by comparing the earth capacitance value of the failed string with that of the good string. Since the earth capacitance was not affected by the irradiance change, the detection method could be applied anytime to locate the disconnection position in the string without the effect of the irradiance change. Moreover, this method could be applied not only to the string consisting of the crystalline Si modules but also to the string consisting of the amorphous Si modules. Copyright © 2008 John Wiley & Sons, Ltd. [source] Assessing the outdoor operating temperature of photovoltaic modulesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2008David Faiman Abstract By a careful study of data collected from seven varieties of photovoltaic (PV) module it is demonstrated that a simple modified form of the Hottel,Whillier,Bliss (HWB) equation, familiar from the analysis of flat-plate solar,thermal collectors, can be employed to predict module temperatures within an accuracy comparable to the cell-to-cell temperature differences typically encountered within a module. Furthermore, for modules within the range of construction parameters employed in this study, the actual values of the two modified HWB constants do not appear to depend upon module type. The implication of these results for the accuracy of outdoor module characterization is discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Investigation to estimate the short circuit current by applying the solar spectrumPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2008Jun Tsutsui Abstract The influence of the solar spectrum is investigated to estimate the outdoor short circuit current (Isc) of various photovoltaic (PV) modules. It is well known that the solar spectrum always changes. Hence, it is rare to fit the standard solar spectrum AM1·5G defined in standard IEC 60904-3. In addition, the spectral response (SR) of PV module is different depending on the material. For example, crystal silicon (c-Si) has broad sensitivity that the wavelength range is between 350 and 1150,nm; meanwhile, amorphous silicon (a-Si) has relatively narrow sensitivity comparing to c-Si. Since Isc of the PV module decides by multiplying the solar spectrum and SR together, it is necessary to investigate the solar spectrum to estimate the outdoor Isc in addition to the solar irradiance and module temperature. In this study, the spectral mismatch is calculated and the outdoor Isc is estimated in the whole year. Copyright © 2007 John Wiley & Sons, Ltd. [source] A new method for estimating insolation based on PV-module currents in a cluster of stand-alone solar systemsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2007Frans Nieuwenhout Abstract In order to evaluate the performance of solar home systems (SHSs), data on local insolation is a prerequisite. We present a new method to estimate insolation if direct measurements are unavailable. This method comprises estimation of daily irradiation by correlating photovoltaic (PV) module currents from a number of SHSs, located a few kilometres apart. The method was tested with a 3-year time series for nine SHS in a remote area in Indonesia. Verification with reference cell measurements over a 2-month period showed that our method could determine average daily irradiation with a mean bias error of 1·3%. Daily irradiation figures showed a standard error of 5%. The systematic error in this method is estimated to be around 10%. Especially if calibration with measurements during a short period is possible, the proposed method provides more accurate monthly insolation figures compared with the readily available satellite data from the NASA SSE database. An advantage of the proposed method over satellite data is that irradiation figures can be calculated on a daily basis, while the SSE database only provides monthly averages. It is concluded that the new method is a valuable tool to obtain information on insolation when long-term measurements are absent. Copyright © 2007 John Wiley & Sons, Ltd. [source] Overcoming the poor short wavelength spectral response of CdS/CdTe photovoltaic modules via luminescence down-shifting: ray-tracing simulationsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2007B.S. Richards Abstract The short-wavelength response of cadmium sulfide/cadmium telluride (CdS/CdTe) photovoltaic (PV) modules can be improved by the application of a luminescent down-shifting (LDS) layer to the PV module. The LDS layer contains a mixture of fluorescent organic dyes that are able to absorb short-wavelength light of ,,<,540,nm, for which the PV module exhibited low external quantum efficiency (EQE), and re-emit it at a longer wavelength (,,>,540,nm), where the solar cell EQE is high. Ray-tracing simulations indicate that a mixed LDS layer containing three dyes could lead to an increase in the short-circuit current density from Jsc,=,19.8,mA/cm2 to Jsc,=,22.9,mA/cm2 for a CdS/CdTe PV module. This corresponds to an increase in conversion efficiency from 9.6% to 11.2%. This indicates that a relative increase in the performance of a production CdS/CdTe PV module of nearly 17% can be expected via the application of LDS layers, possibly without any making any alterations to the solar cell itself. Copyright © 2006 John Wiley & Sons, Ltd. [source] Long-term transient and metastable effects in cadmium telluride photovoltaic modulesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2006J. A. del Cueto Abstract Thin-film cadmium telluride (CdTe) photovoltaic (PV) technology is poised to begin making significant contributions and impact on terrestrial, electric power generation. However, some outstanding issues such as stability and transient behavior, and their impact on reliability and assessment of performance, remain to be thoroughly addressed, which has prompted some unease among PV industry integrators toward deploying this technology. We explore the issues of long-term stability and transient behavior in the performance of CdTe modules herein, using data acquired from indoor light-soaking studies. We find that measurement of current-voltage parameters and their temperature coefficients are entangled with transient effects. Changes in module power depend on recent operating history, such as electrical bias, and can result in either artificially high or low performance. Both the open-circuit voltage (VOC) and fill factor (FF) are significantly impacted by metastable behavior that appears to linger for up to tens of hours, and we observe such increased transient effects after modules have undergone several hundred hours of light exposure. We present and analyze data measured under standard reporting conditions and actual operating conditions for six CdTe modules light-exposed and stressed at 65°C nominal temperatures. Copyright © 2006 John Wiley & Sons, Ltd. [source] Corrosion effects in thin-film photovoltaic modulesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2003D. E. Carlson Abstract Electrochemical corrosion effects can occur in thin-film photovoltaic (PV) modules that are fabricated on tin-oxide-coated glass when operating at high voltages and at elevated temperatures in a humid climate. The current study shows that this corrosion is associated with a delamination of the tin oxide layer from the glass, which is caused by sodium accumulation near the interface between the tin oxide and the glass and by the ingression of moisture into the PV module from the edges. This corrosion in thin-film PV modules can be significantly reduced by altering the growth conditions of the tin oxide or by using zinc oxide as a transparent conductive oxide electrode. Copyright © 2003 John Wiley & Sons, Ltd. [source] A method for modeling the current,voltage curve of a PV module for outdoor conditions,PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2002B. Marion A method has been developed for modeling the current,voltage curve of a photovoltaic (PV) module for outdoor conditions. An indoor characterization procedure determines a PV module's temperature and irradiance correction factors, which are used in conjunction with equations to translate a reference curve to outdoor conditions of PV module temperature and irradiance. A PV technology's spectral response characteristics are accommodated in the equation for irradiance. The modeled and measured energy is compared for a one-year period for seven PV modules of different technologies. The results validate the method's use for modeling the hourly performance of PV modules, and for modeling daily energy production for PV module energy rating purposes. Published in 2002 by John Wiley & Sons, Ltd. [source] Procedure for determining the uncertainty of photovoltaic module outdoor electrical performance,PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2001K. Whitfield This paper sets forth an uncertainty estimation procedure for the measurement of photovoltaic (PV) electrical performance using natural sunlight and calibrated secondary reference cells. The actual test irradiance should be restricted to values between 800 and 1000,W/m2 in order to assume that maximum power varies linearly with irradiance. Only the uncertainty of maximum power at standard test conditions (STC), i.e., 1000,W/m2 plane-of-array irradiance and 25°C cell temperature, is developed in its entirety. The basic uncertainty analysis principles developed herein, however, can be applied to any electrical variable of interest (e.g., short-circuit current, open-circuit voltage and fill factor). Although the equations presented appear cumbersome, they are easily implemented into a computer spreadsheet. Examples of uncertainty analyses are also presented herein to make the concepts more concrete. Published in 2001 by John Wiley & Sons, Ltd. [source] Irrungen und Wirrungen um Biokraftstoffe.CHEMIE IN UNSERER ZEIT (CHIUZ), Issue 5 2010Biokraftstoffe sind nicht per se nachhaltig Die jährliche Photosyntheseleistung auf der Erde übersteigt die anthropogene CO2 -Produktion. Dies legt eine energetische Nutzung der Biomasse nahe und hat die Entwicklung von Biokraftstoffen erheblich gefördert. In vielen Fällen verstößt die Nutzung von Biokraftstoffen jedoch gegen Prinzipien der Nachhaltigkeit. Für die Deckung des Weltenergiebedarfes durch Biomasse würde die gesamte verfügbare landwirtschaftliche Nutzfläche benötigt. Diese Einsicht hat eine kritische Teller-oder-Tank-Diskussion ausgelöst. Energetisch und ökologisch effizienter als die Nutzung von Biokraftstoffen wäre der Anbau schnellwachsender Hölzer und deren direkte Verstromung im Kraftwerk. Die mit großem Abstand effizienteste Nutzung der Sonnenenergie erlauben Photovoltaik und Solarthermie. Wegen ihrer hohen Energiedichte werden flüssige Biokraftstoffe der zweiten Generation aber dort, wo die Elektromobilität an Grenzen stößt, auch in Zukunft Anwendung finden. The annual photosynthesis on the Earth exceeds the anthropogenic CO2 production. This suggests an energetic use of biomass and has greatly promoted the development of biofuels. In many cases, however, the use of biofuels is breaking the rules of sustainability. To meet the world's energy demand from biomass would require the total available agricultural land. This insight has a critical plate or tank discussion triggered. Energetically and environmentally more efficient than the use of biofuels would be the cultivation of fast-growing timber and its direct use in coal power plants for electricity production. By far the most efficient use of solar energy is provided by photovoltaic and solar heat use. Because of their high energy density liquid second-generation biofuels will be applied also in future in such cases where electrical mobility has its limits. [source] Bulk Heterojunctions: Ultrafast Hole-Transfer Dynamics in Polymer/PCBM Bulk Heterojunctions (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Mater. The active layer of the currently most efficient plastic photovoltaic cells is a blend of polymer and methanofullerene molecules. In their article on page 1653, M. S. Pshenichnikov et al. show that hole transfer upon methanofullerene excitation operates simultaneously with electron transfer as the charge generation process in plastic photovoltaics, at a staggering timescale of 30 fs. [source] Interface Engineering for Organic ElectronicsADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Hong Ma Abstract The field of organic electronics has been developed vastly in the past two decades due to its promise for low cost, lightweight, mechanical flexibility, versatility of chemical design and synthesis, and ease of processing. The performance and lifetime of these devices, such as organic light-emitting diodes (OLEDs), photovoltaics (OPVs), and field-effect transistors (OFETs), are critically dependent on the properties of both active materials and their interfaces. Interfacial properties can be controlled ranging from simple wettability or adhesion between different materials to direct modifications of the electronic structure of the materials. In this Feature Article, the strategies of utilizing surfactant-modified cathodes, hole-transporting buffer layers, and self-assembled monolayer (SAM)-modified anodes are highlighted. In addition to enabling the production of high-efficiency OLEDs, control of interfaces in both conventional and inverted polymer solar cells is shown to enhance their efficiency and stability; and the tailoring of source,drain electrode,semiconductor interfaces, dielectric,semiconductor interfaces, and ultrathin dielectrics is shown to allow for high-performance OFETs. [source] A CdSe Nanowire/Quantum Dot Hybrid Architecture for Improving Solar Cell PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Yanghai Yu Abstract Incorporating colloidal CdSe quantum dots (QDs) into CdSe nanowire (NW)-based photoelectrochemical solar cells increases their incident-photon-to-carrier conversion efficiencies (IPCE) from 13% to 25% at 500,nm. While the effect could, in principle, stem from direct absorption and subsequent carrier generation by QDs, the overall IPCE increase occurs across the entire visible spectrum, even at wavelengths where the dots do not absorb light. This beneficial effect originates from an interplay between NWs and QDs where the latter fill voids between interconnected NWs, providing electrically accessible conduits, in turn, enabling better carrier transport to electrodes. The presence of QDs furthermore reduces the residual polarization anisotropy of random NW networks. Introducing QDs therefore addresses an important limiting constraint of NW photoelectrochemical solar cells. The effect appears to be general and may aid the future design and implementation of other NW-based photovoltaics. [source] | |||||||||||||||||||