Papers - Araki Kenji
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Possibility of solar station to EV Reviewed
Araki K., Nagai H., Yamaguchi M.
AIP Conference Proceedings 1766 2016.9
Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
© 2016, American Institute of Physics Inc. All rights reserved. For reduction of the green-house gas emission in the transportation sector, it is important to look for the way to supply renewable energies to automobiles. The car running 30 km a day may be powered by solar panel on the car-roof, but the rest of the cars may be charged by the charging station from solar energy. In this study, feasibility of the charging station powered by the practical size of CPV was investigated using the charging and discharging simulation based on the meteorological database in Japan by three criteria. It was concluded that 6 m x 6 m panel would be sufficient to charge maximum 5 electric vehicles in a day.
DOI： 10.1063/1.4962099
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Study on tolerance control for optical alignment of CPV modules using a Monte Carlo simulation Reviewed
Araki K., Nagai H., Lee K., Yamaguchi M.
AIP Conference Proceedings 1766 2016.9
Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
© 2016, American Institute of Physics Inc. All rights reserved. CPV requires accuracy in optical alignment. It is required to control the assembly tolerance quantitatively. It is convenient to control the tolerance by statistical parameters. A Monte Carlo method was developed to relate how statistical parameters in component and assemble variance affects to the module performance. The rough rule will be the standard deviation of misalignment should be controlled less than 20 % of designed acceptance angle, unless the number of the cells inside the module was not very small (Typically N= 4). Namely, if the acceptance angle of the optics is plus or minus 1 degree, then the standard deviation of assembly error should be less than 0.2 deg.
DOI： 10.1063/1.4962109
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Possibility of static low concentrator PV optimized for vehicle installation Reviewed
Araki K., Ota Y., Ikeda K., Lee K., Nishioka K., Yamaguchi M.
AIP Conference Proceedings 1766 2016.9
Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
© 2016, American Institute of Physics Inc. All rights reserved. One of the most direct and efficient ways in eliminating greenhouse gas emission from cars is to install a PV panel on the roof. Since the area of the roof of the car is limited, high-efficiency III-V cells will be useful. Because of the space limitation, it should be high-efficiency panel. III-V cells may be a candidate, but it should be CPV for saving cost of the cell. Considering its quick movement and appearance, trackers were thought difficult to implement. Our choice was a static concentrator customized to automobile. Special static concentrator that collects sunlight from shallow incident angle was successfully developed.
DOI： 10.1063/1.4962069
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Design and Development of Dome-Shaped Fresnel Lens Reviewed
Araki K., Nagai H., Lee K., Ikeda K., Yamaguchi M.
IEEE Journal of Photovoltaics 6 ( 5 ) 1339 - 1344 2016.9
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Journal of Photovoltaics
© 2011-2012 IEEE. Dome-shaped Fresnel lenses were developed with a new design algorithm. The lens was defined as the integration of pentagon prisms. This method is flexible and generates a dome-shaped Fresnel lens suitable for high concentration by keeping the thickness approximately equal in the entire region of the lens so that the lens becomes mechanically robust with the minimum amount of materials.
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Araki K., Nagai H., Herrero R., Anton I., Sala G., Yamaguchi M.
IEEE Journal of Photovoltaics 6 ( 5 ) 1353 - 1359 2016.9
Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Journal of Photovoltaics
© 2011-2012 IEEE. Concentrator photovoltaics (CPV) requires accuracy in optical alignment. Optical misalignment in the module was measured and analyzed. Such information was useful to identify assembly problems and improved module performance. A Monte Carlo simulation was developed to analyze the impact of alignment errors by assembly errors. The simulation result implied that the key statistical parameters for module performance were not averaged errors but the standard deviation and the worst value. 'Cutting above certain level' was effective, including the introduction of jigs that keep misalignment at a certain level. The standard deviation of misalignment should be controlled to less than 20% of the designed acceptance half angle.
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Optimization of Land Use for a Multitracker System Using a Given Geometrical Site Condition Reviewed
Araki K., Nagai H., Ikeda K., Lee K., Yamaguchi M.
IEEE Journal of Photovoltaics 6 ( 4 ) 960 - 966 2016.7
Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Journal of Photovoltaics
© 2016 IEEE. Shading loss of a multitracker concentrator photovoltaic (CPV) system can be predicted, and for doing this, geometrical optimization will be useful. The optimum allocation for infinite land will be either rectangular allocation parallel to the N-S and E-W axis or checkerboard allocation. We solve an optimization problem with the introduction of nondimensional parameters in geometry, namely, optimum conditions as a function of space factor and panel aspect ratio. The type of optimum allocation pattern and its aspect ratio depend on latitude, climate pattern, aspect ratio of panels, and space factor. Our calculation results show that, in general, checkerboard allocation is preferred for locations with higher latitude, higher sun irradiation in summer, higher space factor, and horizontally longer rectangular solar panels.
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Recent results for concentrator photovoltaics in Japan Reviewed
Yamaguchi M., Takamoto T., Araki K., Kojima N.
Japanese Journal of Applied Physics 55 ( 4 ) 2016.4
Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics
© 2016 The Japan Society of Applied Physics. We summarize the Europe-Japan Collaborative Research Project on Concentrator Photovoltaics (CPV); NGCPV Project (a New Generation of Concentrator PhotoVoltaic cells, modules and systems). The aim of this project was to accelerate the move to very high efficiency and lower cost CPV technologies and to enhance the widespread deployment of CPV systems. Seven European partners and nine Japanese partners have contributed to this international collaboration. The following objectives have been reached: 1) a CPV cell with InGaP/GaAs/InGaAs three-junction world-record efficiency of 44.4% has been developed by Sharp, 2) 50kW and 15kW CPV plant operations with an average DC efficiency of 27.8% have been demonstrated in Spain (since mid-2012), 3) a new "Intrepid" CPV module with 31.3% efficiency has been developed by Daido Steel, 4) standard measurement of CPV cells has been established by FhG-ISE and AIST, and 46.0% efficiency has been confirmed for the direct-bonded GaInP/GaAs/GaInAsP/GaInAs four-junction solar cell under this project, 5) the fundamental research on novel materials and structures for CPV has also been conducted.
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Potential and activities of III-V/Si tandem solar cells Reviewed
Yamaguchi M., Lee K., Araki K., Kojima N., Ohshita Y.
ECS Journal of Solid State Science and Technology 5 ( 2 ) Q68 - Q73 2016
Language：English Publishing type：Research paper (scientific journal) Publisher：ECS Journal of Solid State Science and Technology
© 2015 The Electrochemical Society. All rights reserved. The paper presents efficiency potential of III-V/Si tandem solar cells with efficiencies of more than 35% under 1-sun AM1.5G and effects of dislocation upon solar cell properties of III-V-on-Si single-junction solar cells and III-V/Si tandem solar cells. Because III-V/Si system has large lattice mismatching and difference in thermal expansion coefficient, generation of misfit and thermal stress induced dislocations affect on solar cell properties. Effects of dislocations upon minority-carrier lifetime are derived from considering one dimensional transport of minority carriers to dislocations. In order to realize high efficiency solar cells with similar efficiency by homo-epitaxially grown solar cells, low density dislocation of less than 3 × 105 cm-2 is necessary. This paper also reviews approaches on reduction in dislocation density in III-V compound films on Si and improvements in efficiencies of III-V compound single-junction solar cells on Si substrates and III-V/Si tandem solar cells, along with reviewing the efficiency potentials of using other efficiency potential of other materials/Si tandem solar cells such as II-V compound/Si. Chalcopyrite/Si and Perovskite/Si tandem solar cells.
DOI： 10.1149/2.0311602jss
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Espinet-González P., Algora C., Núñez N., Orlando V., Vázquez M., Bautista J., Araki K.
Progress in Photovoltaics: Research and Applications 23 ( 5 ) 559 - 569 2015.5
Language：English Publishing type：Research paper (scientific journal) Publisher：Progress in Photovoltaics: Research and Applications
Copyright © 2014 John Wiley & Sons, Ltd. A temperature accelerated life test on commercial concentrator lattice-matched GaInP/GaInAs/Ge triple-junction solar cells has been carried out. The acceleration of the aging has been accomplished by subjecting the solar cells at temperatures markedly higher than the nominal working temperature inside a concentrator, and the nominal photo-current condition (820 X) has been emulated by injecting current in darkness. Three tests at different temperatures have been carried out. The failure distributions across the three test temperatures have been fitted to an Arrhenius-Weibull model. An Arrhenius activation energy of 1.59-eV was determined from the fit. The reliability functions and parameters of these solar cells at two nominal working conditions (80-and-100-°C) have been obtained. In both cases, the instantaneous failure rate function monotonically increases, that is, the failures are of the wear-out kind. We have also observed that the reliability data are very sensitive to the nominal temperature condition. In fact, at a nominal working condition of 820 X and 80-°C, assuming that the concentration module works 5-h per day, the warranty time obtained for a failure population of 5% has been 113-years. However, for a nominal working condition of 820 X and 100-°C, the warranty time obtained for a failure population of 5% has been 7-years. Therefore, in order to offer a long-term warranty, the working temperature could be a key factor in the design of the concentration photovoltaic systems.
DOI： 10.1002/pip.2461
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Potential and activities of III-V/si tandem solar cells Reviewed
Yamaguchi M., Lee K., Araki K., Kojima N., Ohshita Y.
ECS Transactions 69 ( 4 ) 11 - 20 2015
Language：English Publishing type：Research paper (scientific journal) Publisher：ECS Transactions
© The Electrochemical Society. The paper presents efficiency potential of III-V/Si tandem solar cells with efficiencies of more than 35% under 1-sun AM1.5G and effects of dislocation upon solar cell properties of III-V-on-Si single-junction solar cells and III-V/Si tandem solar cells. Because III-V/Si system has large lattice mismatching and difference in thermal expansion coefficient, generation of misfit and thermal stress induced dislocations affect on solar cell properties. Effects of dislocations upon minority-carrier lifetime are derived from considering one dimensional transport of minority carriers to dislocations. In order to realize high efficiency solar cells with similar efficiency by homo-epitaxially grown solar cells, low density dislocation of less than 3×105 cm-2 is necessary. This paper also reviews approaches on reduction in dislocation density in III-V compound films on Si and improvements in efficiencies of III-V compound single-junction solar cells on Si substrates and III-V/Si tandem solar cells.
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Characterization of CPV arrays based on differences on their thermal resistances Reviewed
Núñez R., Antón I., Askins S., Sala G., Araki K.
AIP Conference Proceedings 1616 144 - 148 2014
Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
©2014 AIP Publishing LLC. Thermal characterization of Concentrating Photovoltaics (CPV) modules and arrays is needed to determine their performance and modelling of energy forecast. Module-ambient thermal resistance is easily obtained from its definition but the cell-module thermal resistant needs to be estimated from indirect procedures, two of them are presented in this paper. In addition, an equivalent parameter is defined, the Concentrator Nominal Operating Module/Cell Temperature (CNOMT/CNOCT), the temperature at Concentrator Standard Operating Conditions (CSOC). Definitions and expression to relate (CNOMT/CNOCT) to thermal resistances are presented, plus several examples of estimations from real operating arrays.
DOI： 10.1063/1.4897048
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Module optical analyzer: Identification of defects on the production line Reviewed
Herrero R., Askins S., Antón I., Sala G., Araki K., Nagai H.
AIP Conference Proceedings 1616 119 - 123 2014
Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
©2014 AIP Publishing LLC. The usefulness of the module optical analyzer when identifying module defects on production line is presented in this paper. Two different case studies performed with two different kind of CPV modules are presented to show the use of MOA both in IES-UPM and Daido Steel facilities.
DOI： 10.1063/1.4897042
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Oke S., Saeki N., Motoda H., Kemmoku Y., Araki K.
IEEJ Transactions on Power and Energy 134 ( 5 ) 436 - 442 2014
Language：English Publishing type：Research paper (scientific journal) Publisher：IEEJ Transactions on Power and Energy
A concentrator photovoltaic (CPV) system which can reduce the power generation cost of PV system has been developed and assessed for commercialization. An early-type CPV module consists of 20 pairs of dome Fresnel lenses the geometrical concentration ratio of which is X550 and three junction solar cells (InGaP/InGaAs/Ge). We had carried out a field test of the early-type CPV module to evaluate the power generation, the efficiency, and other characteristics from 2004. The Fresnel lenses had never been washed until 2012 were washed and some characteristics of the CPV module were compared in before and after cleaning the lenses. Before the cleaning, many micro particulate dust included 46wt.% of C was on the lenses. Its number density decreased from 600mm-2 to 230mm-2 with cleaning the lenses. However, some characteristics of the CPV module such as I-V curve, FF and electricity efficiency were not changed by cleaning the lenses. The influences of yellow sand (Asian dust) which decreased the direct irradiance and covered on the lens surface from some deserts in interior of East Asia did not continue persistently. This is because, any dirt would not cover easily on the lenses surface, since the CPV module was moved to track to the Sun, and it had the dome-shaped Fresnel lenses which had smooth surface. © 2014 The Institute of Electrical Engineers of Japan.
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Validation of energy prediction method for a concentrator photovoltaic module in Toyohashi Japan Reviewed
Chan N.L.A., Young T.B., Brindley H.E., Ekins-Daukes N.J., Araki K., Kemmoku Y., Yamaguchi M.
Progress in Photovoltaics: Research and Applications 21 ( 8 ) 1598 - 1610 2013.12
Language：English Publishing type：Research paper (scientific journal) Publisher：Progress in Photovoltaics: Research and Applications
III-V concentrator photovoltaic systems attain high efficiency through the use of series connected multi-junction solar cells. As these solar cells absorb over distinct bands over the solar spectrum, they have a more complex response to real illumination conditions than conventional silicon solar cells. Estimates for annual energy yield made assuming fixed reference spectra can vary by up to 15% depending on the assumptions made. Using a detailed computer simulation, the behaviour of a 20-cell InGaP/In0.01GaAs/Ge multi-junction concentrator system was simulated in 5-min intervals over an entire year, accounting for changes in direct normal irradiance, humidity, temperature and aerosol optical depth. The simulation was compared with concentrator system monitoring data taken over the same period and excellent agreement (within 2%) in the annual energy yield was obtained. Air mass, aerosol optical depth and precipitable water have been identified as atmospheric parameters with the largest impact on system efficiency. Copyright © 2012 John Wiley & Sons, Ltd. The behaviour of a 20-cell InGaP/In0.01GaAs/Ge multi-junction concentrator system was simulated in 5-min intervals over an entire year with agreement within 2% between measured and modelled annual energy yields. Air mass, aerosol optical depth and precipitable water have been identified as the atmospheric parameters with the largest impact on system efficiency. Copyright © 2012 John Wiley & Sons, Ltd.
DOI： 10.1002/pip.2241
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Effect of anti-soiling photocatalytic coating for concentrator photovoltaic module Reviewed
Ota Y., Sueto T., Yokota M., Araki K., Nishioka K.
Proceedings of the 20th International Workshop on Active-Matrix Flatpanel Displays and Devices: TFT Technologies and FPD Materials, AM-FPD 2013 193 - 194 2013.11
Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of the 20th International Workshop on Active-Matrix Flatpanel Displays and Devices: TFT Technologies and FPD Materials, AM-FPD 2013
An anti-soiling layer was coated on the surface of polymethylmethacrylate (PMMA), which is the primary material of Fresnel lenses for concentrator photovoltaics. The layer was prepared by coating the photocatalytic surface layer with modified WO3 and partially hydrolyzed tetraethyl orthosilicate. When sand was discharged onto the PMMA samples, the mass of adherent sand was more than 0.010 g for the sample without the coating and approximately 0.005 g for the sample with the coating. The electrostatic potential of the sample without the coating increased with increasing amount of incident sand, reaching a maximum value of 0.25 k V. On the other hand, the electrostatic potential of the sample with the coating was suppressed to 0.1 kV. The presence of electrostatic charges on the surface of the samples was a main factor for the adhesion of sand, and it could be suppressed by the anti-soiling photocatalytic layer.. © 2013 JSAP.
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Durability of polymeric encapsulation materials for concentrating photovoltaic systems Reviewed
Miller D., Muller M., Kempe M., Araki K., Kennedy C., Kurtz S.
Progress in Photovoltaics: Research and Applications 21 ( 4 ) 631 - 651 2013.6
Language：English Publishing type：Research paper (scientific journal) Publisher：Progress in Photovoltaics: Research and Applications
The durability of polymeric encapsulation materials was examined using outdoor exposure at the nominal optical concentration of 500 suns. The results for 12 months' cumulative field deployment are presented for materials including ethylene-co-vinyl acetate, polyvinyl butyral (PVB), ionomer, polyethylene/polyoctene copolymer, thermoplastic polyurethane, poly(dimethylsiloxane), and poly(phenyl-methyl siloxane). Measurements during the experiment included optical transmittance (direct and hemispherical), mass, visual appearance, and fluorescence spectroscopy in addition to the initial thermogravimetry of the materials. Measurements of the field conditions and ultraviolet dose at the test site were facilitated by numerous laboratory instruments; characterization of the specimen temperature was performed using thermography. Discovery experiments identified the importance of a secondary homogenizer optic and the importance of contamination control. To date, the formal experiment verified a thermal-runaway-motivated combustion failure mechanism for one of the PVB formulations and identified densification, cracking, and haze-formation behaviors in some of the silicone specimens. The behaviors observed for the silicone specimens may be facilitated by their greater thickness. Copyright © 2012 John Wiley & Sons, Ltd.
DOI： 10.1002/pip.1241
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Reduction in operating temperature of 25 series-connected 820X concentrator photovoltaic module Reviewed
Ota Y., Sueto T., Nagai H., Araki K., Nishioka K.
Japanese Journal of Applied Physics 52 ( 4 PART 2 ) 2013.4
Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics
Under concentration conditions, it is important to manage the operating temperature of a concentrator photovoltaic (CPV) module, because a high-density solar energy enters into the solar cell. We measured the receiver temperature of the CPV module and evaluated the relationship between the temperature and output of the CPV module. 25 series-connected 820X CPV modules with 2- and 4-mm-thick back chassises were fabricated. In the case of a CPV module with a 4-mm-thick back chassis, the receiver temperature was markedly reduced owing to the effective thermal diffusion of the thicker chassis. The absolute conversion efficiency of the CPV module with the 4-mm-thick back chassis was 1.5% higher than that of the module with the 2-mm-thick back chassis. Moreover, we developed a thermal transfer model of the CPV module and calculated the thermal distribution in the CPV module using a thermal transfer simulator. © 2013 The Japan Society of Applied Physics.
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Heat reduction of concentrator photovoltaic module using high radiation coating Reviewed
Nishioka K., Ota Y., Tamura K., Araki K.
Surface and Coatings Technology 215 472 - 475 2013.1
Language：English Publishing type：Research paper (scientific journal) Publisher：Surface and Coatings Technology
A thermal radiation layer was coated on the aluminum chassis of a concentrator photovoltaic (CPV) module. The temperature of the solar cell in the CPV module with the thermal radiation coating was approximately 10 °C lower than that of the module without the thermal radiation coating. The uniformity of the temperature distribution in the CPV module was considerably improved. The thermal radiation coating acted not only as a thermal radiation layer but also as a thermal conduction layer. The open-circuit voltage of the CPV module with thermal radiation coating was 0.5. V higher than that of the module without the coating during the period evaluated. The conversion efficiency of the CPV module with thermal radiation coating was 0.5% higher than that of the module without the coating. © 2012 Elsevier B.V.
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Sueto Tsuyoshi, Ota Yasuyuki, Araki Kenji, Kumagai Isao, Nishioka Kensuke
The Journal of the Institute of Electrical Installation Engineers of Japan 33 ( 7 ) 547 - 552 2013
Language：English Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Installation Engineers of Japan
We propose a simple guidepost for the installation of photovoltaic systems using the field test data in Miyazaki,Japan. Concentrator photovoltaic (CPV) system generates electricity only from direct solar irradiance. Therefore,the output of CPV system is drastically influenced by scattering ratio due to humidity,aerosols,and yellow sand,The scattering ratio varies with the seasons. We proposed an insta11ation guidepost of CPV systems using the scattering ratio and gradient global irradiance. We measured the output of CPV and flat-p1ate multi-crystalline Si PV systems. We have measurement systems for direct and global solar irradiance. Therefor,we can obtain the scattering ratio. Gradient global irradiance was also measured. These field test results were analyzed and a guidepost was derived. Based on the guidepost,we can decide which systems of CPV or Si PV systems is suitable at a candidate site for system installation
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Espinet-Gonzalez P., Romero R., Orlando V., Gabas M., Nunez N., Vazquez M., Palanco S., Bijani S., Contreras Y., Galiana B., Algora C., Araki K.
Conference Record of the IEEE Photovoltaic Specialists Conference 1666 - 1671 2013
Language：English Publishing type：Research paper (scientific journal) Publisher：Conference Record of the IEEE Photovoltaic Specialists Conference
In this work the failure analysis carried out in III-V concentrator multijunction solar cells after a temperature accelerated life test is presented. All the failures appeared have been catastrophic since all the solar cells turned into low shunt resistances. A case study in failure analysis based on characterization by optical microscope, SEM, EDX, EQE and XPS is presented in this paper, revealing metal deterioration in the bus bar and fingers as well as cracks in the semiconductor structure beneath or next to the bus bar. In fact, in regions far from the bus bar the semiconductor structure seems not to be damaged. SEM images have dismissed the presence of metal spikes inside the solar cell structure. Therefore, we think that for these particular solar cells, failures appear mainly as a consequence of a deficient electrolytic growth of the front metallization which also results in failures in the semiconductor structure close to the bus bars. © 2013 IEEE.