Papers - Araki Kenji
-
Araki K., Lee K., Yamaguchi M.
2018 18th International Workshop on Junction Technology, IWJT 2018 2018-January 1 - 4 2018.4
Language：English Publishing type：Research paper (scientific journal) Publisher：2018 18th International Workshop on Junction Technology, IWJT 2018
© 2018 IEEE. This paper discusses the potential of the power conversion efficiency of solar cells from various materials considering external radiative efficiency, open-circuit voltage loss. The possibility of the power conversion efficiency is summarized in the 1st chapter. The examined cells are Silicon, III-V, CIS, CdTe, Organic, Dye-sensitized and Perovskite. The 2nd and successive chapters discuss the potential of the multijunction cells. The power conversion efficiency can be raised by using multi-junction structure. However, fluctuation of the atmospheric parameters substantially impacts the energy yield. The calculation considering the variation of atmospheric parameters showed a dramatic decline of the annual energy yield from the cells with more than five junctions. Super-multijunction solar cells were proposed, and optimization work was done. The top and the bottom junctions have lower bandgap for buffering to the mismatching and collecting a full range of the sunlight by robust energy conversion, and the annual energy substantially increases even by five or six junctions.
-
Araki K., Ji L., Kelly G., Yamaguchi M.
Coatings 8 ( 7 ) 2018.4
Language：English Publishing type：Research paper (scientific journal) Publisher：Coatings
© 2018 by the authors. A car-roof photovoltaic has enormous potential to change our society. With this technology, 70% of a car can run on the solar energy collected by the solar panel on its roof. Unfortunately, it is not a simple extension of conventional photovoltaic technology. This paper lists what we need to do to achieve the goal of running a majority of cars on renewable solar energy, after clarification of the difference to conventional photovoltaic technology. In addition to technological development, standardization will be important and this list was made highlighting standardization.
-
Possibility of CPV for automobile energy source Reviewed
Araki K., Ota Y., Ikeda K., Lee K., Nishioka K., Yamaguchi M.
2017 IEEE 44th Photovoltaic Specialist Conference, PVSC 2017 1 - 6 2017
Language：English Publishing type：Research paper (scientific journal) Publisher：2017 IEEE 44th Photovoltaic Specialist Conference, PVSC 2017
© 2017 IEEE. Greenhouse gas emission from automobiles cannot be eliminated before having them run by the sun. Toyota Tec. Inst. is serious to develop CPV applications to automobile. One is an innovative static concentrator that selectively collects sunlight from shallow angle. Another is a solar powered EV charging station with practical size and capacity.
-
Araki K., Herrero R., Anton I., Sala G., Nagai H., Lee K., Yamaguchi M.
Conference Record of the IEEE Photovoltaic Specialists Conference 2016-November 549 - 553 2016.11
Language：English Publishing type：Research paper (scientific journal) Publisher：Conference Record of the IEEE Photovoltaic Specialists Conference
© 2016 IEEE. The acceptance angle of concentrator modules measured by short circuit current Isc is always larger than that by maximum power Pm even by use of advanced concentrator optics that keep uniform illumination onto the concentrator cells. The purpose of this study is to investigate the cause of that myth. An expanded Monte Carlo method that calculates acceptance angle of CPV modules was developed with considering 2-dimensional misalignment error vector. It was shown that the gap from Pm-based acceptance angle from that of Isc-based was a function of deviation of assembles misalignment in the module. The rough rule for acceptable assembles misalignment is that the standard deviation of assemble misalignment level will be less than 10 % of acceptance angle of the optics.
-
Possibility of CPV for automobile energy source Reviewed
Araki K., Ota Y., Ikeda K., Lee K., Nishioka K., Yamaguchi M.
Conference Record of the IEEE Photovoltaic Specialists Conference 2016-November 554 - 559 2016.11
Language：English Publishing type：Research paper (scientific journal) Publisher：Conference Record of the IEEE Photovoltaic Specialists Conference
© 2016 IEEE. Greenhouse gas emission from automobiles cannot be eliminated before having them run by the sun. Toyota Tec. Inst. is serious to develop CPV applications to automobile. One is an innovative static concentrator that selectively collects sunlight from shallow angle. Another is a solar powered EV charging station with practical size and capacity.
-
Analysis of impact to optical environment of the land by CPV Reviewed
Araki K., 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. With the increase of installations on the land, the impact to the optical environment result from shading by PV panels is needed to be concerned. This paper describes how to calculate illumination level on the land around the isolated CPV panel. The land under the flat-plate PV is often dark but the shading influence from the tracking CPV is not very significant in most of the cases. This is because the shadow by the tracking panels moves by the movement of the sun. The integrated illumination level is averaged after integration in a day or a year. This effect is enhanced in the high latitude area. The shading influence by CPV is further decreased by the design of a higher pedestal. With this advantage, CPV can be combined with agriculture as a double use of the land.
DOI： 10.1063/1.4962108
-
Intermittent tracking (30 minutes interval) using a wide acceptance CPV module Reviewed
Araki K., Ota Y., 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. For applications of stand-alone systems including an electric vehicle (EV) power station, a tracking system with low power consumption will be demanded. One possible solution to save idling power is intermittent tracking, for example, tracking in every 30 minutes. To achieve this, a new CPV module was designed. With the combination of an advanced feed-forward tracking control, the 30 minutes of intermittent tracking may be possible by 100 x of geometrical concentration (the projected lens area by the cell aperture area with alignment margin).
DOI： 10.1063/1.4962083
-
Solving optimization problem of space factor of multiple CPV trackers using "butterfly approach" Reviewed
Araki K.
AIP Conference Proceedings 1616 224 - 227 2014
Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
©2014 AIP Publishing LLC. Optimization of land use to multi-tracker CPV system is discussed by mathematical approach. Optimization problem using butterfly plot (Contour plot on the shading to adjacent tracker) is discussed to seek optimum allocation pattern. With initial solutions given by this optimum allocation pattern, numerical optimization calculation is done to obtain the optimum allocation including, skew angle to the North-South axis, aspect ratio between X and Y pitch and optimum panel aspect ratio. It is suggested that there are two candidate of optimum allocation pattern.
DOI： 10.1063/1.4897066
-
Araki K., Nagai H., Tamura K.
AIP Conference Proceedings 1477 281 - 284 2012.12
Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
CPV cells are successively exposed by cycles of concentrated sunlight and huge cycling current flows out of contacts. The purpose of this research is to identify if the fatigue will be one of the life-end and wearing modes of CPV cells and how long the life-time will be. One of the best ways of giving cycling stress on cells and contacts is cycling forward bias injection. First, it is important to investigate if forward bias itself damages concentrator III-V cells. To confirm the forward bias current itself does not damage the CPV solar cells but cycling docs, we applied 4 times of Isc continuously in 500 hours, equivalently total injection of 90,000 cycles, but no damage or degradation was observed. What's more, we applied the cycling test after the stress of 500 hour continuous forward bias injection. We did not identify any changes between groups of with stress of continuous forward bias and without them. On-Off tests giving forward bias current as high as 4 times of Isc are conducted. The failure was analyzed by the Weible function. About 2,000 cells in total were examined. A small number of initial failure, that of failure number of cycles lied along exponential distribution and distinct portion of wear mode failure that of failure number of cycles lied along Gaussian distribution were identified. The EL measurement indicated that all the damaged cells in wear mode were local shunt under the top contacts suggesting stress under the top contacts would be possibly responsible to the fatigue failure. Advanced contact design that leads to reduce the stress on the top contact is expected to prolong the lifetime of the III-V concentrator cells. © 2012 American Institute of Physics.
DOI： 10.1063/1.4753886
-
Araki K., Zamora P., Nagai H., Benítez P., Hobo K., Miñano J., Futo M., Sala G., Tamura K., Kumagai I.
Conference Record of the IEEE Photovoltaic Specialists Conference 1815 - 1819 2012.11
Language：English Publishing type：Research paper (scientific journal) Publisher：Conference Record of the IEEE Photovoltaic Specialists Conference
Modules are an important part of the CPV system. By pursing, in our objective of a 35% efficiency module, we need to look forward a significant improvement in the state of the art of CPV modules since no commercial module is capable of achieving that efficiency. Achieving this efficiency will require high efficiency cells, progress in the optics lenses that are implemented in these modules, and also integration into module. Basic design of 35 % CPV module is presented considering for practical and rapid industry application. The output is 385 W while its weight is only 18 kg. In spite of its high concentration ratio reaching 1, X, it acceptance angle is as high as 1.1 degree. © 2012 IEEE.
-
Performance of the 30 KW CPV system installed in coastal area in Japan Reviewed
Araki K.
AIP Conference Proceedings 1277 239 - 242 2010.11
Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
A 30 kW concentrator photovoltaic power plant was constructed and has started operation. The power consumption of the tracking motors was only 19.6 W, namely 0.07 % of the rated power. Improved optics that reduces the mismatching losses associated with variance of optical losses. 25.8 % (STC) of efficiency was achieved even in as large as 23.8 m2 of the array size. The annual energy generation was about 1,000 kWh/kW, corresponding almost equivalent value to the crystalline silicon system in spite of unwanted climate to CPV. © 2010 American Institute of Physics.
DOI： 10.1063/1.3509200
-
30 kW Concentrator photovoltaic system using dome-shaped fresnel lenses Reviewed
Araki K., Yano T., Kuroda Y.
Optics Express 18 ( 101 ) A53 - A63 2010.4
Language：English Publishing type：Research paper (scientific journal) Publisher：Optics Express
A 30 kW concentrator photovoltaic power plant was constructed and has started operation with the following new technologies: A new Concentrating PhotoVoltaic (CPV) tracker developed for high wind area like Korea and Japan by Daido Steel. (The power consumption of the tracking motors was only 19.6 W, namely 0.07% of the rated power.) With improved optics that reduce the mismatch losses associated with optical aberrations, an efficiency of 25.8% was achieved under standard testing conditions (STC) even in a large 23.8 m2 array size. A rapid installation sequence was developed. It was designed for long-term power supply to a local sewage center. Peak power corresponds to 10% of the demand. As a result, the system performance ratio was 0.87, and the capacity factor was 11.7%. The energy generation per rated power was 1, 020 kWh/kWp. While it is true that CPV systems perform better in dry and high irradiance areas, our 30 kW system installed in a cloudy area like Japan, showed satisfactory performance. © 2010 Optical Society of America.
DOI： 10.1364/OE.18.000A53
-
8-3-2 Questionnaire Survey on Renewable Energies to Agricultural High School in Aichi Prefecture Reviewed
AKISAWA Atsushi, Araki Kenji, Kumagai Isao
Proceedings of the Annual Conference of The Japan Institute of Energy 19 ( 0 ) 364 - 365 2010
Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Institute of Energy
Questionnaire survey was conducted to agricultural high schools in Aichi prefecture to survey activities and requirements for teaching renewable energy. Most schools already implement lectures for renewable energy. They are strongly interested in the economy of utilizing renewable energy in agriculture. The results suggest that practical knowledge is required for the students to manage the technologies.
-
A simple rating method for CPV modules and systems Reviewed
Araki K., Kemmoku Y., Yamaguchi M.
Conference Record of the IEEE Photovoltaic Specialists Conference 2008.12
Language：English Publishing type：Research paper (scientific journal) Publisher：Conference Record of the IEEE Photovoltaic Specialists Conference
Right now, there is no agreed definition and measurement method for rating concentrator photovoltaic. This paper discusses present situation of the ratings of CPV modules and systems. First, it was analyzed which factors have influence to the performance to CPV modules and systems. Next, the linear interpolation method that is known as a robust estimator especially to multi-junction thin film modules is discussed. The test data was provided from Toyohashi University of Technology where a 550 X CPV module (20 cells connected in series and the total area is 5,445 cm2) was tested independently. The relative standard deviation was 0.89 %, whereas that of the linear interpolation method was 1.2 %. Different from the linear interpolation method, this stratified averaging method is unbiased. © 2008 IEEE.
-
Araki K., Kondo M., Uozumi H., Ekins-Daukes N.J., Kemmoku Y., Yamaguchi M.
Solar Energy Materials and Solar Cells 90 ( 18-19 ) 3312 - 3319 2006.11
Language：English Publishing type：Research paper (scientific journal) Publisher：Solar Energy Materials and Solar Cells
A 400× and 7056 cm2 concentrator module was fabricated from 36 concentrator receivers, connected in series and with the same number of newly developed dome-shape Fresnel lenses. The averaged outdoor efficiency on a clear sky day was 26.8±1.5% (25C STC). This is the highest module efficiency achieved to date using a module of practical size and electrical rating. The heat was dissipated by the module wall and no heat sinks nor external cooling were used. A glass homogenizer was introduced to give uniform illumination to the square cell, and afforded a reasonable assembly tolerance, without the need for optical alignment. © 2006 Elsevier B.V. All rights reserved.
-
Development of a new 550X concentrator module with 3J cells - Peformance and reliability Reviewed
Araki K., Uozumi H., Kondo M., Takamoto T., Agui T., Kaneiwa M., Egami T., Hiramatsu M., Miyazaki Y., Kemmoku Y., Akisawa A., Lee H.S., Ekins-Daukes N.J., Yamaguchi M.
Conference Record of the IEEE Photovoltaic Specialists Conference 631 - 634 2005.11
Language：English Publishing type：Research paper (scientific journal) Publisher：Conference Record of the IEEE Photovoltaic Specialists Conference
The status of the development of a new concentrator module in Japan is discussed based on three arguments, performance, reliability and cost. The peak uncorrected efficiency for a 7,056 cm2 400 X module with 36 solar cells connected in series was 26.6 % was measured in house. The peak uncorrected efficiencies of the same type of the module with 6 solar cells connected in series and 1,176 cm2 area measured by Fraunhofer ISE and NREL were 27.4 % and 24.8 % respectively. The peak uncorrected efficiency for a 550X and 5,445 cm2 module with 20 solar cells connected in series was 28.9 %. The temperature corrected efficiency under the best sunshine condition in Japan for the 550X module was 31.5 ±2 %. For reliability, some new degradation modes inherent to high concentration III-V solar cell system are discussed and a 20 year lifetime under concentrated flux exposure proven. The fail-safe issues of the concentrated sunlight are also discussed. For cost, the overall scenario for the reduction of material cost is discussed. © 2005 IEEE.
-
Araki K., Uozumi H., Egami T., Hiramatsu M., Miyazaki Y., Kemmoku Y., Akisawa A., Ekins-Daukes N.J., Lee H.S., Yamaguchi M.
Progress in Photovoltaics: Research and Applications 13 ( 6 ) 513 - 527 2005.9
Language：English Publishing type：Research paper (scientific journal) Publisher：Progress in Photovoltaics: Research and Applications
The status of the development of a new concentrator module in Japan is discussed based on three arguments, performance, reliability and cost. We have achieved a 26·6% peak uncorrected efficiency from a 7056 cm2 400× module with 36 solar cells connected in series, measured in house. The peak uncorrected efficiencies of the same type of the module with 6 solar cells connected in series and 1176 cm2 area measured by Fraunhofer ISE and NREL are reported as 27·4% and 24·8% respectively. The peak uncorrected efficiency for a 550× and 5445 cm2 module with 20 solar cells connected in series was 28·9% in house. The temperature-corrected efficiency of the 550× module under optimal solar irradiation condition was 31·5 ± 1·7%. In terms of performance, the annual power generation is discussed based on a side-by-side evaluation against a 14% commercial multicrystalline silicon module. For reliability, some new degradation modes inherent to high concentration III-V solar cell system are discussed and a 20-year lifetime under concentrated flux exposure proven. The fail-safe issues concerning the concentrated sunlight are also discussed. Moreover, the overall scenario for the reduction of material cost is discussed. Copyright © 2005 John Wiley & Sons, Ltd.
DOI： 10.1002/pip.643
-
Material study for the solar module under high concentration UV exposure Reviewed
Araki K., Kondo M., Uozumi H., Yamaguchi M.
Proceedings of the 3rd World Conference on Photovoltaic Energy Conversion A 805 - 808 2003.12
Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of the 3rd World Conference on Photovoltaic Energy Conversion
The use of high concentration constitutes an extremely harsh operating environment with high density and high energy photon flux. However, there is very few literatures on the material study for high concentration receiver. In this study, a super-high intensity UV weathering meter was developed. Initial examination of UV durability of materials used for concentrator receiver has been started.
-
Influences of spectrum change to 3-junction concentrator cells Reviewed
Araki K., Yamaguchi M.
Solar Energy Materials and Solar Cells 75 ( 3-4 ) 707 - 714 2003.2
Language：English Publishing type：Research paper (scientific journal) Publisher：Solar Energy Materials and Solar Cells
PV output of multi-junction cells is strongly influenced by spectrum change. The influence of Sun height was quantitatively analyzed, considering seasonally and daily changes of spectrum. The new model also considered the presence of clouds. The influence of daily random fluctuation of spectrum was shown averaged out in the integration of yearly PV output fluctuation. It was suggested that the overall mismatch loss by the change of Sun height and Sun orbital would be <4% for III-V multi-junction cells for concentration application, when the bandgap of each junction was well balanced. The sensitivity of spectrum fluctuation was shown enlarged with the discrepancy of current matching conditions. © 2002 Elsevier Science B.V. All rights reserved.
-
Novel equivalent circuit model and statistical analysis in parameters identification Reviewed
Araki K., Yamaguchi M.
Solar Energy Materials and Solar Cells 75 ( 3-4 ) 457 - 466 2003.2
Language：English Publishing type：Research paper (scientific journal) Publisher：Solar Energy Materials and Solar Cells
Parameter fitting based on the classical equivalent circuit model does not always reach reasonable solutions. It often gave negative series resistance and exaggerated diode ideality factor. Three problems were identified. The first problem was illuminated I-V is not a simple voltage shift by lumped series resistance. The second problem was rounded I-V curves in concentrator cells. The third problem was statistical instability in data fitting algorithm. A new model was proposed to describe the second problem. It was also effective to partly solve the first and the third problems. © 2002 Elsevier Science B.V. All rights reserved.