Papers - NISHIOKA Kensuke
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Yamaguchi M., Masuda T., Nakado T., Yamada K., Okumura K., Satou A., Ota Y., Araki K., Nishioka K., Kojima N., Ohshita Y.
IEEE Journal of Photovoltaics 2023.2
Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Journal of Photovoltaics
Development of photovoltaic (PV)-powered vehicles is very important to play a critical role in a future carbon neutrality society because it has been reported that the vehicle integrated PVs (VIPVs) have great ability to reduce CO<sub>2</sub> emission from the transport sector. Usage of high-efficiency solar cell modules is essential due to the limited installable area of PV on vehicle exterior. This article presents test driving data of the Toyota Prius demonstration car installed with high-efficiency III-V compound triple-junction solar cell module with an efficiency of more than 30%. Average daily driving distance (DD) of 17 km/day under usage of air conditioning and 62% CO<sub>2</sub> emission reduction are demonstrated by actual driving in Nagoya, Japan. In addition, analytical results for impact of high-efficiency VIPV modules of more than 35% on increases in DD of more than 30 km/day average and reducing CO<sub>2</sub> emission of PV-powered vehicles of more than 70% reduction are also shown.
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Yajima D., Toyoda T., Kirimura M., Araki K., Ota Y., Nishioka K.
Cleaner Engineering and Technology 12 100594 2023.2
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Cleaner Engineering and Technology
Climate change and increasing food production due to population growth are global challenges that need immediate attention. The introduction of renewable energy to mitigate climate change and the requirement of adequate land to increase food production are generally mutually exclusive. However, an agrivoltaic system generates renewable electricity and produces agricultural products from a common piece of land, thus increasing the land productivity. In addition, this system contributes to local production, thus reducing the CO2 emissions from logistics. Photovoltaic arrays in previous studies were designed by calculating the irradiance in W/m2, even in recent studies. A careful design of the farmland's illumination must be developed for effective agriculture. The simulations must be scaled based on photosynthetic photon flux density rather than irradiance commonly applied in photovoltaic technology simulations. This study focused on the photosynthetic photon flux density and employed an all-climate solar spectrum model to calculate the photosynthetic photon flux density accurately on farmland partially shaded by solar panels and supporting tubes. This study described an algorithm for estimating the photosynthetic photon flux density values under solar panels. The calculated data were validated using the photosynthetic photon flux density sensors. To calculate the photosynthetic photon flux density under the solar panels, it is essential to weigh the direct and diffused components shaded by the solar panels separately because they have different spectrums. A method to quantify the shading was explored here by solar panels and their supporting tubes for the direct and diffused component as the sun moves. The calculation formula was established by defining the sun's moves and the positions of solar panels and their supporting tubes in terms of elevation and azimuth angles from the observation point. It was found that the waveform based on the calculation formula for the photosynthetic photon flux density under the solar panels reproduced the same tendency as the measured photosynthetic photon flux density. To evaluate this trend numerically, the measured and calculated photosynthetic photon flux densities were compared using the standard residuals. Generally, the similarity of the two values is confirmed by a standard residual value between −3 and 3. The result of this study showed that the standard residual values were negative in more frequencies except for the zero photosynthetic photon flux density at night. This indicates that the calculated photosynthetic photon flux density tends to be higher than the measured photosynthetic photon flux density. The peak frequency of the standard residuals was between −6 and −3. This difference probably occurred because the established calculation formula targets the shading provided by the solar panels and supporting tubes but does not cover the shading provided by the other system structures. The calculation formula enables farmers to evaluate the economic efficiency of the system before introducing it using measured solar irradiation data at the target farmlands by introducing published neighborhood solar irradiation data and considering, in advance, measures to avoid the effects of shading on agricultural production. The next study will be to improve the accuracy of the calculation formula by increasing the number of days and develop a method that leads to the best practices of agricultural production and solar power generation by introducing the system.
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Thermoelectric Conversion Efficiency of 4% in Environmental-Friendly Kesterite Single Crystal
Nagaoka A., Nagatomo K., Nakashima K., Hirai Y., Ota Y., Yoshino K., Nishioka K.
Materials Transactions 64 ( 10 ) 2535 - 2541 2023
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Materials Transactions
Multinary Cu2ZnSnS4 (CZTS)-based materials have attracted considerable attention for thermoelectric (TE) power generation owing to their cost-effectiveness and abundance. The device structure of the CZTS/Au diffusion barrier layer was effective in impeding chemical diffusion during operation; however, its interfacial contact resistance was relatively higher than that of the Bi2Te3 device. We report the discovery of p-type CZTS single crystals with a record-high dimensionless figure of merit (ZT) of 1.6 at 800 K and TE conversion efficiency of 34% at a temperature difference of 473 K, which is based on the Te-free concept. This study demonstrated the potential of CZTS-based TE materials for environment-friendly TE power generation.
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Controlling the conduction type in a thermoelectric material (Cu1-xAgx)2ZnSnS4 Reviewed
Okamoto K., Nagaoka A., Nagatomo K., Yoshino K., Ota Y., Nishioka K.
Journal of Physics and Chemistry of Solids 171 2022.12
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics and Chemistry of Solids
Quaternary kesterite p-type Cu2ZnSnS4 (CZTS) has the potential to be used as an environmentally friendly thermoelectric (TE) material. Conversion of p-n conduction is required for the realization of a CZTS-based TE device. Herein, we studied the growth of a polycrystalline (Cu1-xAgx)2ZnSnS4 (CAZTS) and its fundamental TE properties. An n-type CAZTS (x = 0.4) with a negative Seebeck coefficient (60–70 μV/K) can be obtained without secondary phases. The electrical conductivity decreased with increasing Ag content owing to defect compensation. The conduction mechanism of the polycrystalline CAZTS can be demonstrated through hopping conduction, thermal activation, and a potential barrier at the grain boundary.
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Wai S.H., Ota Y., Nishioka K.
Journal of Power Sources 546 231991 2022.10
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Power Sources
The solar-to-gas (StG) conversion system is a potential pathway for accelerating zero-carbon energy sources. In our previous study, outdoor StG conversion was accomplished using triple-junction concentrator photovoltaic (CPV) modules. The system achieved the highest performance with sets of DC/DC converters and electrochemical (EC) cells. Therefore, we aimed to investigate the prospective StG conversion from PV systems if such a system is installed in Japan. A power generation prediction model considering all weather conditions, called the Miyazaki Spectrum to Energy (MS2E), has been developed using the METPV-11 meteorological database at the University of Miyazaki. Accordingly, the amount of energy generated by various PV systems could be forecasted nationwide from the global irradiance data. In this study, we applied the MS2E PV energy prediction method and approached the potential StG conversion efficiency of silicon (Si) PV and inverted metamorphic (IMM) PV systems across Japan. Based on the actual StG measurement data, we approximated the conversion of each subsystem. The simulation results show that IMM modules can provide higher StG conversion than Si modules.
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Analysis for the Potential of High-Efficiency and Low-Cost Vehicle-Integrated Photovoltaics Invited Reviewed
Yamaguchi M., Nakamura K., Ozaki R., Kojima N., Ohshita Y., Masuda T., Okumura K., Satou A., Nakado T., Yamada K., Tanimoto T., Zushi Y., Takamoto T., Araki K., Ota Y., Nishioka K.
Solar RRL 2200556 2022.9
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Solar RRL
The spread of the photovoltaic-powered electric vehicle (PV-EV) is desirable and is essential for reduction in CO2 emissions, increasing electric range, and creating a new clean energy infrastructure based on PVs. Development of highly efficient PV modules with reasonable cost is necessary to realize a longer PV-driving range of passenger cars. Herein, the potential of various solar cell modules for vehicle-integrated photovoltaic (VIPV) applications is analyzed. This article shows that the use of highly efficient solar cell modules with an efficiency of higher than 35% enables longer than 30 km day−1 PV driving under average irradiance of 4 kWh m−2day−1 without external charging. Cost reduction of VIPV modules is also very important for spreading the PV-powered vehicles. By considering electricity charging cost saving and reduction in CO2 emission of electric vehicles, the cost target of VIPV is discussed. The cost targets of the solar cell modules for the PV-EV by considering only electricity charging cost saving, $2.6/Wp for a module with conversion efficiency of 20% and $3.7/Wp for a module with that of 40%, are estimated in the case of electric mileage of 10 km kWh−1.
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CPV standardization 2021 - Maintenance and stability Reviewed International coauthorship
Araki K., Algora C., Kresse D., Siefer G., Timò G., Antón I., Nishioka K., Leutz R., Carter S., Wang S., Askins S., Iwasaki T., Ji L., Kelly G.
AIP Conference Proceedings 2550 2022.9
Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
The rapid and substantial decline of the cell-cost, CPV, relied on cell-saving and became less valuable. Many players and systems got off the stage as a result. Also, less and fewer new proposals in the CPV standardization. We decided to continue the standardization activity but separate the tracker's work by creating a new working group, WG9. The technical discussion on VIPV has also been discussed in WG7, and it is to be transferred to a new project team. Besides the existing standards' maintenance work, new proposals of the new CPV standards were posted and approved recently. One is the fire test of the CPV module, and another is a series of standards of the hybrid CPV/PV.
DOI： 10.1063/5.0099174
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Wai S.H., Swe T.H., Ota Y., Sugiyama M., Nishioka K.
AIP Conference Proceedings 2550 2022.9
Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
A sustainable, renewable energy source is highly desirable for a zero-carbon-emission society. A powerful energy supply that can replace the fossil fuel sector is required. Effective energy transformation into synthetic chemical energy has become a promising alternative energy production method that can conveniently store energy produced by renewable sources. Solar-to-gas conversion has caught the attention of researchers to provide green hydrogen for vehicles and synthetic natural methane for the current gas-grid infrastructure. Such systems are run on solar energy converted into storable chemical energy such as hydrogen and methane. In this study, a new method was developed by independently setting the reactor temperatures and evaluating the methane concentration and methanation power consumption. Subsequently, a high methane concentration (97.89%) and lower power consumption of the methanation system (0.148 kW) were observed at low temperatures (180 °C, 260 °C).
DOI： 10.1063/5.0099245
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Effects of Artificial River Water on PEM Water Electrolysis Performance Reviewed
Yoshimura R., Wai S.H., Ota Y., Nishioka K., Suzuki Y.
Catalysts 12 ( 9 ) 934 2022.9
Language：English Publishing type：Research paper (scientific journal) Publisher：Catalysts
Hydrogen, a clean and renewable energy source, is a promising substitute for fossil fuels. Electricity-driven water electrolysis is an attractive pathway for clean hydrogen production. Accordingly, the development of electrolysis cells has drawn researchers’ attention to capital costs related to noble catalyst reduction and membrane degradation by the contaminations. In the literature, polymer electrolyte membranes (PEMs) have been studied on single cations contamination. In this study, we investigated the performance of a PEM on monovalent and divalent cation contamination by feed water. Artificial river water, called soft water, was used to analyze the effect of impurities on the PEM. The results demonstrated that the operating voltage drastically increased and induced cell failure with increasing Mg2+ and Ca2+ concentrations; however, it did not increase for Na+ and K+ after increase in voltage. Therefore, divalent cations have a stronger affinity than monovalent cations to degrade PEM and should be effectively excluded from the feed water.
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Development of High-Efficiency Solar Cell Modules for Photovoltaic-Powered Vehicles Reviewed International coauthorship
Yamaguchi M., Ozaki R., Nakamura K., Lee K.H., Kojima N., Ohshita Y., Masuda T., Okumura K., Satou A., Nakado T., Yamada K., Araki K., Ota Y., Nishioka K., Takamoto T., Zushi Y., Tanimoto T., Thiel C., Tsakalidis A., Jäger-Waldau A.
Solar RRL 6 ( 5 ) 2100429 2022.5
Language：English Publishing type：Research paper (scientific journal) Publisher：Solar RRL
Photovoltaic (PV)-powered vehicles are expected to play a critical role in a future carbon neutral society because it has been reported that the onboard PVs have great ability to reduce CO2 emission from the transport sector. Although the demonstration car with a III−V-based solar cell module has shown the PV-powered driving range of 36.6 km day−1 at solar irradiance of 6.2 kWh m−2 day−1, practical driving ranges of PV-powered vehicles are shown to be lower than estimated values due to some losses such as nonradiative recombination and resistance losses of solar cell modules under sunshine condition. This article presents analytical results for the effects of illumination intensity properties of various solar cell modules on the PV-powered driving range to develop highly efficient solar cell modules for vehicle-integrated applications. The analysis shows that improvements in shunt resistance and saturation current density of solar cell modules are necessary to improve illumination intensity properties of solar cell modules under low intensity sunshine condition. The calculations show that the III−V-based 3-junction solar cell modules with an efficiency of more than 30% have a potential PV-powered driving range of 30 km/day average and more than 50 km day−1 on a clear day.
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Effects of Agrivoltaics (Photovoltaic Power Generation Facilities on Farmland) on Growing Condition and Yield of Komatsuna, Mizuna, Kabu, and Spinach Reviewed
KIRIMURA Masaaki, TAKESHITA Shinichi, MATSUO Mitsuhiro, ZUSHI Kazufumi, GEJIMA Yoshinori, HONSHO Chitose, NAGAOKA Akira, NISHIOKA Kensuke
Ｅｎｖｉｒｏｎｍｅｎｔ Ｃｏｎｔｒｏｌ ｉｎ Ｂｉｏｌｏｇｙ 60 ( 2 ) 117 - 127 2022.4
Language：English Publishing type：Research paper (scientific journal) Publisher：日本生物環境工学会
In a sustainable society, it is necessary to develop systems that produce enough food and energy while also preserving the environment. Both agricultural production for food generation and photovoltaics for renewable energy production require large, open fields. In this research study, we investigate the feasibility of combining food and energy production into a single field by examining the effects of installing photovoltaic equipment above land used for farming. We grew komatsuna, kabu, mizuna, and spinach underneath photovoltaic equipment, and investigated the influence of shading from the photovoltaic equipment on plant growth and yields during winter cultivation. As expected, both the amount of solar radiation and the air and soil temperature were lower under the photovoltaics than those under the open field. The growth rate of komatsuna, kabu, and mizuna were slower. However, yields and qualities sufficient to meet market demands remained possible with extension of the cultivation periods. Therefore, although temperature and solar radiation are reduced under the photovoltaic equipment in winter, it is nevertheless possible to produce vegetables in the farmland, providing a novel opportunity to realize an integrated agricultural system with parallel production of food and energy.
DOI： 10.2525/ecb.60.117
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Chimney-ladder sulfide Sr9Ti8S24 as a thermoelectric material with low thermal conductivity Reviewed
Kamimizutaru K., Nagaoka A., Shigeeda Y., Nishioka K., Higashi T., Yasui S., Yoshino K.
Journal of Physics and Chemistry of Solids 163 2022.4
Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics and Chemistry of Solids
Chimney-ladder sulfide Sr9Ti8S24 (STS) has potential as a thermoelectric (TE) material because of its intrinsic low thermal conductivity. We studied the growth of a polycrystalline STS sample and its fundamental TE properties. The resistivity of n-type polycrystalline STS can be described as thermal activation and the potential barrier at grain boundary. Regarding the TE properties, n-type STS polycrystalline samples exhibit a low thermal conductivity <1 W/mK between 323 and 673 K caused by a large unit cell with an axis = 12.15 Å, c axis = 42.32 Å, and Umklapp scattering. Consequently, the figure of merit for the STS sample reaches 3.0 × 10−4 at 673 K.
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Ota Y., Araki K., Nagaoka A., Nishioka K.
Cleaner Engineering and Technology 7 2022.4
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Cleaner Engineering and Technology
By mounting photovoltaics (PV) on the roof of an electric vehicle (EV), solar energy can be used to supply a considerable portion of the energy demand of the EV. The roof is the best place for PV installation on the vehicle body because doors and engine hood have less yearly-average sunlight available and more stringent mechanical requirements. The roof of a modern passenger vehicle such as a sedan is not flat, and parts with high curvature or a significant slope do not need to be covered. However, there are no design rules available for mounting PV on a vehicle roof, such as determining the coverage ratio. In this study, the distributions of roof shapes and sizes were obtained from trace drawings of various commercially available passenger vehicles. This was then used to calculate the distributions of the mechanical (i.e., local curvature) and optical (i.e., local solar utilization rate) properties. Based on the results, general guidelines were developed, including a potential coverage ratio of 96% for a hemispherical roof with a radius of curvature of 1 m. These guidelines have already been successfully demonstrated and prototyped with a small module.
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Impact of climatic conditions on prospects for integrated photovoltaics in electric vehicles Reviewed International coauthorship
Thiel C., Gracia Amillo A., Tansini A., Tsakalidis A., Fontaras G., Dunlop E., Taylor N., Jäger-Waldau A., Araki K., Nishioka K., Ota Y., Yamaguchi M.
Renewable and Sustainable Energy Reviews 158 2022.4
Language：English Publishing type：Research paper (scientific journal) Publisher：Renewable and Sustainable Energy Reviews
Integrated photovoltaics are an emerging technology which can extend the range of electric vehicles. However, up to now there is a lack of a consensus method that would provide consumers with an estimate of the fraction of annual driving which could be covered by solar power generated onboard in different usage scenarios and locations. To address this, we assess the energy implications of vehicle integrated photovoltaics for a commuter car and light delivery van for six climatic regions and for typical daily usage profiles over a ten-year period. The analysis captures the energy needs for driving and cabin temperature control to an unprecedented level of detail. Our results reveal that the grid power needed to drive such vehicles on identical routes can vary by more than 44% between climate regions. In the best case the solar power generated can cover up to 35% of the driving range per year. This contribution can vary by a factor of 2.5 between different climates, from 1800 to 5100 km annually, considerably mitigating the effect of ambient conditions on electric range. We propose developing consumer labels for solar electric vehicles that would consider this variation according to climatic conditions. The method described in this paper could help to frame initial discussions for such labels. We identify further requirements for research and development, standardisation, and policy needs.
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Impact and recent approaches of high-efficiency solar cell modules for PV-powered vehicles Reviewed
Masafumi Yamaguchi, Taizo Masuda, Kenji Araki, Yasuyuki Ota, and Kensuke Nishioka
Japanese Journal of Applied Physics 61 SC0802 2022.3
Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics and Chemistry of Solids
Chimney-ladder sulfide Sr9Ti8S24 (STS) has potential as a thermoelectric (TE) material because of its intrinsic low thermal conductivity. We studied the growth of a polycrystalline STS sample and its fundamental TE properties. The resistivity of n-type polycrystalline STS can be described as thermal activation and the potential barrier at grain boundary. Regarding the TE properties, n-type STS polycrystalline samples exhibit a low thermal conductivity <1 W/mK between 323 and 673 K caused by a large unit cell with an axis = 12.15 Å, c axis = 42.32 Å, and Umklapp scattering. Consequently, the figure of merit for the STS sample reaches 3.0 × 10−4 at 673 K.
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Curve correction of vehicle-integrated photovoltaics using statistics on commercial car bodies Reviewed
Ota Y., Araki K., Nagaoka A., Nishioka K.
Progress in Photovoltaics: Research and Applications 30 ( 2 ) 152 - 163 2022.2
Language：English Publishing type：Research paper (scientific journal) Publisher：Progress in Photovoltaics: Research and Applications
Typically, car roofs are curved, which means that vehicle-integrated photovoltaics (VIPVs) are also curved along the roof surface. The performance of the PV module is influenced by the local cosine loss and self-shadowing loss due to the curved surface. The ratio between the solar irradiances of curved and flat surfaces is defined as the curve correction factor, and it widely varies with the shape of the curved surface. When the curve correction factor is less than unity, the PV on a curved car roof performs worse than the PV on a flat plate. Understanding the typical range of the curve correction factor is important for the estimation of the energy generated by VIPV. We investigated the curved shapes of 100 lines of cars and 200 cases. The curved shapes were then used to extract eight nondimensional geometric parameters, and the distributions and correlations among the parameters were investigated. The parent population of the curved surfaces was estimated via a Monte Carlo simulation based on an analysis of the statistical characteristics. The distribution of curve correction factors for the car population was calculated via differential geometry weighted by the distribution of incident angles of sunlight (direct and diffused) affected by shading along the streets, which was obtained from 1 year of driving data for Miyazaki City, Japan. The curve correction factors were highly skewed, but the average value was 0.92. This means that VIPV requires a 10% boost in performance to compensate for the inherent loss due to the geometry of curved roofs.
DOI： 10.1002/pip.3473
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Shigeeda Y., Nagaoka A., Yoshino K., Nishioka K.
Journal of Physics and Chemistry of Solids 161 2022.2
Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics and Chemistry of Solids
We investigated the growth mechanism and the thermoelectric (TE) properties of the II-IV-V2 group chalcopyrite ZnSnSb2 with a pseudocubic structure, which is a key strategy for improving the TE performance by increasing the degeneracy at the valence band edge. The growth mechanism of ZnSnSb2 shows the peritectic reaction as: ZnSb + SnSb + liquid phase ↔ ZnSnSb2 for 320–360 °C. The ZnSnSb2 single phase was obtained from the starting composition of Zn:Sn:Sb = 1:5:2. The high-temperature TE properties were measured up to 573 K, and the thermal conductivity values were 1.5 times lower than the reported value, which was caused by enhanced phonon scattering by the off-stoichiometric composition. Consequently, the TE figure of merit for off-stoichiometric ZnSnSb2 reached 0.12 at 573 K, which is 1.4 times higher than that of the reported stoichiometric sample.
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Maeda M., Nagaoka A., Araki K., Nishioka K.
Solar Energy 231 243 - 251 2022.1
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Solar Energy
A precise and practical power generation forecasting method for outdoor photovoltaic (PV) arrays and its performance evaluation are essential for advancements in solar power generation. Specifically, accurate temperature measurements of each of the PV modules in an array, the entire outdoor PV array, and the power generation system are crucial regardless of climatic and irradiance conditions. However, outdoor PV temperatures are often affected by environmental factors, such as wind direction, wind speed, solar irradiance, and outdoor air temperature fluctuations. Hence, the temperature data vary greatly depending on the measurement point of the module, which is affected by the above environmental factors. The variations of and uncertainties in temperature often extend over long arrays of PV modules common to large-scale PV systems. Therefore, it is necessary to establish a straightforward and reproducible inspection method to determine a single and robust representative PV module temperature for an array. In this study, we have established one such inspection method for outdoor PV arrays. It was observed that the temperature at the center of the array was closest to the average temperature regardless of the measurement period and climatic conditions; thus, it can be considered as the unbiased and robust representative temperature for the PV array. Moreover, lower irradiance conditions are better for accurate and repeatable PV module temperature measurements. The mean temperature differences of the PV array from its average measured at the center of the array were 0.2 °C for low irradiance and 0.5 °C for high irradiance. The temperature difference observed will have 0.1% to 0.2% impact on the power estimation for monitoring purposes.
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Akira Nagaoka, Yusuke Shigeeda, Kensuke Nishioka, Taizo Masuda, and Kenji Yoshino
High Temperature Materials and Processes 40 439 - 445 2021.12
Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics and Chemistry of Solids
Chimney-ladder sulfide Sr9Ti8S24 (STS) has potential as a thermoelectric (TE) material because of its intrinsic low thermal conductivity. We studied the growth of a polycrystalline STS sample and its fundamental TE properties. The resistivity of n-type polycrystalline STS can be described as thermal activation and the potential barrier at grain boundary. Regarding the TE properties, n-type STS polycrystalline samples exhibit a low thermal conductivity <1 W/mK between 323 and 673 K caused by a large unit cell with an axis = 12.15 Å, c axis = 42.32 Å, and Umklapp scattering. Consequently, the figure of merit for the STS sample reaches 3.0 × 10−4 at 673 K.
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Analysis of temperature coefficients and their effect on efficiency of solar cell modules for photovoltaics-powered vehicles Reviewed International coauthorship
Yamaguchi M., Masuda T., Araki K., Ota Y., Nishioka K., Takamoto T., Thiel C., Tsakalidis A., Jaeger-Waldau A., Okumura K., Satou A., Nakado T., Yamada K., Zushi Y., Tanimoto T., Nakamura K., Ozaki R., Kojima N., Ohshita Y.
Journal of Physics D: Applied Physics 54 ( 50 ) 2021.12
Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics D: Applied Physics
Development of vehicles that are powered by photovoltaics (PV) is desirable, and is crucial for reduction in CO2 emissions from the transport sector to realize a decarbonized society. Our investigations show that the majority of the passenger cars that cruise only with solar energy can be realized by installing a high-efficiency PV module. Although the Toyota Prius demonstration car, which is equipped with a 860 W rated-output power PV module, has shown a 36.6 km d-1 PV-powered driving range at solar irradiance of 6.2 kWh m-2 d-1, practical driving ranges of PV-powered vehicles are shown to be shorter than the estimated values due to some losses of solar cell modules, such as temperature rise under sunny conditions. In this paper, we conduct a systematic analysis of the effects of these losses on the PV-powered driving range in order to obtain guidelines for the development of highly efficient solar cell modules for vehicle integrated applications. The analytical results show that the III-V compound solar cell modules have more suitable properties compared to other cells because of their higher potential conversion efficiencies of 37% with a smaller temperature coefficient of -0.19% C-1 compared to -0.29% C-1 for Si back contact solar cell modules and -0.26% C-1 for Si heterojunction solar cell modules. Our theoretical calculations that take these losses into account suggest that installing the III-V-based triple-junction solar cell modules provides a potential PV-powered driving range of 30 km d-1 on average, and more than 50 km d-1 on a sunny day under the irradiation conditions in Japan.