Papers - Araki Kenji
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A simple passive cooling structure and its heat analysis for 500 X concentrator PV module Reviewed
Araki K., Uozumi H., Yamaguchi M.
Conference Record of the IEEE Photovoltaic Specialists Conference 1568 - 1571 2002.12
Language：English Publishing type：Research paper (scientific journal) Publisher：Conference Record of the IEEE Photovoltaic Specialists Conference
A new and simple module structure for 500 X concentrator module made by printed epoxy and copper sheet on aluminum plate was pro-posed. The heat analysis was done and indicated that around 10 degree rises at the surface of the cell compared to normal irradiated flat-plane was expected without the help of classical heat sinks. Outdoor test was done and confirmed its cooling performance.
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Si concentrator cell by single photolithography process Reviewed
Araki K., Yamaguchi M.
Solar Energy Materials and Solar Cells 65 ( 1 ) 437 - 443 2001.1
Language：English Publishing type：Research paper (scientific journal) Publisher：Solar Energy Materials and Solar Cells
A mid-range concentrator cell by low-cost process is investigated and a new design is proposed. We tried to develop a single lithography CZ-Si cell process. The current conversion efficiency (not optimized) is 16% under X20 concentration without AR coating. The present moderate efficiency is possibly due to low bulk lifetime (approx. 5 μs after process). Cell efficiency and open-circuit voltage (Voc) are expected to improve by using a better quality Si material and developing a low-stress process to maintain crystal quality. The equivalent circuit analysis reveals degradation of diode characteristics under concentration, which implies decline of fill-factor (FF) by use of low-quality concentrator optics.
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Outdoor evaluation of total cross-tied Si module under driving conditions Reviewed
太田 靖之, 西岡 賢祐
Solar Energy Materials and Solar Cells 274 112989 - 112989 2024.8
Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier BV
This paper presents the fabrication and evaluation of a total cross-tied (TCT) Si module designed to mitigate the partial shading effect, which is known to reduce the output performance of vehicle-integrated photovoltaic (VIPV) modules. The TCT module, consisting of 27 Si solar cells interconnected both vertically and horizontally, demonstrated an 18.8 % decrease in output power when one cell was shaded. In contrast, the output of the series-parallel (SP) Si module decreased by 31.6 % under the same shading condition. Comparative analysis of the output performances of TCT, SP, and single-string commercial modules under three driving conditions revealed that increasing the number of strings helped alleviate the impact of partial shading. Notably, the TCT module configuration showed a positive impact on mitigating the partial shading effect.
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Consideration for importance of concentrating photovoltaics (PV) toward TW-scale PV production Reviewed
Yamaguchi M., Araki K., Zhang Y., Hallam B., Kojima N., Ohshita Y.
AIP Conference Proceedings 2841 ( 1 ) 2023.9
Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
Photovoltaics will play a key role in a future net zero greenhouse gas emission energy systems. Especially, the concentrator photovoltaics (CPV) has great potential of higher efficiency, lower cost and potential overcoming sustainability of material resources compared to conventional crystalline Si PV and thin-film PV. This paper presents impact of material consumption upon annual production capacities of various solar cells by using CPV. Merits of CPV compared to conventional PV (1-sun use) are 190TW/1.6TW for Si (Si limit), 650GW/2.7GW for GaAs (Ga limit), 250GW/4.2GW for CdTe (Te limit) and 950GW/2GW for III-V 3-junction solar cells (Ga limit).
DOI： 10.1063/5.0146171
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Prediction of PPFD (photosynthetic photon flux density) under transparent CPV modules Reviewed
Toyoda T., Yajima D., Kirimura M., Araki K., Ota Y., Nagaoka A., Nishioka K.
AIP Conference Proceedings 2841 ( 1 ) 2023.9
Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
Recently, the agro-photovoltaic (agri-photovoltaic) system is expected to penetrate the market due to its advantages in some crops and significant potential installation areas. In principle, the agro-photovoltaic system shares solar energy with PV and agriculture, and its appropriate and controlled distribution is the key for the economy. Accurate and reproducible optimization design is essential. Any PV modules can be used for the agro-photovoltaic system. The best may be the transparent CPV that uses direct sunlight to concentrate onto solar cells and diffused sunlight to illuminate the farming light through a transparent backplane. The diffused sunlight for typical CPV modules is not used for electricity generation, and the transparent CPV is utilized as the secondary light source to crops. The diffused sunlight does not create shadow and improves the inhomogeneity of PPFD (Photosynthetic Photon Flux Density) from the stripe of shadows by PV modules, thus improving the yield. This paper predicts PPFD by the transparent CPV modules and the effectiveness of its use for the agro-photovoltaic system.
DOI： 10.1063/5.0146145
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Shimizu R., Ota Y., Nagaoka A., Araki K., Nishioka K.
Applied Sciences (Switzerland) 13 ( 18 ) 2023.9
Publishing type：Research paper (scientific journal) Publisher：Applied Sciences (Switzerland)
Featured Application: Solar panel fire accident diagnosis, analysis, and prediction. Fires in photovoltaic modules are caused by hot spots, which are typically monitored by thermal images. This method helps visualize the hot spot, but it is affected by the environment (solar irradiance, wind, ambient temperature) and is not reproducible. Assessing the heat dissipation of the hot cell can be used for alternative assessment of the fire risk. This method was validated by comparing the value measured by the surface potential meter and the module potential measured directly by adding a bypass measurement circuit. The substantial reverse-bias voltage caused by mismatching or partial shading (depending on the operating conditions) leads to local heat consumption of the partially shaded solar cells and potentially causes fire. The fire risk can be assessed in the worst-case conditions (ex. 1380 W/m2 solar irradiance) by non-contact measurement of the reverse-bias voltage and calculating the heat dissipation and temperature rise. This work suggested that −13 V is the criterion and was close to the known value of reverse voltage for Si cells. The current technology inspects solar cells before assembly to the module, and there is no way of inspecting in the product test or detecting after degradation that can be covered by the proposed method in this work.
DOI： 10.3390/app131810391
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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 13 ( 3 ) 343 - 348 2023.5
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 CO2 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% CO2 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 CO2 emission of PV-powered vehicles of more than 70% reduction are also shown.
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Solar Electric Vehicles as Energy Sources in Disaster Zones: Physical and Social Factors Reviewed
Araki K., Ota Y., Maeda A., Kumano M., Nishioka K.
Energies 16 ( 8 ) 2023.4
Publishing type：Research paper (scientific journal) Publisher：Energies
Electric vehicles (EVs) have the advantage of being resilient to natural disasters. However, users hesitate to donate electricity when they lose the chance to recharge at the utility. Solar electric vehicles (SEVs) save energy through vehicle-integrated photovoltaics (VIPV) and make it possible to voluntarily donate excess energy, thus maintaining facility resilience. Given that the supply of solar energy to VIPV systems is not continuous and is difficult to forecast, the contribution of VIPV to the resilience of the larger energy system has been called into question. This is the first study in which the potential of VIPV to maintain utility resilience is investigated in the context of physical factors, such as irradiance, and social factors. The actual energy yield of a VIPV car was determined using an advanced 3D solar irradiation model under a nonuniform shading distribution, with validation from actual measures of solar irradiance on five orthogonal sides of the car body. The Monte Carlo method was used to model the complex factors in VIPV energy storage and energy donations under different scenarios. Depending on the climate, population density, and shading environment, the voluntary contribution of stored electricity in SEV is sufficient to provide disaster relief support.
DOI： 10.3390/en16083580
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Yajima D., Toyoda T., Kirimura M., Araki K., Ota Y., Nishioka K.
Energies 16 ( 7 ) 3261 2023.4
Publishing type：Research paper (scientific journal) Publisher：Energies
Climate change and increasing food demand are global issues that require immediate attention. The agrivoltaic system, which involves installing solar panels above farmland, can simultaneously solve climate and food issues. However, current systems tend to reduce agricultural production and delay the harvest period due to shading by the solar panels. A delayed harvest period impacts the income of farmers who wish to sell produce at specific times. Incorporating a model that calculates the amount of electricity generated by solar irradiation, this study establishes a model to estimate the correct start date of cultivation for solar panel covered crops to ensure the correct harvest date and determines the expected income of farmers by calculating agricultural production and power generation. Using taro cultivation in Miyazaki Prefecture as a case study, the model estimated that the start date of cultivation should be brought forward by 23 days to ensure the ideal harvest period and agricultural production. This would prevent an opportunity loss of USD 16,000 per year for a farm area of 10,000 m2. Furthermore, an additional income of USD 142,000 per year can be expected by adjusting shading rates for the cultivation and non-cultivation periods.
DOI： 10.3390/en16073261
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Analysis for the Potential of High-Efficiency and Low-Cost Vehicle-Integrated Photovoltaics 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 7 ( 8 ) 2023.4
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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Yajima D., Toyoda T., Kirimura M., Araki K., Ota Y., Nishioka K.
Cleaner Engineering and Technology 12 2023.2
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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CPV standardization 2021 - Maintenance and stability Reviewed
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
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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The proposal of a new standard for the measurement procedures of CPV/PV hybrid modules Reviewed
Timò G., Minuto A., Araki K., Siefer G., Askins S., Antón I., Algora C.
AIP Conference Proceedings 2550 2022.9
Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
Hybrid CPV/PV modules include CPV solar cells designed to collect concentrated light and PV solar cells designed to collect diffuse or global light. The power rating, as well as the module energy rating for such PV modules are complicated by the fact that, in some cases, the power is a strong and discontinuous function of angle of incidence (AOI). For such a reason, the IEC 61853 and IEC 62670 series do not sufficiently cover the specific requirements and procedures for evaluating the Hybrid CPV/PV performances. The standard conditions for assessing the power produced by the hybrid CPV/PV modules have also to be differentiated from those used to characterize flat PV or CPV modules. With this contribution, the motivations behind the new work item proposal on "Hybrid CPV/PV modules: General characteristics and measurement procedures"are therefore presented.
DOI： 10.1063/5.0099713
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Optimization of asymmetrical static-LCPV dependent on applications Reviewed
Araki K., Yamaguchi M., Ota Y., Nishioka K.
AIP Conference Proceedings 2550 2022.9
Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
The optimized design of the static-CPV was simplified by the reduction of variables considering geometrical symmetry. The previous works assumed 4-folded symmetry (grid arrangement) for horizontal installation (car-roof) where accumulated solar irradiance is axially symmetrical. Optimizing the lens shape under asymmetrical irradiance distribution may lead to a different story. Moreover, the lens profile optimization depends on the angular distribution of rays and varies by the mode of installations. In this study, the design method of the static LCPV was expanded to the arbitrary angular distribution of the solar ray so that the application of the static LCPV was searched for new applications. At first angular distributions of the annual solar beam were calculated using the METPV-11 database and its 840 sites, including VIPV application, BIPV (vertical) weighted average in 8 orientations, and horizontal single-axis west-east tracking. The lens profile in each condition was optimized, allowing geometrical asymmetry. Despite the optimization, the annual optical efficiency decreased by the concentration ratio. Its trend was almost the same among different modes of installations. The annual efficiency was further dropped by the more expansive and off-centered solar beam distribution. However, the difference was relatively small after optimization according to each distribution pattern of the solar beam, despite the substantial variation of the lens profiles. The relationship "the more concentration, the less energy yield"was unchanged among installations. The peak annual yield depending on the concentration ratios was almost the same among different modes of installations. Thus, the optimum concentration ratios were nearly the same among installations. More concentration saves the cell cost, but this advantage may be seen in the system using expensive solar cells (more than 70% of the system cost), regardless of the mode of installations.
DOI： 10.1063/5.0099173
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Uno T., Ota Y., Kanayama S., Araki K., Nishioka K.
AIP Conference Proceedings 2550 2022.9
Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings
We developed a plastic-integrated concentrator photovoltaic (PIC) module and evaluated the long-term reliability of the PIC module with two concentrator solar cells; one is a conventional Ge-bottom subcell triple-junction solar cell, and the other is a 1-eV-bottom subcell triple-junction solar cell under outdoor operation. The daily energy yield of the PIC module with Ge-bottom subcell slightly decreased in the summer season. Moreover, the 1-eV-bottom subcell triple-junction solar cell is expected to be more affected by the solar spectrum change due to the increased precipitable water vapor in the summer season. The impact of spectral change on the output performance of the PIC module is continuously discussed by actual measurement data.
DOI： 10.1063/5.0099179
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Development of High-Efficiency Solar Cell Modules for Photovoltaic-Powered Vehicles Reviewed
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 ) 2022.5
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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Impact and recent approaches of high-efficiency solar cell modules for PV-powered vehicles Reviewed
Yamaguchi M., Masuda T., Araki K., Ota Y., Nishioka K.
Japanese Journal of Applied Physics 61 ( SC ) 2022.5
Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics
Photovoltaic (PV)-powered vehicles are expected to play a critical role in a future carbon neutrality society because it has been reported that vehicle integrated PVs (VIPVs) have great ability to reduce CO2 emission from the transport sector. The development of high-efficiency solar cell modules is very important for this end. In this paper, analytical results for the impact of high-efficiency solar cell modules on increases in electric vehicle (EV) driving distance, reducing CO2 emission and saving charging cost of EV powered by PV are shown. The III-V triple-junction and Si tandem solar cell modules with an efficiency of more than 35% have the potential of the EV driving distance of more than 30 km d-1 on average and more than 50 km d-1 on a clear day. The effects of temperature, partial shading, curved surface, and color variation of solar cell modules upon output power of the VIPV are also briefly shown.
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Ota Y., Araki K., Nagaoka A., Nishioka K.
Cleaner Engineering and Technology 7 2022.4
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
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
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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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
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