Flexible Photovoltaic Modules Research Articles

Velocity field measurements under Very Large Floating Structures interacting with surface waves

Increasing utilization of ocean space and a global push for renewable energy solutions has spurred interest in wave behavior around Very Large Floating Structures, like floating photovoltaic (PV) systems. Flexible PV modules may be more suitable for the varying wave conditions found in offshore environments. However, while viscoelastic models are commonly used for wave prediction, they show notable discrepancies with experiments, likely due to untested assumptions of inviscid flow. This experimental study aims to fill that gap by investigating both the wave characteristics and velocity fields underneath flexible and rigid structures using simultaneous Particle Image Velocimetry (PIV) and wave elevation measurements. Wave attenuation is observed for short wavelengths over the flexible structure length. The 2nd order Stokes wave theory provides a good approximation of the wave-induced horizontal velocity profiles under the flexible structure but underestimates the velocities under the rigid one which further lacks the typical exponential decay with water depth. The presence of a wave boundary layer is showcased and compared to an adaptation of the Stokes 2nd problem.

Post‐Mortem Analysis of Building‐Integrated Flexible Thin Film Modules

ABSTRACTFlexible, lightweight thin film (TF) photovoltaic (PV) modules offer a unique opportunity for integration into non‐planar surfaces unable to support heavy weights. While such applications increase the potential for PV in urban areas, the reliability implications are yet to be investigated. Here, prototypes of corrugated rooftiles with integrated Cu (In,Ga)Se2 (CIGS) modules were investigated after 3 years of outdoor operation. Their performance before and after the outdoor exposure was compared and defects were localized. An unpackaging method was developed, allowing access to the solar cells for more detailed characterization of present defects without causing additional damage or changes to existing defects. To our knowledge, this was the first time such an unpackaging method was successfully applied to flexible TF PV modules. The relative efficiency loss ranged from 17% to 43%, mostly due to short‐circuit current (ISC) loss and series resistance (RS) increase. The predominant cause of the RS increase was the delamination at the interconnects, ascribed to thermomechanical stresses caused by outdoor temperature fluctuations. The ISC loss was mainly caused by localized delamination of CIGS from the molybdenum (Mo) back‐contact. The occurrence of such delaminated areas pointed to presence of high local stresses during outdoor operation, possibly due to thermal fluctuations, applied deformation and/or mechanical impact. Two other types of delamination defects were found with no observable impact on performance. These results show the necessity for further optimization in the material choice and processing of TF flexible modules, to avoid mechanical stress related failures upon integration into curved surfaces.

Dynamic performance enhancement in 2D and 3D curved flexible photovoltaic modules: Mismatch loss analysis and cell interconnection configurations optimization

The integration of photovoltaic (PV) technology into curved-surface buildings holds promise for energy-efficient eco-cities. However, the surface irradiance field of curved PV modules is uneven, and the distribution varies with the relative position to the sun and the surface shape. In this study, the dynamic irradiance field distributions of 2D and 3D curved PV modules are investigated. Based on this, 3 PV cell interconnection methods are proposed in conjunction with the irradiance balance principle. The electrical performance and power loss mechanisms are analyzed, and the dynamic adaptability, orientation adaptability, and geometric adaptability are evaluated. The results show diverse irradiance field patterns under different central angle conditions: uniform distribution in the north-south or east-west direction, while Gaussian distribution in other directions. Appropriate PV cell interconnection methods for 2D curved PV modules can effectively reduce mismatch losses, demonstrating significant enhancement in power output, up to 1721.21 Wh and 1604.10 Wh respectively. However, for 3D curved PV modules, the 3 interconnection methods fail to effectively adapt to the dynamic variation in irradiance, thus unable to fully exploit the power generation potential. In-depth investigation of mismatch losses in this study contributes to improving the reliability and economic viability of curved PV module, promoting its commercial application.

Study of Performance of the Flexible (Al-Based) N-PVT-TEC Collectors in Different Configurations

AbstractThe opaque photovoltaic thermal (PVT) produces both thermal and electrical energy. In order to increase thermal energy, we have considered flexible (Al-based) photovoltaic (PV) module for the present study. Further, we have considered thermo-electric cooler (TEC) integrated with flexible PV module to enhance electrical power. As a result, an overall power can be increased in flexible PVT-TEC collector. A concept of series and parallel combination of flexible PVT-TEC collectors is proposed to optimize series (n) and parallel (m) combinations for a given number of N (=n × m) collectors for maximum overall exergy depending on thermal and electrical energies which have not been considered yet so far. Further, a new expression has also been developed for the heat removal factor and instantaneous thermal efficiency of the nth flexible PVT-TEC collector to investigate its effect on the nth flexible PVT-TEC collector performance. Numerical computations have been carried out for a given coldest climatic condition of Srinagar, India, and design parameters of Al-based PVT-TEC collectors using matlab R2021b. Based on numerical computations, the following conclusions have been drawn: (i) For case (a) (all flexible PVT-TEC collectors are connected in parallel), the daily overall exergy is 2.7 kW, which is 21.3% more than case (d). (All flexible PVT-TEC collectors are connected in series.) (ii) There is a drop of 20% in the mass flowrate factor due to the correction factor.

Experimental study on critical wind velocity of a 33-meter-span flexible photovoltaic support structure and its mitigation

Flexible photovoltaic (PV) modules support structures are extremely prone to wind-induced vibrations due to its low frequency and small mass. Wind-induced response and critical wind velocity of a 33-m-span flexible PV modules support structure was investigated by using wind tunnel tests based on elastic test model, and the effectiveness of three types of stability cables on enhancing the critical wind velocity of the flexible PV modules support structures was carefully examined. First, an elastic test model of the flexible PV modules support structure was designed and manufactured. Second, a series of wind tunnel tests based on the elastic test model were carried out to obtain the wind-induced responses of the 33-m-span PV modules support structure. Third, three types of stability cables (T1, T2 and T3) were installed on the test model, and a series of wind tunnel tests were carried out to examine the effectiveness of the three types of mitigation countermeasures. Finally, the wind load factor was discussed by using the displacement time histories measured from the wind tunnel tests. The results show that 180° and 0° are the two most unfavorable wind directions, and the critical wind velocity is only about 18.5 m/s for the deformation threshold of 1/100 span. The critical wind velocities for stability cables T1, T2 and T3 (1/100 of the span) are respectively 24.6, 29.3 and 36.7 m/s, which are significantly higher than the value without stability cable (18.5 m/s). The wind load factor at the windward side under wind directions of 0° and 180° are respectively 1.56 and 1.30 for the test case with stability cable T3.

Thin Polymer Films by Oxidative or Reductive Electropolymerization and Their Application in Electrochromic Windows and Thin-Film Sensors.

Electrically conducting and semiconducting polymers represent a special and still very attractive class of functional chromophores, especially due to their unique optical and electronic properties and their broad device application potential. They are potentially suitable as materials for several applications of high future relevance, for example flexible photovoltaic modules, components of displays/screens and batteries, electrochromic windows, or photocatalysts. Therefore, their synthesis and structure elucidation are still intensely investigated. This article will demonstrate the very fruitful interplay of current electropolymerization research and its exploitation for science education issues. Experiments involving the synthesis of conducting polymers and their assembly into functional devices can be used to teach basic chemical and physical principles as well as to motivate students for an innovative and interdisciplinary field of chemistry.

The effect of changing the shape factor on the efficiency of the flexible solar modules

This study investigates the performance of different shapes of the flexible photovoltaic modules. Three shapes of the flexible modules were compared under similar outdoor conditions: The standard flat, convex, and concave. The comparison was based on the solar radiation input, voltage output, current output, and back of the module’s temperature. Results showed that based on the output power and the efficiency for the modules, the standard flat module was of the highest performance, followed by the convex module and then by the concave module. The average output efficiency of the standard flat module was 4.5–6.0% and 0.8–1.2% for the convex module, while it was 0.46–0.53% for the concave module. In addition, a simulated energy analysis was carried out between the standard flat module toward the south direction and the convex module toward the southeast direction. The simulation results showed that an area that holds 50 standard flat modules, could hold 72 convex modules. Moreover, the annual ejected electrical energy into a grid for the standard flat modules and convex modules were 8.61 MWH and 5.462 MWH, respectively. Furthermore, the performance of the standard flat and convex modules were 74.79% and 70.96%, respectively.

Thickness evaluation of AlOx barrier layers for encapsulation of flexible PV modules in industrial environments by normal reflectance and machine learning

AbstractFlexible photovoltaic (PV) devices, such as those based on Cu (In,Ga)Se2 (CIGS) and perovskites, use polymeric front sheets for encapsulation that do not provide sufficient protection against the environment. The addition of nanometric AlxO layers by spatial atomic layer deposition (S‐ALD) to these polymeric materials can highly improve environmental protection due to their low water vapor transmission rate and is a suitable solution to be applied in roll‐to‐roll industrial production lines. A precise control of the thickness of the AlOx layers is crucial to ensure an effective water barrier performance. However, current thickness evaluation methods of such nanometric layers are costly and complex to incorporate in industrial environments. In this context, the present work describes and demonstrates a novel characterization methodology based on normal reflectance measurements and either on control parameter‐based calibration curves or machine learning algorithms that enable a precise, low‐cost, and scalable assessment of the thickness of AlOx nanometric layers. In particular, the proposed methodology is applied for precisely determining the thickness AlOx nanolayers deposited on three different substrates relevant for the PV industry: monocrystalline Si, Cu (In,Ga)Se2 multistack flexible modules, and polyethylene terephthalate (PET) flexible encapsulation foil. The proposed methodology demonstrates a sensitivity <10 nm and acquisition times ≤100 ms which makes it compatible with industrial monitoring applications. Additionally, a specific design for in‐line integration of a normal reflectance system into a roll‐to‐roll production line for thickness control of nanometric layers is defined and proposed.

Distribution of Solar Radiation on Greenhouse Convex Rooftop

Photovoltaic greenhouses became popular in many countries for growing crops and, at the same time, generating electricity mainly for own usage to control the air temperature inside the greenhouse. Solar radiation is essential for their photosynthesis process for crop growing, however, high levels of solar radiation may adversely affect the crop quality. Therefore, a balance between the need for sufficient solar radiation for plant grows and the need for electricity is important to maintain. Many greenhouses are built with curved rooftops of convex shapes and flat-plate photovoltaic (PV) modules are deployed on the rooftops. The present study proposes using flexible PV modules adhering to the curvature of the roof. The incident solar radiation on a curved surface is not uniformly distributed along the surface, therefore the density of the solar irradiation attains higher levels at regions where the PV modules may be deployed to generate greater amounts of electric power. The present study determines the density variation of the solar irradiation, in Wh/m2, (direct beam, diffuse and global) along the curvature of the convex surface of the greenhouse, and proposes the location of the PV modules to be deployed on the roof to obtain desired levels of solar radiation needed for designing the PV systems. North-south and east-west greenhouse orientations are considered.

Built‐In Potential and Operational Stability of Nonfullerene Organic Solar Cells

Many progresses have been made in the advancement of solution‐processable high‐performance organic solar cells (OSCs), offering an encouraging alternative photovoltaic (PV) technology option to traditional solar cells. The solution processing capability provides OSCs with great fabrication flexibility for new device concepts, cell architectures, and applications including lightweight large‐area transparent and flexible PV modules. The unique transparency and flexible features also add an attractive artistic aspect to emerging OSCs for use on curved surfaces, portable electronics, and indoor appliances. However, the stability of the OSCs is still less than satisfactory compared with the conventional inorganic semiconductor solar cells. This work discusses the improvement of the operational stability of OSCs through analyses of the important issues of 1) unbalanced charge mobility, 2) vertical stratification in the bulk heterojunction, and 3) built‐in potential across the photoactive layer, and retaining a stable built‐in potential for enhancing the operational stability of OSCs.

Are the Optimum Angles of Photovoltaic Systems So Important?

Traditional point of view suggests photovoltaic systems to be installed at the optimum angles. However, various reasons require more flexible photovoltaic module installations. In this study, it is found that the optimum angles for photovoltaic systems are not so important. Because photovoltaic modules only suffer 5% of energy losses, compared to the maximum plane-of-array irradiation, in quite a wide range of installation angles which is defined as the 5% Loss Bound. The Annual Bound Equations were derived to quantitatively calculate the annual 5% Loss Bound. If local information on the optimum angles is known, the improved Annual Bound Equation can be used for higher accuracy; if not, its simplified version is suggested at latitudes lower than 40o. Simulations by the Annual Bound Equations are independent of local irradiance data, which is significantly faster and more convenient than conventional irradiance-based approaches.

Fossil Fuels Environmental Challenges and the Role of Solar Photovoltaic Technology Advances in Fast Tracking Hybrid Renewable Energy System

The rise in global urbanization comes with sustainable development challenges, especially in lower-middle-income countries. In response to these urbanization and energy challenges, this study focuses on the roles of energy materials (EMs) advances on community-scale hybrid renewable energy systems (HRES). The study proposes the integration of energy material (EM) RD emits the least CO2 to the global CO2 emissions and yet endangered by climate change challenges and air pollution diseases. The study includes global responses to energy challenges, such as increase alternative energies share, with special attention to solar photovoltaic (PV) power generation technologies; policy framework; HRES and effects of PV materials advances on HRES. This study is of the view that a further breakthrough in the production of low-cost flexible thin film PV modules will facilitate energy trilemma accomplishment. The exploitation of the attributes of atomic layer deposition in manufacturing of thin film is seen as a potential future production technique, suitable for efficient flexible thin-film PV module production.

Nanostructured Transparent Polymer Provides Innovation Design for Solar Cells. Increasing Energy and Improving Performance

Nanostructured transparent polymer (NSTP) developed by Enerize Corporation for encapsulate solar cell / PV module allows to solve the problems of the traditional PV modules that laminated with glass. The traditional PV modules are complex, non-flexible, & expensive, requirement the antireflection coating and adhesive polymer between glass and semiconductor. Encapsulation and protective coating using single layer nanostructured polymer with high level transparency provide new design of thin film flexible photovoltaic modules. Additional benefit of using the NSTP includes: increasing the efficiency of solar cells by 20% relative, reducing price and weight by 30%; flexible design solution and long time durability.

Synthesis of Pseudocapacitive Polymer Chain Anode and Subnanoscale Metal Oxide Cathode for Aqueous Hybrid Capacitors Enabling High Energy and Power Densities along with Long Cycle Life

AbstractAqueous electrochemical energy storages are of enormous attention due to their high safety and being environmentally friendly, but they must satisfy very challenging standards in energy and power densities over long repeated charging/discharging cycles. Herein, a strategy to realize high‐performance aqueous hybrid capacitors (AHCs) using pseudocapacitive negative and positive electrodes is reported. Polymer chains, which are synthesized by in situ polymerization of polyaniline on reduced graphene sheets, show fiber‐like morphologies and the redox‐reactive surface area allowing high capacitance as anode materials even at a high current density of 20 A g−1 and a high loading of ≈6 mg cm−2. Additionally, subnanoscale metal oxide particles on graphene are utilized as pseudocapacitive cathode materials and they show the approximately threefold higher capacitance than nanocrystals of ≈10 nm. Assembling these polymer chain anode and subnanoscale metal oxide cathode in full‐cell AHCs is shown to give the high energy density exceeding those of aqueous batteries along with the ≈100% capacity retention over 100 000 redox cycles. Additionally, AHCs exhibit the high power density allowing ultrafast charging, so that the switching wearable display kit with two AHCs in series can be charged within several seconds by the flexible photovoltaic module and USB switching charger.

High-Efficient Energy Harvester With Flexible Solar Panel for a Wearable Sensor Device

This paper proposes an optimal energy harvester (OEH) that uses a flexible photovoltaic (FPV) module to prolong battery life for a wearable body sensor node under indoor and outdoor conditions. The proposed sensor node uses a Bluetooth low-energy module, which consumes low power to wirelessly communicate with mobile devices for monitoring vital signals. A 19 cm $\times4$ cm FPV module that can easily conform to human body contours is used for generating a peak-power of up to 500 mW to charge the battery in outdoor environments. To optimize the power collected under various irradiances, the OEH is designed with a boost circuit for harvesting the low energy available indoors and a maximum power point tracker for collecting the high energy that is available outdoors. The booster can operate within a wide input voltage range of 0.65–3 V to generate a stable output voltage of 3.3 V, and it has a high conversion efficiency of ~95%. The MPPT uses fuzzy inference engine to find the MPP of the FPV that is required to power the system. The results of our experiment show that the proposed device can prolong the lifetime by up to 950% under an irradiance of only 2.9 mW/cm2, and the proposed node becomes an autonomous node under partial shading and sunlight conditions. Therefore, this paper can provide a useful solution for extending the lifetime of wearable sensor devices.

>10% Efficiency Polymer:Fullerene Solar Cells with Polyacetylene‐Based Polyelectrolyte Interlayers

Polymer solar cells have gained great attention due to their tremendous potential for applications in light‐weight, large‐area, and flexible photovoltaic modules fabricated via continuous roll‐to‐roll processes. Despite the significant progress, however, their efficiency and operating stability are still inadequate for commercial applications. Interfacial engineering of the electron‐collecting buffer layer and the organic photoactive layer through the use of organic dipole interlayers, has been proposed as a simple and scalable way to improve the overall solar cell performance. Here, highly efficient inverted polymer:fullerene solar cells have been successfully developed with a power conversion efficiency of over 10%. The bulk heterojunction layer consists of the poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b]dithiophene‐alt‐3‐fluorothieno[3,4‐b]thiophene‐2‐carboxylate] (PTB7‐Th) and the [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM), as the electron donor and electron acceptor, respectively. Key to this success is the insertion of the ionic polyacetylene‐based conjugated polymer, poly(N‐dodecyl‐2‐ethynylpyridinium bromide), as an interfacial dipole layer. The latter is shown to lower the work function of the electron transporting zinc oxide layer and increase the built‐in potential, consequently facilitating efficient charge transport/extraction. Optimized solar cells exhibit power conversion efficiency values exceeding 10% while their operating stability under continuous solar‐simulated illumination is significantly enhanced when ultraviolet light is effectively blocked using a suitable optical filter.

Methods for modelling and analysis of bendable photovoltaic modules on irregularly curved surfaces

Most photovoltaic modules are planar and as a result, research on panel layout for photovoltaic systems typically uses planar panels. However, the increased availability of thin-film photovoltaic modules opens up possibilities for the application of flexible solar panels on irregularly curved surfaces, including the integration of photovoltaic panels on building roofs with double curvature. In order to efficiently arrange photovoltaic panels on such surfaces, geometric CAD tools as well as radiation analysis tools are needed. This paper introduces a method to generate geometry for flexible photovoltaic modules on curved surfaces, as well as a method to arrange multiple of such modules on a surface. By automating the generation of possible photovoltaic panel arrangements and linking the geometric tools to solar analysis software, large numbers of design options can be analysed in a relatively short time. This combination of geometry generation and solar analysis provides data that is important for electrical design of photovoltaic systems. The merits of the methods we introduce are illustrated with a case study, for which hundreds of design configurations have been explored in an automated manner. Based on analysis of the numeric data generated for each of the configurations, the effects of panel dimensions and orientation on solar insolation potential and panel curvature have been established. The quantitative and qualitative conclusions resulting from this analysis have informed the design of the photovoltaic system in the case study project.

A Power Output Estimate of Cylindrically Shaped Flexible Photovoltaic Module with Polygonal Approximation

SUMMARYFlexible photovoltaic (PV) modules have received a great deal of attention for use in PV systems. At present, the most important issue to be resolved is the optimum shape of flexible PV modules for obtaining maximum power output. A design tool specifically tailored for the flexible PV module is required for this purpose. In the present study, a new method is proposed for estimating the power output of a cylindrically shaped flexible PV module, taking into account the uneven irradiation and temperature that occurs for a curved surface. The average irradiation over the area of the entire module is used in the equation of the proposed method. The temperature is calculated based on the root mean square (RMS) of the irradiation over the area of the entire module. The average and RMS of the irradiation are calculated based on the directional dependence of the global horizontal irradiance. The estimated and measured power outputs are compared. The error rate of the total power output is 2.6%, and the mean absolute percentage error of the power output is 6.8%. The proposed method can reduce the amount of calculation to compare with a conventional method having the same mean absolute percentage error.

Performance of Flexible Photovoltaic Modules Encapsulated by Silicon Oxide/Organic Silicon Stacked Layers

In this paper, flexible silicon thin-film solar cells on polyimide are encapsulated by organic silicon and inorganic silicon oxide (SiO x ) stacked layers. This encapsulation replaces conventional encapsulation, which involves ethylene-vinyl acetate (EVA). The effects of the number of stacked layers on encapsulation of silicon thin-film solar modules are investigated. Experimental results show that the six-pair stacked layer yields a water vapor transmission rate of as low as $10^{-6}$ g/ $\text{m}^{\vphantom {R^{l}}{2}}$ day, satisfying the requirements of solar cell encapsulation. The measurements of internal stress confirm that a thin organic silicon layer greatly reduces the internal stresses over the whole device structure, preventing the cracking of SiO x and the consequent failure of the encapsulation. Solar modules that are encapsulated with a six-pair stacked layer not only exhibit a higher initial conversion efficiency than those encapsulated by EVA but also exhibit less performance degradation after being used outdoors for many hours. Bending test shows that after 5000 bendings, stacked layer encapsulation yields a device performance maintenance of 89.1%, while encapsulation in EVA maintains only 85.1% of device performance. These results suggest that silicon stacked layers have great potential for encapsulating flexible thin-film solar cells, and represent a favorable alternative to conventional EVA.

Flexible lateral organic solar cells with core–shell structured organic nanofibers

One-dimensional conjugated polymer fibers provide unperturbed percolation pathways for efficient charge transport. Here, we report the fabrication of photoresponsive core–shell organic semiconductor fibers by using co-axial electrospinning and their application to the flexible organic photovoltaic devices. The electrospun organic semiconductor fibers are encapsulated with a sheath, polyvinylpyrrolidone (PVP), and consist of the photoactive materials poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (P3HT:PCBM). The electrospun P3HT:PCBM fibers consist of PCBM-rich core and P3HT-rich shell phases with P3HT chains aligned along the fiber direction. This structure exhibits strong photoresponsive behavior after thermal annealing, which was assessed by implementing the fibers in a phototransistor and a photodiode. Finally, we demonstrate a novel flexible photovoltaic module device on a plastic substrate that shows reliable and stable operation under bending conditions. These electrospun polymer:PCBM blend fibers are promising components for flexible optoelectric devices.