Crystalline Modules Research Articles

Convenient Controlled Aqueous C1 Synthesis of Long-Chain Aliphatic AB, AA, and BB Macromonomers for the Synthesis of Polyesters with Tunable Hydrocarbon Chain Segments.

The insertion of long hydrocarbon chains between ester groups in polyester allows for introduction and modulation of crystallinity, which can result in enhanced performance approaching high-density polyethylene. We report a convenient synthesis of building blocks for long-chain aliphatic polyesters via an aqueous C1 polymerization. The macromonomers include ω-hydroxyacid esters, α,ω-diols and α,ω-diacids. The length of hydrocarbon chain segment (C20-C60) can be controlled by the ratio of monomer/initiator in the C1 polymerization. The obtained polyesters from condensation of the long-chain ω-hydroxyacid esters have thermal and mechanical properties indistinguishable from related materials derived from biomass.

Experimental analysis of comparative temperature and exergy of crystalline (c-Si) and amorphous (a-Si) solar PV module using water cooling method

Experimental analysis of comparative temperature and exergy of crystalline (c-Si) and amorphous (a-Si) solar PV module using water cooling method

A Method for the Analytical Extraction of the Single-Diode PV Model Parameters

Determination of PV model parameters usually requires time consuming iterative procedures, prone to initialization and convergence difficulties. In this paper, a set of analytical expressions is introduced to determine the five parameters of the single-diode model for crystalline PV modules at any operating conditions, in a simple and straightforward manner. The derivation of these equations is based on a newly found relation between the diode ideality factor and the open circuit voltage, which is explicitly formulated using the temperature coefficients. The proposed extraction method is robust, cost-efficient, and easy-to-implement, as it relies only on datasheet information, while it is based on a solid theoretical background. Its accuracy and computational efficiency is verified and compared to other methods available in the literature through both simulation and outdoor measurements.

Sequential and combined acceleration tests for crystalline Si photovoltaic modules

The sequential combination test for photovoltaic modules is effective for accelerating degradation to shorten the test time and for reproducing degradation phenomena observed in modules exposed outdoors for a long time. The damp-heat (DH) test, thermal-cycle (TC) test, humidity-freeze (HF) test or dynamic mechanical load (DML) test is combined for the test modules. It was confirmed that chemical corrosion degradation or physical mechanical degradation is reproduced by the combination of the above tests. Cracks on the back sheet and delamination, often observed upon outdoor exposure, were well reproduced by the combination of DH and TC tests and TC and HF tests, respectively. Sequential DH and TC tests and DML and TC tests accelerated the degradation. These sequential tests are expected to be effective in reducing the required time of indoor testing for ensuring long-term reliability.

An Empirical Study on the Building-Integrated Photovoltaic System

As an empirical study for the building-integrated photovoltaic system, the efficiency of several photovoltaic panels with the inclination angle of 17° constructed on the roof of a building was studied. The photovoltaic panels used in this study were crystalline Si, thin-film Si, and thin-film Si modules. The annual average operating time of the panels on the north face was rather low and the annual average operating time of the panels on the south face was rather high. The maximum operating time of the module was obtained at the case of crystalline Si module on the south face (3.5hr), and the annual average operating time of the crystalline Si module on the south face and the north face was 2.99hr. When the module temperature was high (summer season), the operating time of the thin-film module was high. However, when the module temperature was low (winter season), the operating time of the crystalline Si module was high.

Consideration on Na diffusion and recovery phenomena in potential-induced degradation for crystalline Si photovoltaic modules

Potential-induced degradation (PID), which brings about a large rapid decrease in output power has been observed in megawatt-scale photovoltaic power plants. Na diffusion from a cover glass to a cell through an encapsulant is possibly the direct origin of PID for p-type crystalline Si photovoltaic modules. On the other hand, PID is suppressed when using an ionomer encapsulant instead of a conventional ethylene vinyl acetate encapsulant. Some researchers consider that the reason is the suppression of Na diffusion when using an ionomer encapsulant. However, there has been no direct observation of Na diffusion behavior to the best of our knowledge for the modules prepared using an ionomer encapsulant. In this study it was found for the first time that Na diffuses in p-type multicrystalline Si photovoltaic modules prepared using an ionomer encapsulant without PID, suggesting that Na diffusion is not a sufficient condition for PID to occur. Another feature of PID is the recovery phenomenon induced by applying reverse voltage after PID occurs. In this study it was also found that reverse voltage application in the initial stage is effective for suppressing PID.

Behavior of Four Solar PV Modules with Temperature Variation

This paper presents a behavior and performance comparison of four different photovoltaic PV modules: mono-crystalline Silicon, poly-crystalline Silicon, amorphous Silicon and Cupper Indium Gallium diselenide (CIGS) under Iraqi climate conditions of Baghdad city. Temperature influence on the solar modules electric output parameters was investigated experimentally. the temperature coefficients of open circuit voltage, short circuit current and maximum power output for the four modules was calculated. These temperature coefficients are important for all systems design and sizing. Two mathematical models were implemented to extract the governing parameters of the PV modules. A detailed explanation for the temperature influence on the PV module parameters is presented. The results showed that the amorphous silicon and CIGS modules perform better than the crystalline modules in high operating temperature.

Accelerated Testing and Modeling of Potential-Induced Degradation as a Function of Temperature and Relative Humidity

An acceleration model based on the Peck equation was applied to power performance of crystalline silicon cell modules as a function of time and of temperature and humidity, which are the two main environmental stress factors that promote potential-induced degradation (PID). This model was derived from module power degradation data obtained semicontinuously and statistically by in-situ dark current–voltage measurements in an environmental chamber. The modeling enables prediction of degradation rates and times as functions of temperature and humidity. Power degradation could be modeled linearly as a function of time to the second power; additionally, we found that the quantity of electric charge transferred from the active cell circuit to ground during the stress test is approximately linear with time. Therefore, the power loss could be linearized as a function of coulombs squared. With this result, we observed that when the module face was completely grounded with a condensed phase conductor, leakage current exceeded the anticipated corresponding degradation rate relative to the other tests performed in damp heat.

Luminescence imaging analysis of light harvesting from inactive areas in crystalline silicon PV modules

In a crystalline silicon (Si) wafer based photovoltaic (PV) module, a significant fraction of incoming photons falls onto the inactive areas of the module that do not generate electrical carriers (e.g. metal fingers, interconnection ribbons, cell spacing etc.). However, some of those photons can still be harvested via optical scattering at the inactive area and subsequent internal reflection at the glass–air interface, thereby contributing to the module’s output power. We propose a method using luminescence imaging to characterize the light harvesting from the inactive area in crystalline Si PV modules. By exploiting the reciprocity theorem relating luminescence emission to external quantum efficiency (EQE), a relative EQE map is extracted from a luminescence image of a PV module. The light harvesting efficiency at the different inactive areas can thus be directly quantified. For example in this paper, we apply the method to extract the light harvesting efficiency of two different backsheets (i.e. a white backsheet and a scattering tape) and of metal fingers (by screen and stencil printing) in one-cell mini-modules. We show that photons impinging on the white and the scattering tape backsheet close to the solar cell edges have a 20% and a 45% chance, respectively, to be harvested. Similarly, about 60% of the photons impinging on the metal fingers can be harvested. Furthermore, we estimate the enhancement of the effective active area in a typical multicrystalline Si PV module (2.1% due to the metal fingers, 0.2% due to the ribbons, 1.5% due to the white backsheet and 3.2% due to the scattering tape respectively) as well as the corresponding short-circuit current enhancement (0.20A, 0.02A, 0.13A and 0.29A, respectively).

Study of the energy balance and environmental liabilities associated with the manufacture of crystalline Si photovoltaic modules and deployment in different regions

For environmental assessment of photovoltaic systems generation from solar power, it is necessary to consider the fact that a sequence of activities must be accomplished in its production process, not only manufacturing but also installation for proper operation. According to the composition of the energy matrix of the country where this is done, a greater or smaller quantity of CO2 emissions will occur, apart from other environmental degradations. In this case the need of verification is evident, considering the energy matrix of the country where a panel is developed or used, its ability to depreciate the energetic cost and the CO2 emissions, as well as the degradations caused by the manufacturing process. After that, if the photovoltaic panel is still capable of functioning then it will be considered as a source of clean energy. This study has therefore surveyed the energetic costs and CO2 emissions of the manufacturing process of photovoltaic modules. Later this data was used to further analyze the energetic and CO2 mitigation balance and the module capacity for mitigating the environmental liabilities caused by production, by considering different production and using panel׳s sites. The results obtained demonstrated that the greater the emission factor of the panel production country, the greater the required time for emissions reduction due to its production. For instance, in case of panels produced in China and used in Brazil, they could have a truly clean useful life (EULT) up to three times lower than those produced in Germany. The implications of these results were discussed.

Bonding copper ribbons on crystalline photovoltaic modules using various lead-free solders

The requirement for environmentally friendly technology has led to considerable efforts to develop photovoltaic (PV) modules. The copper (Cu) ribbon interconnects of PV modules require alternative bonding materials to replace the current solder that contains lead. Several candidate lead-free solder materials have been developed that are inexpensive and reliable. In this study, we evaluate Cu ribbon interconnection bonding with Sn–0.7Cu and Sn–48Bi–2Ag solder materials to address their feasibility for use in PV modules by investigating material degradation during thermal cycling. After thermal cycling, in the Sn–0.7Cu solder, considerable intermetallic compound (IMC) growth occurred at both interfaces, while Bi-rich grains coarsened with IMC growth in Sn–48Bi–2Ag solder. However, the degradation of the electrical performance of the PV modules was similar for those containing both solder materials. Cracks that appeared at the interface propagated from the fractures of the Ag3Sn IMC layers. This suggests that preventing IMC growth at the interface between the Cu ribbon and Ag sintered electrode is important to improve the reliability of interconnects in PV modules. The use of Pb-free solder in PV modules opens up a novel opportunity to realize high reliability at low cost.

A user-defined finite element for laminated glass panels and photovoltaic modules based on a layer-wise theory

Laminated plates with glass skin layers and a core layer from polyvinyl butyral are widely used in the civil engineering and automotive industry. Crystalline or thin film photovoltaic modules are composed from front and back glass or polymer layers and a solar cell layer embedded in a polymeric encapsulant. For the structural analysis of such laminates, layer-wise theories (LWTs) for plates have been introduced in literature. In this paper, an extended LWT is proposed to assure the C0 continuity. Based on this theory, a finite element formulation and a user-defined quadrilateral serendipity element with quadratic shape functions and nine degrees of freedom (DOFs) is presented. The element is implemented using the Abaqus subroutine “User Element”. Benchmark problems are developed to examine the accuracy and efficiency of the proposed element for a wide range of material properties including the limiting cases of shear compliant and shear rigid laminates. An emphasis is placed on the influence of boundary conditions with respect to additional degrees of freedom as well as on accurate representation of boundary layer effects.

Degradation by acetic acid for crystalline Si photovoltaic modules

The degradation of crystalline Si photovoltaic modules during damp-heat test was studied using some test modules with and without polymer film insertion by observing electrical and electroluminescence properties and by chemical analyses. Acetic acid generated by the hydrolysis decomposition of ethylene vinyl acetate used as an encapsulant is the main origin of degradation. The change in electroluminescence images is explained on the basis of the corrosion of electrodes by acetic acid. On the other hand, little change was observed at the pn junction even after damp-heat test for a long time. Therefore, carrier generation occurs even after degradation; however, such generated carriers cannot be collected owing to corrosion of electrodes. The guiding principle that module structure and module materials without saving acetic acid into the modules was obtained.

Comparative analysis of NOCT values for mono and multi C-Si PV modules in Indian climatic condition

The power output of Photo-voltaic modules is generally rated at STC (Standard Test Condition), 1000W/m2 irradiance, 25°C temperature and 1.5G Air Mass. But in actual field condition the situation is different from STC. Output of PV module is a function of Irradiance, ambient temperature, wind speed and module temperature. It is well established that power output of PV module decreases with increase of module temperature. So it is important to know the temperature of PV module to determine the reduction in power output due to temperature. Module temperature can be determined if irradiance at that instant and NOCT value of that module is known. This work presents the variation in NOCT value with respect to rated power output of PV module and comparison of NOCT values for same rated power mono and multi crystalline Si modules from various manufacturers. According to this study NOCT value increases with the wattage of PV module. For same rated power modules, NOCT value of mono crystalline Si is more than multi crystalline Si.

Degradation of electrical performance of a crystalline photovoltaic module due to dust deposition in northern Poland

The reduction in power output caused by the accumulation of dust on the photovoltaic module surface is an important problem and should receive much more attention in the literature. This study was an evaluation of the performance degradation of crystalline photovoltaic modules due to natural and simulated dust deposition. Dust is created from powdered grains of sand and particles of different bodies. Dust originates from different sources, e.g. from the soil and volcanic eruptions. Dust in the air is an aerosol, and in high concentrations can cause climate change. Deposition of airborne dust on photovoltaic modules may decrease the transmittance of solar cell glazing and cause a significant degradation in the solar conversion efficiency of photovoltaic modules. Dust deposition is closely related to the tilt angle of the module, the exposure period, site climate conditions, wind movement and dust properties. In this article, a brief review of the energy yield losses caused by dust deposition on photovoltaic modules and the results of experimental research conducted in Poland are presented. Dust samples were collected after a few years of natural and artificial dust deposition. The reduction in efficiency had a linear relationship with the dust deposition density.

Development of integrated interconnected crystalline silicon thin film solar cells

In this work the processing sequence for an integrated interconnection concept for crystalline silicon thin-films (c-Si TF) is introduced. This concept is designed to reduce cost in the production of large-area crystalline silicon thin-film modules. Combining the advantages of classical thin-film and wafer technologies, a soldering-free interconnection of cells in the module is realized. In order to investigate the interconnection concept, a small scale laboratory process was developed and is discussed here. Mini-modules were fabricated using this processing sequence on silicon on insulator (SOI) wafers with epitaxially grown back surface field (BSF) and base layer. Despite a non-optimized metallization sequence an open circuit voltage of over 3 V could be achieved for a mini-module consisting of five cells. Mini-modules were also encapsulated without loss in efficiency after encapsulation.

Influence of doping precursor on band gap and morphologies of sol‐gel deposited ZnMgO thin films

AbstractZn1–xMgxO thin films were deposited by sol–gel route on p–type Si (100) and quartz substrates. It is ob‐served that the incorporation of Mg and morphological features of the sol–gel derived Zn1–xMgxO thin films extremely depend upon the selection of doping (Mg) precursor salts. Investigation of different doping precursors such as magnesium acetate, magne‐sium chloride and magnesium nitrate have been carried out. Zn1–xMgxO (x = 0.15) thin films deposited us‐ing each doping source were annealed at 300, 500, 700 and 900 °C in the presence of oxygen for one hour. The results showed that the magnesium nitrate required lower annealing temperature and provided good quality of films, However traces of N were observed in the films. The surface morphology and microstructure of the depos‐ited thin films were analyzed by atomic force microscopy. The crystallite dimension, shape and the growth rate were found to be significantly affected by dopant precursors. The chemical compositions were determined by elemen‐tal dispersive spectra. The band gap modulation is stud‐ied by varying the magnesium content from x = 0.00 to 0.40 for each type of salt for Mg doping. The Zn1–xMgxO films deposited using magnesium chloride exhib‐ited poor band gap modulation and lower quality of mi‐crostructure. The films deposited using magnesium ace‐tate exhibited minimum defects, good crystallinity and higher band gap modulation. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Estimation of the degradation rate of multi-crystalline silicon photovoltaic module under thermal cycling stress

The overall power of an outdoor-exposed photovoltaic (PV) module decreases as a result of thermal cycling (TC) stress, due to the formation of cracks between the solder and metal. In this study, the thermal fatigue life of solder (62Sn36Pb2Ag) interconnection between copper and silver metallization in PV module was studied. This paper describes in detail the degradation rate (RD) prediction model of solder interconnection for crystalline PV module. The RD prediction model is developed which based on published constitutive equations for solder and TC test results on actual PV module. The finite element method was employed to study the creep strain energy density of solder interconnections in TC conditions. Three types of accelerated tests were conducted to determine the prediction model parameters. RD in benchmark condition is predicted and compared with those of TC conditions.

ChemInform Abstract: Updated Assessment of Possibilities and Limits for Solar Cells

AbstractReview: 53 refs.

Updated Assessment of Possibilities and Limits for Solar Cells

The remarkable advances over the past few years in performance of photovoltaic cells, including the advent of new absorber materials, call for an update to the previous assessment of prospects for future progress. The same simple criteria with some refinements, based on cell and module performance data, serve to evaluate and compare most types of solar cells. Apart from Si and InP, for all types the "best cells" have improved in conversion performances (and crystalline Si modules have made major strides in cost reduction). New cell types, such as "perovskite", sustainable chalcogenide, and quantum dot cells, are included. CdTe results bring those cells in line with other well-developed ones, lending some credence to the idea that the criteria provide the reader with knowledge, useful for gauging possible future technological developments. Additionally, the developments of the past few years show that, while the advent of more new cell types cannot be predicted, it can be aided and stimulated by innovative, daring, and creative new materials research.