Showing papers in "Progress in Photovoltaics in 2016"
629 citations
619 citations
TL;DR: In this article, the authors examined the data in several ways to minimize this bias and found median degradation for x-Si technologies in the 0.5-0.6%/year range with the mean in the 2.8-3.9%/month range.
Abstract: Published data on photovoltaic (PV) degradation measurements were aggregated and re-examined. The subject has seen an increased interest in recent years resulting in more than 11 000 degradation rates in almost 200 studies from 40 different countries. As studies have grown in number and size, we found an impact from sampling bias attributable to size and accuracy. Because of the correlational nature of this study we examined the data in several ways to minimize this bias. We found median degradation for x-Si technologies in the 0.5–0.6%/year range with the mean in the 0.8–0.9%/year range. Hetero-interface technology (HIT) and microcrystalline silicon (µc-Si) technologies, although not as plentiful, exhibit degradation around 1%/year and resemble thin-film products more closely than x-Si. Several studies showing low degradation for copper indium gallium selenide (CIGS) have emerged. Higher degradation for cadmium telluride (CdTe) has been reported, but these findings could reflect a convolution of less accurate studies and longer stabilization periods for some products. Significant deviations for beginning-of-life measurements with respect to nameplate rating have been documented over the last 35 years. Therefore, degradation rates that use nameplate rating as reference may be significantly impacted. Studies that used nameplate rating as reference but used solar simulators showed less variation than similar studies using outdoor measurements, even when accounting for different climates. This could be associated with confounding effects of measurement uncertainty and soiling that take place outdoors. Hotter climates and mounting configurations that lead to sustained higher temperatures may lead to higher degradation in some, but not all, products. Wear-out non-linearities for the worst performing modules have been documented in a few select studies that took multiple measurements of an ensemble of modules during the lifetime of the system. However, the majority of these modules exhibit a fairly linear decline. Modeling these non-linearities, whether they occur at the beginning-of-life or end-of-life in the PV life cycle, has an important impact on the levelized cost of energy. Copyright © 2016 John Wiley & Sons, Ltd.
351 citations
TL;DR: In this paper, the authors discuss the current status of kesterite-based solar cells by focusing on three key aspects of the device: (i) the interface between the Kesterite absorber and the Mo back contact, (ii) the kesteritic absorber bulk defects and grain boundaries, and (iii) the interfaces between the buffer layer.
Abstract: Kesterite-based solar cells are attracting considerable attention in recent years, owing to the reduced toxicity and greater abundance of their constituent elements. In this brief review, we discuss the current status of this important technology by focusing on three key aspects of the device: (i) the interface between the kesterite absorber and the Mo back contact, (ii) the kesterite absorber bulk defects and grain boundaries and (iii) the interface between the kesterite absorber and the buffer layer. By identifying key issues to be addressed, we provide suggestions for their potential improvement and future research. Copyright © 2016 John Wiley & Sons, Ltd.
317 citations
TL;DR: The interdigitated back contact (IBC) solar cells developed at the Australian National University have resulted in an independently confirmed (Fraunhofer Institut fur Solare Energiesysteme (ISE) CalLab) designated-area efficiency of 24.4 ± 0.7%, featuring short-circuit current density of 41.95 µm/cm2, open circuit voltage of 703 µmV and 82.7% fill factor as discussed by the authors.
Abstract: The interdigitated back contact (IBC) solar cells developed at the Australian National University have resulted in an independently confirmed (Fraunhofer Institut fur Solare Energiesysteme (ISE) CalLab) designated-area efficiency of 24.4 ± 0.7%, featuring short-circuit current density of 41.95 mA/cm2, open-circuit voltage of 703 mV and 82.7% fill factor. The cell, 2 × 2 cm2 in area, was fabricated on a 230 µm thick 1.5 Ω cm n-type Czochralski wafer, utilising plasma-enhanced chemical vapour deposition (CVD) SiNx front-surface passivation without front-surface diffusion, rear-side thermal oxide/low-pressure CVD Si3N4 passivation stack and evaporated aluminium contacts with a finger-to-finger pitch of 500 µm. This paper describes the design and fabrication of lab-scale high-efficiency IBC cells. Characterisation of optical and electronic properties of the best produced cell is made, with subsequent incorporation into 3D device modelling used to accurately quantify all losses. Loss analysis demonstrates that bulk and emitter recombination, bulk resistive and optical losses are dominant and suggests a clear route to efficiency values in excess of 25%. Additionally, laser processing is explored as a means to simplify the manufacture of IBC cells, with a confirmed efficiency value of 23.5% recorded for cells fabricated using damage-free deep UV laser ablation for contact formation. Meanwhile all-laser-doped cells, where every doping and patterning step is performed by lasers, are demonstrated with a preliminary result of 19.1% conversion efficiency recorded. Copyright © 2014 John Wiley & Sons, Ltd.
155 citations
TL;DR: This paper examines the impact of changes to key PV module and system parameters on the levelized cost of energy (LCOE) and the impacts on the 2015 baseline LCOE due to changes to each parameter are shown.
Abstract: To quantify the potential value of technological advances to the photovoltaics (PV) sector, this paper examines the impact of changes to key PV module and system parameters on the levelized cost of energy (LCOE). The parameters selected include module manufacturing cost, efficiency, degradation rate, and service lifetime. NREL's System Advisor Model (SAM) is used to calculate the lifecycle cost per kilowatt-hour (kWh) for residential, commercial, and utility scale PV systems within the contiguous United States, with a focus on utility scale. Different technological pathways are illustrated that may achieve the Department of Energy's SunShot goal of PV electricity that is at grid price parity with conventional electricity sources. In addition, the impacts on the 2015 baseline LCOE due to changes to each parameter are shown. These results may be used to identify research directions with the greatest potential to impact the cost of PV electricity. Copyright © 2016 John Wiley & Sons, Ltd.
121 citations
TL;DR: In this article, the authors performed a bottom-up techno-economic analysis of three different strategies for substrate reuse in high-volume manufacturing: epitaxial lift-off, spalling, and the use of a porous germanium release layer.
Abstract: The high cost of wafers suitable for epitaxial deposition of III-V solar cells has been a primary barrier to widespread use of these cells in low-concentration and one-sun terrestrial solar applications A possible solution is to reuse the substrate many times, thus spreading its cost across many cells We performed a bottom-up techno-economic analysis of three different strategies for substrate reuse in high-volume manufacturing: epitaxial lift-off, spalling, and the use of a porous germanium release layer The analysis shows that the potential cost reduction resulting from substrate reuse is limited in all three strategies––not by the number of reuse cycles achievable, but by the costs that are incurred in each cycle to prepare the substrate for another epitaxial deposition The dominant substrate-preparation cost component is different for each of the three strategies, and the cost-ranking of these strategies is subject to change if future developments substantially reduce the cost of epitaxial deposition Copyright © 2016 John Wiley & Sons, Ltd
117 citations
TL;DR: In this article, a monolithic solid state module based on organometal CH3NH3PbI3 and CH3 NH3PBI3 using poly-(3-hexylthiophene) and Spiro-OMeTAD as hole transport materials (HTMs) was fabricated and a scalable patterning procedure was developed to minimize the series resistance at the integrated series-interconnections.
Abstract: We fabricated monolithic solid state modules based on organometal CH3NH3PbI3 and CH3NH3PbI3 − xClx perovskites using poly-(3-hexylthiophene) and Spiro-OMeTAD as hole transport materials (HTMs). In particular, we developed innovative and scalable patterning procedures to minimize the series resistance at the integrated series-interconnections. By using these optimization steps, we reached a maximum conversion efficiency of 8.2% under AM1.5G at 1 Sun illumination conditions using the CH3NH3PbI3 − xClx perovskite and the poly-(3-hexylthiophene) as HTM. Finally, we investigated the double-step deposition of CH3NH3PbI3 using the Spiro-OMeTAD, reaching a maximum conversion efficiency on active area (10.08 cm2) equal to 13.0% (9.1% on aperture area) under AM1.5G at 1 Sun illumination conditions. This remarkable result represents the highest PCE value reached for the perovskite solar modules. Copyright © 2014 John Wiley & Sons, Ltd.
114 citations
TL;DR: In this article, a screen-printed rear Al finger grid instead of the conventional full-area aluminum (Al) rear layer while using the same PERC manufacturing sequence was proposed.
Abstract: Passivated emitter and rear cell (PERC) solar cells are currently being introduced into mass production. In this paper, we report a novel PERC solar cell design that applies a screen-printed rear Al finger grid instead of the conventional full-area aluminum (Al) rear layer while using the same PERC manufacturing sequence. We name this novel cell concept PERC+ because it offers several advantages. In particular, the Al paste consumption of the PERC+ cells is drastically reduced to 0.15 g instead of 1.6 g for the conventional PERC cells. The Al fingers create 2-µm-deeper aluminum back surface fields, which increases the open-circuit voltage by 4 mV. The five-busbar Al finger grid enables bifacial applications of the PERC+ cells with front-side efficiencies up to 20.8% and rear-side efficiencies up to 16.5% measured with a black chuck. The corresponding bifaciality is 79%. When applied in monofacial modules where the white back sheet acts as external rear reflector, the efficiency of the PERC+ cells is estimated to 20.9%, which is comparable with conventional PERC cells. Whereas Institute for Solar Energy Research Hamelin developed the aforementioned PERC+ results, SolarWorld independently pioneered a very similar bifacial PERC+ cell process starting in 2014. Transfer into mass production has been successfully accomplished, and novel glass–glass bifacial PERC+ modules have been launched at the Intersolar 2015 based on a most simple, lean, and cost-effective bifacial cell process. These new bifacial PERC+ modules show an increase in annual energy yield between 5% and 25% in simulations, which is confirmed by first outdoor measurements. Copyright © 2015 John Wiley & Sons, Ltd.
103 citations
TL;DR: In this article, a carrier-selective tunnel oxide passivated rear contact for high-efficiency screen-printed large area n-type front junction crystalline Si solar cells was proposed.
Abstract: This paper reports on the implementation of carrier-selective tunnel oxide passivated rear contact for high-efficiency screen-printed large area n-type front junction crystalline Si solar cells. It is shown that the tunnel oxide grown in nitric acid at room temperature (25°C) and capped with n+ polysilicon layer provides excellent rear contact passivation with implied open-circuit voltage iVoc of 714 mV and saturation current density J0b′ of 10.3 fA/cm2 for the back surface field region. The durability of this passivation scheme is also investigated for a back-end high temperature process. In combination with an ion-implanted Al2O3-passivated boron emitter and screen-printed front metal grids, this passivated rear contact enabled 21.2% efficient front junction Si solar cells on 239 cm2 commercial grade n-type Czochralski wafers. Copyright © 2016 John Wiley & Sons, Ltd.
83 citations
TL;DR: In this article, a high-throughput combinatorial method is applied to accelerate development of photovoltaic devices, in this case, using the novel CuSbS2 absorber via a newly developed three-stage self-regulated growth process to control absorber purity and orientation.
Abstract: Development of alternative thin film photovoltaic technologies is an important research topic because of the potential of low-cost, high-efficiency solar cells to produce terawatt levels of clean power. However, this development of unexplored yet promising absorbers can be hindered by complications that arise during solar cell fabrication. Here, a high-throughput combinatorial method is applied to accelerate development of photovoltaic devices, in this case, using the novel CuSbS2 absorber via a newly developed three-stage self-regulated growth process to control absorber purity and orientation. Photovoltaic performance of the absorber, using the typical substrate CuInxGa1 − xSe2 (CIGS) device architecture, is explored as a function of absorber quality and thickness using a variety of back contacts. This study yields CuSbS2 device prototypes with ~1% conversion efficiency, suggesting that the optimal CuSbS2 device fabrication parameters and contact selection criteria are quite different than for CIGS, despite the similarity of these two absorbers. The CuSbS2 device efficiency is at present limited by low short-circuit current because of bulk recombination related to defects, and a small open-circuit voltage because of a theoretically predicted cliff-type conduction band offset between CuSbS2 and CdS. Overall, these results illustrate both the potential and limits of combinatorial methods to accelerate the development of thin film photovoltaic devices using novel absorbers. Copyright © 2016 John Wiley & Sons, Ltd.
TL;DR: In this paper, the positive effect of a Ge nanolayer introduced into the processing of Cu2ZnSnSe4 absorbers (CZTSe) was demonstrated.
Abstract: In our recently published work, the positive effect of a Ge nanolayer introduced into the processing of Cu2ZnSnSe4 absorbers (CZTSe) was demonstrated. In this contribution, the complete optimizatio ...
TL;DR: In this paper, the authors demonstrate MQW solar cells with effective bandgaps ranging from 1.31 eV to as low as 1.15ÕeV, which implies the merit of high photovoltage as compared with bulk cells with the same bandgap.
Abstract: Bandgap engineering of strain-balanced InGaAs/GaAsP multiple quantum wells (MQWs) allows high-quality materials with an absorption edge beyond GaAs to be epitaxially grown in Ge/GaAs-based multijunction solar cells. We demonstrate MQW solar cells with effective bandgaps ranging from 1.31 eV to as low as 1.15 eV. The bandgap-voltage-offset of MQWs is found to be independent of effective bandgaps and superior to a bulk reference by approximately 0.1 V. This implies the merit of high photovoltage as compared with bulk cells with the same bandgap in addition to their widely bandgap-tunable property. Towards the realization of fully lattice-matched quad-junction devices, we demonstrate a 70-period, 1.15-eV bandgap MQW cell as a promising material in 0.66/1.15/1.51/1.99-eV quad-junction cells, whose practical efficiency has a potential to achieve over 50%. With such a large period number of MQWs, the reverse-biased external quantum efficiency reaches an average of over 60% in the spectral region corresponding to a 1.15-eV subcell; this is achieved with only a-few-percent drop at short-circuit condition. The device presented here reaches the target open-circuit voltage and over 75% of the current density required for realizing a 1.15-eV subcell in a 50%-efficient quad-junction solar cell. We believe that future devices which exploit light-trapping structures and enhanced carrier extraction will be able to reach the desired target. Copyright © 2015 John Wiley & Sons, Ltd.
TL;DR: In this paper, the authors compare yield predictions and monitored data for 26 PV power plants located in southern Germany and Spain and conclude that yield predictions for areas where the global brightening effect occurred in general underestimated the energy yield by the same magnitude.
Abstract: Yield predictions are performed to predict the solar resource, the performance and the energy production over the expected lifetime of a photovoltaic (PV) system. In this study, we compare yield predictions and monitored data for 26 PV power plants located in southern Germany and Spain. The monitoring data include in-plane irradiance for comparison with the estimated solar resource and energy yield for comparison with predicted performance. The results show that because of increased irradiance in recent years (‘global brightening’) the yield predictions systematically underestimate the energy yield of PV systems by about 5%. Because common irradiance databases and averaging times were used for the yield predictions analysed in this paper, it is concluded that yield predictions for areas where the global brightening effect occurred in general underestimated the energy yield by the same magnitude. Using recent satellite-derived irradiance time series avoids this underestimation. The observed performance ratio of the analysed systems decreases by 0.5%/year in average with a relatively high spread between individual systems. This decrease is a main factor for the combined uncertainty of yield predictions. It is attributed to non-reversible degradation of PV cells or modules and to reversible effects, like soiling. Based on the results of the validation, the combined uncertainty of state of the art yield predictions using recent solar irradiance data is estimated to about 8%. Copyright © 2015 John Wiley & Sons, Ltd.
TL;DR: In this paper, the authors focus on the analysis of the photovoltaic module electrical characteristics after approximately 20 years of field exposure, considering differences in the design of cells that were used for the production of these modules, which were identified by detailed visual inspection.
Abstract: Standardized tests to assure the reliability of photovoltaic modules and to detect possible early failures of modules when exposed in the field, due to design flaws or to the use of non-appropriate materials, have played an important role in the successful growth of photovoltaic market in recent years. In order for this growth to be sustainable in coming years, it is crucial to keep the confidence of investors in standard well-established technologies and to increase confidence in new emerging technologies. For these reasons, there is an ongoing work for the improvement of current tests and for the development of new ones, which besides assuring module reliability in the field, have also the aim of predicting their lifetime. The analysis of degradation of modules that were field exposed over a long period of time is fundamental to identify the degradation mechanisms and to collect statistics on modules behavior. This work focuses on the analysis of the change of the photovoltaic module electrical characteristics after approximately 20 years of field exposure, considering differences in the design of cells that were used for the production of these modules, which were identified by detailed visual inspection. Failure modes were investigated by comprehensive visual inspection and the use of spatially resolved analysis techniques as follows: laser beam-induced current and electroluminescence. The main failure mode identified was yellowing of the encapsulant. © 2015 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.
TL;DR: In this article, the degradation of PV modules during damp-heat exposure is investigated, and power degradation is analyzed in dependence of temperature and humidity during exposure, and the module's equivalent circuit parameters are calculated from I-V characteristics measured during ageing.
Abstract: The degradation of PV modules during damp-heat exposure is investigated. Power degradation is analysed in dependence of temperature and humidity during exposure. The module’s equivalent circuit parameters are calculated from I-V characteristics measured during ageing. A dose function is developed and degradations of power as well as equivalent circuit parameters can be analysed against the dose, which provides a better understanding of the module ageing behaviour. EL images of modules before and after ageing support the changes of solar cell parameters.
TL;DR: In this article, the photon downshifting coordination complexes have been spin-coated on silicon solar cells and an increase of spectral response of the solar cells was observed in the ultraviolet region.
Abstract: Luminescent lanthanide-doped oxides, nanoparticles, nanocrystals, and coordination complexes are major tools in the fields of optical and laser materials, telecommunications, medical imaging, and fluoroimmunoassays. In particular, coordination complexes are efficient energy converters with high photostability, large ligand-induced Stokes shifts, and tunable excitation and emission spectra. However, their application as light downshifting materials for solar cells has not yet been widely explored. This third generation solar cell concept enables to increase the efficiency of standard solar cells—such as Si or copper indium gallium (di)selenide (CIGS)—that have low performance for ultraviolet photons. The incorporation of such a converter in solar module encapsulants can provide a cheap and effective way to integrate photon conversion. Here, encapsulants functionalised by photon downshifting coordination complexes have been spin-coated on silicon solar cells. For all the coordination complexes, an increase of the spectral response of the solar cells is observed in the ultraviolet region. In the best case, a relative increase of 8% of the conversion efficiency of the solar cell is observed.
TL;DR: In this article, a solar cell was synthesized by large-area electrodeposition of metal stack precursors followed by selenization, which achieved 8.2% power conversion efficiency, a new record for Cu2ZnSnSe4 solar cells.
Abstract: Cu2ZnSnSe4 solar cell absorbers are synthesized by large-area electrodeposition of metal stack precursors followed by selenization. A champion solar cell exhibits 8.2% power conversion efficiency, a new record for Cu2ZnSnSe4 solar cells prepared from electrodeposited metallic precursors. Significant improvements of device performance are achieved by the application of two etching procedures and buffer layer optimization. These results validate electrodeposition as a credible alternative to vacuum processes (sputtering, co-evaporation) for earth-abundant thin-film solar cell fabrication at low cost. Copyright (C) 2015 John Wiley & Sons, Ltd.
TL;DR: In this article, a systematic logical framework is proposed and then used to explain each country's PV policy strategy and results, and the global PV globalization impacts and interactions among them are studied using the international trade theory.
Abstract: Solar photovoltaic (PV) systems have experienced strong market growth over the last decade. Since the mid-2000s, the increase in demand in line with policy supports in Europe has attracted the Chinese players into the PV manufacturing market. Chinese production soared in a short time and managed to quickly reduce the cost thanks to large-scale supply with mass-produced products. Faced with the global economic crisis, the European countries began reducing their policy supports that caused a decrease in the demand for PV installations. Despite such a market situation, Chinese PV manufacturers have continued to produce large quantities of solar PV products and thereby aggravated the global PV industry situation with a global supply–demand imbalance. China's rapid market expansion without domestic market development has brought unexpected results with an oversupply of PV materials and equipment in a global market and destabilized the PV market. It influenced the PV policy mechanisms of other countries. Many PV firms in the world have since gone into bankruptcy. China and Europe lately went through a trade dispute over the Chinese solar panel imports (dumping suspicion). In this context, this study aims to identify the PV policy mechanisms based on a multiperspective approach in Germany, Japan, and China. A systematic logical framework is proposed and then used to explain each country's PV policy strategy and results. Moreover, PV globalization impacts and interactions among them are studied using the international trade theory. At the end, this research also attempts to seek optimal strategies to improve the global PV mechanisms. Copyright © 2014 John Wiley & Sons, Ltd.
TL;DR: In this paper, the influence of the bulk lifetime and the resistivity of the base material on the cell performance was investigated for industrial solar cell architectures and a consistent set of cell and simulation parameters were chosen to allow for a direct quantitative comparison of the different cell types.
Abstract: Solar cell production always requires a tradeoff between cell efficiency and production costs. This also concerns the choice of the silicon base material. In general, a long base lifetime is beneficial to achieve high conversion efficiency, but it strongly depends on the cell concept to which extent the cell performance is improved and whether a payback of the higher material costs can be expected. Therefore, in this comprehensive simulation study of various industrially relevant solar cell architectures, we present an investigation of the influence of the bulk lifetime and the resistivity of the base material on the cell performance. A consistent set of cell and simulation parameters is chosen to allow for a direct quantitative comparison of the different cell types. The parameters were chosen rather conservatively in order to describe realistic industrial cells and not record laboratory cells. The observed trends are analyzed using detailed loss breakdowns and are compared with experimental results. For various cell concepts, critical lifetimes τcrit can be observed for which the optimal material parameters change with increasing bulk lifetime when comparing materials of different base resistivity. The underlying physical reasons are explained in detail to accomplish two major aims: (i) generating a better understanding of limitations and challenges concerning different solar cell concepts and (ii) serving as a guide for an optimal material parameter choice for different cell architectures. Copyright © 2016 John Wiley & Sons, Ltd.
TL;DR: The model validation work showed that most of the simulated results agreed very well with the measured data except for a modest overestimation of heat gains in the afternoons, indicating that the simulation model developed can accurately simulate the overall energy performance of the semi-transparent PV-DSF.
Abstract: A comprehensive simulation model has been developed in this paper to simulate the overall energy performance of an amorphous silicon (a-Si) based photovoltaic double-skin facade (PV-DSF). The methodology and the model simulation procedure are presented in detail. To simulate the overall energy performance, the airflow network model, daylighting model, and the Sandia Array Performance Model in the EnergyPlus software were adopted to simultaneously simulate the thermal, daylighting, and dynamic power output performances of the PV-DSF. The interaction effects between thermal, daylighting, and the power output performances of the PV-DSF were reasonably well modeled by coupling the energy generation, heat-transfer, and optical models. Simulation results were compared with measured data from an outdoor test facility in Hong Kong in which the PV-DSF performance was measured. The model validation work showed that most of the simulated results agreed very well with the measured data except for a modest overestimation of heat gains in the afternoons. In particular, the root-mean-square error between the simulated monthly AC energy output and the measured quantity was only 2.47%. The validation results indicate that the simulation model developed in this study can accurately simulate the overall energy performance of the semi-transparent PV-DSF. This model can, therefore, be an effective tool for carrying out optimum design and sensitivity analyses for PV-DSFs in different climate zones. The methodology developed in this paper also provides a useful reference and starting point for the modeling of other kinds of semi-transparent thin-film PV windows or facades. Copyright © 2015 John Wiley & Sons, Ltd.
TL;DR: In this paper, the authors discussed the bifacial silicon solar cell concepts PERT (passivated emitter, rear totally diffused) and BOSCO (both sides collecting and contacted) in terms of expected module cost and LCOE based on in-depth numerical device simulation and advanced cost modelling.
Abstract: Bifacial solar cells and modules are a promising approach to increase the energy output of photovoltaic systems, and therefore decrease levelized cost of electricity (LCOE). This work discusses the bifacial silicon solar cell concepts PERT (passivated emitter, rear totally diffused) and BOSCO (both sides collecting and contacted) in terms of expected module cost and LCOE based on in-depth numerical device simulation and advanced cost modelling. As references, Al-BSF (aluminium back-surface field) and PERC (passivated emitter and rear) cells with local rear-side contacts are considered. In order to exploit their bifacial potential, PERT structures (representing cells with single-sided emitter) are shown to require bulk diffusion lengths of more than three times the cell thickness. For the BOSCO concept (representing cells with double-sided emitter), diffusion lengths of half the cell thickness are sufficient to leverage its bifacial potential. In terms of nominal LCOE, BOSCO cells are shown to be cost-competitive under monofacial operation compared with an 18% efficient (≙ pMPP = 18 mW/cm2) multicrystalline silicon (mc-Si) Al-BSF cell and a 19% mc-Si PERC cell for maximum output power densities of pMPP ≥ 17.3 mW/cm2 and pMPP ≥ 18.1 mW/cm2, respectively. These values assume the use of $10/kg silicon feedstock for the BOSCO and $20/kg for the Al-BSF and PERC cells. For the PERT cell, corresponding values are pMPP ≥ 21.7 mW/cm2 and pMPP ≥ 22.7 mW/cm2, respectively, assuming the current price offset (≈50%, at the time of October 2014) of n-type Czochralski-grown silicon (Cz-Si) compared with mc-Si wafers. The material price offset of n-type to p-type Cz-Si wafers (≈15%, October 2014) currently accounts for approximately 1 mW/cm2, which correlates to a conversion efficiency difference of 1%abs for monofacial illumination with 1 sun. From p-type mc-Si to p-type Cz-Si (≈30% wafer price offset, October 2014), this offset is approximately 2.5 mW/cm2 for a PERT cell. When utilizing bifacial operation, these required maximum output power densities can be transformed into required minimum rear-side illumination intensities for arbitrary front-side efficiencies ηfront by means of the performed numerical simulations. For a BOSCO cell with ηfront = 18%, minimum rear-side illumination intensities of ≤ 0.02 suns are required to match a 19% PERC cell in terms of nominal LCOE. For an n-type Cz-Si PERT cell with ηfront = 21%, corresponding values are ≤ 0.11 suns with 0.05 suns being the n-type to p-type material price offset. This work strongly motivates the use of bifacial concepts to generate lowest LCOE. Copyright © 2016 John Wiley & Sons, Ltd.
TL;DR: In this paper, a hybrid concentrator photovoltaic (CPV) architecture with a low-cost solar cell (a bifacial crystalline silicon cell) was integrated with a high-efficiency concentrator solar cell to harvest diffuse sunlight.
Abstract: Maximization of module conversion efficiency based on global normal irradiance (GNI) rather than direct normal irradiance (DNI) was experimentally demonstrated using a hybrid concentrator photovoltaic (CPV) architecture in which a low-cost solar cell (a bifacial crystalline silicon cell) was integrated with a high-efficiency concentrator solar cell (III–V triple-junction cell) to harvest diffuse sunlight. The results of outdoor experiments showed that the low-cost cell enhanced the generated power by factors of 1.39 and 1.63 for high-DNI and midrange-DNI conditions, respectively, and that the resultant GNI-based module efficiencies were 32.7% and 25.6%, respectively. © 2016 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.
TL;DR: In this paper, the authors demonstrate a procedure for quantifying efficiency gains that treats resistive, recombinative, and optical losses on an equal footing, and apply their conductive boundary (CoBo) model as implemented in the Quokka cell simulator.
Abstract: We demonstrate a procedure for quantifying efficiency gains that treats resistive, recombinative, and optical losses on an equal footing. For this we apply our Conductive Boundary (CoBo) model as implemented in the Quokka cell simulator. The generation profile is calculated with a novel analytical light trapping model. This model parametrizes the measured reflection spectra and is capable of turning the experimental case gradually into an ideal Lambertian scheme. Simulated and measured short circuit current densities agree for our 21.2%-efficient screen-printed PERC cell and for our 23.4%-efficient ion-implanted laser-processed IBC cell. For the loss analysis of these two cells we set all experimentally accessible control parameters (e.g. saturation current densities, sheet resistances, and carrier lifetimes) one at a time to ideal values. The efficiency gap to the ultimate limit of 29% is thereby fully explained in terms of individual improvements and in terms of their respective synergistic effects. This approach allows comparing loss structures of different types of solar cells, e.g. PERC and IBC cells.
TL;DR: In this paper, the authors presented an up-to-date performance and cost analysis of reverse osmosis (RO) desalination powered with PV connected to the Saudi Arabian grid.
Abstract: Increased water demand and increased drought episodes in the Middle East and other regions necessitate an expansion in desalination projects and create a great market opportunity for photovoltaics (PV). PV-powered desalination has previously been regarded as not being a cost-competitive solution when compared with conventionally powered desalination; however, the decline in PV costs over the last few years has changed this outlook. This paper presents up-to-date performance and cost analysis of reverse osmosis (RO) desalination powered with PV connected to the Saudi Arabian grid. Reference cases include relatively small (i.e., producing 6550 m3 water per day) and large (i.e., 190 000 m3/day) desalination plants using seawater at a salinity of 40 000 ppm. We used data from a King Abdullah University for Science and Technology presentation and Hybrid Optimization Model for Electric Renewables 2.81 Energy Modeling Software (HOMER Energy LLC) in tandem with Desalination Economic Evaluation Program 4.0 (International Atomic Energy Agency) desalination software to analyze the techno-economic feasibility of these plants. The first phase of our work entailed a comparison between dual-axis high concentration PV (CPV) equipped with triple junction III/V solar cells and CdTe PV-powered RO systems. The estimated levelized cost of electricity from CPV is $0.16/kWh, whereas that from CdTe PV is $0.10/kWh and $0.09/kWh for fixed-tilt and one-axis tracking systems, respectively. These costs are higher than the price of diesel-based grid electricity in the region because diesel fuel is heavily subsidized in Saudi Arabia.
In the second phase, we determined the cost of producing desalinated water from the two RO plant sizes powered with CdTe PV. Assuming that the grid acts as zero-loss storage, the total water cost ranges from a high cost of $1.39/m3 for the small RO plant coupled with latitude-tilt, fixed PV to $0.85/m3 for the large RO plant coupled with optimally positioned one-axis tracking systems; these PV power plants would displace 1 158 987 and 33 579 763 l of diesel per year, respectively. Furthermore, the corresponding savings in diesel subsidies enabled by PV are $1.5m and $43.2m per year. Applying these savings to the PV system calls for a levelized cost of electricity of $0.21/kWh, justifying a feed-in-tariff at this level. The avoided CO2 emissions by displacing diesel fuel would be 3115 and 90 241 tonnes per year for the small and large Photovoltaics Powered Reverse Osmosis Water Desalination (PV-RO) plants, respectively. On the basis of the results of this study, we infer that there are great business prospects associated with large deployment of PV-RO plants in the greater Middle East, and we estimate the reduction in regional CO2 emissions from such deployment. Copyright © 2015 John Wiley & Sons, Ltd.
TL;DR: In this paper, the authors evaluated the impact of partial shading on CIGS photovoltaic modules equipped with bypass diodes and found that the worms were caused by the window layer, leading to increased recombination and decay of the solar cell properties.
Abstract: This study evaluated the impact of partial shading on CuInxGa(1-x)Se2 (CIGS) photovoltaic (PV) modules equipped with bypass diodes. When the CIGS PV modules were partially shaded, they were subjected to partial reverse bias, leading to the formation of hotspots and a possible occurrence of junction damage. In a module with a cadmium sulfide buffer layer, hotspots and wormlike defects were formed. The hotspots were formed as soon as the modules were shaded; the hotspots caused permanent damage (wormlike defects) in the CIGS module. Specifically, the wormlike defects were caused by the window layer, leading to increased recombination and decay of the solar cell properties. However, a CIGS module with a zinc sulfide buffer layer did not exhibit the formation of hotspots or any visual damage. The reverse bias breakdown voltage of the CIGS PV module with the cadmium sulfide buffer layer was higher than that of the CIGS PV module with the zinc sulfide buffer layer. Copyright © 2016 John Wiley & Sons, Ltd.
TL;DR: In this article, the authors evaluate the potentials of PV system installation in terms of environmental and economic viewpoints with indices of cost, energy, and greenhouse gas (GHG) emission.
Abstract: Although the Sahara region has a high potential for solar power plants, the amount of installed photovoltaic (PV) system remains relatively low. This paper aims to evaluate these potentials of PV system installation in terms of environmental and economic viewpoints with indices of cost, energy, and greenhouse gas (GHG) emission. Two 1-GW very large-scale PV systems are simulated at Ouarzazate in Morocco and at Carpentras in France. The evaluation was performed using life cycle assessment. The lowest energy consumption and GHG emission are obtained while assuming cadmium telluride module. The result of our simulation shows that energy payback time is 0.9 years and CO2 emission rate is 27.4 g-CO2-eq/kWh in the Ouarzazate case. In cost estimation, generation costs are 0.06 USD/kWh in Ouarzazate and 0.09 USD/kWh in Carpentras in the case of 3% interest rate and 0.5 USD/W for multicrystalline silicon PV module price. In addition, by adapting 15% internal rate of return for 20% of budget, the generation costs become 0.09 USD/kWh in Ouarzazate and 0.13 USD/kWh in Carpentras under the same condition. Furthermore, the selection for suitable locations to install solar power plants in term of GHG emission is identified using geographical information system. Very high-potential locations (lower than 38 g-CO2-eq/kWh) could be obtained in North Chili, east and west Sahara, and Mexico. Copyright © 2015 John Wiley & Sons, Ltd.