Article

Metal dissolution from end-of-life solar photovoltaics in real landfill leachate versus synthetic solutions: One-year study

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Metal dissolution from end-of-life solar photovoltaics in real landfill leachate versus synthetic solutions: One-year study

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Abstract

To investigate the after end-of-life (EoL) concerns of solar panels, four commercially available photovoltaics of 1515cm2 size in broken and unbroken conditions were exposed to three synthetic solutions of pH 4, 7, 10 and one real municipal solid waste (MSW) landfill leachate for one-year. Encapsulant degradation and release, probability of metals exceeding their surface water limit, and change in pollution index of leachate after dumping of solar panels were investigated. Rainwater stimulating solution was found to be predominant for metal leaching from silicon-based photovoltaics, with Ag, Pb and Cr being released to 683.26 mg/L (26.9%), 23.37 mg/L (17.6%), and 14.96 mg/L (13.05%) respectively. Copper indium gallium (de) selenide (CIGS) photovoltaic was found to be least vulnerable in various conditions with negligible release of In, Mo, Se and Ga with value ranging between 0.2 and 1 mg/L (0.30%-0.74%). In contrast, minimal metals were released to MSW leachate compared to other leaching solutions for all photovoltaics. Positive correlation was observed between encapsulant release and metal dissolution with a maximum encapsulant release in silicon-based photovoltaics in rainwater conditions. Probability of exceedance of leached metals to their respective surface water limits for Al (multi and mono crystalline-silicon (c-Si)), Ag (amorphous photovoltaic) and In (CIGS) has shown the maximum exceedance of 92.31%. The regression analysis indicated that conditions of the modules and pH of the leaching solution play significant roles in the leaching of metals. The increase in leachate contamination potential after one-year of photovoltaics dumping was found to be 12.02%, 10.90%, 15.26%, 54.19% for amorphous, CIGS, mono and multi c-Si photovoltaics, respectively. Overall, the maximum metal release observed in the present study is 30% of the initial amount under the most stressful conditions, which suggests that short-term leaching studies with millimeter sized sample pieces do not represent the realistic dumping scenarios. Keywords: End-of-life, solar panel, photovoltaic, metal, leaching

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... Module breakage is very rare during operational phase [12], however, disposal of broken modules could result in human health risk [13]. A recent study by Nain and Kumar,[89] reported the one-year leaching on four PV modules, and reported 17.6% of lead release form c-Si modules in acidic conditions. Another study by Ramos-Ruiz et al. [15] reported arsenic release from GaAs to be about 2.8-fold higher than the TCLP and WET regulatory limits. ...
... Various studies in past have shown metal leaching from dumped solar modules from environment, though, small modules pieces were used [1,14]. Also, there might be a possibility of material release from large module pieces [89], hence, FTA was applied to identify key factors responsible for dumping and material release from modules. The interrelation between various basic events gives the probability of occurrence of an undesired event, which is the top event, such as encapsulated material release from dumped broken module. ...
... Exposure of module partially covered with dust to high humidity can result in corrosion and long-term exposure can cause moisture ingression which results in encapsulant delamination [35]. The moisture ingress between layers can affect the encapsulant stability resulting in delamination [89]. Further, studies have shown that snow or hailstorms can cause severe damage to modules, such as glass cracking or solder joint failure [36]. ...
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The present study addresses the aspect of upcoming stream of solar photovoltaics waste. The aim of this study was to understand the possibility of material release from end-of-life solar modules using an integrated approach of literature review and stakeholders survey. it involved (i) identification of failure events responsible for degradation of photovoltaic modules were identified from literature review , (ii) evaluation of these events by a survey of stakeholders of photovoltaic industry and (iii) investigation of their perceptions on events responsible for generation of end-of-life modules, present management and recycling practices, (iv) conducting of fault tree analysis and risk priority number analysis for finding severe failure events responsible for dumping and material leaching from solar modules. Assessment indicates that environmental factors, like high UV irradiation, humidity, temperature play significant role in module degradation. As per survey, more than 90% of manufacturers were involved in crystalline-silicon photovoltaic business. Only 20% manufacturers replied when asked on the aspect of end-of-life modules, showing that the photovoltaic waste is comparatively a new subject and not enough discussion have been devoted to it. Lack of recycling infrastructure, incentives, and environmental awareness significantly influence recycling and recuse practices. With worst-case scenarios, the maximum probability of the material release from dumped solar panels was found to 0.053. As per manufacturer’s opinion, the most critical factors resulting in modules failure are glass breakage and encapsulant degradation. Among various events, the module breakage during operation event have highest probability value (i.e., 0.313). Risk priority number analysis suggests that generation of end-of-life photovoltaic and environmental damage resulting to metal leaching as the most significant events. Damage during manufacturing and installation were least significant events resulting in degradation. At present, 76% producers do not recycle or reuse photovoltaic waste material, preferably sell them to informal waste recyclers or rag pickers. Findings from the present study highlight the urgency to develop a suitable system for collection and management of end-of-life photovoltaic modules.
... In the same work, high amounts of lead (30 t) and cadmium (2.9 t) releasable from c-Si and thin film panels, respectively, were also predicted for 2050. Nain & Kumar (2020) analyzed the release of metals from broken and unbroken solar panels that were exposed to three synthetic solutions of pH 4, 7, 10 and one real municipal solid waste (MSW) landfill leachate for one year. The results suggested that encapsulant degradation plays a critical role and has a positive correlation with metal dissolution. ...
... They also indicated that the mass of exposed modules per volume of water increases the probability of leached metals exceeding standard limits. Nain & Kumar (2020) reported that the increase in leaching contamination after one year of disposal of polycrystalline silicon modules was 54.19%. ...
... Furthermore, Nain & Kumar (2020) observed that the leaching of metals in stormwater solutions was minimal, except for a few metals. For the initial months after disposal, the PV cells and films maintain their integrity because of encapsulation. ...
Article
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This work investigated the thermal treatment to separate and concentrate economically valuable materials from laminates of crystalline silicon photovoltaic modules (i.e., photovoltaic modules without the aluminum frame and the junction box). Chemical characterization of the metal content was performed by X-Ray Fluorescence (XRF). The polymers of the backsheet were also characterized by Fourier Transform Infrared Spectroscopy (FTIR). The influence of the atmosphere (oxidizing and inert) on the decomposition of the backsheet was investigated by Thermogravimetric Analysis (TGA). Moreover, non-comminuted samples were tested for 4 thermal time lengths (30, 60, 90, and 120 min) in the furnace under ambient air. The degradation of the polymers was measured and 3 material fractions were obtained: silicon with silver and residual polymers (SS), glass and copper ribbons. Furthermore, there was no statistical difference between the mass losses of the samples submitted for 90 (13.62 ± 0.02 wt.%) and 120 min at 500 °C (p-value = 0.062). In the SS fraction, silver was 20 times more concentrated than in the ground photovoltaic laminate and 30 times more concentrated than high silver concentration ores. The SS fraction (about 6 wt.%) also presented low copper concentration and a high concentration of lead (hazardous metal). About 79 wt.% glass was obtained, as well as 1% copper ribbons (55.69 ± 6.39% copper, 23.17 ± 7.51% lead, 16.06 ± 2.12% tin). The limitations of the treatment and its environmental impact are discussed, and suggestions for industrial-scale application are given.
... For other metals, a cationic leaching pattern was observed, which means decrease in leached concentrations with increase in pH. Similar leaching behaviour was observed by Nover et al. (2017) and Nain and Kumar (2020c), providing the significance of investigating long-term leaching behaviour. Maximum correlation between metal leachability and total metal content was observed for Cd, Ga and Se with Pearson's correlation coefficient value (r p ) ! 0.998 and pvalue < 0.05. ...
... The amount of metals release is also restricted by encapsulant, which is used to encapsulate various layers to provide stability and protection from environmental conditions. Earlier E-waste studies have shown the interference of encapsulant in metal release (Nain and Kumar, 2020c). Studies have shown that water penetration through the laminated edges and back sheet of module can result in encapsulant degradation and delamination (Jadhav et al., 2016). ...
... Due to this, moisture can get to the cells and interact with metals present in semiconductor layer. The corrleation between encapsulant release and metal leachability is discussed in a recent study by author (Nain and Kumar, 2020c) and possible schematic is shown in Fig. 5. High metal dissolution from CIGS PV in present study could be explained by the fact that thin-film PV modules are more prone to water penetration than silicon-based modules (Parida et al., 2011). ...
Article
The upcoming end-of-life solar photovoltaics (PV) waste stream is a huge concern before solid waste professionals due to presence of hazardous metals like lead or cadmium. The objective of present study was to understand the metal dissolution from PVs under four standard waste characterization regulatory tests of U.S., Germany, and Japan and their representativeness with actual landfill leachate. Modules were exposed to real municipal solid waste landfill leachate for extended extraction duration, agitation and diluted leachate to investigate the effect of various parameters on metal dissolution. The results indicated that extractions using landfill leachates resulted in lower metal release than standard methods. The leached concentration was within the threshold limit except for cadmium, copper, lead and selenium, with maximum lead release from amorphous-PV of 8.68 mg/L and 6.91 mg/L with respect to TCLP and WET tests, respectively. Arsenic showed negligible release with maximum concentration of 0.046 mg/L from copper indium gallium de-selenide (CIGS) PV. Regardless of small size (1-2 cm pieces) and agitation, Germany and Japan’s standard tests resulted in minimal release except copper from CIGS PV. Leaching without agitation, showed negligible release from all photovoltaics whereas when agitation is applied to diluted leachate, significant release was observed with aluminum and copper leached up to 145.32 mg/L (multi-silicon) and 139.01 mg/L (amorphous-photovoltaic), respectively. CIGS was most hazardous with Metal Hazard Score (calculated on the basis of magnitude of leached metals with respect to their threshold limit and subsequent health effects) of 23.19, when exposed to standard tests. For all scenarios, increased metal release was observed with decrease in sample size and increase in dilution factor and thus, leaching in highly acidic conditions are by no means representative for modules dumping in realistic conditions.
... The metal LF values for first and second generation photovoltaics (FSGP) were also calculated in order to investigate the effect of generation type on metal release potential. These values were calculated using data from a one-year leaching study performed on two first generation and two second generation PVs in pH7 and landfill leachate conditions [13]. Data from only this study was used as no other study with a one-year leaching data in real MSW leachate conditions with two generation PVs was found in literature. ...
... LF values of metals in landfill leachate matrix were found to be lesser by 1-2 orders of magnitude than that observed for pH7 neutral condition. This could possibly be due to slightly alkaline nature of leachate with different ionic strength which might have affected Ksp value and diffusion of metal from its parent compound to solvent [13]. This presents a need for exposing TGSCs to different conditions like rain water or MSW leachate for studying release of metal over a long period and calculating metal LFs using laboratory and/or field data. ...
... Overall, the calculated LF MSW value gives an idea on chance of metal loss from various PVs in realistic solutions. It is important to note that these values depend on leaching conditions and PV brand selected [13]. Thus, the present analysis provides only a preliminary investigation on metal release potential and more work is required to verify the applicability of model of the Celik et al. (2018) [4] study and CFs determined from the present study. ...
Article
With rapid growth in solar industry, the potential fate and management of solar modules has raised concerns due to the presence of few toxic metals. Present work addressed this issue by (i) estimating potential release values or solubility (Ksp at pH 7) of various compounds used in different layers of emerging solar cells in neutral water and landfill leachate conditions, and (ii) further comparing their metal release values (termed as loss factors, LFs) with that of first and second generation photovoltaics. Top five compounds with highest metal release probability (probability>0.5%) were found to be: Lead iodide (highest LF)> Copper iodide> Cadmium hydroxide> Copper thiocyanate> Cadmium oxide (smallest LF). Also, identified compounds with lowest risk were: Lead selenide <Antimony trisulfide <Cadmium selenide <Aluminium oxide <Tin sulphide (lowest probability: 1*E-10 to 1*E-16). With respect to solar cells, perovskite was ranked first in terms of hazard as it mostly contains compounds like Lead iodide, Copper thiocyanate, Copper iodide, Nickel oxide, and Aluminium oxide. Quantum dot solar cells were ranked second due to presence of category II compound (i.e., ZnO). Further, organic and dye-sensitized solar cells are of least concern as they do not contain compounds with high LF values. With respect to different layers of an emerging PV, electron- and hole- transport layers were found to be with highest risk for material release. With respect to third generation solar cells, metal LFs for first generation solar cells were less for lead, cadmium and copper. Following the conservative approach, the calculated conversion factors for metal loss values from neutral water (pH7) to landfill leachate (i.e., CFs =LFMSW leachate/LFpH7) for Pb(0.075), Cu(0.263), Ni(0.426), Zn(0.591) were used for estimating metal loss values from emerging solar cells in landfill leachate conditions. Among all generation solar PVs, mostly lead- containing compounds were found to be exceeding the LF cut-off values. Thus, perovskites solar cells with lead–based compounds might pose risk to groundwater or surface runoff due to lead.
... However, higher amount of Te release was observed at higher pH. Further, the statistical analysis indicated the significant effect of leaching solution type, agitation, and PV type on metal release (Nain and Kumar, 2020c). Still, more studies are required to assess the material leachability and toxicity behaviour under different environmental settings, such as realistic conditions of landfill. ...
... In past, Kumar and Alappat (2004) proposed an index for estimating landfill's leachate contamination potential as "Leachate Pollution Index" (LPI). A latest study by Nain and Kumar (2020c) used this index to investigate the leachate contamination potential of a landfill if dumped with solar modules and calculated LPI values to be 30. 81, 30.50, 31.70, and 42.40 for amorphous-Si, CIGS, mono-Si and multi-Si PVs respectively, after 12 months of dumping. ...
... First study investigated the fate of GaAs (1-2 mm) in a synthetic solution with pH 7.6 stimulating landfill leachate for 120 days reporting a higher As release than regulatory limit (Ramos-Ruiz et al., 2018). In the second study, 15*15 cm 2 sized broken and unbroken PVs were exposed to real MSW landfill leachate for one year (Nain and Kumar, 2020c). The findings suggested that metal release in leachate conditions appears to be relatively small to raise any concerns related to EoL disposal at present. ...
Article
In last two decades, solar photovoltaic industry has shown tremendous growth among all renewable energy sectors, as a result, the concern of their end-of-life waste management increased. This study reviews the current state -of- art on end-of-life photovoltaics in terms of the materials used during manufacturing, their fate in environment, short-term & long-term leaching behaviour, applicability of current standard waste characterisation methods, possible human & ecological risk, manufacturers & consumers perspective towards management and recycling. A comprehensive comparative analysis of various findings from recent studies regarding the subject of end-of-life photovoltaic waste was done. Special emphasis was given on understanding the material release from first and second generation photovoltaics as per various theoretical and experimental studies to identify knowledge gaps. The findings from review shows that metals, such lead, copper, iron and aluminium have the potential to exceed hazardous waste limits, though a majority of them do not exceed the standard waste methods limit. Among the various modules, the highest material release was observed from crystalline-silicon modules. Further, if solar modules are disposed in landfills, the increase in leachate pollution index is mainly due to the leached heavy metals such as lead and chromium as the effect due to other parameters is negligible. At present, solar photovoltaics are generally grouped with electronic waste and is not classified under any waste category (hazardous or non-hazardous) except the United States of America and Europe. Amendments in existing waste characterization tests considering the complexity of photovoltaic waste and disposal mode should be considered. Further, as per various studies, progressing research is needed to establish standardized methods for recycling of photovoltaics. Present study gives a summary and future outlook on end-of-life solar photovoltaics with recommending the future directions for researchers and public policymakers.
... Although photovoltaics is a source of renewable energy, the total environmental impact must be assessed throughout the entire life cycle of the system [84][85][86]. Photovoltaic modules at the end-of-life stage constitute an inevitable waste stream. ...
... As the production of modules is sharply increasing, waste management is an important issue these days. Unfortunately, landfills are the main waste disposal methods for PV systems [86]. Several studies show the environmental consequences of improper management of PV waste, mainly due to the release of heavy metals [79,[87][88][89][90]. Recycling of PV modules is an environmentally favorable method with numerous advantages compared to the landfill. ...
... Several studies show the environmental consequences of improper management of PV waste, mainly due to the release of heavy metals [79,[87][88][89][90]. Recycling of PV modules is an environmentally favorable method with numerous advantages compared to the landfill. It allows the controlled release of hazardous substances into the environment, saves precious and scarce metals (e.g., Ag, Ga, In), and alleviates lifecycle resource depletion [86]. Developing an appropriate recycling method of a particular component of PV modules is a key issue for the environment and can improve the sustainability of the photovoltaic industry. ...
Article
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Photovoltaic systems represent a leading part of the market in the renewable energies sector. Contemporary technology offers possibilities to improve systems converting sun energy, especially for the efficiency of modules. The paper focuses on current concentrated photovoltaic (CPV) technologies, presenting data for solar cells and modules working under lab conditions as well as in a real environment. In this paper, we consider up-to-date solutions for two types of concentrating photovoltaic systems: high-concentration photovoltaics (HCPV) and low-concentration photovoltaics (LCPV). The current status of CPV solar modules was complemented by the preliminary results of new hybrid photovoltaic technology achieving records in efficiency. Compared to traditional Si-PV panels, CPV modules achieve greater conversion efficiency as a result of the concentrator optics applied. Specific CPV technologies were described in terms of efficiency, new approaches of a multijunction solar cell, a tracking system, and durability. The results of the analysis prove intensive development in the field of CPV modules and the potential of achieving record system efficiency. The paper also presents methods for the determination of the environmental impact of CPV during the entire life cycle by life cycle assessment (LCA) analysis and possible waste management scenarios. Environmental performance is generally assessed based on standard indicators, such as energy payback time, CO2 footprint, or GHG emission.
... Currently, the most common PV module uses crystalline silicon technology, followed by cadmium telluride (CdTe) thin-layer modules. The former has the advantage of high efficiency while the latter are more flexible and cost-effective (Nain & Kumar, 2020). Crystalline silicon modules release fewer materials into the environment compared to thinfilm modules. ...
... Distributed PVs are problematic in terms of individual owners not knowing what to do with EoL panels. Given that the working life of a solar panel is approximately 25 to 30 years (Nain & Kumar, 2020), the original purchaser may have moved house when EoL decisions need to be made. ...
Article
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This article reviews the environmental, ecological, and social impacts of current renewable energy technologies. Problems of these technologies are highlighted in terms of manufacturing, installation, lifetime, and end-of-life. What emerges are concerning issues that need to be urgently addressed as they potentially threaten the recovery of the Earth system and therefore also impact society. It is suggested that many of these issues have been overlooked because of our focus on carbon reduction, which, while important, may lead to a failure to deal with other equally concerning threats, and even exacerbate them. These threats are highlighted and then urgent priorities, in terms of policy, regulation, and research, are identified, paving the way to an energy future that does not threaten the functionality of the Earth system. Finally, key underlying themes are identified that may inform our decision-making as we move forward. If we are to aim for a truly sustainable future, in terms of economics, ecology, and society, this article argues that we must seek to aim higher than current practice and plan for a future that not only arrests anthropogenic climate destabilization and its threat to many species, including our own, but that builds the foundations for ecological recovery. Better-than-before is not good enough. We need energy technologies that minimize our impact on our planet.
... [25] A recent study investigated heavy metal leaching from PV modules in three synthetic and one actual municipal solid waste (MSW) landfill leachate over a year. [26] The results showed that short-term studies are not representative of realistic dumping scenarios, and that the condition of the modules and pH of the leaching solution significantly affect metal dissolution. [26] A recent literature review showed that interest in EoL PV is increasing based on publications, but there is a lack of studies in battery energy storage systems. ...
... [26] The results showed that short-term studies are not representative of realistic dumping scenarios, and that the condition of the modules and pH of the leaching solution significantly affect metal dissolution. [26] A recent literature review showed that interest in EoL PV is increasing based on publications, but there is a lack of studies in battery energy storage systems. [27] It has been anticipated that disposing of Li-ion batteries in landfills could present environmental risks from the leaching of organic electrolytes, toxic metals, lithium salts, and carbonaceous material. ...
Article
Photovoltaic (PV) modules and batteries can either be recycled or disposed of in landfills at end-of-life (EoL). This work focuses on disposal since the benefit of recycling PV modules and batteries is well established. This study characterizes the potential toxicity due to metals leaching from selected PV modules and batteries through both the Toxicity Characteristic Leaching Procedure (TCLP) and in-house batch leaching protocols to probe the impact on metallic ion mobility as a function of the different types of e-waste entering the waste stream, the magnitude of device damage when placed into the waste stream, and the simulated municipal solid waste (SMSW) composition. Our results showed that one PV module and three battery types in this study should be classified as hazardous waste within the U.S. However, for some of the other e-wastes, metals of concern including Cr, Cu, Hg, Ni, Pb, and Zn leached during the batch tests but not in the TCLP regulatory method. For most of the waste types, the amounts of metals that leached in the TCLP test and batch tests were much lower than the total extractable amounts, demonstrating the potential for additional unaccounted for amounts of metals to leach. These results demonstrate that the TCLP regulatory method might fail at predicting potential leaching and at capturing the complexity of e-waste leaching in landfill conditions. It confirms that additional work is needed urgently to develop appropriate EoL procedures for MSW with PV and battery e-waste.
... Lately, solar cells are becoming a widespread and important source of green energy. They contain several valuable metals such as cadmium (Cd), chromium Cr), lead (Pb), silver (Ag), selenium (Se) and tellurium (Te), copper (Cu), manganese (Mn), zinc (Zn) [75,76], titanium (Ti) and antimony (Sb) [77] based on the type of product. The production of waste solar cells is slow in comparison to other e-wastes due to their long lifetime (25-30 years) [76]; however, it is expected to increase in the near future [65]. ...
Article
Full-text available
There is a growing interest in electronic wastes (e-wastes) recycling for metal recovery because the fast depletion of worldwide reserves for primary resources is gradually becoming a matter of concern. E-wastes contain metals with a concentration higher than that present in the primary ores, which renders them as an apt resource for metal recovery. Owing to such aspects, research is progressing well to address several issues related to e-waste recycling for metal recovery through both chemical and biological routes. Base metals, for example, Cu, Ni, Zn, Al, etc., can be easily leached out through the typical chemical (with higher kinetics) and microbial (with eco-friendly benefits) routes under ambient temperature conditions in contrast to other metals. This feature makes them the most suitable candidates to be targeted primarily for metal leaching from these waste streams. Hence, the current piece of review aims at providing updated information pertinent to e-waste recycling through chemical and microbial treatment methods. Individual process routes are compared and reviewed with focus on non-ferrous metal leaching (with particular emphasis on base metals dissolution) from some selected e-waste streams. Future outlooks are discussed on the suitability of these two important extractive metallurgical routes for e-waste recycling at a scale-up level along with concluding remarks.
... This waste stream is a cause of concern because it has serious implications for the environment and human health. Owing to the presence of hazardous elements like lead, cadmium etc. in it, regulated disposal is crucial [13,[20][21][22]. Apart from the environmental challenges, competitive consumption and supply crunch in respect of critical metals like silicon, germanium, lithium etc., used in the manufacturing of solar panels, also present a significant resource challenge for this sector [23]. ...
Article
Increasing energy demands and commitments in relation to climate change have accelerated the deployment of solar power globally, especially in India. Grid-connected solar capacity in the country has increased ∼11 times in just five years, from 2.6 GW in March 2014 to 28.18 GW in March 2019. However, this development has inevitably also led to the emergence of significant volumes of solar photovoltaic (PV) waste, which will only increase in the upcoming years, a considerable challenge for its waste management system. The environmental and human health risks associated with the unscientific dumping of solar PV waste have been well established in the existing literature, presenting the need to develop an effective strategy to manage this emerging waste stream. This paper presents a review of literature about India's solar PV waste management sector with a view to understanding the ground realities and identifying challenges and barriers that hinder the adoption of a regularised strategy for its management using the DPSIR framework approach. It goes on to propose a regulatory framework aimed at mainstreaming the end-of-life (EOL) management of solar PV waste in India after evaluating strategies that have already been used worldwide. In line with the Extended Producer Responsibility (EPR) concept, a multistakeholder, multi-sectoral and systematic approach has been adopted to develop a specific regulatory framework for India. The framework was subjected to a SWOT analysis to evaluate its functionality. The SWOT analysis indicates that one of the critical strengths of the framework is that it is based on a participatory approach to be adopted by all stakeholders for managing this emerging waste stream.
... Open-burning also promotes chronic exposure of metals to resident via air-born particulate matter, as confirmed by the analyses of the blood samples from the locals (Gangwar et al., 2019). Disposal of WEEE in landfills can promote the release of metals or persistent organic pollutants into the environment through leachate discharge (Jin et al., 2021;Nain and Kumar, 2020). Simulated landfill studies showed a high level of metals in the solid waste samples surrounding the e-waste, suggesting that metals from e-waste could leak into the environment over a long period of time (Li et al., 2009). ...
Article
Full-text available
The continuous growth of e-waste necessitates an efficient method to recover their metal contents to improve their recycling rate. The successful recovery of the metallic component from Waste Electrical and Electronic Equipment (WEEE) can generate great economic benefits to incentivize the industrial recycling effort. In this study, we report the use of slurry electrolysis (SE) in pH-neutral ethylene glycol (EG) electrolyte to extract and recover the metallic component from waste printed circuit broad (WPCB) powder. The system operates at room temperature and atmospheric pressure, and the electrolyte can be recycled multiple times with no signs of chemical degradation. The EG electrolyte system can oxidize the metallic component without triggering anodic gas evolution, which allowed us to incorporate a reticulated vitreous carbon (RVC) foam anode to maximize the capture and oxidation of the metal content. The system demonstrated up to 99.1% Faraday efficiency for the cathodic metal deposition and could recover Cu from the WPCB powder in a selective manner of 59.7% in the presence of 12 other metals. The SE reaction system was also scalable and displayed no compromises on the Cu recovery selectivity. With the ability to leach and recover metallic content from WPCB in a mild and chemically benign condition, the SE system displayed much promise to be adapted for industrial-scale metal recovery from WPCB.
... Solar photovoltaic cells (PV) are installed across vast landfills in sunny climates to generate additional electricity [10]. Solar PV has generated some interest in the industry, and its use has increased significantly as the cost of manufacturing materials has decreased and energy demand has increased [11]. Another variation is the bioreactor landfill, in which the environment is controlled to promote organic waste biodegradation. ...
Article
Full-text available
As more studies were conducted and global events unfold, a greater emphasis is being placed on the importance of preserving the Earth's natural resources and cycles before we face a catastrophic climate crisis. Thus, developed countries are constantly adapting their policies and legislation to promote green development for the sake of sustainable development, which benefits both the environment and the socioeconomic segment. As populations grow and living standards improve, more waste is generated. Appropriate municipal waste management is necessary to avoid harm to the environment, wildlife, and human health. Sustainable municipal solid waste management is even included in the United Nations' (UN) Sustainable Development Goals, which aim to improve the world's environment and economy. The European Union (EU) member states' waste management systems can be considered exemplary. In some countries, landfills have been prohibited, promoting the use of more sustainable technologies such as organic waste incineration, recycling, and composting. However, a divide exists between member countries, with some lagging behind in terms of waste management strategies. Thus, this paper examined the current state of municipal waste in EU member states, followed by a review of the various disposal technologies implemented. The difficulties and environmental concerns that must be overcome are discussed, as are the recommendations and possible future directions.
... Open-burning also promotes chronic exposure of metals to resident via air-born particulate matter, as confirmed by the analyses of the blood samples from the locals (Gangwar et al., 2019). Disposal of WEEE in landfills can promote the release of metals or persistent organic pollutants into the environment through leachate discharge (Jin et al., 2021;Nain and Kumar, 2020). Simulated landfill studies showed a high level of metals in the solid waste samples surrounding the e-waste, suggesting that metals from e-waste could leak into the environment over a long period of time (Li et al., 2009). ...
... The long-term performance of PV systems [9], as well as efficiency of grids and energy storage management [10], are also identified as areas where there is space for further advancements. The end life management of PV systems (waste management and recycling in general), [11] is also a crucial and important research area that needs careful attention since there are projections for an intense cumulative growth of waste volumes caused by PV technologies, [12]. In recent years, various technical possibilities have been investigated to detect novel application areas for current PV technologies, i.e. to ensure increases in PV capacities since some regions of the world have limited land resources for the J o u r n a l P r e -p r o o f installation of PV systems. ...
Article
This work was focused on the investigation of various photovoltaic thermal (PVT) solar collector designs incorporating phase change materials (PVT-PCM systems) as suitable material for thermal management. In general, the PCM materials utilized in such systems were analyzed along with a discussion regarding the main thermal properties. The experimental works were covered from existing literature and related to PVT-PCM systems in various climates. The results revealed the importance of a PVT-PCM collector design concerning the overall efficiency improvement of systems. Depending on the specific design, as well as on the specific working fluid (water, air, or nanofluids), the electrical efficiency improvement was usually less than 20%, while the improvement in thermal efficiency was usually up to 70%. The electrical efficiency improvement is especially sensitive to the specific PVT-PCM collector design. The economy of the PVT-PCM system was not addressed well in the existing literature as well as its environmental evaluation. The usual payback time of the PTV-PCM systems ranged from 4 to 15 years. The conducted review indicated the necessity for more intense research investigations related to improvements in collector designs (tube geometry and layout, novel absorbers, optimization of the PCM layer) and for an integral assessment of PVT-PCM collector designs, considering performance, economic and environmental evaluations.
... Toxicity associated with photovoltaic technologies are of concern because lead, tin, cadmium, silicon, and copper are known to be harmful to the ecosystem and human health (Kwak et al., 2020) and inappropriate disposal of this waste may cause the leaching of such toxic metals to soil or water (Li et al., 2019). However, recent toxicity studies have found metal concentrations from waste PV leachates to be within regulations, implying that their discard may be safe (Nain and Kumar, 2020a;Savvilotidou et al., 2017). The polymers associated with the panel are also of concern since they can release toxic gasses when incinerated (Liao et al., 2020). ...
Article
Photovoltaic (PV) panel manufacturing is increasing worldwide, which subsequently increases the amount of waste PV. This study proposes to recycle waste PV using organic solvent delamination followed by downstream thermal and leaching procedures. Firstly, experimental data is obtained using small commercial modules by replicating a recycling route taken from the literature. Based on the experimental results, life cycle cost analysis (LCCA) and life cycle assessment (LCA) are applied to evaluate the experimental and optimized industry scale processes. Results show that the main profitable recycling avenues are for aluminum frame and junction box removal; and that downstream processes can separate and recover all the remaining materials, but not profitably. The laboratory and high-throughput-optimized processes, considering the median costs and revenues, have a net cost of 29.00 and 3.30 USD per module, respectively. The complete recovery of materials using the proposed method is unlikely to be profitable and this may only be achievable where labor is not expensive. Alternatively, the complete recycling of waste PV could be made economically viable by reducing process time, increasing automation and/or providing financial subsidies. The environmental analysis, however, shows that the optimized process modelled here has a positive net environmental impact. The results are also compared against the cost/environmental impact of landfilling such waste. In summary, the proposed recycling route is capable of completely recovering the main materials in waste PV (aluminum frames, junction box, silver, copper tabbing, silicon, backsheet and unbroken glass) and can have a positive environmental impact, but it is not economically profitable.
... Recent research on the possibility of metal leaching from PV panels discovered that a significant amount of lead was released from c-Si cells and panels [15,16]. Furthermore, under simulated conditions, the metal release was predominant in silicon-based photovoltaics [17]. ...
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The present study highlighted the issue of end-of-life photovoltaic waste before government, policy makers, waste regulators and fills the gaps between various stakeholders by exploring their perceptions towards end-of-life solar waste management. Respondents’ waste handling practices, willingness to pay towards recycling, and their mindset towards problematic situation of upcoming photovoltaic waste were investigated via a survey-based study. Findings indicated that consumers are less concerned about photovoltaic waste as 60% of them are planning to sell their used panels to rag-pickers, however, willing to pay a part of recycling/handling cost, if required. Majority of respondents (> 80%) never considered fate of end-of-life photovoltaics, though willing to pay 15% of handling costs. In terms of responsibility for recycling, 60% consumers think that it is government’s responsibility, whereas 51% manufacturers think that it is a common responsibility of government, consumer, seller/manufacturer. In respect to ranking of drivers, barriers and enablers towards solar waste management, consumers scored factors more moderately than manufacturers, highlighting the less apprehension and thoughtfulness concerning the issue. The most critical barrier identified was high recycling cost, and can possibly be overcome by implementation of research & development on feasible and economically sound recycling processes. Statistical analysis shows that the respondent category and their respective regions significantly affect the ranking of factors and point-of-view towards various aspects. The findings clearly indicate that self-take-back collection and recycling facilities, material recovery and recycling incentives are the main factors affecting end-of-life panels handling. As an input to policy makers, it is necessary to understand the findings presented in present study on consumers and manufacturers’ mindsets regarding photovoltaic waste issue and their willingness to participate in recycling activities. Graphical abstract
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The present study addresses the aspect of upcoming stream of solar photovoltaics waste. The aim of this study was to understand the possibility of material release from end-of-life solar modules using an integrated approach of literature review and stakeholders survey. it involved (i) identification of failure events responsible for degradation of photovoltaic modules were identified from literature review , (ii) evaluation of these events by a survey of stakeholders of photovoltaic industry and (iii) investigation of their perceptions on events responsible for generation of end-of-life modules, present management and recycling practices, (iv) conducting of fault tree analysis and risk priority number analysis for finding severe failure events responsible for dumping and material leaching from solar modules. Assessment indicates that environmental factors, like high UV irradiation, humidity, temperature play significant role in module degradation. As per survey, more than 90% of manufacturers were involved in crystalline-silicon photovoltaic business. Only 20% manufacturers replied when asked on the aspect of end-of-life modules, showing that the photovoltaic waste is comparatively a new subject and not enough discussion have been devoted to it. Lack of recycling infrastructure, incentives, and environmental awareness significantly influence recycling and recuse practices. With worst-case scenarios, the maximum probability of the material release from dumped solar panels was found to 0.053. As per manufacturer’s opinion, the most critical factors resulting in modules failure are glass breakage and encapsulant degradation. Among various events, the module breakage during operation event have highest probability value (i.e., 0.313). Risk priority number analysis suggests that generation of end-of-life photovoltaic and environmental damage resulting to metal leaching as the most significant events. Damage during manufacturing and installation were least significant events resulting in degradation. At present, 76% producers do not recycle or reuse photovoltaic waste material, preferably sell them to informal waste recyclers or rag pickers. Findings from the present study highlight the urgency to develop a suitable system for collection and management of end-of-life photovoltaic modules.
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Solar photovoltaic trees (SPVT's) are chosen as an alternative option for electricity generation due to numerous benefits (especially in land utilization, urban infrastructure, and landscaping). Currently, SPVT's are available in many designs, and one among them is the novel phyllotaxy pattern. Technically, SPVT's seem to be more reliable and cost-effective. The expected average lifetime of the photovoltaic (PV) modules used in SPVT's is around 25 years. Once, the lifetime is over, these SPVT's must undergo a waste management process, and the scope for recycling is very high. Even though the scope for PV waste recycling is very high, many recyclers face the problems especially in estimating material recovery potential. In this paper, thermal and chemical treatments based end-of-life (EOL) method is used to estimate the material recovery potential from the phyllotaxy pattern-based SPVT. Initial estimations on the total embodied materials of the SPVT system is evaluated based on the components material fraction. Next, under the applied EOL management method, material recovery potential is estimated as per the material (aluminum, copper, glass, silver, and steel). Lastly, a few limitations with this EOL method are highlighted, and presented results aim to serve as useful data for the recyclers to have decisions.
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Even with a long lifetime of 25-30 years of green energy production, end-of-life treatment of solar photovoltaic modules can negatively impact the environment if not handled properly. This is particularly urgent when the use of photovoltaics has grown at an unprecedented rate, generating clean energy all over the world. Therefore, it is essential to develop commercially viable end-of-life recycling technologies to guarantee a sustainable future for the photovoltaic technology. Silicon photovoltaic modules, the most popular photovoltaic technology, have been shown to be economically unattractive for recycling-the materials are mixed and difficult to separate, and have low value, so that the cost of recycling is hardly recovered. In this paper, we review the state-of-art recycling technology and associate it with a quantitative economic assessment to breakdown the cost structure and better understand the presented economic barrier. The techno-economic review allows us to identify essential framework and technology changes required to overcome the current barrier to implementing commercial-scale recycling. (i) The authority may impose price signal to impress direct landfill of end-of-life modules while proactively establish an effective collection network. (ii) The local recyclers may aim at value recovery as a step beyond mass recovery, especially targeting at recovery of intact silicon wafers and silver to guarantee the recycling revenue. Meanwhile, efforts should be put on reducing the recycling processing cost. (iii) Photovoltaic module manufacturers may take end-of-life responsibilities and up-design the product to facilitate end-of-life recycling, which includes features for simple disassembly, recycling, and reducing or eliminating the use of toxic components.
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The goal of this study was to assess the sustainability of a modified cellulose nanofiber material for the recovery of precious gold from chloride solution, with a special focus on gold recovery from acidic solutions generated by cupric and ferric chloride leaching processes. TEMPO-oxidized cellulose nanofiber in hydrogel (TOCN), dry (H-TOCN, F-TOCN) and sheet form (S-TOCN) was examined for gold adsorptivity from chloride solution. Additionally, this work describes the optimum conditions and parameters for gold recovery. The data obtained in this investigation are also modeled using kinetic (pseudo first-order and pseudo second-order), isotherm best fit (Freundlich, Langmuir and Langmuir-Freundlich), and thermodynamic (endothermic process) parameters. Results demonstrate that high levels of gold removal can be achieved with TEMPO-oxidized cellulose nanofibers (98% by H-TOCNF) and the interaction characteristics of H-TOCN with gold suggests that other precious metals could also be efficiently recovered.
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The issue of recycling waste solar cells is critical with regard to the expanded use of these cells, which increases waste production. Technology establishment for this recycling process is essential with respect to the valuable and hazardous metals present therein. In the present study, the leaching potentials of Acidithiobacillus thiooxidans, Acidithiobacillus ferrooxidans, Penicillium chrysogenum, and Penicillium simplicissimum were assessed for the recovery of metals from spent solar cells, with a focus on retrieval of the valuable metal Te. Batch experiments were performed to explore and compare the metal removal efficiencies of the aforementioned microorganisms using spent media. P. chrysogenum spent medium was found to be most effective, recovering 100% of B, Mg, Si, V, Ni, Zn, and Sr along with 93% of Te at 30 °C, 150 rpm and 1% (w/v) pulp density. Further optimization of the process parameters increased the leaching efficiency, and 100% of Te was recovered at the optimum conditions of 20 °C, 200 rpm shaking speed and 1% (w/v) pulp density. In addition, the recovery of aluminum increased from 31 to 89% upon process optimization. Thus, the process has considerable potential for metal recovery and is environmentally beneficial.
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The EVA, decomposition of single junction amorphous silicon solar module (a-Si:H) observed during outdoor deployment has been studied. The decay and thermal breakdown of EVA in the encapsulating material of PV module is a sign of low quality in thin film solar cell. The decomposition of EVA due to localized heating affects the reliability and efficiency of PV module. It also has negative influence on the conductive ZnO2 layer and the heat dissipating mechanisms of the PV module. The thermal susceptibility and stability of the encapsulating material was investigated using Thermogravometric (TGA), result shows low quantity of EVA substance in the affected region due to loss of volatile substance from the affected region after decomposition.
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Recently the potential environmental hazard of photovoltaic modules together with their management as waste has attracted the attention of scientists. Particular concern is aroused by the several metals contained in photovoltaic panels whose potential release in the environment were scarcely investigated. Here, for the first time, the potential environmental hazard of panels produced in the last 30 years was investigated through the assessment of up to 18 releasable metals. Besides, the corresponding ecotoxicological effects were also evaluated. Experimental data were compared with the current European and Italian law limits for drinking water, discharge on soil and landfill inert disposal in order to understand the actual pollution load. Results showed that less than 3% of the samples respected all law limits and around 21% was not ecotoxic. By considering the technological evolutions in manufacturing, we have shown that during the years crystalline silicon panels have lower tendency to release hazardous metals with respect to thin film panels. In addition, a prediction of the amounts of lead, chromium, cadmium and nickel releasable from next photovoltaic waste was performed. The prevision up to 2050 showed high amounts of lead (30 t) and cadmium (2.9 t) releasable from crystalline and thin film panels respectively.
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Cadmium telluride (CdTe) and cadmium selenide (CdSe) are increasingly being applied in photovoltaic solar cells and electronic components. A major concern is the public health and ecological risks associated with the potential release of toxic cadmium, tellurium, and/or selenium species. In this study, different tests were applied to investigate the leaching behavior of CdTe and CdSe in solutions simulating landfill leachate. CdTe showed a comparatively high leaching potential. In the Toxicity Characteristic Leaching Procedure (TCLP) and Waste Extraction Test (WET), the concentrations of cadmium released from CdTe were about 1500 and 260 times higher than the regulatory limit (1 mg/L). In contrast, CdSe was relatively stable and dissolved selenium in both leaching tests was below the regulatory limit (1 mg/L). Nonetheless, the regulatory limit for cadmium was exceeded by 5- to 6- fold in both tests. Experiments performed under different pH and redox conditions confirmed a marked enhancement in CdTe and CdSe dissolution both at acidic pH and under aerobic conditions. These findings are in agreement with thermodynamic predictions. Taken as a whole, the results indicate that recycling of decommissioned CdTe-containing devices is desirable to prevent the potential environmental release of toxic cadmium and tellurium in municipal landfills. Copyright © 2015 Elsevier Ltd. All rights reserved.
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Grid-connected solar photovoltaic (PV) power is currently one of the fastest growing power-generation technologies in the world. While PV technologies provide the environmental benefit of zero emissions during use, the use of heavy metals in thin-film PV cells raises important health and environmental concerns regarding the end-of-life disposal of PV panels. To date, there is no published quantitative assessment of the potential human health risk due to cadmium leaching from cadmium telluride (CdTe) PV panels disposed in a landfill. Thus, we used a screening-level risk assessment tool to estimate possible human health risk associated with disposal of CdTe panels into landfills. In addition, we conducted a literature review of potential cadmium release from the recycling process in order to contrast the potential health risks from PV panel disposal in landfills to those from PV panel recycling. Based on the results of our literature review, a meaningful risk comparison cannot be performed at this time. Based on the human health risk estimates generated for PV panel disposal, our assessment indicated that landfill disposal of CdTe panels does not pose a human health hazard at current production volumes, although our results pointed to the importance of CdTe PV panel end-of-life management.
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The major potential environmental impacts related to landfill leachate are pollution of groundwater and surface waters. Landfill leachate contains pollutants that can be categorized into four groups (dissolved organic matter, inorganic macrocomponents, heavy metals, and xenobiotic organic compounds). Existing data show high leachate concentrations of all components in the early acid phase due to strong decomposition and leaching. In the long methanogenic phase a more stable leachate, with lower concentrations and a low BOD/COD-ratio, is observed. Generally, very low concentrations of heavy metals are observed. In contrast, the concentration of ammonia does not decrease, and often constitutes a major long-term pollutant in leachate. A broad range of xenobiotic organic compounds is observed in landfill leachate. The long-term behavior of landfills with respect to changes in oxidation-reduction status is discussed based on theory and model simulations. It seems that the somewhere postulated enhanced release of accumulated heavy metals would not take place within the time frames of thousands of years. This is supported by a few laboratory investigations. The existing data and model evaluations indicate that the xenobiotic organic compounds in most cases do not constitute a major long-term problem. This may suggest that ammonia will be of most concern in the long run.
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The photovoltaic (PV) technology is one of the fastest growing renewable and environmental friendly sources of electricity. However, this huge deployment rate is associated with generation of end-of-life (EoL) PV waste containing particularly, carcinogenic metals, once their operation phase ends. This study attempted to address this upcoming waste issue by systematically reviewing about 300 review/theoretical/ case/research papers/books/patents published between 2000 and 2018. The information was compiled and synthesized on: (i) initial metal concentration/content (IMC) for silicon-PV, amorphous-PV, CIGS and CdTe PVs; ii) statistical characterization and distribution of compiled IMCs; iii) leached metal concentrations (mg/l) from various PVs in water-based leaching solutions, as per standard waste characterization methods, in acid leaching and landfill matrix; iv) metal leaching rate constants (LRC) by fitting exponential model on reported plots of leached metal concentration values versus time using the GetData software; v) feasible application of compiled IMC and LRC data for Leachate Pollution Index (LPI) determination of an MSW landfill dumped with solar-PV waste; vi) human health risk assessment (HHRA) for exposure to lead leached from solar PV waste in an MSW landfill; vii) data/knowledge gaps from literature review and highlight the required future research actions. The ranges of IMC values for top three solar PV-associated carcinogens, arsenic, cadmium and lead (% weight) were obtained to be: 0.00-0.001, 0.0001-19.84, and 0.003-5.09, respectively. Further, the range of LRC of solar PV-associated leached arsenic, cadmium and lead were obtained to be (per day): 0.00-0.129, 0.001-0.031, and 0.003-0.041, respectively. Leaching of Cd, Pb and Se from PVs have been mostly studied in acidic conditions (pH 3.0-6.5), whereas, fate of solar PVs in landfill conditions was not observed to be studied much. The estimation of contribution of solar PV in leachate pollution potential of an existing MSW landfill at T90 values (i.e., time required for 90% leaching of metals) showed an increase of 5.15% in pollution potential of landfill if landfill were to be dumped with EoL PV waste as well. HHRA for exposure to groundwater contaminated with leachate from a landfill dumped with lead containing solar PV waste did not pose any significant risk, however, the carcinogenic effects due to other metals under this scenario cannot be neglected. Out of 85 studies selected for content analysis, only 2.39 % of them investigated the fate of PVs in landfill stimulating conditions. To address fate of EoL waste and reduce uncertainty in present work, following future research actions need to be initiated: (i) conduct experimental studies to obtain data on metal leaching under realistic dumping scenarios and landfill conditions (intact solar panels with bigger size in MSW landfill) ; (ii) revise the expression of LPI for including solar PV-based LPI with critical parameters, like carcinogenic metals (cadmium); (iii) investigate suitability of existing standard hazardous waste characterizing methods (TCLP or WET) for PV waste.
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Solar cell industry produces high quantities of waste in form of broken, damaged, and rejected cells, whereas milling and filtering practices are typically used to recover the valuable materials (Al, Ag and Si) from such Waste Solar Cell Wafers (WSCWs). This recycling approach has its disadvantages, e.g. excessive energy consumption and dust emission causing loss of valuable metals. To fulfil the concept of Zero Waste for WSCWs, the authors present a sustainable technology for liberation of valuable metals from WSCWs and synthesis of added value products, in particular Ag nanoparticles and Al microparticles. The suggested technology consisted of three different approaches combined to liberate each material individually. The technology started with an Al layer disintegration process using Dimethyl Sulfoxide (as an eco-friendly and sustainable solvent) supported by ultrasonic treatment to break van der Waals’ bonding between spherical Al microparticles that compose the Al paste layer, thus liberating Al in microparticle suspension form with particle size ∼3 μm, recovery rate >98%. After that, leaching by nitric acid and other eco-friendly reagents (Sodium Chloride, Ammonia solution and glucose syrup) assisted by ultrasonic treatment was used to dissolve Ag and later precipitate it in form of nanoparticles with avg. size 30 nm, yield >92%. Finally, etching using paste containing phosphoric acid was done to remove anti-reflection coating and purify the Si substrate with final recovery rate >99%. SEM-EDS, XRD, FTIR, and TEM were used for analysis of extracted materials as well as changes in the solvent. Investigation was also concerned with determining economic/global warming impacts of the technology.
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Thin-film solar panels (TFSPs) are widely used in integrated photovoltaic and solar power systems because of their perfect photovoltaic characteristics and ductility. These panels differ from the traditional silicon-based solar panels, in that the metal thin-film layers contain some potentially toxic metals such as zinc (Zn), copper (Cu), nickel (Ni), gallium (Ga), lead (Pb), indium (In) and chromium (Cr). In this study, we examined the environmental pollution that might be caused by disposing of TFSP as domestic trash at the end of their useful life. We used acid extract to simulate metal leaching toxicity and acidic corrosion, and then buried TFSPs in three types of soils to determine if metals might be released into the soil. Our results indicated that the amounts of dissolved metals increased as both the contact time with the acid and the acid concentration in the solution increased during nitric acid extraction. Heavy metals were released from TFSPs in the burial experiment, and the rates of metal release changed with variations in both the amounts of TFSPs in the soil and the soil properties. The increased concentrations of heavy metals such as Zn, Cu, Ni, Ga, Pb, In and Cr in soil samples were correlated to the amounts of TFSPs added. The results of this study confirmed that, when buried, TFSPs polluted the soil.
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PV modules which are installed worldwide have a defined lifetime for useful service after which the panels become End-of-Life (EoL) products. An enormous amount of obsolete solar PV modules will be added to the waste stream in the near future. Hence, the EoL photovoltaic waste stream could cause an appalling problem in the future if a holistic management strategy is not considered. Despite the vast research on photovoltaic technology, little is known about the perspective of how the EoL PV modules will be handled. The current study systematically investigates global research on EoL PV modules to identify gaps for further exploration. The review reveals that most of the research concentrates on the recovery and recycling of PV panels. Also, the vast majority of the research is mostly carried out in laboratory-scale. The geographical distribution of the studies was concentrated on 15 countries including the USA, Italy, and Taiwan, the latter of which has produced the most publications. Life-cycle-assessment and reverse logistics (RL) are two critical aspects of PV waste management and have only recently received attention from researchers, with 11 and six papers respectively. There are still many countries which have not attempted to forecast their EoL solar-panel waste stream and develop recycling infrastructure. Based on review findings, the future research must be focused on forecasting the PV waste streams, development of recycling technologies, reverse logistics and the policies of individual PV consumer countries. Finally, this study develops a foundation for future research on Photovoltaic waste management to build upon.
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Precious metals are widely applied in many industry fields due to their excellent corrosion resistance, good electrical conductivity and high catalytic activity. However, the reserves of precious metals falls short of the production globally. The rapid generation of end-of-life products has become the significant resources of precious metals. Among these products, electronic waste (e-waste) and spent catalysts are more concentrated since they account for over 90% of precious metals in industry. This article provides an overview of various technologies on the recovery of precious metals from e-waste and spent catalysts. It shows that recycling technologies have been significantly improved in recent years. The recycling processes have transferred from leaching by aqua regia, cyanide and chlorine in acid solution to less pollution agents leaching. Environment-oriented technologies have been raised great attention in precious metals recycling. The advantages and environmental impacts of these recycling technologies have been discussed in detail. However, there are still some challenges for future promotion. In order to achieve the environment-friendly and sustainable recycling for precious metals with high recovery rate, several considerations have been proposed.
Conference Paper
Hazardous elements like lead, cadmium etc. are growingly being used in solar photovoltaics (PV). The major distress is the risk related to the potential release of these constituents in the environment. This paper reviews the leaching behaviour of various metallic constituents in soil & water and compiles the latest literature on PV. Analysis shows that there is substantial release of various metallic components in the environment and exist data gaps in (1) lack of information for solar PV disposal, (2) standardized leaching tests representing actual landfill conditions (e.g., studies with actual landfill waste and leachate) (3) Life Cycle Inventories from cradle to grave (4) kinetics data for metal leaching (5) PV wastewater characterization. These identified data gaps need to be filled by conducting more research in this direction so that exposure to toxic metals can be estimated with more confidence and efforts for protecting them can be made.
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The influence of the ethylene-vinyl acetate (EVA) film quality on potential induced degradation was studied on in-house developed mini modules with p-type monocrystalline silicon solar cells. The modules were assembled with EVA films of equivalent qualities, but different ages and exposed to an accelerated test (relative humidity = 85%, T = 60 °C, V $_{\text{bias}}$ = +1000 V). The age of the EVA film was determined from the time we received the EVA film, and opened the sealed enclosure and the time of lamination. After the EVA film was removed from the sealed enclosure, it was kept in a dark place at room temperature. The storage times of the “fresh,” “aged,” and “expired” films were: less than 14 d, around 5 mo, and more than 5 years, respectively. While modules with a “fresh” EVA film exhibit almost no degradation, the modules with the “aged” EVA film degrade very rapidly and severely. Their degradation rate was around 0.2%/d during the 2000 h of damp heat test. We also observed a strong silver line corrosion, which occurs because of the peroxide leftovers in the “aged” EVA films.
Article
In this study, copper (Cu) and aluminum (Al) particles derived from waste crystalline silicon solar cell modules were etched with mixed acid containing HNO3 and HCl, and the optimal mixing conditions were examined for the purpose of recovering silicon with high yield. The crushed particles of waste silicon solar cells were used after sieving between 450 and 600 μm particle size. The Cu etching rate decreased with the increasing HCl concentration in the region of HNO3/HCl ≧ 3.36, whereas it increased at HNO3/HCl < 3.36. The Al etching rate increased when HCl was added, although it was almost independent of the amount of HNO3. 99.6% silicon purity was achieved at the treatment time of 30 min. The rate-determining step of Cu and Al etchings was represented by the volume reaction model instead of the surface reaction model. The CuCl coating was observed on the residuals of Cu. The increasing HCl blocked the Cu etching, but the excess Cl− promoted the dissolution of CuCl due to complex formation, corresponding to the regions of HNO3/HCl ≧ 3.36 and HNO3/HCl < 3.36, respectively. In the region of HNO3/HCl < 3.36, the spontaneous complete etching time of Cu and Al was achieved with higher HNO3 concentration of 8.5–10 mol/L.
Article
Gallium arsenide (GaAs) is a material widely used in electronic devices. Disposal of electronic waste containing GaAs in municipal solid waste landfills raises concerns about the public health and ecological risks associated with the potential release of toxic arsenic (As) species. In this study, different tests were performed to investigate the leaching behavior of particulate GaAs in aqueous solutions. In the U.S. Toxicity Characteristic Leaching Procedure (TCLP) and California Waste Extraction Test (WET), the concentrations of As released from the GaAs particles were about 2.6-2.8-fold higher than the regulatory limit (5 mg/L). A much higher As concentration (72 mg/L), accounting for as much as 15.4% of the initial As in GaAs, was solubilized in a pH-7.6 synthetic landfill leachate under ambient atmosphere after 120 days. Additional tests performed to evaluate the dissolution of GaAs under a range of redox conditions, pH levels, ionic strength, and presence of organic constituents commonly found in landfills revealed that oxic environments and mildly alkaline conditions (pH 8.1-8.5) promote release of As (chiefly arsenite) and gallium species to the surrounding aqueous environment. The rate of As release in long-term exposure experiments was initially constant but later progressively diminished, likely due to the formation of a passivating layer on the surface of GaAs consisting of corrosion products rich in poorly soluble gallium oxides (Ga2O3 and Ga(OH)3). This hypothesis was confirmed by surface analysis of GaAs particles subjected to leaching using X-ray photoelectron spectroscopy (XPS). These findings suggest that further research is needed to assess the potential release of toxic As from electronic waste in municipal landfills.
Article
To determine if there are potential concerns related to the environmental end-of-life impacts of photovoltaic (PV) or quantum-dot display (QD) technologies, the goal of this study was to assess the magnitude of heavy metal leaching using simulated landfill methodologies from devices in an attempt to forecast the lifecycle environmental impacts of subsequent generations QD-enabled PV technologies. The underlying hypotheses are (H1) existing PV and QD thin-film technologies do not release heavy metals at concentrations exceeding RCRA or State of California regulatory limits; and (H2) the disposal of PV and QD thin-film technologies does not exceed Land Disposal Restrictions (LDR). Three task-oriented objectives were completed: (O1) five representative PV panels and two representative thin-film displays with QD technology were obtained from commercial sources; (O2) RCRA Toxicity Characteristics Leaching Procedure (TCLP) tests and California Waste Extraction Tests (WET) were conducted in addition to microwave-assisted nitric acid digestion; and (O3) results were compared to the existing regulatory limits to examine the potential environmental end-of-life concerns. The heavy metal concentrations obtained from PV panels and QD thin-film displays when exposed to simulated landfill environments and extreme case leaching scenarios were generally several orders of magnitude lower than the promulgated standards and probably not of major concerns related to end-of-life safe disposal of these commercially available products. With exception to the findings for lead under the RCRA rules, the results confirmed that PV and QD thin-film technologies do not release heavy metals at concentrations exceeding RCRA or State of California characteristic hazardous waste regulatory limits. However, lead, mercury, and potentially other heavy metal releases have to be monitored to ensure that the disposal of this type of waste is in compliance with RCRA’s LDR requirements and universal treatment standards because the second underlying hypothesis could not be completely supported for the leaching of these heavy metals. It could be anticipated that newer and more sophisticated soldering materials and approaches in the next generation of PV panels would significantly reduce the use of RCRA heavy metals or nanomaterials. However, although the generated data is limited to these representative PV and QD technologies and as such should not be considered applicable to the entire gamete of present-day technologies, these findings suggest that their release from future PV QD technologies would likely be greater from non-end-of-life processes, than from traditional land disposal routes.
Article
With the enormous growth in the development and utilization of solar-energy resources, the proliferation of waste solar panels has become problematic. While current research into solar panels has focused on how to improve the efficiency of the production capacity, the dismantling and recycling of end-of-life (EOL) panels are seldom considered, as can be seen, for instance, in the lack of dedicated solar-panel recycling plants. EOL solar-panel recycling can effectively save natural resources and reduce the cost of production. To address the environmental conservation and resource recycling issues posed by the huge amount of waste solar panels regarding environmental conservation and resource recycling, the status of the management and recycling technologies for waste solar panels are systemically reviewed and discussed in this article. This review can provide a quantitative basis to support the recycling of PV panels, and suggests future directions for public policy makers. At present, from the technical aspect, the research on solar panel recovery is facing many problems, and we need to further develop an economically feasible and non-toxic technology. The research on solar photovoltaic panels' management at the end of life is just beginning in many countries, and there is a need for further improvement and expansion of producer responsibility.
Article
Recent trends in the international photovoltaic (PV) sector indicate strong growth in terms of capacity and production, which is positively influencing the process of energy system decarbonisation. The aim of this review was to promote productive paradigms for a ‘closed cycle’ economy based on the enhancement of resource efficiency and the reduction of waste. To this end, the articulate framework for the management of end-of-life PV panels was analysed, highlighting strengths and weaknesses from the perspective of transitioning towards a circular economy. The conceptual framework is based on a comprehensive review and analysis of relevant literature to describe the main technological and environmental implications associated with PV energy production. Consequently, this paper highlights the most important critical elements, potential opportunities, and limitations deriving from the technological, managerial and organisational aspects of enhancing recovery and recycling rates. The review and the proposed framework might be useful for further research on this important yet complex topic.
Book
The Photovoltaic Engineering Handbook is the first book to look closely at the practical problems involved in evaluating and setting up a photovoltaic (PV) power system. The author’s comprehensive knowledge of the subject provides a wealth of theoretical and practical insight into the different procedures and decisions that designers need to make. Unique in its coverage, the book presents technical information in a concise and simple way to enable engineers from a wide range of backgrounds to initiate, assess, analyze, and design a PV system. It is beneficial for energy planners making decisions on the most appropriate system for specific needs, PV applications engineers, and anyone confronting the practical difficulties of setting up a PV power system.
Article
Some photovoltaic module technologies use toxic materials. We report long-term leaching on photovoltaic module pieces of 5 × 5 cm² size. The pieces are cut out from modules of the four major commercial photovoltaic technologies: crystalline and amorphous silicon, cadmium telluride as well as from copper indium gallium diselenide. To simulate different environmental conditions, leaching occurs at room temperature in three different water-based solutions with pH 3, 7, and 11. No agitation is performed to simulate more representative field conditions. After 360 days, about 1.4% of lead from crystalline silicon module pieces and 62% of cadmium from cadmium telluride module pieces are leached out in acidic solutions. The leaching depends heavily on the pH and the redox potential of the aqueous solutions and it increases with time. The leaching behavior is predictable by thermodynamic stability considerations. These predictions are in good agreement with the experimental results.
Article
China is the world’s largest PV market now. At the end of lifetime, large waste volumes of PV modules need to be recycled. In this paper, the expected PV waste volume is overviewed. By 2034, the EOL PV modules will reach 60 to 70GW. But there are currently no specific regulations for EOL PV modules and the technology research has just started. Technology status is illustrated for crystalline silicon and thin film PV modules. Policy suggestion and technology R&D tendency have been carried out for future.
Article
Ethylene vinyl acetate (EVA) is the dominating material for the encapsulation of solar cells. A better understanding of the cross-linking reaction progress during PV module lamination could lead to promising approaches for shortening of PV module lamination times but also for optimization of the EVA formulation. Therefore, the main aim of this study is to investigate the cross-linking behavior of EVA but also for optimization potentials of the EVA formulation. Currently, a degree of cross-linking higher than 70% obtained from Soxhlet extraction, is used as quality control standard in PV industry. Thermomechanical properties of the investigated EVA films demonstrate a sufficient state of cross-linking already after 5 min, which corresponds to a Soxhlet value of around 50%. Nevertheless, the effect of the remaining, still reactive peroxide cross-linker under service relevant conditions cannot be neglected. Therefore, the behavior of mini-modules manufactured at different lamination times and stored under various aging conditions is investigated. EVA not fully cured during lamination are undergoing postlamination cross-linking. At the same time, remaining active cross-linker causes discoloration at soldering ribbons after accelerated aging. The cross-linking time in the lamination process may be reduced to ≥6 min, compromising between high throughput in production and the need of avoiding degradation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 133, 44912.
Article
The effects of sulfide levels on arsenic leaching and speciation were investigated using leachate generated from laboratory-scale construction and demolition (C&D) debris landfills, which were simulated lysimeters containing various percentages of gypsum drywall. The drywall percentages in lysimeters were 0, 1, 6, and 12.4 wt% (weight percent) respectively. With the exception of a control lysimeter that contained 12.4 wt% of drywall, each lysimeter contained chromated copper arsenate (CCA) treated wood, which accounts for 10 wt% of the C&D waste. During the period of study, lysimeters were mostly under anaerobic conditions. Leachate analysis results showed that sulfide levels increased as the percentage of drywall increased in landfills, but arsenic concentrations in leachate were not linearly correlated with sulfide levels. Instead, the arsenic concentrations decreased as sulfide increased up to approximately 1000 μg/L, but had an increase with further increase in sulfide levels, forming a V-shape on the arsenic vs. sulfide plot. The analysis of arsenic speciation in leachate showed different species distribution as sulfide levels changed; the fraction of arsenite (As(III)) increased as the sulfide level increased, and thioarsenate anions (As(V)) were detected when the sulfide level further increased (>10⁴ μg/L). The formation of insoluble arsenic sulfide minerals at a lower range of sulfide and soluble thioarsenic anionic species at a higher range of sulfide likely contributed to the decreasing and increasing trend of arsenic leaching.
Article
End-of-Life (EoL) photovoltaic (P/V) modules, which are recently included in the 2012/19/EU recast, require sound and sustainable treatment. Under this perspective, this paper deals with 2nd generation P/V waste modules, known as thin-film, via applying chemical treatment techniques. Two different types of modules are examined: (i) tandem a-Si:H/μc-Si:H panel and, (ii) Copper-Indium-Selenide (CIS) panel. Panels’ pretreatment includes collection, manual dismantling and shredding; pulverization and digestion are further conducted to identify their chemical composition. A variety of elements is determined in the samples leachates’ after both microwave-assisted total digestion and Toxicity Characteristic Leaching Procedure (TCLP test) using Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) analysis. The analysis reveals that several elements are detected in the two of panels, with no sample exceeds the TCLP test. Concentrations of precious and critical metals are also measured, which generates great incentives for recovery. Then, further experiments, for P/V recycling investigation, are presented using different acids or acid mixtures under a variety of temperatures and a stable S/L ratio, with or without agitation, in order to determine the optimal recycling conditions. The results verify that chemical treatment in P/V shredded samples is efficient since driving to ethylene-vinyl acetate (EVA) resin’s dissolution, as well as valuable structural materials recovery (P/V glass, ribbons, cells, P/V intermediate layers). Among the solvents used, sulfuric acid and lactic acid demonstrate the most efficient and strongest performance on panels’ treatment at gentle temperatures providing favorably low energy requirements.
Article
Leachate pollution index (LPI) is an environmental index which quantifies the pollution potential of leachate generated in landfill site. Calculation of Leachate pollution index (LPI) is based on concentration of 18 parameters present in leachate. However, in case of non-availability of all 18 parameters evaluation of actual values of LPI becomes difficult. In this study, a model has been developed to predict the actual values of LPI in case of partial availability of parameters. This model generates eleven equations that helps in determination of upper and lower limit of LPI. The geometric mean of these two values results in LPI value. Application of this model to three landfill site results in LPI value with an error of ±20% for ∑i(n)wi⩾0.6.
Article
There is a global consensus on making full use of renewable energy because of human concern for energy security and environmental deterioration. Power generation with large-scale renewable energy such as solar and wind energy has become the trend of modern power systems, and the resulting impacts on power systems are more and more prominent. Therefore, there is great concern from academic and engineering areas of all countries. In China, as the fastest growing country in the photovoltaic (PV) industry in the world, these problems are particularly outstanding. This paper extensively reviews the present research and application status of large-scale PV (LSPV) power generation in China, discusses the modelling and simulation techniques of LSPV, explores impacts of LSPV integration on dynamic and static characteristics of power systems, and describes key technologies about LSPV power generation delivery and consumption from the perspective of power system planning, simulation, dispatching and control. Additionally, this paper also refines academic and engineering problems, and recommendations are proposed for future research and development of LSPV power generation in China.
Article
The appropriateness of regulatory methods to characterise the toxicity of photovoltaic (PV) modules was investigated to quantify potential environmental impacts for modules disposed of in landfills. Because solar energy is perceived as a green technology, it is important to ensure that end-of-life issues will not be detrimental to solar energy's success. United States Environmental Protection Agency Method 1311, California waste extraction test, and modified versions of both were performed on a multi-crystalline silicon module and cells and a copper indium gallium diselenide (CIGS) module. Variations in metal leachate concentrations were found with changes in testing parameters. Lead concentrations from the multi-crystalline module ranged from 16.2 to 50.2 mg/L. Cadmium concentrations from the CIGS module ranged from 0.1 to 3.52 mg/L. This raises doubt that regulatory methods can adequately characterise PV modules. The results are useful for developing end-of-life procedures, which is a positive step towards avoiding an e-waste problem and continuing trends of increasing installation and cost reduction in the PV market.
Article
The crude processing of electronic waste (e-waste) has led to serious contamination in soils. While microorganisms may play a key role in remediation of the contaminated soils, the ecological effects of combined pollution (heavy metals, polychlorinated biphenyls and polybrominated diphenyl ethers) on the composition and diversity of microbial communities remain unknown. In this study, a suite of e-waste contaminated soils were collected from Guiyu, China, and the indigenous microbial assemblages were profiled by 16S rRNA high-throughput sequencing and clone library analysis. Our data revealed significant differences in microbial taxonomic composition between the contaminated and the reference soils, with Proteobacteria, Acidobacteria, Bacteroidetes and Firmicutes dominating the e-waste-affected communities. Genera previously identified as organic pollutants-degrading bacteria, such as Acinetobacter, Pseudomonas and Alcanivorax, were frequently detected. Canonical correspondence analysis revealed that approximately 70% of the observed variation in microbial assemblages in the contaminated soils was explained by eight environmental variables (including soil physiochemical parameters and organic pollutants) together, among which moisture content, decabromodiphenyl ether (BDE-209) and copper were the major factors. These results provide the first detailed phylogenetic look at the microbial communities in e-waste contaminated soils, demonstrating that the complex combined pollution resulting from improper e-waste recycling may significantly alter soil microbiota.
Article
It is important to understand photovoltaic (PV) module degradation for the design of PV systems. In the present study results of degradation in mono-crystalline-silicon PV generator of a solar water pump after 28 years of outdoor exposure at a western Himalayan location in the Indian state of Himachal Pradesh, are presented. The main objective is to study the impact of PV degradation on solar pump performance, reliability and life-expectancy under field conditions. Main defects observed in PV modules are encapsulant discolouration, delamination, oxidation of front grid fingers and anti-reflective coating, glass breakage and bubbles in back sheet. Hot spots are identified using thermal imaging and degradation is quantified by measuring PV parameters under indoor and outdoor conditions. Sun simulator is used to test degraded modules under standard testing conditions. Average power degradation of PV generator is found to increase 1.4% per year which is reasonable considering materials and technology used about three decades ago. The open circuit voltage is found to show an average increase of 2.8% requiring further experimental investigations. The study has relevance in improving the performance and life-expectancy of PV based systems beyond the warranty period of 25 years by replacing most degraded modules. Follow up research areas are also identified.
Article
The photovoltaic effect of thin-film Copper Indium Gallium Selenide cells (CIGS) is conferred by the latter elements. Organic photovoltaic cells (OPV), relying on organic light-absorbing molecules, also contain a variety of metals (e.g. Zn, Al, In, Sn, Ag). The environmental impact of such technologies is largely unknown, in particular when the physical integrity deteriorates upon end-of-life, possibly facilitating cell constituent leaching. This study analyzed long-term inorganic leaching from damaged OPV and CIGS into different model waters. Leachate concentrations were put into perspective by calculating Predicted Environmental Concentrations (PEC) for several scenarios. Roof-top acidic rain run-off from CIGS was found to be the predominant emission source for metals and metalloids, with Cd released to such extents that PEC (173.4 µg Cd L-1) would considerably exceed acute toxicity concentrations for Daphnia magna. Other PEC for CIGS (9.9 mg Mo L-1, 9.4 µg Se L-1, resp.) were in the range of teratogenic effects. In contrast, OPV released little metals with calculated PEC being below even conservative drinking water guidelines. Time-resolved single-particle ICP-MS indicated that some metals (Zn, Mo, Ag) were in nanoparticulate form, raising nano-toxicity concerns. Leaching kinetics called for revision of existing standardized (accelerated) leaching protocols, since long-term release was most relevant.
Article
Water vapor ingress significantly impacts the performance and the long-term reliability of copper indium gallium selenide photovoltaic modules. A cost effective packaging method that can protect photovoltaic modules from the operating environment is critical to their widespread commercialization. Due to the sensitivity of both the copper indium gallium selenide cells and the electrodes to water vapor, they need an encapsulant with low water vapor permeation as well as side sealing materials, resulting in a high cost of manufacturing. Hence, a packaging strategy without sealing materials is proposed with new encapsulant materials. In this study, the overall amount of permeated water vapor through ionomer and polyvinyl butyral encapsulants was investigated and compared with widely used encapsulants such as ethylene vinyl acetate. The diffusion and solubility coefficients were calculated from the experimentally determined water vapor transmission rate in both transient and steady state transport regimes. To understand the permeation mechanism of water vapor through the encapsulant, the temperature dependence of the diffusion and solubility coefficients was investigated. Based on experimentally determined permeation properties, the amount of water vapor absorption and the ingress speed into the PV module under a continuously varying environment were investigated. Ethylene vinyl acetate shows its excellence among encapsulants, when simply considering ingress speed of water vapor (slower permeation), while ionomer dominantly outperforms other materials, when focusing on the total amount of water absorption (less permeation).
Article
The energetic and environmental life cycle assessment of a 4.2kWp stand-alone photovoltaic system (SAPV) at the University of Murcia (south-east of Spain) is presented. PV modules and batteries are the energetically and environmentally most expensive elements. The energy pay-back time was found to be 9.08years and the specific CO2 emissions was calculated as 131g/kWh. The SAPV system has been environmentally compared with other supply options (diesel generator and Spanish grid) showing lower impacts in both cases. The results show the CO2-emission reduction potential of SAPV systems in southern European countries and point out the critical environmental issues in these systems.
Article
A technique to quantify the leachate pollution potential of landfills on a comparative scale using an index known as the Leachate Pollution Index (LPI) has been developed and reported elsewhere. The LPI is a quantitative tool by which the leachate pollution data of the landfill sites can be reported uniformly. It is an increasing scale index and has been formulated based on the Delphi technique. The formulation process involved selecting variables, deriving weights for the selected pollutant variables, formulating their subindices curves, and finally aggregating the pollutant variables to arrive at the LPI. The aggregation function is one of the most important steps in calculating any environmental index. If the aggregation function is ambiguous, the result will raise an unnecessary alarm, indicating a comparatively less polluted environmental situation as more contaminated. Similarly, if the aggregation function is eclipsed, a false sense of security may be created, indicating a highly polluted environmental situation as less polluted. In this paper, the concept of LPI is described in brief and the various possible aggregation functions are described and used to calculate LPI values for an actual landfill site to select the most appropriate aggregation function. Based on the results, it is concluded that the weighted linear sum aggregation function is the best possible aggregation function for calculating LPI. Sensitivity analysis of the six short-listed aggregation functions is performed to substantiate this conclusion.
Article
This paper evaluates the performance parameters of five photovoltaic (PV) modules comprising crystalline silicon, multi-crystalline silicon and edge-defined film-fed growth (EFG) silicon technologies. This evaluation was accomplished by measuring and analysing the modules' performances during initial, intermediate and final stages of a 17-month test period. The effect of temperature and irradiance on the performance parameters was investigated. Results obtained indicate that some modules exhibited shunting behaviour and that the EFG silicon module experienced moisture ingress, which in part, resulted in 14% performance degradation. An analysis of the results revealed that the moisture ingress effectively reduced the active module area, resulting in reduced photon absorption, consequently reducing the electron-hole generation as indicated by the reduced short-circuit current. In addition, the EFG-Si module's shunt resistance appeared to decrease over the test period. The rest of the modules showed relatively stable performance, information that is crucial to the system designer and consumer.
Article
Global environmental concerns and the escalating demand for energy, coupled with steady progress in renewable energy technologies, are opening up new opportunities for utilization of renewable energy resources. Solar energy is the most abundant, inexhaustible and clean of all the renewable energy resources till date. The power from sun intercepted by the earth is about 1.8 x 1011 MW, which is many times larger than the present rate of all the energy consumption. Photovoltaic technology is one of the finest ways to harness the solar power. This paper reviews the photovoltaic technology, its power generating capability, the different existing light absorbing materials used, its environmental aspect coupled with a variety of its applications. The different existing performance and reliability evaluation models, sizing and control, grid connection and distribution have also been discussed.
Article
The dumping of solid waste in uncontrolled landfills can cause significant impacts on the environment and human health. The principal concern is focussed on the pollution potential due to migration of the leachate generated from the landfill sites into the groundwater, the surface water or the sea. In this paper, the concept of the leachate pollution index, a tool for quantifying the leachate pollution potential of landfill sites, has been described and its practical application has been demonstrated by comparing the leachate contamination potential of two active and two closed landfills sites in Hong Kong. It has been found that the leachate generated from the closed landfills can have equal or more contamination potential in comparison to the active landfill sites and hence, the remediation actions and post-closure monitoring should be ensured at the closed landfills till the leachate generated is stabilized and poses no further threat to the environment.