Electrical characterization of P3HT:PCBM organic solar cells by admittance spectroscopy: defect investigation

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Switched-capacitors as local converters for snake PV modules : a cost/efficiency exploration

In order to reduce the negative effect of partial shading and other sources of current mismatch within a module, smart reconfigurable modules allow altering the connections between groups of cells (cell-strings). With a proper algorithm managing these connections, we can make sure that the majority of the cells are operating close to their MPP, even when a part of the module is shaded. Such a smart reconfigurable module consists of some extra components. Switches are needed to change the interconnection scheme. Small, local converters collect power from multiple cell-strings. They step-up the voltage to reduce the current on the central bus they are connected to. At the end where we connect to the string-level bus, a module converter further regulates the voltage for the grid or the PV array. This topology was presented before where we showed that a smart reconfigurable module could recover up to 70% of the power lost to partial shading. In this paper we take a closer look at the local DC-DC converter. More precisely, we present a cost-efficiency analysis of different converter topologies. Taking into account practical limitations (economical limitations, number of components, maximum switch currents, maximum capacitance values, etc..) we estimate efficiency and projected cost. We show that Dickson pump (CR3) with 30-35mOhm switches is the best candidate. This would result in a chip cost of about €1.

Comparative Indoor and Outdoor Degradation of Organic Photovoltaic Cells via Inter-laboratory Collaboration

We report on the degradation of organic photovoltaic (OPV) cells in both indoor and outdoor environments. Eight different research groups contributed state of the art OPV cells to be studied at Pomona College. Power conversion efficiency and fill factor were determined from IV curves collected at regular intervals over six to eight months. Similarly prepared devices were measured indoors, outdoors, and after dark storage. Device architectures are compared. Cells kept indoors performed better than outdoors due to the lack of temperature and humidity extremes. Encapsulated cells performed better due to the minimal oxidation. Some devices showed steady aging but many failed catastrophically due to corrosion of electrodes not active device layers. Degradation of cells kept in dark storage was minimal over periods up to one year

Critical material reduction in PV interconnection

International audienceGiven the exponential growth of deployed photovoltaic (PV) energy sources, we have to question how to make such growth sustainable. Transition at global scale from fossil fuels to mineral-based renewable energies will indeed induce a sharp turn in materials supply chains. The concept of critical materials covers various sources of supply tensions. More precisely in PV sector, concerns grow for the last few years about Silver price volatility, relative to its scarcity, or about Indium related to its availability.Raw material criticity definition is open to question. No consensus seems to arise yet from literature in order to define influencing factors on criticity. For this study, five supply hazard criteria are selected in order to represent accurately each material supply situation: geological, logistical, geopolitical, industrial and commercial. With those criteria, the materials (and their substitutes) used in PV modules interconnection are listed and for each one, criticity is assessed. List of those elements is the following: Aluminum, Bismuth, Copper, Indium, Nickel, Silver and Tin.Although different dynamics may be observed depending on the concerned material, the main conclusion is that, except Aluminum, all listed elements supplies should face supply tensions by 2050, or even 2030 for the most critical ones [1]. It is important to note that for most of these materials, PV sector has not triggered its critical status.Two material groups should be distinguished. In the first hand, high production and consumption volumes materials (Aluminum and Copper) should not restrict PV energy production capacity expansion projections in the short term but could adversely affect growth in the mid term: by 2050, Copper demand to electrify the whole society should deplete global reserves so its supply is unreliable; it is then compulsory to deeply rethink energy networks, as well as implement a circular approach (reduce, repair, reuse and finally recycle). Moreover, aluminum needed volume for PV on TW scale would induce huge CO2 emissions [2]. On the other hand, other materials (Bismuth, Indium, Silver, and Tin) are used in PV interconnection in dispersive ways: even though PV sector requires a limited amount, they are difficult to recover. These applications must evolve otherwise the known reserves will end around 2040.It draws one main conclusion in the specific case of PV sector: conception has to evolve from dispersive cells interconnection processes, such as low temperature soldering or conductive adhesive bonding. In general, conception step has to focus on end-of-life step to introduce more circular methodologies. Change may happen at three levels: process, material or architecture. Changing or optimizing the deposition process is largely covered in literature over the last 15 years and Silver consumption reduction potential seems to reach its limit [3]. Alternative materials have been rising for the last 5 years and could have a great impact on metallization criticity. In the meantime, critical materials consumption in interconnection could further shrink with a disruptive innovation in module architecture. A few innovation examples, from NICE concept to non-uniform metallization, will be presented

Critical material reduction in PV interconnection

International audienceGiven the exponential growth of deployed photovoltaic (PV) energy sources, we have to question how to make such growth sustainable. Transition at global scale from fossil fuels to mineral-based renewable energies will indeed induce a sharp turn in materials supply chains. The concept of critical materials covers various sources of supply tensions. More precisely in PV sector, concerns grow for the last few years about Silver price volatility, relative to its scarcity, or about Indium related to its availability.Raw material criticity definition is open to question. No consensus seems to arise yet from literature in order to define influencing factors on criticity. For this study, five supply hazard criteria are selected in order to represent accurately each material supply situation: geological, logistical, geopolitical, industrial and commercial. With those criteria, the materials (and their substitutes) used in PV modules interconnection are listed and for each one, criticity is assessed. List of those elements is the following: Aluminum, Bismuth, Copper, Indium, Nickel, Silver and Tin.Although different dynamics may be observed depending on the concerned material, the main conclusion is that, except Aluminum, all listed elements supplies should face supply tensions by 2050, or even 2030 for the most critical ones [1]. It is important to note that for most of these materials, PV sector has not triggered its critical status.Two material groups should be distinguished. In the first hand, high production and consumption volumes materials (Aluminum and Copper) should not restrict PV energy production capacity expansion projections in the short term but could adversely affect growth in the mid term: by 2050, Copper demand to electrify the whole society should deplete global reserves so its supply is unreliable; it is then compulsory to deeply rethink energy networks, as well as implement a circular approach (reduce, repair, reuse and finally recycle). Moreover, aluminum needed volume for PV on TW scale would induce huge CO2 emissions [2]. On the other hand, other materials (Bismuth, Indium, Silver, and Tin) are used in PV interconnection in dispersive ways: even though PV sector requires a limited amount, they are difficult to recover. These applications must evolve otherwise the known reserves will end around 2040.It draws one main conclusion in the specific case of PV sector: conception has to evolve from dispersive cells interconnection processes, such as low temperature soldering or conductive adhesive bonding. In general, conception step has to focus on end-of-life step to introduce more circular methodologies. Change may happen at three levels: process, material or architecture. Changing or optimizing the deposition process is largely covered in literature over the last 15 years and Silver consumption reduction potential seems to reach its limit [3]. Alternative materials have been rising for the last 5 years and could have a great impact on metallization criticity. In the meantime, critical materials consumption in interconnection could further shrink with a disruptive innovation in module architecture. A few innovation examples, from NICE concept to non-uniform metallization, will be presented

Module reliability: lessons learned for a smart tandem integration

International audienceModule reliability: lessons learned for a smart tandem integrationPresentation au tandemPV workshop en remplacement Ulrike Jahn: talk invit

Module reliability: lessons learned for a smart tandem integration

International audienceModule reliability: lessons learned for a smart tandem integrationPresentation au tandemPV workshop en remplacement Ulrike Jahn: talk invit

Overview and Perspectives for Vehicle-Integrated Photovoltaics

On-board photovoltaic (PV) energy generation is starting to be deployed in a variety of vehicles while still discussing its benefits. Integration requirements vary greatly for the different vehicles. Numerous types of PV cells and modules technologies are ready or under development to meet the challenges of this demanding sector. A comprehensive review of fast-changing vehicle-integrated photovoltaic (VIPV) products and lightweight PV cell and module technologies adapted for integration into electric vehicles (EVs) is presented in this paper. The number of VIPV projects and/or products is on a steady rise, especially car-based PV integration. Our analysis differentiates projects according to their development stage and technical solutions. The advantages and drawbacks of various PV cell and module technologies are discussed, in addition to recommendations for wide-scale deployment of the technologies

Standardized cross-linking determination methods applied to POE encapsulants in lamination recipe emphasizing

International audienceEthylene vinyl acetate is the most common encapsulation material in photovoltaic panels. Due to gradual engineering, it ensures to meet performance requirement of standard cells, low-cost and well understood cross-linking behaviour, both physically and chemically. Nowadays polyolefin elastomers (POE) have been entering the PV industry requirements by advanced cells concepts and/or novel degradation phenomena noticed on bifacial modules. POE exhibit several advantages based on its intrinsic high volume resistivity, low permeation, processability and most importantly, the absence of harmful by-products (such as acetic acid) generated upon humidity exposure[1, 2]. However, this new family of materials may behave differently from EVA during crosslinking, thus it is necessary to verify and adapt standard measurement methods. Therefore, the main objective of this study is to investigate the cross-linking behaviour of POEs with the final goal of exploring the process window of the lamination. The characterization methods like differential scanning calorimetry (DSC) and Soxhlet extraction have been used to determine crosslinking rate and chemical structure of several encapsulants. Similar to EVAs, cross-linking rate of POEs measured by Soxhlet extraction increases with lamination duration until reaching a plateau. The indirect cross-linking rate measurement by DSC analysis is usually favoured through its simple, fast implementation, absence of toxic chemicals when compared to Soxhlet extraction. Remarkable correlations between the two techniques were obtained for a commercially available POE, allowing the extension of the IEC standard to new encapsulants. Nevertheless, in the case of highly engineered materials, clear deviations are recorded, highlighting validity limits of direct correlation between Soxhlet and DSC methods