The Experts below are selected from a list of 2907 Experts worldwide ranked by ideXlab platform
Christian Hagendorf - One of the best experts on this subject based on the ideXlab platform.
-
sodium decoration of pid s crystal defects after corona induced degradation of bare silicon solar cells
Energy Procedia, 2015Co-Authors: Volker Naumann, Dominik Lausch, Christian HagendorfAbstract:Abstract It is proven that potential-induced degradation leading to shunting of crystalline silicon solar cells (PID-s) is caused by stacking fault-like planar crystal defects penetrating the p-n junction that become decorated with sodium due to high electric fields across the dielectric antireflective coating (ARC). Often it is assumed that sodium found in PID-s affected cells originates from the cover glass used for photovoltaic modules. In this contribution, we show that PID-s also occurs at bare silicon solar cells without Polymer Foil or glass encapsulation. Using corona discharge induced degradation, it is shown that sodium decorated, shuntingcrystal defectsare generated. This sodium likely originates from contaminations present on the solar cell surface. Therefore, it is concluded that PID-s of solar modules also mainlyarises from sodium contaminationsof the solar cell surfaceand not from the glass. Whether PID-s occurs or not depends on the electric field across the ARC, influenced by theelectrical resistance of Polymer Foil and glass. So called sodium-free glass results in a low electric field due to the high resistance of the glass.
-
Polymer Foil additives trigger the formation of snail trails in photovoltaic modules
Solar Energy Materials and Solar Cells, 2014Co-Authors: Sylke Meyer, S Timmel, M Glaser, U Braun, Volker Wachtendorf, Christian HagendorfAbstract:Abstract After several months of operation, many photovoltaic (PV) modules develop a discolouration defect called snail trails which appear as irregular dark traces across the cells. These traces are caused by silver nanoparticles accumulating within the encapsulation Foil directly above the grid finger. In this work we systematically investigate combinations of encapsulation and back-sheet Foils with respect to their susceptibility for snail trails. We can show that certain additive compositions within the encapsulation and back sheet Foils are critical for the formation of the discolouring silver nanoparticles. We suggest a reaction model explaining the formation of snail trails from a chemical point of view. This fundamental understanding allows the rapid testing of Foils for their snail trail sensitivity as well as the special design of resistant Foils.
-
Polymer Foil additives trigger the formation of snail trails in photovoltaic modules
Energy Procedia, 2014Co-Authors: Sylke Meyer, S Timmel, U Braun, Christian HagendorfAbstract:Abstract After several months of operation, many photovoltaic (PV) modules develop a discoloration defect called “snail trails” or “snail traces”, which appears as irregular dark traces across the cells. These traces have been identified as discolored silver grid fingers along the cell edges or at cell cracks. Previously we were able to show that silver nanoparticles accumulating within the encapsulation Foil directly above the grid finger cause the brownish discoloration. In this work we present results showing that certain properties of the encapsulation and back-sheet Foils trigger the formation of these nanoparticles. We developed a special test method to test Polymer Foils for their snail trail susceptibility in advance to module assembly.
De Vries H. W. - One of the best experts on this subject based on the ideXlab platform.
-
The role of carrier gas flow in roll-to-roll AP-PECVD synthesized silica moisture barrier films
Surface and Coatings Technology 339 20-26, 2018Co-Authors: Meshkova A. S., Elam F. M., Starostin S. A., M. C. M. Van De Sanden, De Vries H. W.Abstract:Moisture barrier films are deposited on a Polymer Foil by roll-to-roll Atmospheric Pressure Plasma Enhanced CVD reactor using a N2, O2, TEOS gas mixture. The film microstructure and permeation properties are studied as a function of the carrier gas flow rate with both static and dynamic film transport. The microstructure is analyzed by spatially resolved attenuated total reflectance (ATR)-FTIR and correlated with the vertical density gradient obtained in the dynamic films and the moisture barrier performance. It is shown that by varying the carrier gas flow rate the vertical density gradient, or the network porosity, can be tuned by governing the convective transport inside the reactor consequently densifying the inorganic film at fixed energy cost (i.e. Yasuda parameter) of the process. Moreover, adopting the bilayer architecture allows to achieve the same moisture barrier properties of 2 · 10−3 g·m−2·day−1 (40 °C, 90% RH) at only half the film thickness of a single layer barrier films, which consequently leads to a throughput increase of almost two times.
Bengt Perers - One of the best experts on this subject based on the ideXlab platform.
-
simulation of a solar collector array consisting of two types of solar collectors with and without convection barrier
Energy Procedia, 2015Co-Authors: Federico Bava, Simon Furbo, Bengt PerersAbstract:Abstract The installed area of solar collectors in solar heating fields is rapidly increasing in Denmark. In this scenario even relatively small performance improvements may lead to a large increase in the overall energy production. Both collectors with and without Polymer Foil, functioning as convection barrier, can be found on the Danish market. Depending on the temperature level at which the two types of collectors operate, one can perform better than the other. This project aimed to study the behavior of a 14 solar collector row made of these two different kinds of collectors, in order to optimize the composition of the row. Actual solar collectors available on the Danish market (models HT-SA and HT-A 35-10 manufactured byARCON Solar A/S) were used for this analysis. To perform the study, a simulation model in TRNSYS was developed based onthe Danish solar collector field in Braedstrup. A parametric analysis was carried out by modifying the composition of the row, in order to find both the energy and economy optimum.
Stefan Zimmermann - One of the best experts on this subject based on the ideXlab platform.
-
continuous noninvasive monitoring of cell growth in disposable bioreactors
Sensors and Actuators B-chemical, 2017Co-Authors: Tobias Reinecke, Philipp Biechele, Dorte Solle, Maciej Sobocinski, H Suhr, Kai Bakes, Heli Jantunen, Thomas Scheper, Stefan ZimmermannAbstract:Abstract To ensure high quality output of biotechnological processes, relevant process parameters need to be monitored. As bioprocesses are increasingly executed in single use bioreactors, there is an increasing demand for new sensors applicable to these processes. In this work, we investigate different approaches for continuous non-invasive cell growth monitoring, especially for single use bioreactor applications. Therefore, the permittivity of the cell culture is used as a measure for the biomass. In a first step, a measuring procedure based on the transmission measurement of an electromagnetic wave is investigated. It appears that the penetration depth of this sensor is not sufficient for a noninvasive measurement through the Polymer wall of a single use bioreactor. Therefore, alternative setups based on magnetic induction are investigated. The initial setup is very simple. It consists of a planar coil connected to an impedance analyzer. The coil is attached to the outside of the Polymer Foil of the single use bioreactor and an impedance spectrum is measured. To evaluate the sensor, E. coli cultivations are performed in a modified cultivation setup, which enables measurements through the Polymer Foil of a Sartorius BIOSTAT® CultiBag RM, and additionally allows sampling of culture medium for optical density reference measurements. The resonance peak of the coil in the impedance spectrum, is observed as measure for the optical density. Regardless of the simple sensor construction, we found a good correlation between optical density and the damping ratio of the resonance peak. However, the sensor signal shows saturation towards high optical densities. Therefore, an LTCC coil producing a higher magnetic flux density in the culture medium is investigated subsequently. This sensor shows a linear response up to high optical densities, but the sensitivity is reduced compared to the former used coil and therefore scattering of the data is increased. However, to increase the sensitivity, a linear variable differential transformer is realized. Using this setup, the influence of the primary magnetic flux is eliminated from the measuring voltage. This approach delivers the most promising results, as the sensor response is linear up to high optical densities and data scattering is low.
-
differential inductive sensor for continuous non invasive cell growth monitoring in disposable bioreactors
2017Co-Authors: Maria Allers, Dorte Solle, Kai Bakes, Tamanna Nagraik, Marc Berger, Tobias Reinecke, Thomas Scheper, Stefan ZimmermannAbstract:In this work, we present a low-cost sensor system for continuous non-invasive cell growth monitoring, especially for single use bioreactor (SUB) applications. The sensor system is based on a differential transformer. Using this differential setup, the influence of the primary magnetic flux is eliminated from the measuring signal, enabling highly sensitive non-invasive detection of permittivity changes in the culture medium. To evaluate the sensor, E. coli cultivations are performed and the cell density is measured through the Polymer Foil of a SUB. We found a linear dependency with low data scattering between measuring signal and cell density.
-
non invasive online monitoring of cell growth in disposable bioreactors with a planar coil
Procedia Engineering, 2016Co-Authors: Tobias Reinecke, Philipp Biechele, M Frickhoffer, Thomas Scheper, Stefan ZimmermannAbstract:Abstract To ensure high quality output of biotechnological processes, relevant process parameters need to be monitored. As bioprocesses are increasingly executed in single use bioreactors, there is an increasing demand for new sensors applicable to these processes. In this work, we present a low-cost sensor system for continuous non-invasive cell growth monitoring, especially for single use bioreactor applications. The system consists of a planar coil connected to a low cost network analyzer. The coil is attached to the outside of the Polymer Foil of the single use bioreactor and an impedance spectrum is measured. To evaluate the sensor, E. coli cultivations are performed in a modified cultivation setup, which enables measurements through the Polymer Foil of a Sartorius BIOSTAT ® CultiBag RM, and additionally allows sampling of culture medium for optical density reference measurements. The resonance peak of the coil in the impedance spectrum, is observed as measure for the optical density. Regardless of the simple sensor construction, we found a good correlation between optical density and the damping ratio of the resonance peak.
Meshkova A. S. - One of the best experts on this subject based on the ideXlab platform.
-
The role of carrier gas flow in roll-to-roll AP-PECVD synthesized silica moisture barrier films
Surface and Coatings Technology 339 20-26, 2018Co-Authors: Meshkova A. S., Elam F. M., Starostin S. A., M. C. M. Van De Sanden, De Vries H. W.Abstract:Moisture barrier films are deposited on a Polymer Foil by roll-to-roll Atmospheric Pressure Plasma Enhanced CVD reactor using a N2, O2, TEOS gas mixture. The film microstructure and permeation properties are studied as a function of the carrier gas flow rate with both static and dynamic film transport. The microstructure is analyzed by spatially resolved attenuated total reflectance (ATR)-FTIR and correlated with the vertical density gradient obtained in the dynamic films and the moisture barrier performance. It is shown that by varying the carrier gas flow rate the vertical density gradient, or the network porosity, can be tuned by governing the convective transport inside the reactor consequently densifying the inorganic film at fixed energy cost (i.e. Yasuda parameter) of the process. Moreover, adopting the bilayer architecture allows to achieve the same moisture barrier properties of 2 · 10−3 g·m−2·day−1 (40 °C, 90% RH) at only half the film thickness of a single layer barrier films, which consequently leads to a throughput increase of almost two times.