S Müller; A Dittrich; R Reineke-Koch; F Giovannetti; B Hafner
Thermochrome Absorberbeschichtungen für solarthermische Kollektoren - Stand der Technik, Schichtentwicklung und Systembewertung Proceedings Article
In: in.RET, (Hrsg.): 1. Regenerative Energietechnik-Konferenz in Nordhausen, S. 15-26, Nordhausen, Germany, 2018.
@inproceedings{Müller2018,
title = {Thermochrome Absorberbeschichtungen für solarthermische Kollektoren - Stand der Technik, Schichtentwicklung und Systembewertung},
author = {S Müller and A Dittrich and R Reineke-Koch and F Giovannetti and B Hafner},
editor = {in.RET},
year = {2018},
date = {2018-02-09},
booktitle = {1. Regenerative Energietechnik-Konferenz in Nordhausen},
pages = {15-26},
address = {Nordhausen, Germany},
abstract = {Thermochrome Absorberbeschichtungen weisen einen für langwellige Wärmestrahlung stark tempera-turabhängigen Emissionsgrad auf. Im Allgemeinen beschreibt der Begriff „Thermochromie“ eine tem-peraturgesteuerte Änderung von optischen Eigenschaften eines Materials. Die hier untersuchten auf Vanadiumdioxid basierenden Schichtsysteme besitzen unterhalb einer gewissen Schalttemperatur (Absorbertemperatur) von TS ≈ 68 °C einen für hochselektive Beschichtungen üblichen Emissionsgrad (ε20°C ≈ 5 %), welcher sich bei höherer Absorbertemperatur auf bis zu ε100°C ≈ 35 % erhöht. Die Strahlungswärmeverluste über die transparente Abdeckung an die Umgebung erhöhen sich dadurch signifikant, wodurch die Stagnationstemperatur um bis zu 30 K reduziert und eine Ver¬dampfung des Wärmeträgers verhindert werden kann. Es wurden stationäre Kollektorleistungsmes¬sungen nach ISO 9806:2013 an ersten Prototypen und industriell gefertigten Flachkollektoren durchgeführt, um die Leistungsfähigkeit des Kollektors und die „Schaltung“ der Emissivität zu bewer¬ten. In dynamischen Systemtests nach ISO 9459-5 wurde die Systemleistung eines Trinkwarmwas¬sersystems mit thermochromen Flachkollektoren gegen die mit Standard-Flachkollektoren verglichen. Mit einer Reduzierung des solaren Deckungsgrades um 1 Prozentpunkt und einer maximalen Erhö¬hung des konventionellen Nachheizenergiebedarfes von 2,5 % konnte die hohe Leistungsfähigkeit der neuartigen Beschichtung bestätigt werden. Das Stagnationsverhalten wurde hinsichtlich der Dampf-reichweite und der Maximaltemperaturen im Solarkreislauf experimentell bewer¬tet. Die Stagnationszeit konnte bei üblichen Systemüberdrücken um 60 % reduziert und die Stagnati¬onstemperatur unter Um-gebungsbedingungen auf 145 °C begrenzt werden.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
F Hüsing; O Mercker
Energieversorgung im Einfamilienhaus mittels Wärmepumpe, horizontalen Erdwärmekollektoren und photovoltaisch-thermischen Solarkollektoren Proceedings Article
In: in.RET, (Hrsg.): 1. Regenerative Energietechnik-Konferenz in Nordhausen, S. 121-128, Nordhausen, Germany, 2018.
@inproceedings{Hüsing2018,
title = {Energieversorgung im Einfamilienhaus mittels Wärmepumpe, horizontalen Erdwärmekollektoren und photovoltaisch-thermischen Solarkollektoren},
author = {F Hüsing and O Mercker},
editor = {in.RET},
year = {2018},
date = {2018-02-09},
booktitle = {1. Regenerative Energietechnik-Konferenz in Nordhausen},
pages = {121-128},
address = {Nordhausen, Germany},
abstract = {Ein Energieversorgungssystem im Einfamilienhaus, bestehend aus Wärmepumpe (WP), horizontalen Erdwärmekollektor (EWK) und unabgedeckten photovoltaisch-thermischen Solarkollektoren wird
untersucht. Neben der Möglichkeit die benötigte EWK-Fläche durch Kombination mit Solarwärme zu reduzieren steht insbesondere die Betrachtung der elektrischen Energieflüsse im Fokus dieses Beitrags. Auf saisonaler und tageszeitlicher Ebene wird das Systemverhalten analysiert und bestimmt, welchen Beitrag der lokale PV-Ertrag zur Deckung des elektrischen Bedarfs der WP leistet. Der relative geringe Anteil in der rein bedarfsgeführten Wärmeerzeugung wird auf sowohl im Tagesverlauf als auch saisonal gegensätzliche Verläufe von PV-Ertrag und Wärmebedarf zurückgeführt.
Schließlich werden Optionen zur Optimierung des Systems vorgestellt.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
untersucht. Neben der Möglichkeit die benötigte EWK-Fläche durch Kombination mit Solarwärme zu reduzieren steht insbesondere die Betrachtung der elektrischen Energieflüsse im Fokus dieses Beitrags. Auf saisonaler und tageszeitlicher Ebene wird das Systemverhalten analysiert und bestimmt, welchen Beitrag der lokale PV-Ertrag zur Deckung des elektrischen Bedarfs der WP leistet. Der relative geringe Anteil in der rein bedarfsgeführten Wärmeerzeugung wird auf sowohl im Tagesverlauf als auch saisonal gegensätzliche Verläufe von PV-Ertrag und Wärmebedarf zurückgeführt.
Schließlich werden Optionen zur Optimierung des Systems vorgestellt.
F Haase; S Schäfer; C Klamt; F Kiefer; J Krügener; R Brendel; R Peibst
In: IEEE Journal of Photovoltaics, Bd. 8, Nr. 1, S. 23-29, 2018, ISSN: 2156-3381.
@article{Haase2018,
title = {Perimeter Recombination in 25%-Efficient IBC Solar Cells With Passivating POLO Contacts for Both Polarities},
author = {F Haase and S Schäfer and C Klamt and F Kiefer and J Krügener and R Brendel and R Peibst},
doi = {10.1109/JPHOTOV.2017.2762592},
issn = {2156-3381},
year = {2018},
date = {2018-01-01},
journal = {IEEE Journal of Photovoltaics},
volume = {8},
number = {1},
pages = {23-29},
abstract = {We introduce a method for the quantification of perimeter recombination in solar cells based on infrared lifetime measurements. We apply this method at a 25.0%-efficient interdigitated back contact (IBC) silicon solar cell with passivating contacts. The implied pseudo-efficiency determined by infrared lifetime mapping is 26.2% at an intermediate process step. The 1.2%abs loss is attributed to a process-related reduction in surface passivation quality, recombination in the perimeter area, and series resistance. The 2 × 2 cm2 -sized cell is processed on a 100 mm wafer. We determine the implied pseudo-efficiency with illuminated and with shaded perimeter area during infrared lifetime mapping. The difference between both implied pseudo-efficiencies yields the efficiency loss by perimeter recombination, which is determined to be 0.4%abs for a wafer resistivity of 1.3 Ω cm and even 0.9%abs for a wafer resistivity of 80 Ω cm.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
D Bredemeier; D C Walter; J Schmidt
In: Solar RRL, Bd. 2, Nr. 1, S. 1700159, 2018, ISSN: 2367-198X.
@article{Bredemeier2018,
title = {Possible Candidates for Impurities in mc-Si Wafers Responsible for Light-Induced Lifetime Degradation and Regeneration},
author = {D Bredemeier and D C Walter and J Schmidt},
doi = {10.1002/solr.201700159},
issn = {2367-198X},
year = {2018},
date = {2018-01-01},
journal = {Solar RRL},
volume = {2},
number = {1},
pages = {1700159},
abstract = {We examine the light‐induced carrier lifetime degradation and regeneration at elevated temperature in multicrystalline silicon (mc‐Si) wafers of different thicknesses. The experimental results show that the thinner the wafer the less pronounced the degradation is and the faster the regeneration takes place. We interpret this result in the framework of a recently proposed defect model, where the lifetime regeneration is attributed to the diffusion of the recombination‐active impurity to the wafer surfaces, where it is permanently trapped. Modeling the measured thickness‐dependent lifetime evolutions enables us to determine the diffusion coefficient of the impurity to be in the range (5 ± 2) × 10−11 cm2 s−1 at a temperature of 75 °C. Comparing the diffusion coefficient extracted from our measurements with data published in the literature allows us to exclude most impurities. Despite the large uncertainties in the diffusion coefficient data reported in the literature, reasonable agreement is only obtained for nickel, cobalt, and hydrogen. One important practical implication of our study is that mc‐Si wafers thinner than 120 μm do not suffer from pronounced light‐induced lifetime degradation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
B Veith-Wolf; R Witteck; A Morlier; H Schulte-Huxel; M R Vogt; J Schmidt
Spectra-Dependent Stability of the Passivation Quality of Al2O3/c-Si Interfaces Artikel
In: IEEE Journal of Photovoltaics, Bd. 8, Nr. 1, S. 96-102, 2018, ISSN: 2156-3381.
@article{Veith-Wolf2018,
title = {Spectra-Dependent Stability of the Passivation Quality of Al2O3/c-Si Interfaces},
author = {B Veith-Wolf and R Witteck and A Morlier and H Schulte-Huxel and M R Vogt and J Schmidt},
doi = {10.1109/JPHOTOV.2017.2775147},
issn = {2156-3381},
year = {2018},
date = {2018-01-01},
journal = {IEEE Journal of Photovoltaics},
volume = {8},
number = {1},
pages = {96-102},
abstract = {We examine the stability of the c-Si surface passivation quality by spatial atomic-layer-deposited aluminum oxide (Al2O3), plasma-enhanced chemical vapor deposited silicon nitride (SiNx), and Al2O3/SiNx stacks under illumination with two different spectra. The Al2O3-passivated c-Si surfaces annealed at 350 °C show a weak degradation due to UV illumination, with surface recombination velocities (SRVs) of 122 cm/s after receiving a ultraviolet (UV) dose of 275 kWh/m2. Silicon samples passivated with Al2O3 layers that received a fast-firing step show an improvement due to UV illumination with a reduction of the SRVs initially from 14 to 5 cm/s for single Al2O3 layers. For the fired Al2O3 layers the negative fixed charge density increases from -6×1012 cm-2 up to -1.2×1013 cm-2 during UV illumination. We demonstrate that for the SiNx and the fired Al2O3 single layers, photons with energy greater than 3.4 eV are necessary to reduce the passivation quality. In contrast, low-temperature-annealed Al2O3 single layers and nonfired Al2O3/SiNx stacks showed a degradation already under illumination with a halogen lamp. Importantly, we observe a perfectly stable passivation on boron-diffused p+ emitter for fired Al2O3/SiNx stacks featuring a stable saturation current density of 18 fA/cm2 for a p+ sheet resistance of 90 Ω/sq.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
D C Walter; R Falster; V V Voronkov; J Schmidt
On the equilibrium concentration of boron-oxygen defects in crystalline silicon Artikel
In: Solar Energy Materials and Solar Cells, Bd. 173, S. 33-36, 2017, ISBN: 0927-0248, (Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics).
@article{Walter2017b,
title = {On the equilibrium concentration of boron-oxygen defects in crystalline silicon},
author = {D C Walter and R Falster and V V Voronkov and J Schmidt},
doi = {10.1016/j.solmat.2017.06.036},
isbn = {0927-0248},
year = {2017},
date = {2017-12-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {173},
pages = {33-36},
abstract = {We determine the equilibrium concentration of the BO defect in boron-doped Czochralski-grown silicon after prolonged (up to 150 h) annealing at relatively low temperatures between 200 and 300 °C. We show that after sample processing, the BO concentration has not necessarily reached the equilibrium state. The actually reached state depends on the detailed temperature profile of the last temperature treatment before the light-induced degradation (LID) is performed. For the investigated Cz-Si materials with base resistivities ranging between 0.5 and 2.5 Ω cm, we observe that an annealing step at 200 °C for 50 h establishes the equilibrium, independent of the base resistivity. Experiments performed at different temperatures reveal that the equilibrium defect concentration decreases with increasing annealing temperature. This observation can be understood, assuming a mobile species which is distributed between at least two different sinks. A possible defect model is discussed.},
note = {Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
J Krügener; F Haase; M Rienäcker; R Brendel; H J Osten; R Peibst
In: Solar Energy Materials and Solar Cells, Bd. 173, S. 85-91, 2017, ISSN: 0927-0248, (Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics).
@article{Krügener2017b,
title = {Improvement of the SRH bulk lifetime upon formation of n-type POLO junctions for 25% efficient Si solar cells},
author = {J Krügener and F Haase and M Rienäcker and R Brendel and H J Osten and R Peibst},
doi = {10.1016/j.solmat.2017.05.055},
issn = {0927-0248},
year = {2017},
date = {2017-12-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {173},
pages = {85-91},
abstract = {Carrier-selective contact schemes, like polysilicon on oxide (POLO), provide low contact resistivities while preserving an excellent passivation quality. These junctions offer an important additional feature compared to a-Si/c-Si heterojunctions. We find that the formation of n-type POLO junctions lead to a huge increase of the Shockley-Read-Hall (SRH) lifetime of the substrate, a prerequisite for highly efficient solar cells. The SRH lifetime improvement can be observed for both bulk polarities and for a variety of bulk resistivities. Thus we suggest that the highly doped POLO junction getters impurities that have more or less symmetric SRH capture cross sections. We are able to achieve SRH lifetimes of > 50 ms. By applying POLO junctions to interdigitated back contact cells, we achieve cells with an efficiency of 25%.},
note = {Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
D Tetzlaff; J Krügener; Y Larionova; S Reiter; M Turcu; F Haase; R Brendel; R Peibst; U Höhne; J -D Kähler; T F Wietler
In: Solar Energy Materials and Solar Cells, Bd. 173, S. 106-110, 2017, ISSN: 0927-0248, (Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics).
@article{Tetzlaff2017c,
title = {A simple method for pinhole detection in carrier selective POLO-junctions for high efficiency silicon solar cells},
author = {D Tetzlaff and J Krügener and Y Larionova and S Reiter and M Turcu and F Haase and R Brendel and R Peibst and U Höhne and J -D Kähler and T F Wietler},
doi = {10.1016/j.solmat.2017.05.041},
issn = {0927-0248},
year = {2017},
date = {2017-12-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {173},
pages = {106-110},
abstract = {Polycrystalline silicon (poly-Si) layers on thin silicon oxide films have received strong research interest as they form excellent carrier selective junctions on crystalline silicon substrates after appropriate thermal processing. Recently, we presented a new method to determine the pinhole density in interfacial oxide films of poly-Si on oxide (POLO)-junctions with excellent electrical properties. The concept of magnification of nanometer-size pinholes in the interfacial oxide by selective etching of the underlying crystalline silicon is used to investigate the influence of annealing temperature on pinhole densities. Eventually, the pinholes are detected by optical microscopy and scanning electron microscopy. We present results on the pinhole density in POLO-junctions with J0 values as low as 1.4 fA/cm2. The stability of this method is demonstrated by proving that no new holes are introduced to the oxide during the etching procedure for a wide range of etching times. Finally, we show the applicability to multiple oxide types and thickness values, differently doped poly-Si layers as well as several types of wafer surface morphologies. For wet chemically grown oxides, we verified the existence of pinholes with an areal density of 2×10^7 cm−2 even already after annealing at a temperature of 750 °C (lower than the optimum annealing temperature for these junctions).},
note = {Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
D Bredemeier; D Walter; J Schmidt
In: Solar Energy Materials and Solar Cells, Bd. 173, S. 2-5, 2017, ISSN: 0927-0248, (Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics).
@article{Bredemeier2017b,
title = {Light-induced lifetime degradation in high-performance multicrystalline silicon: Detailed kinetics of the defect activation},
author = {D Bredemeier and D Walter and J Schmidt},
doi = {10.1016/j.solmat.2017.08.007},
issn = {0927-0248},
year = {2017},
date = {2017-12-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {173},
pages = {2-5},
abstract = {We examine the defect activation kinetics in block-cast high-performance multicrystalline silicon (HP mc-Si) under illumination at elevated temperature. Our lifetime analysis shows that the observed light-induced lifetime degradation consists of two separate stages: a fast stage followed by a slow stage. Our experiments reveal that both degradation stages can be fitted using a sum of two exponential decay functions. The resulting degradation rate constants depend both on the temperature and the light intensity applied during degradation. For the fast component, we determine an activation energy of (0.89 ± 0.04) eV from an Arrhenius plot of the degradation rate and for the slow component we determine a value of (0.94 ± 0.06) eV. The activation energies are relatively large, leading to a very pronounced dependence of the degradation rates on temperature. We also observe that both degradation rates show a linear dependence on the applied light intensity during degradation in the examined intensity range between 0.25 and 1.5 suns.},
note = {Proceedings of the 7th international conference on Crystalline Silicon Photovoltaics},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
T Dullweber; H Schulte-Huxel; S Blankemeyer; H Hannebauer; S Schimanke; U Baumann; R Witteck; R Peibst; M Köntges; R Brendel; Y Yao
Industrial implementation of bifacial PERC+ solar cells and modules: Present status and future opportunities Sonstige
Photovoltaics International Volume 38, 2017.
@misc{Dullweber2017c,
title = {Industrial implementation of bifacial PERC+ solar cells and modules: Present status and future opportunities},
author = {T Dullweber and H Schulte-Huxel and S Blankemeyer and H Hannebauer and S Schimanke and U Baumann and R Witteck and R Peibst and M Köntges and R Brendel and Y Yao},
year = {2017},
date = {2017-12-01},
abstract = {Since its first publication in 2015, the PERC+ cell concept, which is based on a passivated emitter and rear cell (PERC) design with a screen-printed Al finger grid on the rear, has been rapidly adopted by several solar cell manufacturers worldwide. The rapid industrial implementation of bifacial PERC+ cells is facilitated by the very similar process technology to that of mainstream monofacial PERC cells. Conversion efficiencies of industrial PERC+ solar cells of up to 22.1% (ISFH) with front-side illumination, and of 17.3% (LONGi) with rear-side illumination, have been reported. Meanwhile, four companies offer commercial bifacial PERC+ modules with a maximum rated power of around 200 Wp when illuminated from the front side only. These modules incorporate 60 PERC+ cells with four or five busbars, which are interconnected by conventional stringing and tabbing technology. The first small-scale outdoor installations have confirmed an increase in energy yield relative to monofacial PERC modules of between 13 and 22%. Two large-scale outdoor installations with peak capacities of 2 MWp and 20 MWp are currently under construction in Taiwan in China respectively. A novel bifacial PERC+ prototype module that uses Smart Wire Connection Technology (SWCT) is reported in this paper: a set of 18 halved PERC+ solar cells are interconnected by soldering 18 wires directly to the Ag front and Al rear fingers. The resulting prototype module exhibits independently confirmed front- and rear-side efficiencies of 19.8% and 16.4% respectively. Additionally, Meyer Burger has certified a full-size PERC+ SWCT module in accordance with the IEC 61215 norm, thereby demonstrating the long-term reliability of this novel module technology.},
howpublished = {Photovoltaics International Volume 38},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
S Helbig; M Adam; D Eggert
Energetic and Economic Efficiency Evaluation of Solar Assisted Heating Systems for Multi-Family Houses Proceedings Article
In: ISES, (Hrsg.): Conference Proceedings 33rd Solar World Congress 2017 / 5th SHC Conference, Abu Dhabi, UAE, 2017.
@inproceedings{Helbig2017b,
title = {Energetic and Economic Efficiency Evaluation of Solar Assisted Heating Systems for Multi-Family Houses},
author = {S Helbig and M Adam and D Eggert},
editor = {ISES},
doi = {10.18086/swc.2017.29.04},
year = {2017},
date = {2017-11-02},
booktitle = {Conference Proceedings 33rd Solar World Congress 2017 / 5th SHC Conference},
address = {Abu Dhabi, UAE},
abstract = {For holistic efficiency evaluation of solar-assisted heating systems in multi-family houses common system designs are tested with hardware-in-the-loop measurements. The experimental results provide the basis for the subsequent energetic and economic efficiency analysis. A previously introduced efficiency measure called "central performance factor of the heating facility" (CPF) is used to evaluate energetic efficiency of the overall heating system. Using this measure it can be explained, how system designs comprising low heat distribution losses (e.g. 2-pipe heat distribution networks or an ultrafiltration module in the DHW circulation return flow) feature the highest CPF. Cost analysis show, however, that such designs incorporate elevated levelized cost of heat compared to the other systems under investigation. Carbon abatement cost are combining the energetic and economic evaluation into one parameter. The results show that concepts with a bivalent heat storage tank and a fresh water unit connected to a 4-pipe heat distribution network, are leading to the lowest carbon abatement cost, at a minimum value of 46 €/tCO2.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
B Schiebler; F Giovannetti; F Weiland
Experimental Evaluation of Evacuated Tube Collectors with Heat Pipes to Avoid Stagnation Loads in a Domestic Hot Water System Proceedings Article
In: ISES, (Hrsg.): Conference Proceedings 33rd Solar World Congress 2017 / 5th SHC Conference, Abu Dhabi, UAE, 2017.
@inproceedings{Schiebler2017b,
title = {Experimental Evaluation of Evacuated Tube Collectors with Heat Pipes to Avoid Stagnation Loads in a Domestic Hot Water System},
author = {B Schiebler and F Giovannetti and F Weiland},
editor = {ISES},
doi = {10.18086/swc.2017.31.16},
year = {2017},
date = {2017-11-02},
booktitle = {Conference Proceedings 33rd Solar World Congress 2017 / 5th SHC Conference},
address = {Abu Dhabi, UAE},
abstract = {Heat pipes in solar thermal collectors can reduce thermal loads in the solar circuit by using the physical effect of dry out limitation. By avoiding high temperatures and vapor formation, simplified, more reliable and cost effective solar thermal systems can be designed. The paper investigates a newly developed evacuated tube collector based on optimized heat pipes able to limit the temperature loads at the manifold up to a desired value. On the basis of efficiency measurements on a prototype heat pipe collector, we determine the annual yield of a collector field in a domestic hot water system compared to an identical system with direct flow collector according to ISO 9459-5. The results are validated by simulations with TRNSYS and show no significant difference between the performances of the two systems. By means of extensive outdoor stagnation tests on the same fields, we report a maximum temperature of 125 °C in the solar circuit of the heat pipe system, which is 95 K lower compared to temperature measured in the reference system.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
S Müller; F Giovannetti; B Hafner; R Reineke-Koch
Flat Plate Collectors with Thermochromic Absorber Coating Under Dynamic System Tests Proceedings Article
In: ISES, (Hrsg.): Conference Proceedings 33rd Solar World Congress 2017 / 5th SHC Conference, Abu Dhabi, UAE, 2017.
@inproceedings{Müller2017b,
title = {Flat Plate Collectors with Thermochromic Absorber Coating Under Dynamic System Tests},
author = {S Müller and F Giovannetti and B Hafner and R Reineke-Koch},
editor = {ISES},
doi = {10.18086/swc.2017.31.10},
year = {2017},
date = {2017-11-02},
booktitle = {Conference Proceedings 33rd Solar World Congress 2017 / 5th SHC Conference},
address = {Abu Dhabi, UAE},
abstract = {Thermochromic absorber coatings switch their emissivity for long wave radiation depending on the absorber temperature. Below the specific switching temperature of 68 °C the coating’s emittance is quite similar to a commercial, highly selective absorber coating (ε = 5 %). At higher absorber temperatures the emittance reaches ε ≈ 35 %, whereby the collector heat losses increase. As a result, the stagnation temperature is reduced by 30 K and an overheating or vaporization of the heat transfer fluid can be entirely prevented. We have carried out collector performance measurements according to ISO 9806. By means of dynamic system tests (ISO 9459 5) we predict the performance of a domestic hot water system with standard and thermochromic collectors. At typical daily tapping rates the marginally lower absorptance of the thermochromic coating raises the auxiliary energy demand up to 2.5 % and reduces the solar fraction by about 1 %-absolute. In additional system stagnation tests, we analyzed the stagnation behavior of thermochromic collectors, especially the vaporization of the heat transfer fluid, the steam expansion into the solar pipes and the thermal stagnation load on sensitive solar loop components. A reduction of the stagnation period by 60 % and a limitation of the stagnation temperature to 145 °C were investigated.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
A Morlier; M Siebert; I Kunze; G Mathiak; M Köntges
In: IEEE Journal of Photovoltaics, Bd. 7, Nr. 6, S. 1710-1716, 2017, ISSN: 2156-3381.
@article{Morlier2017b,
title = {Detecting Photovoltaic Module Failures in the Field During Daytime With Ultraviolet Fluorescence Module Inspection},
author = {A Morlier and M Siebert and I Kunze and G Mathiak and M Köntges},
doi = {10.1109/JPHOTOV.2017.2756452},
issn = {2156-3381},
year = {2017},
date = {2017-11-01},
journal = {IEEE Journal of Photovoltaics},
volume = {7},
number = {6},
pages = {1710-1716},
abstract = {We present the potential of ultraviolet fluorescence imaging for the detection of function and safety failures of photovoltaic modules in the field. We apply this method to detect hotspots, mismatched cells, power-loss-inducing cracks, and we show how we use it to evaluate the crack history of a module. We present a device able to acquire fluorescence images in the field in the daytime without disconnecting the modules and with a throughput of more than 200 modules per hour for a single operator. Furthermore, we show how the technique allows for the discrimination of specific damages caused to the photovoltaic modules by sudden events such as hailstorms. We demonstrate that this method possesses an informative potential comparable to both thermography and electroluminescence together with less practical limitations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
B Min; M Müller; H Wagner; G Fischer; R Brendel; P P Altermatt; H Neuhaus
A Roadmap Toward 24 % Efficient PERC Solar Cells in Industrial Mass Production Artikel
In: IEEE Journal of Photovoltaics, Bd. 7, Nr. 6, S. 1541-1550, 2017, ISSN: 2156-3381.
@article{Min2017c,
title = {A Roadmap Toward 24 % Efficient PERC Solar Cells in Industrial Mass Production},
author = {B Min and M Müller and H Wagner and G Fischer and R Brendel and P P Altermatt and H Neuhaus},
doi = {10.1109/JPHOTOV.2017.2749007},
issn = {2156-3381},
year = {2017},
date = {2017-11-01},
journal = {IEEE Journal of Photovoltaics},
volume = {7},
number = {6},
pages = {1541-1550},
abstract = {Many manufacturers choose the passivated emitter and rear cell (PERC) approach in order to surpass the 20% cell efficiency level in mass production. In this paper, we study the efficiency potential of the PERC approach under realistic assumptions for incremental improvements of existing technologies by device simulations. Based on the most recent published experimental results, we find that the PERC structure is able to reach about 24% cell efficiency in mass production by an ongoing sequence of incremental improvements. As a guideline for future developments, we provide a method to improve cell efficiency most effectively by monitoring the current losses at the maximum power point. By means of numerical device modeling, we identify some key technologies toward 24% efficient PERC cells and provide its technology-related target requirements.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
B A Veith-Wolf; J Schmidt
In: physica status solidi (RRL) – Rapid Research Letters, Bd. 11, Nr. 11, S. 1700235, 2017, ISSN: 1862-6270, (1700235).
@article{Veith-Wolf2017,
title = {Unexpectedly High Minority-Carrier Lifetimes Exceeding 20 ms Measured on 1.4-Ω cm n-Type Silicon Wafers},
author = {B A Veith-Wolf and J Schmidt},
doi = {10.1002/pssr.201700235},
issn = {1862-6270},
year = {2017},
date = {2017-11-01},
journal = {physica status solidi (RRL) – Rapid Research Letters},
volume = {11},
number = {11},
pages = {1700235},
publisher = {WILEY?VCH Verlag Berlin GmbH},
abstract = {We measure very high minority‐carrier lifetimes exceeding 20 ms on 1.4‐Ω cm n‐type Czochralski silicon wafers passivated using plasma‐assisted atomic‐layer‐deposited Al2O3 on both wafer surfaces. The measured maximum effective lifetimes are surprisingly high as they significantly exceed the intrinsic lifetime limit previously reported in the literature. We are able to measure such high lifetimes by realizing an exceptionally homogeneous Al2O3 surface passivation on large‐area samples (12.5 × 12.5 cm2). The importance of the homogeneous passivation is demonstrated by comparison with samples of locally reduced passivation quality.},
note = {1700235},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
S R Nabavi; F Haase; E Jansen; R Rolfes
In: Solar Energy Materials and Solar Cells, Bd. 170, S. 263-277, 2017, ISSN: 0927-0248.
@article{Nabavi2017b,
title = {Monte-Carlo simulation of the cofiring process in polycrystalline silicon solar cells: Effects of material heterogeneity and thickness uncertainties},
author = {S R Nabavi and F Haase and E Jansen and R Rolfes},
doi = {10.1016/j.solmat.2017.06.012},
issn = {0927-0248},
year = {2017},
date = {2017-10-01},
journal = {Solar Energy Materials and Solar Cells},
volume = {170},
pages = {263-277},
abstract = {During production, solar cells undergo significant thermomechanical loadings that lead to permanent deformations before being laminated in photovoltaic (PV) modules. One of these thermomechanical production processes is cofiring. In this work, the permanent deformation of solar cells after the cofiring process was investigated. The experimental measurements revealed a great scatter in the measured deflection at the deformed edges of the polycrystalline silicon solar cells after the cofiring process. A finite element (FE) framework was developed to investigate factors contributing to this scatter. The framework predicts the multistable response of the solar cell to the thermomechanical loading of the cofiring process. It accounts for the uncertainties arising from the heterogeneity of the polycrystalline silicon layer (grain orientations and non-uniform grain sizes) and uncertainties regarding the layer thicknesses of the silicon and aluminum paste. Employing the developed framework in a Monte-Carlo simulation the relative significance of the mentioned uncertainties on the deflection at the solar cell edge after the cofiring process was analyzed. Numerical results for a commercially produced polycrystalline silicon solar cell were compared with an analytical model and validated with experimental measurements.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
R Peibst; Y Larionova; S Reiter N Orlowski; S Schäfer; M Turcu; B Min; R Brendel; D Tetzlaff; J Krügener; T Wietler; U Höhne; J-D Kähler; H Mehlich; S Frigge
Industrial, Screen-Printed Double-Side Contacted Polo Cells Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 33rd European Photovoltaic Solar Energy Conference and Exhibition, S. 451-454, Amsterdam, The Netherlands, 2017, ISBN: 3-936338-47-7.
@inproceedings{Peibst2017,
title = {Industrial, Screen-Printed Double-Side Contacted Polo Cells},
author = {R Peibst and Y Larionova and S Reiter N Orlowski and S Schäfer and M Turcu and B Min and R Brendel and D Tetzlaff and J Krügener and T Wietler and U Höhne and J-D Kähler and H Mehlich and S Frigge},
editor = {WIP},
doi = {10.4229/EUPVSEC20172017-2DO.2.2},
isbn = {3-936338-47-7},
year = {2017},
date = {2017-09-28},
booktitle = {Proceedings of the 33rd European Photovoltaic Solar Energy Conference and Exhibition},
pages = {451-454},
address = {Amsterdam, The Netherlands},
abstract = {We demonstrate an industrial double-side-contacted, screen-printed large area cell with POLO junctions on both sides and an in-house-measured energy conversion efficiency of 22.3 % (A = 244.15 cm2},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
D C Walter; V Steckenreiter; L Helmich; T Pernau; J Schmidt
Production-Compatible Regeneration of Boron-Doped Czochralski-Silicon in a Combined Fast-Firing and Regeneration Belt-Line Furnace Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 33rd European Photovoltaic Solar Energy Conference and Exhibition, S. 377-381, Amsterdam, The Netherlands, 2017, ISBN: 3-936338-47-7.
@inproceedings{Walter2017,
title = {Production-Compatible Regeneration of Boron-Doped Czochralski-Silicon in a Combined Fast-Firing and Regeneration Belt-Line Furnace},
author = {D C Walter and V Steckenreiter and L Helmich and T Pernau and J Schmidt},
editor = {WIP},
doi = {10.4229/EUPVSEC20172017-2CO.9.4},
isbn = {3-936338-47-7},
year = {2017},
date = {2017-09-27},
booktitle = {Proceedings of the 33rd European Photovoltaic Solar Energy Conference and Exhibition},
pages = {377-381},
address = {Amsterdam, The Netherlands},
abstract = {Boron-doped Czochralski-grown silicon (Cz-Si), as used in the industrial production of solar cells today, is suffering from a light-induced degradation (LID) of the carrier lifetime during illumination. It has been known since a decade that under lab conditions, this degradation can be permanently cured by illumination at increased temperature, which has been known as ‘regeneration’ treatment. In this contribution, we examine the permanent regeneration of the carrier lifetime in standard boron-doped Cz-Si using an industrial combined fast-firing and regeneration furnace - the c.FIRE REG of centrotherm photovoltaics. Our study reveals that for an optimized firing and regeneration process, very high implied open-circuit voltages Voc.impl exceeding 740 mV are achieved on standard 1-2 cm p-type Cz-Si wafers. These very high measured Voc.impl values clearly indicate the suitability of the process for highly efficient PERC cell production. Additionally, as the c.FIRE REG furnace is realized in a belt-line configuration, which exposes each wafer for less than 70 s to the firing and regeneration conditions, our experiments clearly demonstrate the excellent suitability of the examined tool for the implementation into industrial solar cell production lines. We also demonstrate the successful application to industrial PERC solar cells produced by two different manufacturers.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
G Mathiak; N Pfeiffer; L Rimmelspacher; W Herrmann; J Althaus; F Reil; C Holze; A Morlier
PV Module Sand Abrasion Testing Proceedings Article
In: WIP, (Hrsg.): Proceedings of the 33rd European Photovoltaic Solar Energy Conference and Exhibition, S. 1383-1390, Amsterdam, The Netherlands, 2017, ISBN: 3-936338-47-7.
@inproceedings{Mathiak2017,
title = {PV Module Sand Abrasion Testing},
author = {G Mathiak and N Pfeiffer and L Rimmelspacher and W Herrmann and J Althaus and F Reil and C Holze and A Morlier},
editor = {WIP},
doi = {10.4229/EUPVSEC20172017-5CO.5.2},
isbn = {3-936338-47-7},
year = {2017},
date = {2017-09-27},
booktitle = {Proceedings of the 33rd European Photovoltaic Solar Energy Conference and Exhibition},
pages = {1383-1390},
address = {Amsterdam, The Netherlands},
abstract = {Due to the high solar irradiation and the large number of sunny days the use of large PV systems in desert areas is very profitable. However, the PV modules are exposed to harsh environmental conditions such as high temperatures, high UV radiation or sandstorms. Currently there is no suitable standardized method for testing the abrasion resistance of PV modules and solar glass under sandstorm conditions. Qualification testing of PV modules for arid climate conditions will require to include a sand abrasion test and a dry cleaning resistivity test. In order to be able to assess the individual influencing factors in more detail, this work examines the sand trickling tests defined in DIN 52348 [1] and ASTM D968-05 [2] in detail. Furthermore, we developed a test facility, which can be used to simulate the impacts of desert sand on the surface of PV modules and solar glasses. Via transmittance and reflectance measurements on PV modules and solar glass sheets before and after sand abrasion tests, the samples are characterized and their resistance to desert conditions is assessed.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}