1.
B Schiebler; F Weiland; F Giovannetti; O Kastner; S Jack
Improved flat plate collector with heat pipesfor overheating prevention in solar thermal systems Proceedings Article
In: Proceedings ISES Solar World Congress 2019 / IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2019, S. 61-72, 2020.
@inproceedings{Schiebler2020,
title = {Improved flat plate collector with heat pipesfor overheating prevention in solar thermal systems},
author = {B Schiebler and F Weiland and F Giovannetti and O Kastner and S Jack},
doi = {10.18086/swc.2019.01.08},
year = {2020},
date = {2020-06-10},
booktitle = {Proceedings ISES Solar World Congress 2019 / IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2019},
pages = {61-72},
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. This paper presents a theoretical study ondifferentheat pipe andmanifoldconfigurationsfor flat plate collectors. The focus is ona highthermal efficiency in the operating rangeand a significant temperature limitation in stagnation mode. Several prototype collectorsaremanufactured and experimentallyinvestigated by means of indoor performance measurements. Thereby,a conversion factor of 73%isreported, whichrepresents an increase of 4percentage pointscompared to a previous prototype. Duringstagnationeventswe localizea maximum fluid temperature about130°C within the manifold, whichdecreases to values below 100°C towardsthe collector connections.Finally, we evaluate the system performance of the prototypewithanexemplary solar DHW-systemby means of dynamic TRNSYS-simulations. The results show that the calculated annual yield ispredictedonly 5% lower than the one of a comparabledirect flow collectorand critical stagnation eventscan be fully avoided.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
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. This paper presents a theoretical study ondifferentheat pipe andmanifoldconfigurationsfor flat plate collectors. The focus is ona highthermal efficiency in the operating rangeand a significant temperature limitation in stagnation mode. Several prototype collectorsaremanufactured and experimentallyinvestigated by means of indoor performance measurements. Thereby,a conversion factor of 73%isreported, whichrepresents an increase of 4percentage pointscompared to a previous prototype. Duringstagnationeventswe localizea maximum fluid temperature about130°C within the manifold, whichdecreases to values below 100°C towardsthe collector connections.Finally, we evaluate the system performance of the prototypewithanexemplary solar DHW-systemby means of dynamic TRNSYS-simulations. The results show that the calculated annual yield ispredictedonly 5% lower than the one of a comparabledirect flow collectorand critical stagnation eventscan be fully avoided.
2.
B Schiebler; S Jack; H Dieckmann; F Giovannetti
In: Solar Energy, Bd. 171, S. 271-278, 2018, ISSN: 0038-092X.
@article{Schiebler2018d,
title = {Experimental and theoretical investigations on temperature limitation in solar thermal collectors with heat pipes: Effect of superheating on the maximum temperature},
author = {B Schiebler and S Jack and H Dieckmann and F Giovannetti},
doi = {10.1016/j.solener.2018.06.036},
issn = {0038-092X},
year = {2018},
date = {2018-09-01},
journal = {Solar Energy},
volume = {171},
pages = {271-278},
abstract = {Heat pipes in solar thermal collectors enable to reduce the temperature loads in the solar circuit during stagnation periods by exploiting their dry-out limit. With this approach vapour formation in the solar circuit can be completely avoided, which is essential to reduce costs of solar thermal systems by simplified and more reliable solar circuits. The design of “deactivating” collector heat pipes with a desired maximum temperature requires a comprehensive understanding of the heat transfer processes in the heat pipe, in particular when dry-out takes place. We developed a model, which allows calculating the maximum fluid temperature in the collector for various working fluids. Compared to existing approaches, the effect of superheated vapour in the heat pipe during stagnation is additionally considered. The paper describes the theoretical model in detail and its extensive experimental validation. The results show that the model is able to predict the maximum fluid temperature with an accuracy better than 5 K. Based on parametric studies with different working fluids, we analyse and discuss the temperature limitation and its effect on the collector performance.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Heat pipes in solar thermal collectors enable to reduce the temperature loads in the solar circuit during stagnation periods by exploiting their dry-out limit. With this approach vapour formation in the solar circuit can be completely avoided, which is essential to reduce costs of solar thermal systems by simplified and more reliable solar circuits. The design of “deactivating” collector heat pipes with a desired maximum temperature requires a comprehensive understanding of the heat transfer processes in the heat pipe, in particular when dry-out takes place. We developed a model, which allows calculating the maximum fluid temperature in the collector for various working fluids. Compared to existing approaches, the effect of superheated vapour in the heat pipe during stagnation is additionally considered. The paper describes the theoretical model in detail and its extensive experimental validation. The results show that the model is able to predict the maximum fluid temperature with an accuracy better than 5 K. Based on parametric studies with different working fluids, we analyse and discuss the temperature limitation and its effect on the collector performance.
3.
F Giovannetti; M Kirchner; R Sass; G Rockendorf
Enameled Glass Panels for Solar Thermal Building Envelopes Artikel
In: Energy Procedia, Bd. 91, S. 49-55, 2016, ISSN: 1876-6102, (Proceedings of the 4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2015)).
@article{Giovannetti2016b,
title = {Enameled Glass Panels for Solar Thermal Building Envelopes},
author = {F Giovannetti and M Kirchner and R Sass and G Rockendorf},
doi = {10.1016/j.egypro.2016.06.170},
issn = {1876-6102},
year = {2016},
date = {2016-06-01},
journal = {Energy Procedia},
volume = {91},
pages = {49-55},
abstract = {The paper presents a novel concept of solar thermal panel specifically intended for building integration, aiming at a higher architectural quality and at a reduction of installation costs. The panel consists of a low-emissivity enameled flat glass as solar absorber and a metallic heat exchanger, which are glued together by an adhesive layer. It features high design flexibility and can be used as roof or façade cladding in combination with common frames and profiles. We analyze the potential of the panel both as uncovered and covered collector by means of efficiency measurements on large-sized prototypes according to ISO 9806. Our results show that panels equipped with black enameled glass can achieve performance values competitive with those of commercial available products (uncovered panel: η0 = 0.75},
note = {Proceedings of the 4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2015)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The paper presents a novel concept of solar thermal panel specifically intended for building integration, aiming at a higher architectural quality and at a reduction of installation costs. The panel consists of a low-emissivity enameled flat glass as solar absorber and a metallic heat exchanger, which are glued together by an adhesive layer. It features high design flexibility and can be used as roof or façade cladding in combination with common frames and profiles. We analyze the potential of the panel both as uncovered and covered collector by means of efficiency measurements on large-sized prototypes according to ISO 9806. Our results show that panels equipped with black enameled glass can achieve performance values competitive with those of commercial available products (uncovered panel: η0 = 0.75
4.
S Föste; B Schiebler; F Giovannetti; G Rockendorf; S Jack
Butane Heat Pipes for Stagnation Temperature Reduction of Solar Thermal Collectors Artikel
In: Energy Procedia, Bd. 91, S. 35-41, 2016, ISSN: 1876-6102, (Proceedings of the 4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2015)).
@article{Föste2016b,
title = {Butane Heat Pipes for Stagnation Temperature Reduction of Solar Thermal Collectors},
author = {S Föste and B Schiebler and F Giovannetti and G Rockendorf and S Jack},
doi = {10.1016/j.egypro.2016.06.168},
issn = {1876-6102},
year = {2016},
date = {2016-06-01},
journal = {Energy Procedia},
volume = {91},
pages = {35-41},
abstract = {Heat pipes in solar thermal collectors enable to reduce the temperature loads in the solar circuit during stagnation periods by exploiting their dry out limit. Typically water, pentane or acetone are used as heat transfer media in collector heat pipes. Butane is very suitable to reach a high temperature gradient of the dry out even if the maximum temperature in the fluid circuit should be designed to 120 ̊C or below. The paper presents experimental results with butane heat pipes that operate up to a maximum temperature of 120 ̊C with a high temperature gradient in the dry-out region. This ensures that the collector performance in the operating range (typically up to 100 ̊C) is not affected negatively by the dry-out. Different approaches to increase the thermal conductance of butane heat pipes by enhancing the inner surface of the condenser or of both, the condenser and the evaporator are experimentally assessed and discussed. Measurement results report an increase of the heat pipes’ thermal conductance from 3 W/K (standard geometry) to 23 W/K.},
note = {Proceedings of the 4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2015)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Heat pipes in solar thermal collectors enable to reduce the temperature loads in the solar circuit during stagnation periods by exploiting their dry out limit. Typically water, pentane or acetone are used as heat transfer media in collector heat pipes. Butane is very suitable to reach a high temperature gradient of the dry out even if the maximum temperature in the fluid circuit should be designed to 120 ̊C or below. The paper presents experimental results with butane heat pipes that operate up to a maximum temperature of 120 ̊C with a high temperature gradient in the dry-out region. This ensures that the collector performance in the operating range (typically up to 100 ̊C) is not affected negatively by the dry-out. Different approaches to increase the thermal conductance of butane heat pipes by enhancing the inner surface of the condenser or of both, the condenser and the evaporator are experimentally assessed and discussed. Measurement results report an increase of the heat pipes’ thermal conductance from 3 W/K (standard geometry) to 23 W/K.
5.
S Föste; A Pazidis; R Reineke-Koch; B Hafner; D Mercs; C Delord
Flat Plate Collectors with Thermochromic Absorber Coatings to Reduce Loads During Stagnation Artikel
In: Energy Procedia, Bd. 91, S. 42-48, 2016, ISSN: 1876-6102, (Proceedings of the 4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2015)).
@article{Föste2016c,
title = {Flat Plate Collectors with Thermochromic Absorber Coatings to Reduce Loads During Stagnation},
author = {S Föste and A Pazidis and R Reineke-Koch and B Hafner and D Mercs and C Delord},
doi = {10.1016/j.egypro.2016.06.169},
issn = {1876-6102},
year = {2016},
date = {2016-06-01},
journal = {Energy Procedia},
volume = {91},
pages = {42-48},
abstract = {Thermochromic absorber coatings, which switch their emissivity for thermal radiation depending on temperature, are developed to reduce the stagnation temperature of solar thermal collectors: In the operating range of the collector, the surface exhibits a low emissivity (ɛ = 10%). At higher temperatures, the emissivity is increased by a multiple (ɛ = 35%). Thus, the collector heat losses raise and the stagnation temperature is reduced. Efficiency measurements on a prototype collector employing this thermochromic absorber show, that below the switching temperature the efficiency is nearly identical to that of a conventional collector with a highly selective absorber plate. Due to the increased emissivity in the switched state of the coating, the stagnation temperature is lowered by more than 30 K. System simulations exhibit, that the performance of the system is not significantly affected: in a combined system for space heating and domestic hot water preparation the conventional energy demand of the gas boiler is increased by 1.5% to 4.5% using the thermochromic collector instead of a standard collector. In contrast, the duration when formation of vapour in the collector circuit occurs, is reduced by 70% to 75%. By further optimizing thermochromic collectors, the formation of vapour in the solar circuit could be completely prevented during stagnation. This would allow the use of lower cost materials in the solar circuit and reduce the cost of installation and maintenance of the solar circuit significantly.},
note = {Proceedings of the 4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2015)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Thermochromic absorber coatings, which switch their emissivity for thermal radiation depending on temperature, are developed to reduce the stagnation temperature of solar thermal collectors: In the operating range of the collector, the surface exhibits a low emissivity (ɛ = 10%). At higher temperatures, the emissivity is increased by a multiple (ɛ = 35%). Thus, the collector heat losses raise and the stagnation temperature is reduced. Efficiency measurements on a prototype collector employing this thermochromic absorber show, that below the switching temperature the efficiency is nearly identical to that of a conventional collector with a highly selective absorber plate. Due to the increased emissivity in the switched state of the coating, the stagnation temperature is lowered by more than 30 K. System simulations exhibit, that the performance of the system is not significantly affected: in a combined system for space heating and domestic hot water preparation the conventional energy demand of the gas boiler is increased by 1.5% to 4.5% using the thermochromic collector instead of a standard collector. In contrast, the duration when formation of vapour in the collector circuit occurs, is reduced by 70% to 75%. By further optimizing thermochromic collectors, the formation of vapour in the solar circuit could be completely prevented during stagnation. This would allow the use of lower cost materials in the solar circuit and reduce the cost of installation and maintenance of the solar circuit significantly.
6.
F Giovannetti; M Kirchner
Performance and reliability of insulated glass collector prototypes Proceedings Article
In: ISES, (Hrsg.): Conference Proceedings EuroSun 2014, Aix-les-Bains, France, 2014.
@inproceedings{Giovannetti2014cb,
title = {Performance and reliability of insulated glass collector prototypes},
author = {F Giovannetti and M Kirchner},
editor = {ISES},
doi = {10.18086/eurosun.2014.16.07},
year = {2014},
date = {2014-09-19},
booktitle = {Conference Proceedings EuroSun 2014},
address = {Aix-les-Bains, France},
abstract = {Insulated glass collectors represent a novel design intended for improved building integration, combining a multiple window glazing with a flat plate collector. Gas-filled gaps and low-emittance glass coatings can provide for a high performance, comparable to that of commercially available flat plate products by reducing the overall thickness from 90-100 mm to 50 mm. The paper presents the results of our investigations on optimized triple-glazed, argon-filled prototypes. Aim of the work is to compare different absorber technologies and integration solutions and to identify the most suitable design with regards to aesthetical appearance and long-term reliability. Efficiency measurements according to EN ISO 9806 confirm the findings of previous investigations: zero-loss efficiency η0 between 0.74 and 0.79 as well as an effective heat loss coefficient a40 between 4.2 and 4.5 W/m²K are reported, depending on the specific design considered. Indoor and outdoor reliability tests show promising results: no significant decrease of gas concentration has been detected in most cases and no degradation of the collector components, even after long-term exposure. Due to the gas-tightness of the unit, outgassing has been identified as a critical aspect to be taken into special consideration in the collector design and in the choice of components and materials.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Insulated glass collectors represent a novel design intended for improved building integration, combining a multiple window glazing with a flat plate collector. Gas-filled gaps and low-emittance glass coatings can provide for a high performance, comparable to that of commercially available flat plate products by reducing the overall thickness from 90-100 mm to 50 mm. The paper presents the results of our investigations on optimized triple-glazed, argon-filled prototypes. Aim of the work is to compare different absorber technologies and integration solutions and to identify the most suitable design with regards to aesthetical appearance and long-term reliability. Efficiency measurements according to EN ISO 9806 confirm the findings of previous investigations: zero-loss efficiency η0 between 0.74 and 0.79 as well as an effective heat loss coefficient a40 between 4.2 and 4.5 W/m²K are reported, depending on the specific design considered. Indoor and outdoor reliability tests show promising results: no significant decrease of gas concentration has been detected in most cases and no degradation of the collector components, even after long-term exposure. Due to the gas-tightness of the unit, outgassing has been identified as a critical aspect to be taken into special consideration in the collector design and in the choice of components and materials.
7.
S Föste; S Jack; B Schiebler; F Giovannetti; G Rockendorf
Heat Pipe Collectors for Cost Reduction of Solar Installations Proceedings Article
In: ISES, (Hrsg.): Conference Proceedings EuroSun 2014, Aix-les-Bains, France, 2014.
@inproceedings{Föste2014bb,
title = {Heat Pipe Collectors for Cost Reduction of Solar Installations},
author = {S Föste and S Jack and B Schiebler and F Giovannetti and G Rockendorf},
editor = {ISES},
doi = {10.18086/eurosun.2014.16.06},
year = {2014},
date = {2014-09-19},
booktitle = {Conference Proceedings EuroSun 2014},
address = {Aix-les-Bains, France},
abstract = {Heat pipes in solar thermal collectors offer the advantage of a simpler hydraulic interconnection of the solar circuit while reducing the system load during stagnation compared to direct flow collectors. Within a research project, we basically analyzed heat pipe solutions for collectors, developed design methods and optimization potential and investigated the integration of heat pipes in flat plate collectors. Novel flat plate collector prototypes with an inherent overheating protection have been built and tested successfully. The maximum fluid temperature was limited to 140 °C, thus compared to a direct flow collector, a temperature decrease of more than 40 K is achieved. This paper presents the developed technology and explains, that the transfer of complexity from the system to the collector by the use of heat pipes can lead to a reduction of system costs of more than 25 %.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Heat pipes in solar thermal collectors offer the advantage of a simpler hydraulic interconnection of the solar circuit while reducing the system load during stagnation compared to direct flow collectors. Within a research project, we basically analyzed heat pipe solutions for collectors, developed design methods and optimization potential and investigated the integration of heat pipes in flat plate collectors. Novel flat plate collector prototypes with an inherent overheating protection have been built and tested successfully. The maximum fluid temperature was limited to 140 °C, thus compared to a direct flow collector, a temperature decrease of more than 40 K is achieved. This paper presents the developed technology and explains, that the transfer of complexity from the system to the collector by the use of heat pipes can lead to a reduction of system costs of more than 25 %.
8.
S Föste; F Giovannetti; N Ehrmann; G Rockendorf
Performance and Reliability of a High Efficiency Flat Plate Collector – Final Results on Prototypes Artikel
In: Energy Procedia, Bd. 48, S. 48-57, 2014, ISSN: 1876-6102, (Proceedings of the 2nd International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2013)).
@article{Föste2014b,
title = {Performance and Reliability of a High Efficiency Flat Plate Collector – Final Results on Prototypes},
author = {S Föste and F Giovannetti and N Ehrmann and G Rockendorf},
doi = {10.1016/j.egypro.2014.02.007},
issn = {1876-6102},
year = {2014},
date = {2014-04-01},
journal = {Energy Procedia},
volume = {48},
pages = {48-57},
note = {Proceedings of the 2nd International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2013)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
9.
F Giovannetti; M Kirchner; F Kliem; T Hoeltje
Development of an Insulated Glass Solar Thermal Collector Artikel
In: Energy Procedia, Bd. 48, S. 58-66, 2014, ISSN: 1876-6102, (Proceedings of the 2nd International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2013)).
@article{Giovannetti2014c,
title = {Development of an Insulated Glass Solar Thermal Collector},
author = {F Giovannetti and M Kirchner and F Kliem and T Hoeltje},
doi = {10.1016/j.egypro.2014.02.008},
issn = {1876-6102},
year = {2014},
date = {2014-04-01},
journal = {Energy Procedia},
volume = {48},
pages = {58-66},
note = {Proceedings of the 2nd International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2013)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
10.
S Jack; J Parzefall; T Luttmann; P Janßen; F Giovannetti
Flat Plate Aluminum Heat Pipe Collector with Inherently Limited Stagnation Temperature Artikel
In: Energy Procedia, Bd. 48, S. 105-113, 2014, ISSN: 1876-6102, (Proceedings of the 2nd International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2013)).
@article{Jack2014b,
title = {Flat Plate Aluminum Heat Pipe Collector with Inherently Limited Stagnation Temperature},
author = {S Jack and J Parzefall and T Luttmann and P Janßen and F Giovannetti},
doi = {10.1016/j.egypro.2014.02.013},
issn = {1876-6102},
year = {2014},
date = {2014-04-01},
journal = {Energy Procedia},
volume = {48},
pages = {105-113},
note = {Proceedings of the 2nd International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2013)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
11.
F Giovannetti; S Föste; N Ehrmann; G Rockendorf
In: Energy Procedia, Bd. 30, S. 106-115, 2012, ISSN: 1876-6102, (1st International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2012)).
@article{Giovannetti2012b,
title = {High transmittance, Low Emissivity Glass Covers for Flat Plate Collectors: Applications and Performance},
author = {F Giovannetti and S Föste and N Ehrmann and G Rockendorf},
doi = {10.1016/j.egypro.2012.11.014},
issn = {1876-6102},
year = {2012},
date = {2012-12-01},
journal = {Energy Procedia},
volume = {30},
pages = {106-115},
note = {1st International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2012)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
12.
S Föste; N Ehrmann; F Giovannetti; G Rockendorf
Basics for the Development of a High Efficiency Flat Plate Collector with a Selectively Coated Double Glazing Proceedings Article
In: ISES, (Hrsg.): Proceedings of the ISES Solar World Congress 2011, Kassel, Germany, 2011.
@inproceedings{Föste2011,
title = {Basics for the Development of a High Efficiency Flat Plate Collector with a Selectively Coated Double Glazing},
author = {S Föste and N Ehrmann and F Giovannetti and G Rockendorf},
editor = {ISES},
doi = {10.18086/swc.2011.19.14},
year = {2011},
date = {2011-09-02},
booktitle = {Proceedings of the ISES Solar World Congress 2011},
address = {Kassel, Germany},
abstract = {Many future applications of solar thermal energy, like heating with a high solar fraction and solar industrial process heat or solar cooling will require high collector efficiencies at temperatures above 80°C and/or at a low irradiance level. Advanced flat-plate collectors show a high potential for these applications, they are less expensive and mechanically simpler than evacuated tube collectors. To raise the performance of flat-plate collectors the thermal resistance of the transparent cover has to be increased, while keeping the solar transmittance at a high level. Within a research project1 ISFH achieved this goal by adding a second glass pane with a low emitting coating and using argon in the hermetically sealed gap, thus reducing heat losses by both convection and radiation (see Fig. 1). A high solar transmittance must be realized by using high quality glass with antireflective coatings and an optimized low-e coating. Long term reliability of the coated glass as well as of the glazing system for the use in solar thermal collectors has to be assured. The objective of the project is to assess the technological and scientific basics for this collector concept. This paper gives an overview of the main project results.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Many future applications of solar thermal energy, like heating with a high solar fraction and solar industrial process heat or solar cooling will require high collector efficiencies at temperatures above 80°C and/or at a low irradiance level. Advanced flat-plate collectors show a high potential for these applications, they are less expensive and mechanically simpler than evacuated tube collectors. To raise the performance of flat-plate collectors the thermal resistance of the transparent cover has to be increased, while keeping the solar transmittance at a high level. Within a research project1 ISFH achieved this goal by adding a second glass pane with a low emitting coating and using argon in the hermetically sealed gap, thus reducing heat losses by both convection and radiation (see Fig. 1). A high solar transmittance must be realized by using high quality glass with antireflective coatings and an optimized low-e coating. Long term reliability of the coated glass as well as of the glazing system for the use in solar thermal collectors has to be assured. The objective of the project is to assess the technological and scientific basics for this collector concept. This paper gives an overview of the main project results.
13.
F Giovannetti; O Kehl; M Kirchner; G Rockendorf
Cellulose Triacetate Honeycomb Compounds for Improved Flat-Plate Collectors: Performance and Reliability Proceedings Article
In: ISES, (Hrsg.): Proceedings of the ISES Solar World Congress 2011, Kassel, Germany, 2011.
@inproceedings{Giovannetti2011,
title = {Cellulose Triacetate Honeycomb Compounds for Improved Flat-Plate Collectors: Performance and Reliability},
author = {F Giovannetti and O Kehl and M Kirchner and G Rockendorf},
editor = {ISES},
doi = {10.18086/swc.2011.19.15},
year = {2011},
date = {2011-09-02},
booktitle = {Proceedings of the ISES Solar World Congress 2011},
address = {Kassel, Germany},
abstract = {Honeycomb structures are a well known device to reduce convective and radiative heat losses in solar thermal flat-plate collectors, thus improving their efficiency at high temperature and/or low irradiance (Hollands, 1965). Despite several investigations of the last decades no suitable material has been found so far which can provide for the requested high performance and durability at reasonable costs. A commercially available modified cellulose triacetate film, already in use assembled in honeycomb compounds as transparent insulation, exhibits promising properties. The present work experimentally investigates the suitability of these compounds for solar thermal applications, focusing on their performance and long-term reliability. Beside this commercial product, other kinds of acetate films were tested. Special attention is given to the ageing effects caused by UV radiation and high temperature as well as on outgassing, which are collector specific occurrences, not considered by the technical specifications of the materials and not yet reported in the literature.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Honeycomb structures are a well known device to reduce convective and radiative heat losses in solar thermal flat-plate collectors, thus improving their efficiency at high temperature and/or low irradiance (Hollands, 1965). Despite several investigations of the last decades no suitable material has been found so far which can provide for the requested high performance and durability at reasonable costs. A commercially available modified cellulose triacetate film, already in use assembled in honeycomb compounds as transparent insulation, exhibits promising properties. The present work experimentally investigates the suitability of these compounds for solar thermal applications, focusing on their performance and long-term reliability. Beside this commercial product, other kinds of acetate films were tested. Special attention is given to the ageing effects caused by UV radiation and high temperature as well as on outgassing, which are collector specific occurrences, not considered by the technical specifications of the materials and not yet reported in the literature.
14.
S Föste; F Limprecht; N Tiedemann; G Rockendorf
Heat Losses of Highly Efficient Flat Plate Collectors with a Selectively Coated Double Glazing Proceedings Article
In: ISES, (Hrsg.): Conference Proceedings EuroSun 2010, Graz, Austria, 2010.
@inproceedings{Föste2010,
title = {Heat Losses of Highly Efficient Flat Plate Collectors with a Selectively Coated Double Glazing},
author = {S Föste and F Limprecht and N Tiedemann and G Rockendorf},
editor = {ISES},
doi = {10.18086/eurosun.2010.09.10},
year = {2010},
date = {2010-10-01},
booktitle = {Conference Proceedings EuroSun 2010},
address = {Graz, Austria},
abstract = {The heat losses of a flat plate collector with a selectively coated double glazing depend among other parameters on the height of the two gas-filled gaps. Within the hermetically sealed glazing cavity inert gases instead of air can be used to decrease the convective heat transfer. To identify the impact of the mentioned parameters, heat loss measurements at a prototype collector were carried out. Therefore the gap sizes were varied and as filling gases of the glazing cavities air, argon and krypton were applied. For each filling gas optimum gap sizes are experimentally identified. These results are in accordance to the Nusselt-equation developed by Hollands . Further the impact of different inclination angles on the heat losses of the collector was determined experimentally.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The heat losses of a flat plate collector with a selectively coated double glazing depend among other parameters on the height of the two gas-filled gaps. Within the hermetically sealed glazing cavity inert gases instead of air can be used to decrease the convective heat transfer. To identify the impact of the mentioned parameters, heat loss measurements at a prototype collector were carried out. Therefore the gap sizes were varied and as filling gases of the glazing cavities air, argon and krypton were applied. For each filling gas optimum gap sizes are experimentally identified. These results are in accordance to the Nusselt-equation developed by Hollands . Further the impact of different inclination angles on the heat losses of the collector was determined experimentally.