1.
S Müller; F Giovannetti; R Reineke-Koch; O Kastner; B Hafner
In: Solar Energy, Bd. 188, S. 865 - 874, 2019, ISSN: 0038-092X.
@article{Müller2019c,
title = {Simulation study on the efficiency of thermochromic absorber coatings for solar thermal flat-plate collectors},
author = {S Müller and F Giovannetti and R Reineke-Koch and O Kastner and B Hafner},
doi = {10.1016/j.solener.2019.06.064},
issn = {0038-092X},
year = {2019},
date = {2019-08-01},
journal = {Solar Energy},
volume = {188},
pages = {865 - 874},
abstract = {We present a comparative simulative study to evaluate the efficiency and stagnation behavior of commercially available absorber coatings for solar thermal flat-plate collectors. A market survey has revealed different absorber coatings, which exhibit solar absorptances of α > 90% and thermal emittances ε of 5–90%. All these coatings can be classified as wet-chemically electroplated coatings on the basis of black chrome, highly selective sputtered PVD coatings, solar paints and novel thermochromic coatings. We calculated the annual solar collector energy output by means of collector simulations with the tool ScenoCalc and compared the collector efficiency of several absorber coatings. We have carried out TRNSYS simulations both with systems for solar domestic hot water preparation and solar-assisted space heating. In a solar domestic hot water system with a daily tapping volume of 100 L we report an increase in the auxiliary energy demand of up to 6% with black chrome, 7% with thermochromic and 21% with solar paint coatings compared to sputtered PVD coatings. In a solar combisystem the increase in the auxiliary energy demand does not exceed 1.4% for thermochromic and black chrome coatings and 6.1% for solar paints. The stagnation period can be reduced from 178 h per year (PVD coatings) to 118 h, 62 h and 11 h for black chrome, thermochromic and solar paint coatings, respectively. The maximum absorber temperatures decrease from 175 °C (PVD coatings) to 165 °C for black chrome, 145 °C for thermochromic and 135 °C for solar paint coatings.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We present a comparative simulative study to evaluate the efficiency and stagnation behavior of commercially available absorber coatings for solar thermal flat-plate collectors. A market survey has revealed different absorber coatings, which exhibit solar absorptances of α > 90% and thermal emittances ε of 5–90%. All these coatings can be classified as wet-chemically electroplated coatings on the basis of black chrome, highly selective sputtered PVD coatings, solar paints and novel thermochromic coatings. We calculated the annual solar collector energy output by means of collector simulations with the tool ScenoCalc and compared the collector efficiency of several absorber coatings. We have carried out TRNSYS simulations both with systems for solar domestic hot water preparation and solar-assisted space heating. In a solar domestic hot water system with a daily tapping volume of 100 L we report an increase in the auxiliary energy demand of up to 6% with black chrome, 7% with thermochromic and 21% with solar paint coatings compared to sputtered PVD coatings. In a solar combisystem the increase in the auxiliary energy demand does not exceed 1.4% for thermochromic and black chrome coatings and 6.1% for solar paints. The stagnation period can be reduced from 178 h per year (PVD coatings) to 118 h, 62 h and 11 h for black chrome, thermochromic and solar paint coatings, respectively. The maximum absorber temperatures decrease from 175 °C (PVD coatings) to 165 °C for black chrome, 145 °C for thermochromic and 135 °C for solar paint coatings.
2.
S Helbig; J Steinweg; D Eggert; M Adam
Performance Testing and Optimization of Solar Assisted Heating Systems for Multi Family Houses Proceedings Article
In: ISES, (Hrsg.): Conference Proceedings EuroSun 2016, Palma de Mallorca, Spain, 2016.
@inproceedings{Helbig2016,
title = {Performance Testing and Optimization of Solar Assisted Heating Systems for Multi Family Houses},
author = {S Helbig and J Steinweg and D Eggert and M Adam},
editor = {ISES},
doi = {10.18086/eurosun.2016.04.13},
year = {2016},
date = {2016-10-14},
booktitle = {Conference Proceedings EuroSun 2016},
address = {Palma de Mallorca, Spain},
abstract = {The variety of designs for solar assisted heating systems (also called solar combisystems) in multi-family houses is wide and has not been evaluated systematically. Functional insufficiencies, resulting from unfavorable device combinations as well as improper control design place significant market barriers for the application of this technology. Using hardware-in-the-loop tests, functional aspects of the most common system designs are investigated and evaluated. Further dynamic system simulations on an annual basis allow an energetic evaluation and later a comparison of the different design options. In this contribution we present the results for the first tested solar assisted heating system. Furthermore, the study suggests the introduction of a novel evaluation parameter referred to as the performance factor of the central heating facility, and a novel reference parameter referred to as the demand-specific collector area. A newly developed benchmark procedure is comparing the central heat demand of the building to the maximum solar thermal gain of the solar circuit in order to calculate the maximum performance factor possible for an idealized central heating facility. Using this benchmark procedure, optimization potentials are exemplarily disclosed for the tested solar combisystem. The results highlight a high optimization potential of the system control and the process layout of central heating facilities, achievable with low cost at the same time.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The variety of designs for solar assisted heating systems (also called solar combisystems) in multi-family houses is wide and has not been evaluated systematically. Functional insufficiencies, resulting from unfavorable device combinations as well as improper control design place significant market barriers for the application of this technology. Using hardware-in-the-loop tests, functional aspects of the most common system designs are investigated and evaluated. Further dynamic system simulations on an annual basis allow an energetic evaluation and later a comparison of the different design options. In this contribution we present the results for the first tested solar assisted heating system. Furthermore, the study suggests the introduction of a novel evaluation parameter referred to as the performance factor of the central heating facility, and a novel reference parameter referred to as the demand-specific collector area. A newly developed benchmark procedure is comparing the central heat demand of the building to the maximum solar thermal gain of the solar circuit in order to calculate the maximum performance factor possible for an idealized central heating facility. Using this benchmark procedure, optimization potentials are exemplarily disclosed for the tested solar combisystem. The results highlight a high optimization potential of the system control and the process layout of central heating facilities, achievable with low cost at the same time.
3.
J Glembin; C Büttner; J Steinweg; G Rockendorf
Optimal Connection of Heat Pump and Solar Buffer Storage under Different Boundary Conditions Artikel
In: Energy Procedia, Bd. 91, S. 145-154, 2016, ISSN: 1876-6102, (Proceedings of the 4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2015)).
@article{Glembin2016c,
title = {Optimal Connection of Heat Pump and Solar Buffer Storage under Different Boundary Conditions},
author = {J Glembin and C Büttner and J Steinweg and G Rockendorf},
doi = {10.1016/j.egypro.2016.06.190},
issn = {1876-6102},
year = {2016},
date = {2016-06-01},
journal = {Energy Procedia},
volume = {91},
pages = {145-154},
abstract = {The paper presents the results of a simulation study, in which the connection of heat pumps and buffer storage tanks has been investigated. The simulations are carried out for a new type of a solar thermal combi system with a 32 m2 collector field leading to a solar fraction of more than 50%. In the first stage, the most influencing installation and operation parameters have been identified and optimized for typical boundary conditions of weather/climate, hot water demand, building and space heating system. Within further simulations these boundary conditions are varied to find generalized design rules for the connection of heat pumps and storage tanks. These results are presented and discussed.},
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 the results of a simulation study, in which the connection of heat pumps and buffer storage tanks has been investigated. The simulations are carried out for a new type of a solar thermal combi system with a 32 m2 collector field leading to a solar fraction of more than 50%. In the first stage, the most influencing installation and operation parameters have been identified and optimized for typical boundary conditions of weather/climate, hot water demand, building and space heating system. Within further simulations these boundary conditions are varied to find generalized design rules for the connection of heat pumps and storage tanks. These results are presented and discussed.
4.
J Glembin; T Haselhorst; J Steinweg; G Rockendorf
In: Energy Procedia, Bd. 91, S. 450-459, 2016, ISSN: 1876-6102, (Proceedings of the 4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2015)).
@article{Glembin2016d,
title = {Simulation and Evaluation of Solar Thermal Combi Systems with Direct Integration of Solar Heat into the Space Heating Loop},
author = {J Glembin and T Haselhorst and J Steinweg and G Rockendorf},
doi = {10.1016/j.egypro.2016.06.176},
issn = {1876-6102},
year = {2016},
date = {2016-06-01},
journal = {Energy Procedia},
volume = {91},
pages = {450-459},
abstract = {Usually, solar heat in combi systems is used via a buffer storage. In contrast to that, the solar collectors may be connected directly to the space heating circuit in order to store the heat in the building itself. Such a direct solar integration is investigated within system simulations for different layouts and heating elements. The simulations show significant reductions in the final energy demand as well as an increasing solar yield due to less thermal losses of the storage tank compared to the usual solution with one buffer storage. A prototype of one of the investigated heating concepts within a single family house proofs the functionality of the system concept and the high solar yield, particularly at low radiation levels. Since only a few manufacturers provide such system solutions with a direct solar integration, the results may have an important impact on the future development of combi systems.},
note = {Proceedings of the 4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2015)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Usually, solar heat in combi systems is used via a buffer storage. In contrast to that, the solar collectors may be connected directly to the space heating circuit in order to store the heat in the building itself. Such a direct solar integration is investigated within system simulations for different layouts and heating elements. The simulations show significant reductions in the final energy demand as well as an increasing solar yield due to less thermal losses of the storage tank compared to the usual solution with one buffer storage. A prototype of one of the investigated heating concepts within a single family house proofs the functionality of the system concept and the high solar yield, particularly at low radiation levels. Since only a few manufacturers provide such system solutions with a direct solar integration, the results may have an important impact on the future development of combi systems.
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.
J Glembin; C Büttner; J Steinweg; G Rockendorf
In: Energy Procedia, Bd. 73, S. 331-340, 2015, ISSN: 1876-6102, (9th International Renewable Energy Storage Conference, IRES 2015).
@article{Glembin2015b,
title = {Thermal Storage Tanks in High Efficiency Heat Pump Systems – Optimized Installation and Operation Parameters},
author = {J Glembin and C Büttner and J Steinweg and G Rockendorf},
doi = {10.1016/j.egypro.2015.07.700},
issn = {1876-6102},
year = {2015},
date = {2015-06-01},
journal = {Energy Procedia},
volume = {73},
pages = {331-340},
note = {9th International Renewable Energy Storage Conference, IRES 2015},
keywords = {},
pubstate = {published},
tppubtype = {article}
}