Testing of Components for Solar Thermal Collectors in Respect of Saline Atmospheres
Energy Procedia, Vol. 48, 2014, 731-738
March 2014
Editor: Andreas Häberle
Publisher: Elsevier Ltd.
--- Typical components for solar thermal collectors like glazing materials, absorbers and reflectors are exposed to accelerated weathering tests to analyze their stability and behavior under different climatic conditions including a saline atmosphere. The samples are characterized before, during and after the tests with different methods, including FT-IR spectroscopy and microscopic technologies like AFM microscopy to measure the degradation on different scales and identify the processes taking place. In this article we focus on the solar reflector

Methoden zur beschleunigten Alterungsprüfung von Kunsststoffen
ee-erneuerbare energie 2013-01
January 2013
Publisher: AEE - Arbeitsgemeinschaft ERNEUERBARE ENERGIE - Dachverband
--- Bei großen Saisonalwärmespeichern aber auch kleinen Wasserspeichern adaptierbarer Geometrie kommen zunehmend Kunststoffhalbzeuge (sogenannte Liner) zum Einsatz. Eine Hauptanforderung an den Kunststoffliner ist die Langzeitbeständigkeit (>20 Jahre) bei Temperaturen von 60 bis 90°C. In der Materialentwicklung aber auch zur Lebensdauervorhersage sind beschleunigte Prüfmethoden von zentraler Bedeutung.

Aging tests of components for solar thermal collectors
Energy Procedia 30 (2012) 805-814
November 2012
Publisher: Elsevier Ltd.
--- Components for solar thermal collectors like glazing materials, absorbers and reflectors are exposed to outdoor weathering and accelerated weathering tests in order to analyze their stability and behavior under different climatic conditions. To measure the degradation on different scales and to identify the processes taking place, the samples are characterized before, during and after the tests with different methods, including FT-IR spectroscopy, contact angle measurement and microscopic technologies such as Atomic Force Microscopy (AFM).

Black pigmented polypropylene materials for solar absorbers
Energy Procedia 30 (2012) 438-445
November 2012
Publisher: Elsevier Ltd.
--- Polyolefin materials are of high relevance and interest for absorbers of solar thermal collectors with integrated overheating protection. In this work the effect of various black pigments (carbon black (CB) and carbon nanotubes (CNT)) on optical and mechanical properties of PP-RCT grades (Polypropylene-Random Copolymer with special crystalline structure (ß phase) for elevated temperature applications) is investigated. To meet the requirements of high absorbance in the solar wavelength range (> 90%) and enhanced mechanical properties at service temperatures up to 90°C for at least 10 years, black pigmented specimens are characterized in an unaged state by UV/Vis/NIR- spectrometry and tensile testing. The experimental results reveal ...

Fracture behavior of degraded polyethylene thin films for solar thermal applications
Energy Procedia 30 (2012) 783-792
November 2012
Publisher: Elsevier Ltd.
--- Thin polymer films and tubes are under consideration as materials for use in roof top mounted solar thermal collectors. When polymer components are exposed to chlorinated water or UV light, degradation can lead to diminished mechanical performance and premature failure from rupture. In this paper, fracture toughness and crack growth of degraded polyethylene (MDPE) are investigated. Thin film PE samples (0.3mm thick) are degraded through exposure to 80°C chlorinated water (8 ppm chlorine) for up to 45 days ...

Degradation model for an extruded polymeric solar thermal absorber
Solar Energy Materials and Solar Cells (94) 6, pp. 1031-1037
June 2010
--- A mechanical test is used to characterize the ageing process of a polymeric solar absorber as a consequence of exposure to high temperature. Specimens from the polymeric absorber sheet were exposed to different temperature and time conditions. Specimens were then tested using mechanical indentation to evaluate the damage level produced. Based on these measurements, this work proposes a model to predict degradation of the polymeric solar absorber during their service life. Model predictions are compared with results from a polymeric absorber exposed to outdoor conditions during two years.

Aging behavior and lifetime modeling for polycarbonate
Solar Energy, (84) 5, pp. 755-762
May 2010
--- In this paper, polycarbonate (PC) as a material candidate for solar absorber applications is investigated as to the aging behavior at different temperatures in air and water. The aging conditioning was performed in air in the temperature range from 120 to 140 °C and in water between 70 and 95 °C. Tensile tests were performed on unaged and aged PC film specimens at ambient temperature using strain-to-break values as a performance indicator for the degree of aging. For PC the effect of aging was found to strongly depend on the ageing conditions ...

Aging behavior of polymeric solar absorber materials – Part 2: Commodity plastics
Solar Energy (8) 9, pp. 1577-1586
May 2010
--- In this series of two papers, various polymeric materials are investigated as to their potential applicability as absorber materials for solar thermal collectors. Part 2 treats the aging behavior of semi-crystalline so-called “commodity” plastics (two types of crosslinked polyethylene (PE-X) and two types of polypropylene (PP)). The focus of the investigation is to study the aging behavior of these materials under maximum operating conditions (80 °C in water up to 16,000 h) and stagnation conditions (140 °C in air up to 500 h) typical for northern climate. The materials supplied or produced as polymer films were first characterized in the unaged state and then for different states of aging by differential scanning calorimetry (DSC), by size exclusion chromatography (SEC) and by mechanical tensile tests. DSC was applied primarily to obtain information on [...]

Aging behavior of polymeric solar absorber materials – Part 1: Engineering plastics
Solar Energy (8) 9, pp. 1567-1576
April 2010
--- In this series of two papers, various polymeric materials are investigated as to their potential applicability as absorber materials for solar thermal collectors. The focus of the investigation is to study the aging behavior of these materials under maximum operating conditions (80 °C in water up to 16,000 h) and stagnation conditions (140 °C in air up to 500 h) typical for northern climate. The materials supplied or produced as polymer films were first characterized in the unaged state and then for different states of aging by differential scanning calorimetry (DSC), by size exclusion chromatography (SEC) and by mechanical tensile tests. Physical aging phenomena were studied by DSC, SEC analysis provided information on chemical degradation of the materials. In addition, physical and chemical aging were both analyzed via the small and large strain mechanical behavior. Part 1 of this paper series deals with the aging behavior of engineering plastics, including two amorphous polymers (a polyphenylene ether polystyrene blend (PPE + PS) and polycarbonate (PC)) and two semi-crystalline polymers (two types of polyamide 12 (PA12)).

Aging behavior of polymeric solar absorber materials: Aging on the component level
Solar Energy (84) 3, pp. 459-465
March 2010
--- Within this study, the aging behavior of a PPE + PS absorber material was investigated on the absorber component level. To indicate aging, characteristic mechanical values were determined by indentation tests of specimens taken from components and exposed to laboratory aging (140 °C in air, 80 °C in water) and service near outdoor aging conditions (stagnation in northern climate). In addition to the mechanical tests, the unaged and aged specimens were also characterized thermo-analytically via differential scanning calorimetry (DSC) ...

Characterization of physical and chemical aging of polymeric solar materials by mechanical testing
Polymer Testing, vol. 29, pp. 72-81
February 2010
--- The potential of mechanical tensile testing to characterize aspects of physical and chemical aging of polymeric solar materials as films was investigated. For this purpose, two types of polymer films, one being a multi-phase amorphous material (blend of polyphenylene ether and polystyrene (PPE + PS)) the other being a crosslinked semi-crystalline material (polyethylene (PEX-1)), were exposed to water at 80 °C for up to 16,000 h prior to being tested mechanically at room temperature. The properties deduced from mechanical tests to indicate aging were the modulus of the films, characteristic for the small-strain behavior, and the values for strain-to-break, characteristic for the post-yield behavior and ultimate failure at large strains ...

Untersuchung der Witterungsbeständigkeit von Polymermaterialien mit Nanofillern
2. Solarthermie-Technologiekonferenz, Berlin, Germany
January 2010
Presentation is available as PDF-file and online video. Image: © Creventis Services 2010

A test procedure for extruded polymeric solar thermal absorbers
Solar Energy Materials and Solar Cells, 92 (2008) 445-452
April 2008
Publisher: Elsevier Ltd.
--- An indentation test is proposed to study the degradation of extruded polymeric solar absorbers. The thermal degradation caused by accelerated aging is investigated. The results are compared with the thermal and mechanical impacts during the operation of the solar collector.