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Furth im Wald, Germany

Max J.F.J.,Forschungs zentrum Julich GmbH | Reisinger G.,Forschungs zentrum Julich GmbH | Reisinger G.,University of Bonn | Hofmann T.,Centrosolar Glas GmbH and Co KG | And 8 more authors.
Energy and Buildings | Year: 2012

A combination of anti-reflection coated glass and ethylene tetrafluoroethylene film is introduced as a novel glazing system for greenhouses and similar buildings. It combines the advantages of the individual materials (durability/low weight; favourable condensation behaviour/self-cleaning) and of single and double layer systems (light transmission/insulation). By inflating/deflating the glass-film interspace, the additional insulation can be switched on and off. Since no standard method for this purpose is available, a hot box-system was developed to measure heat transfer coefficients (U-values) of different models of the glass-film-combination (GFC) and other commonly used greenhouse glazing materials at different surface inclinations; with or without condensation. Surface inclination did not greatly influence heat transfer. Condensation increased the U-values more pronounced for single layer-systems than for the GFC. Influences of wind velocity on heat transfer decreased with the degree of insulation. Overall, when mounted with adhesive tape, the energy efficiency of the GFC was 38% higher compared to customary float glass. The energy saving potential of plastic profile mounted GFC versions was 50% and 64% for the double and triple layer system (ETFE-film on both sides of the glass pane), respectively. PAR transmission of the GFC was similar to single pane float glass, its UV transmittance markedly higher. © 2012 Elsevier B.V. All rights reserved. Source


Max J.F.J.,Julich Research Center | Schurr U.,Julich Research Center | Tantau H.-J.,Leibniz University of Hanover | Mutwiwa U.N.,Jomo Kenyatta University of Agriculture and Technology | And 2 more authors.
Horticultural Reviews | Year: 2012

Beginning in the 1950s greenhouse horticulture expandedrapidly fromtemperate climate zones to the subtropics and tropics. As a result of the tremendous diversification of application fields for greenhouses, the diversity of greenhouse covering materials has increased dramatically. The current number of new products entering the markets is growing constantly but there has yet to be a comprehensive overview on this topic. This review aims at providing a compendium on the most commonly used types of greenhouse cladding materials. Following an overview on greenhouse superstructure designs, the various materials used for greenhouse glazing are introduced and divided into four subgroups. Their properties are characterized with respect to the suitability and significance as covers for protected horticultural cultivation. Since coating of greenhouse cladding materials became a common practice for each material class, an additional subsection deals with coatings and their possible interactions with the covermaterial.Acombination of glassandfilmis introduced anddiscussed. Plant responses to the conditions resulting from different covering materials are presented using case studies. Finally, an attempt is made to summarize the fundamental information including economic aspects in tabular form. © 2012 Wiley-Blackwell. Published 2012 by John Wiley & Sons, Inc. Source


Tantau H.-J.,Leibniz University of Hanover | Hinken J.,Leibniz University of Hanover | Von Elsner B.,Leibniz University of Hanover | Hofmann T.,Centrosolar Glas GmbH and Co KG | And 4 more authors.
Acta Horticulturae | Year: 2012

Light is an important growth factor in greenhouses. The choice of a covering material strongly influences the light transmittance of a greenhouse. For low energy greenhouses double and even triple covering materials are available. Also covering materials with higher light transmittances than conventional float glass are available. When these materials are used for double glazing the light transmittance might be equal or even higher than that of single glazing units. The aim of this project was to measure the transmittance of different covering materials for solar radiation and PAR under greenhouse conditions. For this purpose 20 different covering materials were installed on the southern roof of an east-west oriented greenhouse. Underneath these specimens, PAR and solar radiation were continuously measured and compared to the outside conditions from 2006 to 2011. Transmittance was determined for different incident angles of solar irradiation, direct and diffuse radiation, as well as under the influence of condensation, dust and dirt accumulation, and the aging of the materials. Drop wise condensation on the inner surfaces of the covering materials reduced PAR transmittance. Dust had an impact on the transmittance as well but its influence varied over time since dust particles accumulated during dry periods were partially removed by rain. An influence of aging on the materials' light transmission could, however, not yet be detected. © ISHS 2012. Source


Noack J.,Humboldt University of Berlin | Scheurell K.,Humboldt University of Berlin | Kemnitz E.,Humboldt University of Berlin | Garcia-Juan P.,Solvay Group | And 9 more authors.
Journal of Materials Chemistry | Year: 2012

Magnesium fluoride sols for the wet chemical processing of porous MgF 2 antireflective coatings were prepared by the reaction of MgCl 2 with HF. The formation and crystallisation of MgF 2 nanoparticles were followed by 19F NMR spectroscopy, X-ray diffraction (XRD) and dynamic light scattering (DLS) in the liquid phase. The crystallization of the resulting films was monitored by XRD experiments. At temperatures exceeding 550 °C the film material and glass substrates undergo a chemical reaction, MgO is formed and SiF 4 evaporates as a volatile product. Microstructure and optical properties were characterized as a function of the annealing temperature. The mechanical stability of MgF 2 films was evaluated by the Crockmeter test using both felt and steel wool. It is shown that porous MgF 2 films prepared by this synthesis have a vast potential for the large-area processing of antireflective coatings. © 2012 The Royal Society of Chemistry. Source

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