| 1. |
- Jönsson, Arne, et al.
(författare)
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A Note on Aeneid 6.893-8
- 1996
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Ingår i: Eranos. - 0013-9947. ; 94, s. 21-28
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Tidskriftsartikel (refereegranskat)abstract
- One of the most puzzling passages of Vergil's Aeneid is the last lines of book VI where Aeneas and the Sibyl leave the underworld through the gate of ivory, the gate of false dreams. "Few passages of the Aeneid have given rise to more controversies and divergence of judgement" (Brooks Otis). In this article we analyse the linguistic context and propose a new solution to the problem.
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| 2. |
- Andersson, Kent, et al.
(författare)
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High stability titanium nitride based solar control films
- 1992
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 214:2, s. 213-218
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Tidskriftsartikel (refereegranskat)abstract
- Triple-layer structures of TiO2TiN/TiO2 and quadruple layer structures of TiO2Al/TiN/TiO2 have been sputtered on glass substrates at temperatures ranging from room temperature to 300°C. The reflectance and transmittance were measured in the visible and the near-IR wavelength regions. The thin layer of aluminium, in the quadruple layer, oxidizes and forms a dense diffusion barrier. The multilayers exhibit improved optical selectivity which also improves with substrate temperature up to 300°C.
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| 3. |
- Andersson, Kent
(författare)
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Preparation and Characterisation of Sputtered Titanium- and Zirconium Nitride Optical Films
- 1993
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Multilayered interference coatings based on titanium- and zirconium nitride and designed for solar control have been prepared using reactive d c magnetron sputtering. Preparation effects and degradation mechanisms were investigated. It was shown that the quality of the nitride strongly depends on the degree of crystallinity in the underlying oxide. It has been shown that the nitride layer partly oxidizes as the top oxide layer is deposited. The degradation is enhanced with temperature. A thin sacrificial layer of aluminium deposited between successive depositions of nitride and oxide is shown to improve the optical performance of the coating as preparedm as well as after accelerated ageing tests.The optical properties of opaque and semitransparent films of zirconium nitride have been studied. A thorough investigation of the influence of composition, deposition rate, substrate temperature and film thickness on the optical response of the film was performed. Both photometric and ellipsometric methods were used to determine thicknesses and the optical constants at wavelengths ranging from 0.23 to 25 μm. The resulting values of n and k, in the wavelength intervals where these independent methods are applicable, have been shown to agree extremely well. The results so far indicate an even larger potential for zirconium nitride based solar control coatings as compared to the titanium nitride based.Access to optical constants derived from films of zirconium nitride of variable quality made multilayer modelling a powerful tool in the design and analysis of solar control coatings.
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| 4. |
- Andersson, Kent, et al.
(författare)
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Zirconium nitride based transparent heat mirror coatings : preparation and characterisation
- 1994
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X .- 1471-1257. ; 32:2, s. 199-212
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Tidskriftsartikel (refereegranskat)abstract
- Transparent heat mirror coatings based on thin zirconium nitride films have been prepared using reactive magnetron sputtering. The zirconium nitride films have been sandwiched between layers of zirconium oxide. It is shown that the multilayer configuration ZrO2/ZrN/ZrO2 can be used as solar control coatings on window glazings. A visible transmittance of around 60% and a thermal emittance lower than 0.2 can be obtained, and the ratio between visible transmittance and total solar transmittance can be as high as 1.7. The influence of substrate temperature on the optical quality of the films is evaluated and it is shown that the crystal structure of the first oxide layer is of importance for the optical quality of the nitride. The influence of preparation conditions and accelerated ageing has been modelled using the optical constants of thin films prepared under identical conditions as the films in the multilayer coatings.
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| 5. |
- Andreas, Jonsson, 1977-, et al.
(författare)
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Simulations of the energy performance of smart windows based on user presence using a simplified balance temperature approach
-
Ingår i: Energy and Buildings. - 0378-7788 .- 1872-6178.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this paper a simulation tool for simulating and comparing windows have been further developed so that the software also can simulate smart windows with the ability to vary the g-value or the solar heat gain coefficient. The g-value can be controlled using different control strategies, which can be based on time control, user control and different types of daylight control. The software is basically a simulation tool to calculate the energy for heating and cooling caused by the windows as a building component. Due to the simplicity of the program, it is suitable as a tool for selecting the right type of window for a certain building. Six different control strategies have been developed to show different approaches for controlling smart windows. Some results are shown as examples of how the new functionality is working. This new functionality of the software makes it easy to compare smart windows between themselves and also to make fair comparisons with static windows.
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| 6. |
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| 7. |
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| 8. |
- Björn, Lars Olof, et al.
(författare)
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Thermal emissivity of avian eggshells
- 2016
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Ingår i: Journal of Thermal Biology. - : Elsevier BV. - 0306-4565 .- 1879-0992. ; 57, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- The hypothesis has been tested that evolution has resulted in lower thermal emissivity of eggs of birds breeding openly in cold climates than of eggs of birds that nest under protective covering or in warmer climates. Directional thermal emissivity has been estimated from directional–hemispherical reflectance spectra. Due to several methodological difficulties the absolute emissivity is not accurately determined, but differences between species are obvious. Mostnotably, small waders of the genus Calidris, breeding in cold climates on the tundra, and in most cases with uniparental nest attendance, have low directional emissivity of their eggshells, about 0.92 when integration is carried out for wavelengths up to 16 μm. Species belonging to Galloanserinae have the highest directional emissivity, about 0.96, of their eggs. No differences due to climate or breeding conditions were found within this group. Eggs of most other birds tested possess intermediate emissivity, but the values for Pica pica and Corvus corone cornix are as low as for Calidris. Large species-dependent differences in spectral reflectance were found at specific wavelengths. For instance, at 4.259 μm the directional–hemispherical reflectance for galliforms range from 0.05 to 0.09, while for Fratercula arctica and Fulmarus glacialis it is about 0.3.The reflection peaks at 6.5 and 11.3 μm due to calcite are differentially attenuated in differents pecies. In conclusion, the hypothesis that evolution has resulted in lower thermal emissivity of bird-eggs being exposed in cold climates is not supported by our results.The emissivity is not clearly related to nesting habits or climate, and it is unlikely that the small differences observed are ecologically important. The spectral differences between eggs that nevertheless exist should be taken into account when using infrared thermometers for estimating the surface temperature of avian eggs.
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| 9. |
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Brogren, Maria, 1974-
(författare)
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Optical Efficiency of Low-Concentrating Solar Energy Systems with Parabolic Reflectors
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Solar electricity is a promising energy technology for the future, and by using reflectors for concentrating solar radiation onto photovoltaic cells, the cost per produced kWh can be significantly reduced. The optical efficiency of a concentrating system determines the fraction of the incident energy that is transferred to the cells and depends on the optical properties of the system components. In this thesis, low-concentrating photovoltaic and photovoltaic-thermal systems with two-dimensional parabolic reflectors were studied and optimised, and a new biaxial model for the incidence angle dependence of the optical efficiency was proposed. Concentration of light generally results in high cell temperatures, and the uneven irradiance distribution on cells with parabolic reflectors leads to high local currents and temperatures, which reduce fill-factor and voltage. Cooling the cells by means of water increases the voltage and makes it possible to utilize the thermal energy. The performance of a 4X concentrating photovoltaic-thermal system was evaluated. If operated at 50°C, this system would produce 250 kWhelectrical and 800 kWhthermal per m2 cell area and year. Optical performance can be increased by 20% by using better reflectors and anti-reflectance glazing. Low-concentrating photovoltaic systems for façade-integration were studied and optimised for maximum annual electricity production. The optimisation was based on measured short-circuit currents versus solar altitude. Measurements were performed outdoors and in a solar simulator. It was found that the use of 3X parabolic reflectors increases the annual electricity production by more than 40%. High solar reflectance is crucial to system performance but by using a low-angle scattering reflector, the fill-factor and power are increased due to a more even irradiance on the modules. Long-term system performance depends on the durability of the components. The optical properties and degradation of reflector materials were assessed using spectrophotometry, angular resolved scatterometry, Fresnel modelling, optical microscopy, and surface profilometry before and after ageing. The degradation of reflectors was found to be strongly dependent on material composition and environmental conditions. Back surface mirrors, all-metal reflectors, and polymer-metal laminates degraded in different ways, and therefore accelerated ageing must be tailored for testing of different types of reflector materials. However, new types of reflector laminates showed a potential for increasing the cost-effectiveness of low-concentrating solar energy systems.
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| 14. |
- Brogren, M, et al.
(författare)
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Optical properties, durability, and system aspects of a new aluminium-polymer-laminated steel reflector for solar concentrators
- 2004
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 82:3, s. 387-412
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Tidskriftsartikel (refereegranskat)abstract
- A newly developed aluminium-polymer-laminated steel reflector for use in solar concentrators was evaluated with respect to its optical properties, durability, and reflector performance in solar thermal and photovoltaic systems. The optical properties of the reflector material were investigated using spectrophotometer and scatterometry. The durability of the reflector was tested in a climatic test chamber as well as outdoors in Alvkarleby (60.5degreesN, 17.4degreesE), Sweden. Before ageing, the solar weighted total and specular reflectance values were 82% and 77%, respectively, and the reflector scattered light isotropically. After I year's outdoor exposure, the total and specular solar reflectance had decreased by less than 11%. However, after 2000 h in damp heat and 1000 W/m(2) simulated solar radiation, the optical properties had changed significantly: The light scattering was anisotropic and the total and specular solar reflectance values had decreased to 75% and 42%, respectively. The decrease was found to be due to degradation of the protective polyethylene terephthalate (PET) layer, caused by UV radiation and high temperature. The conclusions are that the degradation is climate dependent and that PET is not suitable as a protective coating under extreme conditions, such as those in the climatic test chamber. However, the results from outdoor testing indicate that the material withstands exposure in a normal Swedish climate.
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| 15. |
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| 16. |
- Böhnke, Tobias, et al.
(författare)
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Surfaces with high solar reflectance and high thermal emittance on structured silicon for spacecraft thermal control
- 2008
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Ingår i: Optical materials (Amsterdam). - : Elsevier BV. - 0925-3467 .- 1873-1252. ; 30:9, s. 1410-1421
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Tidskriftsartikel (refereegranskat)abstract
- Presented here is an examination of unstructured and structured (by anisotropic etching), monocrystalline silicon wafers coated with sputter deposited aluminum and chemical vapor deposited silicon dioxide for high solar reflectance and high thermal emittance, respectively. The topography of the samples was characterized with optical and scanning electron microscopy. Optical properties were examined with reflectance and transmittance spectroscopy, partly by usage of an integrating sphere. The measurement results were used to estimate the equilibrium temperature of the surfaces in space. The suitability of the surfaces with high solar reflectance and high thermal emittance to aid in the thermal control of miniaturized, highly integrated components for space applications is discussed. A silicon dioxide layer on a metal layer results in a slightly lower reflectance when compared to surfaces with only a metal layer, but might be beneficial for miniaturized space components and modules that have to dissipate internally generated heat into open space. Additionally, it is an advantage to microstructure the emitting surface for enhanced radiation of excess heat.
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| 17. |
- Engfeldt, Johnny D., et al.
(författare)
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GLAZING FOR ENERGY EFFICIENT BUILDINGS: : The Almost Forgotten Role of Angular-Dependent Solar Transmittance
- 2020
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Ingår i: Society of Vacuum Coaters Bulletin. - : Society of Vacuum Coaters. ; :spring, s. 72-78
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Tidskriftsartikel (refereegranskat)abstract
- Glazing for energy efficient buildings comprises multi-pane units with surface coated glass. According to today’s standards, glazing is characterized by optical measurements at normal light incidence. Here we show that this prerequisite is grossly inadequate for common vertical glazing, in particular regarding solar transmittance and total energy transmittance (g-value). We present data on spectral and angular-dependent transmittance in the 300–2500-nm wavelength range for several types of glass samples with hard (tin-oxide-based) and soft (silver-based) coatings. Furthermore, we use standard procedures to compute g-values for triple-pane glazing embodying such glass and find that the g-value at 60° off-normal angle typically is as low as 65–68% of the g-value for normal incidence. This difference is essential for assessing the energy efficiency of modern buildings and highlights that the glazing’s angularity must be accounted for.
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| 18. |
- Engfeldt, Johnny D., et al.
(författare)
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Glazing for Energy Efficient Buildings: The Almost Forgotten Role of Angular-Dependent Solar Transmittance
- 2019
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Ingår i: Society of Vacuum Coaters 2019 Technical Conference Proceedings. - : Society of Vacuum Coaters.
-
Konferensbidrag (refereegranskat)abstract
- Glazing for energy efficient buildings comprises multi-pane units with surface coated glass. According to today’s standards, glazing is characterized by optical measurements at normal light incidence. Here we show that this prerequisite is grossly inadequate for common vertical glazing, in particular regarding solar transmittance and total energy transmittance (g-value). We present data on spectral and angular-dependent transmittance in the 300–2500-nm wavelength range for several types of glass samples with hard (tin-oxide-based) and soft (silver-based) coatings. Furthermore, we use standard procedures to compute g-values for triple-pane glazing embodying such glass and find that the g-value at 60° off-normal angle typically is as low as 65–68% of the g-value for normal incidence. This difference is essential for assessing the energy efficiency of modern buildings and highlights that the glazing’s angularity must be accounted for.
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| 19. |
- Fogelqvist, Johan, et al.
(författare)
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Analysis of the hybrid genomes of two field isolates of the soil-borne fungal species Verticillium longisporum
- 2018
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Ingår i: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 19
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Tidskriftsartikel (refereegranskat)abstract
- Background: Brassica plant species are attacked by a number of pathogens; among them, the ones with a soilborne lifestyle have become increasingly important. Verticillium stem stripe caused by Verticillium longisporum is one example. This fungal species is thought to be of a hybrid origin, having a genome composed of combinations of lineages denominated A and D. In this study we report the draft genomes of 2 V. longisporum field isolates sequenced using the Illumina technology. Genomic characterization and lineage composition, followed by selected gene analysis to facilitate the comprehension of its genomic features and potential effector categories were performed.Results: The draft genomes of 2 Verticillium longisporum single spore isolates (VL1 and VL2) have an estimated ungapped size of about 70 Mb. The total number of protein encoding genes identified in VL1 was 20,793, whereas 21,072 gene models were predicted in VL2. The predicted genome size, gene contents, including the gene families coding for carbohydrate active enzymes were almost double the numbers found in V. dahliae and V. albo-atrum. Single nucleotide polymorphisms (SNPs) were frequently distributed in the two genomes but the distribution of heterozygosity and depth was not independent. Further analysis of potential parental lineages suggests that the V. longisporum genome is composed of two parts, A1 and D1, where A1 is more ancient than the parental lineage genome D1, the latter being more closer related to V. dahliae. Presence of the mating-type genes MAT1-1-1 and MAT1-2-1 in the V. longisporum genomes were confirmed. However, the MAT genes in V. dahliae, V. albo-atrum and V. longisporum have experienced extensive nucleotide changes at least partly explaining the present asexual nature of these fungal species.Conclusions: The established draft genome of V. longisporum is comparatively large compared to other studied ascomycete fungi. Consequently, high numbers of genes were predicted in the two V. longisporum genomes, among them many secreted proteins and carbohydrate active enzyme (CAZy) encoding genes. The genome is composed of two parts, where one lineage is more ancient than the part being more closely related to V. dahliae. Dissimilar mating-type sequences were identified indicating possible ancient hybridization events.
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| 20. |
- Forsth, Michael, et al.
(författare)
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Absorptivity and its dependence on heat source temperature and degree of thermal breakdown
- 2011
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Ingår i: Fire and Materials. - : Wiley. - 0308-0501 .- 1099-1018. ; 35:5, s. 285-301
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Tidskriftsartikel (refereegranskat)abstract
- The spectral absorptivity of 62 products has been measured in the wavelength region of 0.3-20 mu m. Effective absorptivity for fire-induced heat radiation typically lies in the range of 0.75-0.95. It was found that the effective absorptivity varies significantly with the temperature of the heat source. This has implications on the heating of a surface. The effect is more important when the absorptivity is used as input for calculations of ignition temperature and thermal inertia. It was also found that the absorptivity of radiation from fires for products exposed to irradiation in many cases decreased with increased exposure time. This is surprising since, for example, wood that is darkened when exposed to heat obviously has a higher absorptivity in the visual part of the spectrum than fresh non-darkened wood. The reason that was identified for this is because the absorptivity in the IR drops, and measurement results are given which clearly illustrate this.
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| 21. |
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| 22. |
- Försth, Michael, et al.
(författare)
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Spectrally selective and adaptive surfaces for protection against radiative heating : ITO and VO2
- 2014
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Ingår i: Fire and Materials. - : Wiley. - 0308-0501 .- 1099-1018. ; 38:1, s. 111-124
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Tidskriftsartikel (refereegranskat)abstract
- Two surface materials for reducing absorptivity of heat radiation from fires have been investigated. The first is VO2, which is a thermochromic material. When the temperature of a VO2 surface increases over a certain temperature, it switches, ideally, from infrared (IR)-absorbing to IR-reflecting. VO2 window coatings are still on a research level, yet to be commercialized. In this study, VO2 powder available on the market was investigated. The thermochromic effect could be identified but was not large enough to significantly improve the fire properties of treated surfaces. Some thoughts concerning how to improve the performance of VO2 are discussed. The second investigated material is indium tin oxide (ITO), which is a so called low-e coating, which means that it has low emissivity and absorptivity in the IR part of the spectrum. ITO is spectrally selective in the sense that it transmits visible light while reflecting a large fraction of the IR radiation, which is a rare property for surfaces in general but a typical property of thin electrically conducting non-metallic films. It is shown that the application of ITO to poly(methyl methacrylate) (PMMA) significantly improves its fire properties. ITO coating is a mature technology already in widespread use today in the electronics industry.
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| 23. |
- Gelin, Kristina, 1975-
(författare)
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Preparation and Characterization of Sputter Deposited Spectrally Selective Solar Absorbers
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The optical efficiency of a commercially available sputter deposited spectrally selective solar absorber was improved. The main purposes were to decrease the thermal emittance, increase the solar absorbtance of the absorber and to protect the substrate from degradation due to environmental influence. The adhesion properties between the corrosion-protecting barrier and the substrate were also studied. This project was focused on process improvements that are realistic to implement in industrial production.The thermal emittance of the absorber was decreased from 0.12 to 0.06 by changing the material of the corrosion-protecting layer from nickel-chromium to copper-nickel. Copper-nickel was less sensitive to variations in the sputter parameters than nickel-chromium. A novel method that could simplify the search for alternative corrosion resistant materials with a low thermal emittance has been purposed. Since resistivity data usually exist or can easily be measured and infrared measurements require more sophisticated measurements, the Hagen-Rubens relation was investigated for copper-nickel and nickel-chromium alloys. The dc-resistivity was found to be related to the infrared emittance or the integrated thermal emittance for alloys in their solid soluble fcc phase.The solar absorbtance was increased when a graded index absorbing coating was tailored for a crossover of the reflectance from low to high reflectance at about 2.5 µm. The solar absorber graded index coating was optimized for nickel metal content in nickel oxide and a solar absorptance of 0.89-0.91 was achieved. The solar absorptance was further increased to 0.97 when an antireflection coating was added on top of the absorbing layer.Finally, extrapolation algorithms were developed to assure correct determination of the thermal emittance for coatings on glass since modern spectrometers that do not cover the complete wavelength interval required to calculate the thermal emittance of surfaces at room temperatures accurately. The error arising from the extrapolation algorithms were smaller than the noise from the optical measurements. Similar strategies can be used for other surfaces.
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| 24. |
- Gelin, Kristina, et al.
(författare)
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Thermal emissivity of coated glazing - simulation versus measurements
- 2005
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Ingår i: Optical materials (Amsterdam). - : Elsevier BV. - 0925-3467 .- 1873-1252. ; 27:4, s. 705-712
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Tidskriftsartikel (refereegranskat)abstract
- A large variety of coated glazing products are available on the market today. These are used in energy efficient low emissivity (low-e) or solar control windows. Not only the solar optical properties, but also the thermal emissivity of these coated glazing materials are of importance for the performance of such energy efficient windows. The thermal emissivity is calculated from the IR reflectance. A problem is that for accurate determination of the emissivity according to international standards, the reflectance needs to be known between 2000 and 200 cm−1, and many FTIR spectrophotometers cannot measure below 400 cm−1. In this paper some different strategies for the extrapolation to 200 cm−1 are discussed. A sensitivity analysis for different types of materials is presented for a few different extrapolation algorithms. The simplest extrapolation procedure assumes a constant reflectance value throughout the extrapolation interval. This appears to work well for surfaces with high reflectance values. A procedure based on a linear relation between the values at a starting wavelength and at the end point of the extrapolation interval or one using a simple second-degree polynomial function can be used when coatings on glass having medium or low reflectance values are evaluated. A guide on how to extrapolate the spectra, according to the different strategies, is included in the Appendix.
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| 25. |
- Granqvist, Claes Göran, et al.
(författare)
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Electrochromic foil-based devices : Optical transmittance and modulation range, effect of ultravioled irradiation, and quality assessment by 1/f current noise
- 2008
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 516:17, s. 5921-5926
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Tidskriftsartikel (refereegranskat)abstract
- We introduce electrochromic (EC) technology for modulating the transmittance of visible light and solar radiation in window apertures, with focus on recent work on foil-type devices embodying sputter deposited WO3 and NiO films joined by a polymer electrolyte. The purpose of this paper is to present a number of new and preliminary results showing that (i) double-sided antireflection coatings based on dip coating can enhance the transmittance significantly, (ii) tandem foils can yield a ratio between bleached-state and colored-state transmittance exceeding fifty, (iii) solar irradiance onto the EC device can enhance its charge insertion dynamics and thereby its optical modulation, and (iv) electromagnetic noise spectroscopy may serve as quality assessment of EC devices.
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| 26. |
- Hansson, Peter, 1967-
(författare)
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Surface Characterization using Radiometric and Fourier Optical Methods
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis treats static and dynamic surface characterization using radiometric and Fourier optical methods. A Fourier optical method has been developed for real time image processing in paper production and printing applications. It has been shown that the method can be used to measure crepe frequency, an important parameter in tissue paper production, as well as to monitor the wire mark pattern at paper web velocities of up to 20 m/s. The wire mark pattern has been used to measure dimensional variations across a paper web. These are important for the mechanical properties of paper. Imaging of the moving surfaces onto a spatial light modulator, necessary for Fourier optical analysis of opaque objects, constitutes a motion blur problem. This problem has been solved by means of optical motion compensation using a rotating mirror. A rotating mirror system has also been developed for the inspection of small particles fixed to a rotating sample disc. The optical motion compensation configurations have made exposure times of more than two orders of magnitude longer than the exposure time without compensation possible. A light scattering model for opaque objects, for example coated paper, has also been developed and verified, with a coefficient of determination between theory and measurement ranging from r2=0.84 to r2=0.98, on various paper samples. The light scattering model has been used in the development of an instrument based on the photometric stereo principle. In this instrument the reflectance (or color) and topography of opaque samples are determined from two or more images of the sample illuminated from different directions. The method has been successfully used for studies of the relation between topography and print results in gravure and flexographic printing. Comparisons of surface height profiles measured with the photometric stereo method and profiles obtained with mechanical and optical scanning stylus instruments have shown coefficients of determination of up to r2=0.97. The main advantages of the method are the high speed, the scalability and the ability to obtain reflectance and surface height maps of a surface simultaneously.
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| 27. |
- Hatwaambo, Sylvester, et al.
(författare)
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Mitigating the non-uniform illumination in low concentrating CPCs using structured reflectors
- 2009
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 93:11, s. 2020-2024
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Tidskriftsartikel (refereegranskat)abstract
- One problem in concentrating photovoltaic systems without active cooling is the formation of hot spots on the solar module cells. These hotspots are a result of uneven concentration of radiation within the solar module cells. The overall effect of concentrated heating is the reduction in the fill-factor of the solar module cell and the subsequent decrease in the overall efficiency of the system. In this paper, we investigate one alternative of improving the performance of a low concentrating photovoltaic system using semi-diffuse rolled reflective elements. Our results indicate that rolling marks on the reflector aligned parallel to the plane of the solar module cell improve the performance of the photovoltaic system. (C) 2009 Elsevier B.V. All rights reserved.
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| 28. |
- Jonsson, Andreas, 1977-, et al.
(författare)
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Evaluation of control strategies for different smart window combinations using computer simulations
- 2010
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X .- 1471-1257. ; 84:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have shown that the use of switchable windows could lower the energy consumption of buildings. Since the main function of windows is to provide daylight and visual contact with the external world, high visible transmittance is needed. From an energy perspective it is always best to have the windows in their low-transparent state whenever there are cooling needs, but this is generally not preferable from a daylight and visual contact point of view. Therefore a control system, which can be based on user presence, is needed in connection with switchable windows. In this study the heating and cooling needs of the building, using different control mechanisms were evaluated. This was done for different locations and for different combinations of switchable windows, using electrochromic glazing in combination with either low-e or solar control glazing. Four control mechanisms were investigated; one that only optimizes the window to lower the need for heating and cooling, one that assumes that the office is in use during the daytime, one based on user presence and one limiting the perpendicular component of the incident solar irradiation to avoid glare and too strong daylight. The control mechanisms were compared using computer simulations. A simplified approach based on the balance temperature concept was used instead of performing complete building simulations. The results show that an occupancy-based control system is clearly beneficial and also that the best way to combine the panes in the switchable window differs depending on the balance temperature of the building and on the climate. It is also shown that it can be beneficial to have different window combinations for different orientations.
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| 29. |
- Jonsson, Andreas, 1977-, et al.
(författare)
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Investigation of side shift and edge losses of surface scattering samples in integrating sphere measurements
-
Ingår i: Applied Optics. - 1559-128X .- 2155-3165.
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Tidskriftsartikel (refereegranskat)abstract
- Light scattering materials are frequently used in solar energy applications, for instance as cover glass in solar thermal absorbers or to increase the path length of photons in solar cells. Knowing the transmittance of such materials is essential to modeling, designing or characterizing a system with these materials as components. The transmittance is traditionally obtained using an integrating sphere spectrophotometer. However, it is known that most commercial spectrophotometers might underestimate the true transmittance of surface scattering samples. Some of the scattered light might hit the edge and escape out of the sample. Thereby the transmitted light exits the sample in such a fashion, that it is not collected by the integrating sphere. The detected signal from the light entering the sphere then underestimates the real transmittance or reflectance of the sample. In this paper this side shift and edge losses of surface scattering samples have been studied and the results show that this might have a significant impact on measured values. Several different techniques have been used to quantify the influence on measurements.
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| 30. |
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| 31. |
- Jonsson, Andreas, 1977-
(författare)
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Optical Characterization and Energy Simulation of Glazing for High-Performance Windows
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on one important component of the energy system - the window. Windows are installed in buildings mainly to create visual contact with the surroundings and to let in daylight, and should also be heat and sound insulating. This thesis covers four important aspects of windows: antireflection and switchable coatings, energy simulations and optical measurements. Energy simulations have been used to compare different windows and also to estimate the performance of smart or switchable windows, whose transmittance can be regulated. The results from this thesis show the potential of the emerging technology of smart windows, not only from a daylight and an energy perspective, but also for comfort and well-being. The importance of a well functioning control system for such windows, is pointed out. To fulfill all requirements of modern windows, they often have two or more panes. Each glass surface leads to reflection of light and therefore less daylight is transmitted. It is therefore of interest to find ways to increase the transmittance. In this thesis antireflection coatings, similar to those found on eye-glasses and LCD screens, have been investigated. For large area applications such as windows, it is necessary to use techniques which can easily be adapted to large scale manufacturing at low cost. Such a technique is dip-coating in a sol-gel of porous silica. Antireflection coatings have been deposited on glass and plastic materials to study both visual and energy performance and it has been shown that antireflection coatings increase the transmittance of windows without negatively affecting the thermal insulation and the energy efficiency. Optical measurements are important for quantifying product properties for comparisons and evaluations. It is important that new measurement routines are simple and applicable to standard commercial instruments. Different systematic error sources for optical measurements of patterned light diffusing samples using spectrophotometers with integrating spheres have been investigated and some suggestions are made for how to avoid such errors.
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| 32. |
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| 33. |
- Jonsson, Andreas, et al.
(författare)
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The effect on transparency and light scattering of dip coated antireflection coatings on window glass and electrochromic foil
- 2010
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 94:6, s. 992-997
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Tidskriftsartikel (refereegranskat)abstract
- Modern windows tend to include an increasing number of functional coatings and in order to keep the light transmittance at an acceptably high level antireflection coatings are likely to be used in future high performance windows. For switchable coatings this may be necessary in order to make them sufficiently light in the bleached state. In this paper we have investigated how haze levels of a selection of coatings on glass and plastics, including electrochromic PET foil, are influenced by the additional antireflection coatings. The results indicate a possible increase in light scattering levels for the antireflection coatings on PET foil and a reduction of haze for tin oxide coated glass.
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| 34. |
- Jonsson, Andreas, 1977-, et al.
(författare)
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The effect on transparency and light scattering of dip coated antireflection coatings on window glass and plastics
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Ingår i: Solar Energy Materials and Solar Cells. - 0927-0248 .- 1879-3398.
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Tidskriftsartikel (refereegranskat)abstract
- High visible transmittance values are interesting for windows in general and for the bleached state of smart windows in particular. For smart windows it is always possible to darken them and therefore the transparency of the bleached state can never become too high. One way of achieving a higher transmittance could be the use of antireflective coatings on the surfaces of the smart window. In this project the use of dip coating for putting antireflective coatings on window surfaces has been studied. The effect on transmittance and surface light scattering has been investigated and the results show that antireflective coatings on windows can have a positive impact on both.
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| 35. |
- Jonsson, Andreas, 1977-, et al.
(författare)
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Visual and energy performance of switchable windows with antireflection coatings
- 2010
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X .- 1471-1257. ; 84:8, s. 1370-1375
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this project was to investigate how the visual appearance and energy performance of switchable or smart windows can be improved by using antireflective coatings. For this study clear float glass, low-e glass and electrochromic glass were treated with antireflection (AR) coatings. Such a coating considerably increases the transmittance of solar radiation in general and the visible transmittance in particular. For switchable glazing based on absorptive electrochromic layers in their dark state it is necessary to use a low-emissivity coating on the inner pane of a double glazed window in order to reject the absorbed heat. In principle all surfaces can be coated with AR coatings, and it was shown that a thin AR coating on the low-e surface neither influences the thermal emissivity nor the U-value of the glazing. The study showed that the use of AR coatings in switchable glazing significantly increases the light transmittance in the transparent state. It is believed that this is important for a high level of user acceptance of such windows.
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| 36. |
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| 37. |
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| 38. |
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| 39. |
- Jonsson, Jacob, 1974-
(författare)
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Optical Characterisation of Miniature Structures and Translucent Sheets for Daylighting Applications
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For a long time spectrophotometry has been a powerful method of determining optical material properties. Since the technique measures the parameters of interest, reflectance and transmittance, it is in general easy to use and interpret. Certain materials, such as miniature structures or scattering materials, must be given a more careful analysis to avoid incorrect interpretation. General solutions to measurement challenges for thick scattering samples and anisotropically scattering samples are presented.Thorough knowledge about the components of a spectrophotometer gives a solid base which is necessary when trying to design or modify an instrument for the characterisation of miniature components. Focusing optics and pinhole apertures are two methods investigated for studying samples on a millimeter scale. Focusing optics retain a high intensity but might cause internal reflection. Pinhole apertures are easy to build into a sample holder, but they will reduce light intensity which can give problems with signal to noise ratio. Using a microscope as a focusing lens system permits the measurement of samples of a size down to the order of ten micrometers. However, absolute measurements are difficult due to the strong focusing properties of the microscope.Translucent sheets are of interest for daylighting applications, a growing field in today's energy-conscious society. If sunlight is to be used for indoor illumination it is preferable to make it diffuse. By using Transparent Refractive Index Matched Micro (TRIMM) particles in a transparent polymer sheet, it is possible to obtain high transmittance in combination with tailorability of the scattering profile. Such sheets have been characterised experimentally, as well as by Monte Carlo raytracing simulations. The good agreement between simulation and experiment shows that this type of simulation can be used in the materials design process. A more theoretical study of patterns in multiple Mie scattering has been carried out using the Monte Carlo program developed for characterisation of the TRIMM particle sheets.
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| 40. |
- Jonsson, Jacob, et al.
(författare)
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Optical characterization of fritted glass for architectural applications
- 2009
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Ingår i: Optical materials (Amsterdam). - : Elsevier BV. - 0925-3467 .- 1873-1252. ; 31:6, s. 949-958
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Tidskriftsartikel (refereegranskat)abstract
- Fritted glass is commonly used as a light diffusing element in modern buildings. Traditionally it has been used for aesthetic purposes but it can also be used for energy savings by incorporating it in novel daylighting systems? To answer such questions the light scattering properties must be properly characterized.This paper contains measurements of different varieties of fritted glass, ranging from the simplest direct-hemispherical measurements to angle-resolved goniometer measurements. Modeling the light scattering to obtain the full bidirectional scattering distribution function (BSDF) extends the measured data, making it useful in simulation programs such as Window 6 and Radiance. Surface profilometry results and SEM micrographs are included to demonstrate the surface properties of the samples studied.
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| 41. |
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| 42. |
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| 43. |
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| 44. |
- Lansåker, Pia C., et al.
(författare)
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Au-Based Transparent Conductors for Window Applications : Effect of Substrate Material
- 2010
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Ingår i: Advances in Science and Technology. - 1662-0356. ; 75, s. 25-30
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of Au were made by sputter deposition onto glass substrates with and without transparent and electrically conducting layers of SnO2:In. The Au films were up to ~11 nm in thickness and covered the range for thin film growth from discrete islands, via large scale coalescence and formation of a meandering conducting network, to the formation of a more or less “holey” film. Scanning electron microscopy and atomic force microscopy showed that the SnO2:In films were considerably rougher than the glass itself. This roughness influenced the Au film formation so that large scale coalescence set in at a somewhat larger thickness for films on SnO2:In than on glass. Measurements of spectral optical transmittance and electrical resistance could be reconciled with impeded Au film formation on the SnO2:In layer, leading to pronounced “plateaus” in the near infrared optical properties for Au films on SnO2:In and an accompanying change from such two-layer films having a lower resistance than the single gold film at thicknesses below large scale coalescence to the opposite behavior for larger film thicknesses.
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| 45. |
- Lansåker, Pia C, et al.
(författare)
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Au thin films deposited on SnO2:In and glass : Substrate effects on the optical and electrical properties
- 2011
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 519:6, s. 1930-1933
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Tidskriftsartikel (refereegranskat)abstract
- We report on a detailed study on the optical and electrical properties of Au films made by sputter deposition onto glass substrates with and without transparent and electrically conducting layers of SnO2:In. The Au films had thicknesses up to 10.7 nm and hence spanned the range for thin film growth from discrete islands, via large scale coalescence and formation of a meandering conducting network, to the formation of a more or less "holey" film. Scanning electron microscopy and atomic force microscopy demonstrated that the SnO2:In films were considerably rougher than the glass itself, and this roughness influenced the Au film formation so that large scale coalescence set in at a somewhat larger thickness for films on SnO2:In than on glass. Measurements of spectral optical transmittance and reflectance and of electrical resistance gave a fully consistent picture that could be reconciled with impeded Au film formation on the SnO2:In layer; this led to pronounced "plateaus" in the near infrared optical spectra for Au films on SnO2:In and a concomitant change from such two-layer films having a lower resistance than the single gold film at thicknesses below large scale coalescence to the opposite behavior for larger film thicknesses. Our work highlights the importance of the substrate roughness for transparent conductors comprising coinage metal films backed by wide band gap transparent conducting oxides.
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| 46. |
- Liljeholm, Lina, et al.
(författare)
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Reactive sputtering of SiO2–TiO2 thin film from composite Six/TiO2 targets
- 2010
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Ingår i: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 85:2, s. 317-321
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Tidskriftsartikel (refereegranskat)abstract
- Coatings of SiO2–TiO2 films are frequently used in a number of optical thin film applications. In this work we present results from depositing films with variable Si/Ti ratios prepared by reactive sputtering. The different Si/Ti ratios were obtained by varying the target composition of composite single targets. Compared to co-sputtering this facilitates process control and composition uniformity of the films. Varying the oxygen supply during sputter deposition can result in films ranging from metallic/substoichiometric to stoichiometric oxides. Transmittance spectra of the different films are presented and the optical constants are determined from these spectra. Furthermore, the deposition process, films structure and composition of the films are discussed. The study shows that by choosing the right composition and working in the proper oxygen flow range, it is possible to tune the refractive index.
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| 47. |
- Linderholm, Mats, et al.
(författare)
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Local host response in the lower respiratory tract in nephropathia epidemica
- 1993
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Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 1651-1980 .- 0036-5548. ; 25:5, s. 639-646
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Tidskriftsartikel (refereegranskat)abstract
- Various lines of evidence suggest a respiratory route of transmission of nephropathia epidemica (NE). To study the response of the respiratory tract in NE, fiberoptic bronchoscopy with bronchoalveolar lavage (BAL) was performed in 5 patients in the acute phase of the disease. Compared to a reference group of 15 healthy individuals, BAL fluid of NE patients contained significantly higher total numbers of cells (p < 0.05) and significantly higher numbers of lysozyme-positive macrophages (p < 0.01), CD8+ T cells (p < 0.01), and natural killer (NK) cells (p < 0.01). There was no significant difference in numbers of CD4+ T cells, B cells, or neutrophils. When blood samples of 16 patients were examined at various intervals after onset of NE, a significant decrease in the number of NK cells (p < 0.01) was found in the acute phase of the disease. The findings are compatible with the presence of a local host response in the lower respiratory tract to NE virus infection.
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| 48. |
- Maestre, I. R, et al.
(författare)
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A single-thin-film model for the angle dependent optical properties of coated glazings
- 2007
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X .- 1471-1257. ; 81:8, s. 969-976
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Tidskriftsartikel (refereegranskat)abstract
- Technology for the manufacture of coated glazings with spectrally selective optical properties, such as low-e and solar-control glazings, has been developed in the last few decades. This is leading researchers to develop new optical and thermal models in order to ascertain glazing performance. These new models must accurately reproduce the optical properties for any incident solar angle by using the available experimental data, which often means only information for normal incident radiation. In this paper, a new model is presented that characterizes the angular dependence of coated glazings. To provide a simple, intuitive understanding, this model uses only one thin film to characterize optical performance. In addition an optimization algorithm has been developed to obtain the spectral optical properties of that equivalent film using spectral experimental data under normal incidence. Finally, the model is validated with experimental data and the results are compared with other known models.
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| 49. |
- Magnus, Fridrik, et al.
(författare)
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Tunable giant magnetic anisotropy in amorphous SmCo thin films
- 2013
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 102:16, s. 162402-
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Tidskriftsartikel (refereegranskat)abstract
- SmCo thin films have been grown by magnetron sputtering at room temperature with a composition of 2-35 at.% Sm. Films with 5 at.% or higher Sm are amorphous and smooth. A giant tunable uniaxial in-plane magnetic anisotropy is induced in the films which peaks in the composition range 11-22 at.% Sm. This cross-over behavior is not due to changes in the atomic moments but rather the local configuration changes. The excellent layer perfection combined with highly tunable magnetic properties make these films important for spintronics applications.
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| 50. |
- Mottamchetty, Venkatesh, et al.
(författare)
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Terahertz emission from epitaxial α-W/Co60Fe40 spintronic emitters
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We report efficient terahertz (THz) generation in epitaxial α-W/Co60Fe40 spintronic emitters. Two types of emitters have been investigated; epitaxial α-W(110)/Co60Fe40(110) and α-W(001)/Co60Fe40(001) deposited on single crystalline Al2O3(11-20) and MgO(001) substrates, respectively. The generated THz radiation is about 10% larger for α-W(110)/Co60Fe40(110) grown on single crystalline Al2O3(11-20), which is explained by the fact that the α-W(110)/Co60Fe40(110) interface for this emitter is more transparent to the spin current due to the presence of Ångström-scale interface intermixing at the W/CoFe interface. Our results also reveal that the generation of THz radiation is larger when pumping with the laser light from the substrate side, which is explained by a larger part of the laser light due to interference effects in the film stack being absorbed in the ferromagnetic Co60Fe40 layer in this measurement configuration.
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