Mixed-Dimensionality Approach for Advanced Ray Tracing of Lamellar Structures for Daylighting and Thermal Control

The appropriate choice of the type of glazing and glazed area in a façade depends on many factors. They include amongst other criteria: location, orientation, climatic condition, energetic efficiency, usage of the building, required user comfort, and the architectural concept. All requirements cannot be fulfilled at all times and priorities have to be set to find a compromise between occupant comfort, design objective, cost and energetic efficiency. An innovative glazing system combining daylighting, glare protection, seasonal thermal control and clear view was developed [1] and patented by the authors. This design was developed using a novel ray tracing approach to obtain a strongly angular dependent transmission with specific angular distribution. Taking advantage of the changing elevation of the sun between seasons, a seasonal variation is created by a strongly angular dependent transmittance. In this paper we present the mixed dimensionality approach used to achieve a very fast and accurate ray tracing of any lamellar structure that has a two dimensional profile. The originality of the presented Monte Carlo algorithm is the separation of intersection and interaction. Intersections are computed using only the two dimensions of the profile thereby increasing significantly computational speed. Interactions are computed using vector calculus in three dimensions and provide accurate results with very little computational load. With such optimizations, the user interface could be designed to give an instantaneous idea of the light path in the modelled system. The model also calculates an accurate bidirectional transmittance distribution function that is used in a Radiance simulation to obtain a rendering of the daylighting distribution in an office space. Hereby we can compare the daylighting performances of the novel design based on optical microstructures with those of other CFSs. Finally the combination of simulated angular dependent transmittance and Meteonorm data provides an estimate of transmitted energy over the year and proves the efficiency of the presented optical microstructures for dynamic thermal control. The proposed working principles of redirection and angular dependent transmittance are thereby demonstrated. The software provides all the mentioned results in the user interface where the performances of different designs can also be compared, making the optimization process of a profile with a defined objective very intuitive

Bringing colours to solar collectors: a contribution to an increased building "integrability"

One main obstacle to facade integration of solar thermal collectors lies in the formal characteristics and low flexibility of available products. Major problems are the black and irregular appearance of their absorbers, their low dimensional flexibility and large size at the façade scale, and finally the lack of dummy elements. This paper presents a revolutionary though simple solution to all these problems, consisting in a novel coloured glass, able to mask absorber and piping while letting the solar energy pass through. Different colours can be produced and combined with different diffusing surface treatments on the glass outer side, finally offering a broad palette of novel glazing. These resulting glazing not only hide the black colour of the absorber and its imperfections, but can also be used as facade cladding on the non exposed areas of the building envelope, opening the way to the concept of active solar facades and offering a new level of freedom to architect

High‐Saturated‐Fat Diet Increases Circulating Angiotensin‐Converting Enzyme, Which Is Enhanced by the rs4343 Polymorphism Defining Persons at Risk of Nutrient‐Dependent Increases of Blood Pressure

Background Angiotensin‐converting enzyme (ACE) plays a major role in blood pressure regulation and cardiovascular homeostasis. Contrary to the assumption that ACE levels are stable, circulating ACE has been shown to be altered in obesity and weight loss. We sought to examine effects of a high‐saturated‐fat (HF) diet on ACE within the NUtriGenomic Analysis in Twins (NUGAT) study. Methods and Results Forty‐six healthy and nonobese twin pairs initially consumed a carbohydrate‐rich, low‐fat diet over a period of 6 weeks to standardize for nutritional behavior prior to the study, followed by 6 weeks of HF diet under isocaloric conditions. After 6 weeks of HF diet, circulating ACE concentrations increased by 15% (P=1.6×10−30), accompanied by an increased ACE gene expression in adipose tissue (P=3.8×10−6). Stratification by ACE rs4343, a proxy for the ACE insertion/deletion polymorphism (I/D), revealed that homozygous carriers (GG) of the variant had higher baseline ACE concentrations (P=7.5×10−8) and additionally showed a 2‐fold increase in ACE concentrations in response to the HF diet as compared to non‐ or heterozygous carriers (AA/AG, P=2×10−6). GG carriers also responded with higher systolic blood pressure as compared to AA/AG carriers (P=0.008). The strong gene‐diet interaction was confirmed in a second independent, cross‐sectional cohort, the Metabolic Syndrome Berlin Potsdam (MeSyBePo) study. Conclusions The HF‐diet‐induced increase of ACE serum concentrations reveals ACE to be a potential molecular link between dietary fat intake and hypertension and cardiovascular disease (CVD). The GG genotype of the ACE rs4343 polymorphism represents a robust nutrigenetic marker for an unfavorable response to high‐saturated‐fat diets. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT01631123

Quantum dot containing nanocomposite thin films for phtoluminescent solar concentrators

Silicon oxide films containing CdS quantum dots have been deposited on glass substrates by a sol–gel dip-coating process. Hereby the CdS nanocrystals are grown during the thermal annealing step following the dip-coating procedure. Total hemispherical transmittance and reflectance measurements were carried out by means of a spectrophotometer coupled to an integrating sphere. For CdS-rich films, an absorption edge at photon energies in the vicinity of the band gap value of bulk CdS is observed. For lower CdS concentrations, the absorption edge shifts to higher photon energies, as expected for increasing quantum confinement. The samples show visible photoluminescence which is concentrated by total internal reflection and emitted at the edges of the substrate. The edge emission has been characterized by angle-dependent photoluminescent (PL) spectroscopy. Information on the lateral energy transport within the sample can be extracted from spectra obtained under spatial variation of the spot of excitation. The color of the photoluminescence can be tuned by varying the annealing temperature which governs crystal growth and thus the cluster size distribution. The characteristic features observed in the PL spectra clearly exhibit a blueshift for lower annealing temperatures, confirming the presence of quantum size effects. Advantages of the proposed concept of quantum dot containing coatings on glass panes for photoluminescent solar concentrators are the high potential for low-cost fabrication on the large scale and the suitability for architectural integration

Air cooling powered by façade integrated coloured opaque solar thermal panels

For building integration of solar-powered energy systems, aesthetic aspects play an importantrole. Covering a standard solar collector with a coloured glazing, opaque to the human eye but highly transparent to solar energy, permits a perfect architectural integration of solar thermal panels into glazed building façades. The thermal energy produced can be used for both solar heating and cooling, as well as for domestic hot water. The principle of the coloured appearance is based on interference in the thin-film coating on the reverse side of the cover glass. Different interference filters based on nano-composite materials deposited by the solgel method were presented at CISBAT 2007 [1]. Currently, we are developing new plasma-deposition processes, which are more suitable for industrial large-scale production. A new state-of-the-art ultra-high vacuum (UHV) system for magnetron sputtering deposition of novel nano-composite solar coatings has recently been designed, constructed, and installed at the Solar Energy and Building Physics Laboratory (LESO-PB). Up to five different magnetron sources can be used simultaneously, in reactive and non-reactive mode. The geometric configuration of the chamber has been optimised for best film homogeneity and allows the deposition on substrates up to 100 mm in diameter. The optical and electronic properties of thin films are closely interrelated and highly relevant for solar coatings. Photoelectron spectroscopy provides information on the coating structure, the deposited material and its chemical state inside the coating, as well as the nature of the interface between different layers. A system for ESCA analysis (Electron Spectroscopy for Chemical Analysis) has recently been installed and put into operation at LESO-PB. By ellipsometry and spectrophotometry, we can determine exactly the different optical properties of the coating, such as layer thickness, refractive index, or absorption coefficient. This provides best conditions for highly efficient research and development on new materials for further optimisation of the coloured interference filters.First results have been obtained with our new experimental infrastructure and will be presented in this contribution

Coloured coatings for glazing of active solar thermal façades by reactive magnetron sputtering

For building integration of solar-powered energy systems, aesthetic aspects play an important role. Covering a standard solar collector with a coloured glazing, opaque to the human eye but highly transparent to solar energy, permits a perfect architectural integration of solar thermal panels into glazed building façades. The thermal energy produced can be used for both solar heating and cooling, as well as for domestic hot water. The principle of the coloured appearance is based on interference in the thin-film coating on the reverse side of the cover glass. Different interference filters based on nano-composite materials deposited by the solgel method were presented at CISBAT 2007 [1]. Currently, we are developing new plasma-deposition processes, which are more suitable for industrial large-scale production. A new state-of-the-art ultra-high vacuum (UHV) system for magnetron sputtering deposition of novel nano-composite solar coatings has recently been designed, constructed, and installed at the Solar Energy and Building Physics Laboratory (LESO-PB). Up to five different magnetron sources can be used simultaneously, in reactive and non-reactive mode. The geometric configuration of the chamber has been optimised for best film homogeneity and allows the deposition on substrates up to 100 mm in diameter. The optical and electronic properties of thin films are closely interrelated and highly relevant for solar coatings. Photoelectron spectroscopy provides information on the coating structure, the deposited material and its chemical state inside the coating, as well as the nature of the interface between different layers. A system for ESCA analysis (Electron Spectroscopy for Chemical Analysis) has recently been installed and put into operation at LESO-PB. By ellipsometry and spectrophotometry, we can determine exactly the different optical properties of the coating, such as layer thickness, refractive index, or absorption coefficient. This provides best conditions for highly efficient research and development on new materials for further optimisation of the coloured interference filters. First results have been obtained with our new experimental infrastructure and will be presented in this contribution

Energy-Efficient Sol-Gel Process for Production of Nanocomposite Absorber Coatings for Tubular Solar Thermal Collectors

The energy efficiency of production processes for components of solar energy systems is an important issue. Other factors which are important for the production of products such as black selective solar coatings include production speed, cycle time and homogeneity of the coating, as well as the minimization of the quantity of the needed chemical precursors. In this paper a new energy efficient production process is presented for production of optically selective coatings for solar thermal absorbers. The latter should ideally behave as a black body, absorbing a maximum of the incoming solar radiation, while minimizing energy losses by infrared radiation, acting as an infrared mirror. The used method to produce such coatings is sol-gel dip-coating. The optical and morphological properties of the Cu-Co-Mn-Si-O based triple layer have been characterized by spectrophotometry, electron microscopy and time of flight secondary electron microscopy. After optimization of the multilayer design, a solar absorptance of 0.95 and a thermal emissivity of 0.12 at 100°C have been achieved. The intermediate Cu-Co-Mn-Si-O layer was analyzed by high resolution transmission electron microscopy. The likewise obtained images show an agglomeration of crystalline grains with 10-20nm in diameter. Therefore, we can consider that the Cu-Co-Mn-Si-O phase is nanocrystalline. In order to roughly estimate the corrosion resistance of the coating in an acidic environment, a simple corrosion test in harsh conditions was designed. With respect to a commercially available durable black chrome coating, this test of corrosion resistance confirmed the durability of the novel sol-gel coating in an acidic environment. Moreover, the excellent stability at elevated temperatures in ambient air makes the coating an interesting candidate for solar applications involving concentrated solar radiation, such as the generation of solar electricity (concentrated solar power), industrial process heating and solar cooling. For that reason, prototype coatings consisting of stacks of three individual layers were deposited on 2 meter long stainless steel tubes