Window | EPFL Graph Search

A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent material, a sash set in a frame in the opening; the sash and frame are also referred to as a window. Many glazed windows may be opened, to allow ventilation, or closed, to exclude inclement weather. Windows may have a latch or similar mechanism to lock the window shut or to hold it open by various amounts. In addition to this, many modern day windows may have a window screen or mesh, often made of aluminum or fibreglass, to keep bugs out when the window is opened. Windows are primarily designed to facilitate a vital connection with the outdoors, offering those within the confines of the building visual access to the everchanging events occurring outside. The provision of this connection serves as an integral safeguard for t

Demand Side Management for Enhanced Integration of Photovoltaics into Grid

Christophe Ballif, Christophe Germain Boillat, Yannick Samuel Riesen, Raffael Fabian Tschui

Demand side management could be a very effective way to shift electric consumption of households to the maximum production hours of photovoltaic (PV) systems. A field study on more than 100 households were performed to evaluate the share of electric consumption that could be easily shifted. Assuming a fixed time window for the PV production (namely 11:00 to 15:00) the share of consumption already in this window was found to be around 20 % while the flexible consumption outside of that window was ca. 5% (not including hot water heating). Information to households was found insufficient to push households to change behaviour and shift consumption demonstrates that information is not sufficient. However, financial incentive households were able to shift ca. 3% of their consumption, Hot water heating at mid-day (rather than during the night) is shown to be a very effective demand side management measure.

WIP Wirtschaft und Infrastruktur GmbH & Co Planungs KG2015

A Novel Louver System for Increasing Daylight Usage in Buildings

Marilyne Andersen

Advanced daylighting systems can be effective in increasing light levels in building spaces and reducing energy consumption due to electric lighting. However, a recurring issue found in most existing daylighting systems is the necessity of coupling the light-redirecting technology with a separate light shade to reduce glare risks. A different approach is proposed here, based on the use of a louver system which scatters incoming light onto a reflective ceiling, where it is redirected deep into the space. This type of system is effective for both diffuse daylight and direct sunlight without causing glare and without the need for a shading system. Annual simulations of workplane illuminance were conducted with Radiance using Tokyo weather data and a generic south-facing deep-plan office space. Glare was evaluated through testing of a physical prototype of the system. The new system was compared to a base case consisting of an unshaded window of equal area to the louver system. The results show that the novel louver system enables a significant decrease in electric lighting usage and outperforms the uncovered window, while adequately controlling direct sunlight to prevent glare.

2011

Transition metal clusters on h-BN/Rh(111)

Hamed Achour

The main aim of this dissertation is to study the catalytic aspects of very small transition metal clusters supported on h-BN/Rh(111). The catalytic reactions of interest were ammonia synthesis and CO oxidation on mass selected and soft landed iron and platinum clusters, respectively. A special focus was devoted to the investigation of the stability of these very small clusters on h-BN before and after the reaction. It was found that Pt7 clusters soft landed at room temperature with an energy of 1.2 eV per atom and annealed to 700 K exhibit Smoluchowski ripening. Above this temperature, these clusters undergo partial intercalation between the h-BN monolayer and the Rh(111). The intercalation initiates at 900 K and becomes more pronounced when the clusters are annealed under gas reaction conditions. A high catalytic activity was observed when the Pt catalyst remains supported on h-BN. In this case, the reaction starts at 480 K and follows Langmuir-Hinshelwood mechanism. However, the catalytic activity strongly reduces when the Pt clusters undergo partial intercalation. Nevertheless, in this case the reaction starts at only 380 K, revealing a reduction by 100 K in the Pt poisoning as a result of substrate effect and charge redistribution. In a second trail, the cluster-h-BN interaction was studied through h-BN irradiation with Pt clusters, at room temperature, within an energy window of 30-416 eV/atom. The results show that even irradiation at 30 eV/atom can lead to entire non thermal intercalation of the clusters. The energetic Pt clusters were found to be site selective as they settle only under the h-BN wires, in contrast to soft landed Pt7 clusters that were found to settle at the side edge of the h-BN depressions. After being exposed to irradiated Pt clusters, at an energy above 100 eV/atom, the h-BN layer starts to display visual cavity-type defects. These defects, induced by collision, disappeared after annealing to 600 K under gas reaction leaving behind an h-BN with no visual defects. CO temperature desorption spectroscopy (TDS) indicates that the intercalated Pt is inactive towards CO oxidation due to h-BN screening. Subsequently, we were able to produce a catalyst system made of soft-landed Pt/h-BN/intercalated Pt/Rh(111) using a combination between soft and energetic Pt deposition with which a reduction by 100 K in CO poisoning was obtained. Finally, ammonia synthesis was conducted on soft landed Fe clusters, supported on h-BN/Rh(111) and deposited at 100 K under Ultra High Vacuum (UHV). Scanning tunneling microscopy (STM) displays two imaging states of the as deposited clusters; a ring state surrounding h-BN depression which disappears above 300 K and a dot like structure. The Fe clusters are found to grow by Ostwald ripening after annealing to 600 K and above this temperature, they endure partial intercalation. It was found that, in the presence of iron, the nitrogen reaction gas experienced an exchange with the nitrogen species forming the h-BN layer. TPR (Temperature Programmed Reduction) of N

_2

with hydrogen revealed that nitrogen reduction occurs at 620 K under high vacuum following the Haber-Bosch method. The detection of reaction intermediates NH and NH

_2

together with desorbed atomic nitrogen, during ammonia synthesis, confirms that NH

_3

formation involves the stepwise hydrogenation of adsorbed nitrogen.

EPFL2017