Solar Absorption by Each Element in a Glazing/Shading Layer Array

©2006, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions, Volume 112, Part 2. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE’s prior written permission.Window solar gain can strongly influence building energy consumption and peak cooling load. Shading devices such as venetian blinds, roller blinds, and drapes are routinely used to control solar gain. There is a strong need for models that allow shading layers to be included in glazing system analysis. This paper presents methods by which existing solar optical models for systems of specular glazing layers can be extended to include the effect of layers that create scattered, specifically diffuse, radiation in reflection and/or transmission. Spatially averaged optical properties (i.e., “effective” optical properties) can be used to characterize shading layers, including their beam-diffuse split. Solution techniques can be formulated on the basis of matrix reduction. However, an alternative technique has been developed with the goal of computational simplicity and speed. These attributes are important in the context of hour-by-hour building energy analysis. Sample calculations are presented.Natural Sciences and Engineering Research Council (Canada

Simplified Solar Optical Calculations For Windows With Venetian Blinds

Solar gain through a window represents the most variable heat gain imposed on an indoor space. It is also likely to represent the largest heat gain of the indoor space. Shading devices like venetian blinds roller blinds and drapes are routinely used to control solar gain through windows and their potential for reduction of building load and annual energy consumption is recognized to be large. As such, there is a strong need for models that allow shading layers to be included in glazing system analysis. In this paper, three sets of calculations are presented for a window with light- and dark-coloured venetian blinds using simplified models and computational procedures. For each of the three sets; hourly transmitted, reflected and absorbed fluxes are calculated for both summer and winter conditions. In the first set, the venetian blind is placed on the indoor-side of the window. For the second set the venetian blind is placed between the glazings. Finally, the third set of results is obtained by placing the venetian blind on the outdoor-side of the window.Natural Sciences and Engineering Council (Canada

Emergent Collectivity in Nuclei and Enhanced Proton-Neutron Interactions

Enhanced proton-neutron interactions occur in heavy nuclei along a trajectory of approximately equal numbers of valence protons and neutrons. This is also closely aligned with the trajectory of the saturation of quadrupole deformation. The origin of these enhanced p-n interactions is discussed in terms of spatial overlaps of proton and neutron wave functions that are orbit-dependent. It is suggested for the first time that nuclear collectivity is driven by synchronized filling of protons and neutrons with orbitals having parallel spins, identical orbital and total angular momenta projections, belonging to adjacent major shells and differing by one quantum of excitation along the z-axis. These results may lead to a new approach to symmetry-based theoretical calculations for heavy nuclei.Comment: 6 pages, 4 figure

Demonstration Of New ESP-R Capability For Quantifying The Energy Savings Potential Of Window Shading Devices

Buildings with highly glazed facades and well insulated, air-tight envelopes result in interior spaces that are highly sensitive to solar gain. Solar gain through glazing is the largest and most variable gain in buildings and has major implications on energy consumption and peak cooling loads. The peak electricity demand in Ontario, for example, is dominated by space cooling of residential and commercial buildings. The appropriate use of window shading devices can reduce cooling energy consumption and substantially lower the peak cooling load. The potential for reducing the electricity demand on peak summer days is especially significant as the cost to construct and maintain the power distribution grid and generating capacity is directly related to the peak demand. Recently, new capabilities for modeling windows with shading devices were incorporated into ESP-r. The work is based on a set of shading models, designated the ASHWAT (ASHRAE Window Attachment) models, which were developed with emphasis on generality and computational efficiency. Measurements performed at the National Solar Test Facility (NSTF) on a full scale window with various shading attachments were compared to calculated values predicted by the ASHWAT models. The predicted results aligned well with measured data, giving confidence to the applicability of the models. To demonstrate the new modeling capability within ESP-r, simulation examples illustrating the impact of different shading configurations on cooling energy, peak load and thermal comfort are presented. In particular, a simulation of an automated external shading system highlights the role of shading on the energy performance of a solar house design entered into the Solar Decathlon 2009 competition. The external shading design is compared with other options including a solar protective coating on the outside glass as well as indoor shades. Simulations were also carried out to illustrate the impact of shading devices on winter nighttime heat loss and thermal comfort. Finally, a general procedure for using the shading models within ESP-r is outlined, highlighting straightforward user input by means of a user-friendly graphical interface.Natural Sciences and Engineering Research Council of Canad

Determining Off-Normal Solar Optical Properties of Insect Screens

© 2009, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions 2009, vol. 115, part 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE’s prior written permission.Shading attachments may have a strong influence on solar gain. The determination of off-normal solar optical properties of individual layers of glazing/shading systems is required in order to estimate this solar gain, which influences building peak load and annual energy consumption. Recently, a unique test method was developed for the experimental determination of off-normal solar optical properties of flat shading devices (e.g., drapery fabrics and roller blinds). The study described in this research applies the same method to insect screens. More specifically, semi-empirical models were developed from measured data, obtained at varying angles of incidence using an integrating sphere installed in a spectrophotometer. The measurements were taken on six samples of screen material with various mesh sizes and wire reflectances. The measured data were compared with analytical models recently developed from geometry and ray tracing techniques. The results of this study demonstrate the reliability of using special sample holders attached to an integrating sphere to obtain off-normal solar optical properties of flat shading materials.Natural Sciences and Engineering Research Council of Canada || American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

Determining Off-Normal Solar Optical Properties of Roller Blinds

© 2009, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions 2009, vol. 115, part 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE’s prior written permission.Solar gain through fenestration constitutes a significant portion of peak cooling load and annual energy consumption in buildings. As such, any reduction in solar gain translates into savings associated with the cost of purchasing and operating cooling equipment. Shading devices in general, and roller blinds in particular, can be used to reduce solar gain appreciably. The performance of a roller blind is largely determined by its solar optical properties. In this study, an integrating sphere was used to obtain off-normal solar properties of six typical roller blind samples. Measurements were used to develop semi-empirical models for the off-normal beam-beam, beam-diffuse, and diffuse-diffuse solar optical properties. The models provide a means to calculate off-normal properties by adjusting known values of beam-beam transmittance (i.e., openness), beam-total transmittance, and beam-total reflectance measured at normal incidence. The properties that apply to normal incidence are readily obtained. Such models are valuable components of building energy simulation software.Natural Sciences and Engineering Research Council || ASHRAE 1311-TR

A Detailed Model to Determine the Effective Solar Optical Properties of Draperies

© 2009, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions 2009, vol. 115, part 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE’s prior written permission.Drapes have the potential to reduce peak cooling load and annual energy consumption because they can be used to control solar gain. Thus, the need to model a drapes in a glazing system analysis is important. A detailed model that can be used to estimate the spatially averaged (effective) solar optical properties of a drapery is presented. This model approximates a drapery as a series of uniformly arranged rectangular pleats. The effective solar optical properties of the drapery are then determined by considering a representative enclosure. The solar properties of the fabric are incidence angle dependent, and the effects of beam and diffuse components, in both reflection and transmission, are included. Furthermore, the model can be applied to fabrics with differing front and back properties. The model therefore offers new possibilities in calculating the effective solar optical properties of draperies made with practically any fabric. Results are presented for both incident beam and diffuse radiation.Natural Science and Engineering Research Council || American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc

Determining Off-Normal Solar Optical Properties of Drapery Fabrics

© 2009, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions 2009, vol. 115, part 2. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE’s prior written permission.The determination of off-normal solar optical properties of drapery fabrics is particularly useful in modelling the effective solar optical properties of pleated drapery. Special sample holders were designed and fabricated to facilitate measurements using an integrating sphere installed in a commercially available spectrophotometer. Measurements were taken for eight of the nine fabric designations documented in the ASHRAE Handbook – Fundamentals. Measurements were also obtained for a sheer fabric which does not fall into any of the customary fabric designations. Semi-empirical models were developed to quantify the variation of solar optical properties with respect to incidence angle. Given solar optical properties obtained at normal incidence, these models can be used to characterize the off-normal beam-beam and beam-diffuse properties of a drapery fabric. The fabric models comprise a useful component of pleated drapery models and, in turn, a valuable tool for building energy simulation. The measurement technique described in this study can be used to obtain the off-normal solar optical properties of additional flat shading devices such as roller blinds and insect screens.Natural Sciences and Engineering Research Council (NSERC) || ASHRA

Determining Longwave Radiative Properties Of Flat Shading Materials

Solar gain through fenestration has a significant impact on building peak load and annual energy consumption. Shading devices, attached to fenestration, offer a cost effective strategy in controlling solar gain. The performance of a particular shading device is dependent on solar optical and longwave radiative properties of the device. The current study considers longwave properties of three flat shading materials; drapery fabrics, insect screens and roller blinds. Each of these materials consists of a structure (i.e., yarn, wire, sheet) that is opaque with respect to longwave (infrared) radiation and each material is likely to have some openness. Material emittance and longwave transmittance measurements were taken with an infrared reflectometer using two backing surfaces. The results show emittance and longwave transmittance to be simple functions of openness, emittance and longwave transmittance of the structure. This is especially useful because openness can be determined from solar transmittance measurements while emittance and longwave transmittance of the structure was found to be constant for each category of shading material.NSERC || ASHRA