@article {31851, title = {Split-pane electrochromic window control based on an embedded photometric device with real-time daylighting computing}, journal = {Building and Environment}, volume = {161}, year = {2019}, month = {08/2019}, pages = {106229}, abstract = {

Well-designed electrochromic (EC) glazing control can improve the energy performance of buildings and visual comfort of occupants in highly glazed buildings. This paper designed and demonstrated a compact integrated EC glazing automation system to control tint states of a split-pane EC window according to variations of sky conditions. The control is based on monitoring the luminance distribution of the sky and real-time lighting computation for a building interior, using an embedded photometric device (EPD). It optimizes tint states of EC glazing to offer sufficient daylight provision and temper discomfort glare for occupants, which potentially mitigates excessive solar heat gain. {\textquoteright}In-situ{\textquoteright} experiments were conducted in a full-scale testbed to demonstrate the daylighting performance under various sky conditions. Experimental results showed 83\% of the working time for work-plane illuminance (WPI) and 95\% of the time for daylight glare probability (DGP) were constrained in comfort range (WPI[500, 2000] lux, DGP\ <=\ 0.35) by the automated EC glazing (controlled by EPD) under clear skies; 68\% of the time for WPI and 94\% of the time for DGP in confined range under clear skies with thin clouds; 62\% of the time for WPI and 85\% of the time for DGP in confined range under partly cloudy skies.

}, keywords = {daylighting, electrochromic, Embedded Controller, HDR, windows}, issn = {03601323}, doi = {10.1016/j.buildenv.2019.106229}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0360132319304391}, author = {Yujie Wu and Taoning Wang and Eleanor S. Lee and J{\'e}r{\^o}me H. K{\"a}mpf and Jean-Louis Scartezzini} } @techreport {58686, title = {Simulated daylight performance of a new prototype prismatic window film in deep open plan offices}, year = {2013}, month = {09/2013}, type = {DOE/ CEC PIER Technical Report}, author = {Andrew McNeil and Eleanor S. Lee} } @article {58927, title = {Spectroscopic imaging of self-organization in high power impulse magnetron sputtering plasmas}, journal = {Applied Physics Letters}, volume = {103}, year = {2013}, month = {07/2013}, pages = {054104}, abstract = {

Excitation and ionization conditions in traveling ionization zones of high power impulse magnetron sputtering plasmas were investigated using fast camera imaging through interference filters. The images, taken in end-on and side-on views using light of selected gas and target atom and ion spectral lines, suggest that ionization zones are regions of enhanced densities of electrons, and excited atoms and ions. Excited atoms and ions of the target material (Al) are strongly concentrated near the target surface. Images from the highest excitation energies exhibit the most localized regions, suggesting localized Ohmic heating consistent with double layer formation.

}, keywords = {Aluminium, ionization, Ionizing radiation, plasma ionization, visible spectra}, issn = {00036951}, doi = {10.1063/1.4817257}, author = {Joakim Andersson and Pavel A Ni and Andr{\'e} Anders} } @techreport {1217, title = {On the sensitivity of daylight simulations to the resolution of the hemispherical basis used to define bidirectional scattering distribution functions}, year = {2011}, month = {09/2011}, pages = {19}, type = {DOE / CEC PIER Technical Memorandum}, abstract = {

The Radiance simulation program includes new tools that enable daylight modeling of complex fenestration systems (CFS) using bi-directional transmission distribution functions (BTDF). The tools use the Klems angle basis to define the number of paired incoming and outgoing data values. However, the Klems angle basis was developed for thermal simulations and may be too low of a resolution for some types of daylight systems, particularly those that exhibit peaky, specular transmission. This study evaluates the sensitivity of the angle basis resolution by comparing simulation results for the Klems angle basis against results using two higher resolution angle bases. The first evaluation compares results for specific points in time. The second evaluation compares simulation results using annual performance metrics. Annual lighting energy data were found to agree to within 1\%. Annual assessments of discomfort glare were found to disagree by 7\% because high resolution basis resolved glare sources into smaller, more intense sources. We concluded that high resolution bases are appropriate for specific types of CFS and performance metrics.

}, author = {Andrew McNeil} } @article {1799, title = {Simulating the Daylight Performance of Complex Fenestration Systems Using Bidirectional Scattering Distribution Functions within Radiance}, journal = {Leukos, The Journal of the Illuminating Engineering Society}, volume = {7}, year = {2011}, month = {04/2011}, chapter = {241}, abstract = {

We describe two methods which rely on bidirectional scattering distribution functions (BSDFs) to model the daylighting performance of complex fenestration systems (CFS), enabling greater flexibility and accuracy in evaluating arbitrary assemblies of glazing, shading, and other optically-complex coplanar window systems. Two tools within Radiance enable a) efficient annual performance evaluations of CFS, and b) accurate renderings of CFS despite the loss of spatial resolution associated with low-resolution BSDF datasets for inhomogeneous systems. Validation, accuracy, and limitations of the methods are discussed.

}, keywords = {bidirectional scattering distribution function (BSDF), Complex fenestration systems, daylighting systems, energy, Radiance software, Shading Systems, windows}, issn = {1550-2724}, doi = {10.1080/15502724.2011.10732150}, author = {Gregory J. Ward and Richard G. Mistrick and Eleanor S. Lee and Andrew McNeil and Jacob C. Jonsson} } @conference {1807, title = {Singapore{\textquoteright}s Zero-Energy Building{\textquoteright}s Daylight Monitoring System}, booktitle = {International Conference on Applied Energy 2010: Energy Solutions for a Sustainable World}, year = {2010}, month = {04/2010}, address = {Singapore}, abstract = {

A setup to monitor the daylighting performance of different glazing types in Singapore is presented. The glazing is installed in the facade of four dedicated testing chambers in BCAA{\textquoteright}s Zero Energy Building in Singapore. These test rooms are equipped with sensors that both record illuminances on the work plane, and luminances as seen by occupants. The physical and logical design of the monitoring system is presented. Criteria to assess the daylighting performance are introduced, and initial results of the work in progress are presented.

}, author = {Stephen E. Selkowitz} } @article {1869, title = {Supersonic metal plasma impact on a surface: an optical investigation of the pre-surface region}, journal = {Journal of Physics D: Applied Physics}, volume = {43}, year = {2010}, month = {04/2010}, chapter = {135201}, abstract = {

Aluminum plasma, produced in high vacuum by a pulsed, filtered cathodic arc plasma source, was directed onto a wall where if formed a coating. The accompanying "optical flare" known from the literature was visually observed, photographed, and spectroscopically investigated with appropriately high temporal (1 μs) and spatial (100 μm) resolution. Consistent with other observations using different techniques, it was found that the impact of the fully ionized plasma produces metal neutrals as well as desorbed gases, both of which interact with the incoming plasma. Most effectively are charge exchange collisions between doubly charged aluminum and neutral aluminum, which lead to a reduction of the flow of doubly charged before they reach the wall, and a reduction of neutrals as the move away from the surface. Those plasma-wall interactions are relevant for coating processes as well as for interpreting the plasma properties such as ion charge state distributions.

}, keywords = {cathodic arc plasma, ions, neutrals, optical emission spectroscopy, plasma-wall interaction}, doi = {10.1088/0022-3727/43/13/135201}, author = {Pavel A Ni and Andr{\'e} Anders} } @conference {1798, title = {Simulating Complex Window Systems Using BSDF Data}, booktitle = {26th Conference on Passive and Low Energy Architecture (PLEA), June-22-24}, year = {2009}, month = {06/2009}, address = {Quebec City, Canada}, abstract = {

Nowadays, virtual models are commonly used to evaluate the performance of conventional window systems. Complex fenestration systems can be difficult to simulate accurately not only because of their geometry but also because of their optical properties that scatter light in an unpredictable manner. Bi-directional Scattering Distribution Functions (BSDF) have recently been developed based on a mixture of measurements and modelling to characterize the optics of such systems. This paper describes the workflow needed to create then use these BSDF datasets in the Radiance lighting simulation software. Limited comparisons are made between visualizations produced using the standard ray-tracing method, the BSDF method, and that taken in a full-scale outdoor mockup.

}, author = {Maria Konstantoglou and Jacob C. Jonsson and Eleanor S. Lee} } @article {12244, title = {Self-sputtering far above the runaway threshold: an extraordinary metal ion generator}, journal = {Physical Review Letters}, year = {2008}, abstract = {

When self-sputtering is driven far above the runaway threshold voltage, energetic electrons are made available to produce excess plasma far from the magnetron target. Ionization balance considerations show that the secondary electrons deliver the necessary energy to the remote zone. Thereby, such a system can be an extraordinarily prolific generator of useable metal ions. Contrary to other known sources, the ion current to a substrate can exceed the discharge current. For gasless self-sputtering of copper, the useable ion current scales exponentially with the discharge voltage.

}, author = {Joakim Andersson and Andr{\'e} Anders} } @article {1791, title = {Self-sputtering runaway in high power impulse magnetron sputtering: The role of secondary electrons and multiply charged metal ions}, journal = {Applied Physics Letters}, volume = {92}, year = {2008}, month = {08/2004}, chapter = {201501}, address = {Boulder, CO}, abstract = {

Self-sputtering runaway in high power impulse magnetron sputtering is closely related to the appearance of multiply charged ions. This conclusion is based on the properties of potential emission of secondary electrons and energy balance considerations. The effect is especially strong for materials whose sputtering yield is marginally greater than unity. The absolute deposition rate increases ~ Q1/2, whereas the rate normalized to the average power decreases ~ Q-1/2, with Q being the mean ion charge state number.

}, doi = {10.1063/1.2936307}, author = {Andr{\'e} Anders} } @article {1834, title = {Spatial distribution of average charge state and deposition rate in high power impulse magnetron sputtering of copper}, journal = {Journal of Physics D}, volume = {41}, year = {2008}, pages = {135210-1-6}, abstract = {

The spatial distribution of copper ions and atoms in high power impulse magnetron sputtering (HIPIMS) discharges was determined by (i) measuring the ion current to electrostatic probes and (ii) measuring the film thickness by profilometry. A set of electrostatic and collection probes were placed at different angular positions and distances from the target surface. The angular distribution of the deposition rate and the average charge state of the copper species (including ions and neutrals) were deduced. The discharge showed a distinct transition to a high current mode dominated by copper self-sputtering when the applied voltage exceeded the threshold of 535 V. For a lower voltage, the deposition rate was very low and the average charge state was found to be less than 0.4. For higher voltage (and average power), the absolute deposition rates were much higher, but they were smaller than the corresponding direct current (DC) rates if normalized to the same average power. At the high voltage level, the spatial distribution of the average charge state showed some similarities with the distribution of the magnetic field, suggesting that the generation and motion of copper ions is affected by magnetized electrons. At higher voltage, the average charge state increases with the distance from the target and locally may exceed unity, indicating the presence of significant amounts of doubly charged copper ions.

}, author = {David Horwat and Andr{\'e} Anders} } @article {1859, title = {The structure and electron energy loss near edge structure of tungsten oxide thin films prepared by pulsed cathodic arc deposition and plasma-assisted pulsed magnetron sputtering}, journal = {Journal of Physics: Condensed Matter}, volume = {20}, year = {2008}, month = {04/2008}, pages = {175216}, abstract = {

The microstructure and energy-loss near-edge structure (ELNES) of pulsed cathodic arc and pulsed magnetron sputtered WO3 thin films were investigated. It was found that the cathodic arc deposited material consisted of the α-WO3 phase with a high degree of crystallinity. In contrast, the magnetron sputtered material was highly disordered making it difficult to determine its phase. A self-consistent real space multiple scattering approach was used to calculate the NES of the various phases of WO3. Each phase was found to exhibit a unique NES allowing different phases of WO3 to be identified. The real space approach also allowed the origin of the main features in the NES to be investigated as the cluster size increased. The calculated NES for the room temperature γ-WO3 was found to compare well to previous X-ray absorption spectra and to NES obtained by full-potential band structure calculation.

}, doi = {10.1088/0953-8984/20/17/175216}, author = {Matthew R. Field and Dougal G. McCulloch and Sunnie H.N. Lim and Andr{\'e} Anders and Vicki J. Keast and R.W. Burgess} } @techreport {1846, title = {State-of-the-Art Highly Insulating Window Frames - Research and Market Review}, number = {Project report 6}, year = {2007}, institution = {INTEF Building and Infrastructure}, address = {Olso}, abstract = {

This document reports the findings of a market and research review related to state-of-the-art highly insulating window frames. The market review focuses on window frames that satisfy the Passivhaus requirements (window U-value less or equal to 0.8 W/m2K), while other examples are also given in order to show the variety of materials and solutions that may be used for constructing window frames with a low thermal transmittance (U-value). The market search shows that several combinations of materials are used in order to obtain window frames with a low U-value. The most common insulating material seems to be Polyurethane (PUR), which is used together with most of the common structural materials such as wood, aluminum, and PVC.

The frame research review also shows examples of window frames developed in order to increase the energy efficiency of the frames and the glazings which the frames are to be used together with. The authors find that two main tracks are used in searching for better solutions. The first one is to minimize the heat losses through the frame itself. The result is that conductive materials are replaced by highly thermal insulating materials and air cavities. The other option is to reduce the window frame area to a minimum, which is done by focusing on the net energy gain by the entire window (frame, spacer and glazing). Literature shows that a window with a higher U-value may give a net energy gain to a building that is higher than a window with a smaller U-value. The net energy gain is calculated by subtracting the transmission losses through the window from the solar energy passing through the windows. The net energy gain depends on frame versus glazing area, solar factor, solar irradiance, calculation period and U-value.

The frame research review also discusses heat transfer modeling issues related to window frames. Thermal performance increasing measures, surface modeling, and frame cavity modeling are among the topics discussed. The review shows that the current knowledge gives the basis for improving the calculation procedures in the calculation standards. At the same time it is room for improvement within some areas, e.g. to fully understand the natural convection effects inside irregular vertical frame cavities (jambs) and ventilated frame cavities.

}, keywords = {energy use, Passivhaus, thermal transmittance, U-value, window frame, windows}, isbn = {978-82-536-0970-6}, author = {Arlid Gustavsen and Bj{\o}rn Petter Jelle and Dariush K. Arasteh and Christian Kohler} } @article {1812, title = {Smoothing of ultrathin silver films by transition metal seeding}, journal = {Applied Physics Letters}, year = {2006}, abstract = {

The nucleation and coalescence of silver islands on coated glass was investigated by in-situ measurements of the sheet resistance. Sub-monolayer amounts of transition metals (Nb, Ti, Ni, Cr, Zr, Ta, and Mo) were deposited prior to the deposition of silver. It was found that some, but not all, of the transition metals lead to coalescence of silver at nominally thinner films with smoother topology. The smoothing effect of the transition metal at sub-monolayer thickness can be explained by a thermodynamic model of surface energies.

}, author = {Andr{\'e} Anders and Eungsun Byon and Dong-Ho Kim and Kentaro Fukuda and Sunnie H.N. Lim} } @article {1857, title = {Structural, optical and electrical properties of WOxNy films deposited by reactive dual magnetron sputtering}, journal = {Surface and Coatings Technology}, volume = {201}, year = {2006}, pages = {2977-2983}, chapter = {2977}, abstract = {

Thin films of tungsten oxynitrides were prepared by dual magnetron sputtering of tungsten using argon/oxygen/nitrogen gas mixtures with various nitrogen/oxygen ratios. The presence of even relatively small amounts of oxygen led to close-to-stoichiometric WO3, with little incorporation of nitrogen, therefore the films were labeled as WOx(Ny). Oxygen had a great effect not only on the composition but on the structure of WOx(Ny) films, as shown by Rutherford backscattering and X-ray diffraction, respectively. Significant incorporation of nitrogen occurred only when the nitrogen partial pressure exceeded 89\% of the total reactive gas pressure. Sharp changes in the stoichiometry, deposition rate, room temperature resistivity, electrical activation energy and optical band gap were observed when the nitrogen/oxygen ratio was high. The deposition rate increased from 0.31 to 0.89 nm/s, the room temperature resistivity decreased from 1.65 {\texttimes} 108 to 1.82 {\texttimes} 10- 2 Ω cm, the electrical activation energy decreased from 0.97 to 0.067 eV, and the optical band gap decreased from 3.19 to 2.94 eV upon nitrogen incorporation into the films. WOx(Ny) films were highly transparent as long as the nitrogen incorporation was low, and were brownish (absorbing) and partially reflecting as nitrogen incorporation became significant.

}, keywords = {Dual magnetron sputtering, electrical, optical properties, structural, tungsten oxynitride thin films}, doi = {10.1016/j.surfcoat.2006.06.008 }, author = {Sodky H. Mohamed and Andr{\'e} Anders} } @article {1861, title = {Subject Response to Electrochromic Windows}, journal = {Energy and Buildings}, volume = {38}, number = {7}, year = {2006}, month = {07/2006}, pages = {758-779}, chapter = {758}, abstract = {

Forty-three subjects worked in a private office with switchable electrochromic windows, manually-operated Venetian blinds, and dimmable fluorescent lights. The electrochromic window had a visible transmittance range of approximately 3-60\%. Analysis of subject responses and physical data collected during the work sessions showed that the electrochromic windows reduced the incidence of glare compared to working under a fixed transmittance (60\%) condition. Subjects used the Venetian blinds less often and preferred the variable transmittance condition, but used slightly more electric lighting with it than they did when window transmittance was fixed.

}, keywords = {Electrochromic windows, energy use, Subjective response, Venetian blind use}, doi = {10.1016/j.enbuild.2006.03.011}, author = {Robert D. Clear and Vorapat Inkarojrit and Eleanor S. Lee} } @techreport {58563, title = {Summary results of visual comfort measurements at the electrochromic windows testbed}, year = {2006}, note = {

Included as an attachment to the Advancement of Electrochromic Windows final report.

}, month = {03/2006}, address = {Berkeley}, abstract = {

The study was performed at the Lawrence Berkeley National Laboratory (LBNL) windows testbed in Berkeley California. The location is 37.4{\textdegree}N latitude. The maximum solar altitude ranges from approximately 29{\textdegree} to 76{\textdegree}, with a yearly average of about 53{\textdegree}. The testbed rooms have their windows mounted due south. The azimuthal angle at sunrise varies from approximately 60{\textdegree} from due south in the winter to 120{\textdegree} in summer. The analysis was restricted to the period from 6:00-18:00 standard time. Sunrise ranges from 4:42 to 7:17 (solar time), so the sun was not visible during part of the winter study periods.

}, author = {Robert D. Clear} } @conference {1871, title = {Surface Engineering of Glazing Materials and Structures Using Plasma Processes}, booktitle = {Glass Processing Days 2003 }, year = {2003}, month = {06/2003}, address = {Tampere, Finland}, abstract = {

A variety of coatings is commercially produced on a very large scale, including transparent conducting oxides and multi-layer silver-based low-emissivity and solar control coatings. A very brief review of materials and manufacturing process is presented and illustrated by ultrathin silver films and chevron copper films. Understanding the close relation between manufacturing processes and bulk and surface properties of materials is crucial for film growth and self-assembly processes.

}, keywords = {nano-structures, plasma processing, surface engineering, thin films}, author = {Andr{\'e} Anders and Othon R. Monteiro} } @conference {1854, title = {Structural and Electronic Properties of Magnesium-3D Transition Metal Switchable Mirrors}, booktitle = {Fifth International Meeting on Electrochromism}, year = {2002}, month = {12/2002}, address = {Golden, CO}, abstract = {

We have observed reversible mirror-to-transparent state switching in a variety of mixed metal thin films containing magnesium and first-row transition elements including Ni, Fe, Co, Mn, and Ti. The very large changes in both reflectance and transmittance on loading these films with hydrogen are accompanied by significant structural and electronic transformations. The valence states and coordination of metal atoms during hydrogen loading were followed using dynamic in situ transmissionmode X-ray absorption spectroscopy. Time-resolved Mg K-edge and Ni, Co, Mn, and Ti L-edge spectra reflect both reversible and irreversible changes in the metal environments. These spectra are compared to those of reference materials and to predictions from calculations.

}, keywords = {EXAFS, Hydrogen storage materials, NEXAFS, thin films, x-ray diffraction}, doi = {10.1016/j.ssi.2003.08.041}, author = {Baker Farangis and Ponnusamy Nachimuthu and Thomas J. Richardson and Jonathan L. Slack and Bruno K. Meyer and Rupert C.C. Perera and Michael D. Rubin} } @conference {1803, title = {Simulating the Operation of Photosensor-Based Lighting Controls}, booktitle = {2001 Building Simulation 7th International Building Performance Simulation Association Conference}, year = {2001}, month = {08/2001}, address = {Rio de Janeiro, Brazil}, abstract = {

Energy savings from the use of daylighting in commercial buildings are realized through implementation of photoelectric lighting controls that dim electric lights when sufficient daylight is available to provide adequate workplane illumination. The dimming level of electric lighting is based on the signal of a photosensor. Current simulation approaches for such systems are based on the questionable assumption that the signal of the photosensor is proportional to the task illuminance. This paper presents a method that simulates the performance of photosensor controls considering the acceptance angle, angular sensitivity, placement of the photosensor within a space, and color correction filter. The method is based on the multiplication of two fisheye images: one generated from the angular sensitivity of the photosensor and the other from a 180- or 360-degree fisheye image of the space as seen by the photosensor. The paper includes a detailed description of the method and its implementation, example applications, and validation results based on comparison with measurements in an actual office space.

}, author = {Charles K. Ehrlich and Konstantinos M. Papamichael and Judy Lai and Kenneth L. Revzan} } @conference {1820, title = {Solar Heat Gain through a Skylight in a Light Well}, booktitle = {ASHRAE Chicago}, volume = {108, Part 1}, year = {2001}, month = {01/2003}, pages = {512-524}, address = {Chicago, IL}, abstract = {

Detailed heat flow measurements on a skylight mounted on a light well of significant depth are presented. It is shown that during the day much of the solar energy that strikes the walls of the well does not reach the space below. Instead, this energy is trapped in the stratified air of the light well and eventually either conducted through the walls of the well or back out through the skylight. The standard model for predicting fenestration heat transfer does not agree with the measurements when it is applied to the skylight/well combination as a whole (the usual practice), but does agree reasonably well when it is applied to the skylight alone, using the well air temperature near the skylight. A more detailed model gives good agreement. Design implications and future research directions are discussed.

}, author = {Joseph H. Klems} } @article {1875, title = {Switchable Mirrors Based on Nickel-Magnesium Films}, journal = {Applied Physics Letters}, volume = {78}, number = {20}, year = {2001}, month = {05/2001}, pages = {3047-3049}, chapter = {3047}, abstract = {

An electrochromic mirror electrode based on reversible uptake of hydrogen in nickel magnesium alloy films is reported. Thin, magnesium-rich Ni-Mg films prepared on glass substrates by cosputtering from Ni and Mg targets are mirror-like in appearance and have low visible transmittance. Upon exposure to hydrogen gas or on cathodic polarization in alkaline electrolyte, the films take up hydrogen and become transparent. When hydrogen is removed, the mirror properties are recovered. The transition is believed to result from reversible formation of Mg2NiH4 and MgH2. A thin overlayer of palladium was found to enhance the kinetics of hydrogen insertion and extraction, and to protect the metal surface against oxidation.

}, doi = {10.1063/1.1371959 }, author = {Thomas J. Richardson and Jonathan L. Slack and Robert D. Armitage and Robert Kostecki and Baker Farangis and Michael D. Rubin} } @techreport {1822, title = {Solar Heat Gain Through Fenestrations Containing Shading: Procedures for Estimating Performace from Minimal Data}, year = {2000}, abstract = {

The computational methods for calculating the properties of glazing systems containing shading from the properties of their components have been developed, but the measurement standards and property data bases necessary to apply them have not. It is shown that with a drastic simplifying assumption these methods can be used to calculate system solar-optical properties and solar heat gain coefficients for arbitrary glazing systems, while requiring limited data about the shading. Detailed formulas are presented, and performance multipliers are defined for the approximate treatment of simple glazings with shading. As higher accuracy is demanded, the formulas become very complicated.

}, author = {Joseph H. Klems} } @article {1828, title = {Solid State Gadolinium-Magnesium Hydride Optical Switch}, journal = {Applied Physics Letters}, volume = {75}, number = {13}, year = {1999}, month = {09/1999}, pages = {1863-1865}, chapter = {1863}, abstract = {

The optical switching properties of gadolinium-magnesium hydride have been demonstrated in a solid-state electrochromic device. With positive polarization of the hydride electrode, the visible reflectance approaches 35\% with virtually zero transmission, while with negative polarization, the visible transmission exceeds 25\% at 650 nm. The switching is reversible, with intermediate optical properties between the transparent and reflecting states.

}, url = {http://dx.doi.org/10.1063/1.124853}, author = {Robert D. Armitage and Michael D. Rubin and Thomas J. Richardson and Nada O{\textquoteright}Brien and Yong Chen} } @techreport {58590, title = {Spectrally Selective Glazings}, year = {1998}, month = {08/1998}, pages = {47}, institution = {New Technology Energy Management Program, Federal Energy Management Program}, abstract = {

Spectrally selective glazing is window glass that permits some portions of the solar spectrum to enter a building while blocking others. This high-performance glazing admits as much daylight as possible while preventing transmission of as much solar heat as possible. By controlling solar heat gains in summer, preventing loss of interior heat in winter, and allowing occupants to reduce electric lighting use by making maximum use of daylight, spectrally selective glazing significantly reduces building energy consumption and peak demand. Because new spectrally selective glazings can have a virtually clear appearance, they admit more daylight and permit much brighter, more open views to the outside while still providing the solar control of the dark, reflective energy-efficient glass of the past, as shown in the figures on the left.

Because of its solar heat transmission properties, spectrally selective glazing benefits both buildings in warm climates where solar heat gain can be a problem and buildings in colder climates where solar heat gains in summer and interior heat loss in winter are both of concern. In other words, these glazings are appropriate for residential and commercial buildings throughout the United States. The energy efficiency of spectrally selective glazing means that architects who use it can incorporate more glazing area than was possible in the past within the limitations of codes and standards specifying minimum energy performance. When spectrally selective glazing is used, the capacity of the building{\textquoteright}s cooling system can also be downsized because of reduced peak loads.

Spectrally selective glazings screen out or reflect heat-generating ultraviolet and infrared radiation arriving at a building{\textquoteright}s exterior surface while permitting most visible light to enter. Spectral selectivity is achieved by a microscopically thin, low-emissivity (low-E) coating on the glass or on a film applied to the glass. There are also carefully engineered types of blue- and green-tinted glass that can perform as well in a double-pane unit as some glass with a low-E coating. Conventional blue- and green-tinted glass can offer some of the same spectral properties as these special absorbers because impurities in tinted glass absorb portions of the solar spectrum. Absorption is less efficient than reflection, however, because heat absorbed by tinted glass continues to radiate to the building{\textquoteright}s interior.

This technology is most costeffective for residential and nonresidential facilities that have high cooling loads, high utility rates, poorly performing existing glazing (such as single-pane clear glass or dark tinted glass), or are located in the southern United States. In the northern United States, spectrally selective low-E windows can also be cost-effective for buildings with both heating and cooling requirements.

In general, the technology pays back in 3 to 10 years for U.S. commercial buildings where it replaces clear single-pane or tinted doublepane glass and for most commercial buildings in the southern United States where it replaces low-E, double-pane windows. Spectrally selective glazing is applicable in both new and retrofit construction.

This Federal Technology Alert provides detailed information and procedures for Federal energy managers to consider spectrally selective glazings. The principle of spectrally selective glazings is explained. Benefits related to energy efficiency and other architectural criteria are delineated. Guidelines are provided for appropriate application of spectrally selective glazing, and step-by-step instructions are given for estimating energy savings. Case studies are also presented to illustrate actual costs and energy savings. Current manufacturers, technology users, and references for further reading are included for users who have questions not fully addressed here.

}, author = {Eleanor S. Lee} } @conference {1847, title = {State-of-the-Art Software for Window Energy-Efficiency Rating and Labeling}, booktitle = {ACEEE 1998 Summer Study on Energy Efficiency in Buildings}, year = {1998}, month = {08/1998}, address = {Pacific Grove, CA}, abstract = {

Measuring the thermal performance of windows in typical residential buildings is an expensive proposition. Not only is laboratory testing expensive, but each window manufacturer typically offers hundreds of individual products, each of which has different thermal performance properties. With over a thousand window manufacturers nationally, a testing-based rating system would be prohibitively expensive to the industry and to consumers.

Beginning in the early 1990s, simulation software began to be used as part of a national program for rating window U-values. The rating program has since been expanded to include Solar Hear Gain Coefficients and is now being extended to annual energy performance.

This paper describes four software packages available to the public from Lawrence Berkeley National Laboratory (LBNL). These software packages are used to evaluate window thermal performance: RESFEN (for evaluating annual energy costs), WINDOW (for calculating a products thermal performance properties), THERM (a preprocessor for WINDOW that determines two-dimensional heat-transfer effects), and Optics (a preprocessor for WINDOWs glass database).

Software not only offers a less expensive means than testing to evaluate window performance, it can also be used during the design process to help manufacturers produce windows that will meet target specifications. In addition, software can show small improvements in window performance that might not be detected in actual testing because of large uncertainties in test procedures.

}, author = {Dariush K. Arasteh and Elizabeth U. Finlayson and Yu Joe Huang and Charlie Huizenga and Robin Mitchell and Michael D. Rubin} } @article {1794, title = {The Significance of Bolts in the Thermal Performance of Curtain-Wall Frames for Glazed Fa{\c c}ades}, journal = {ASHRAE Transactions}, volume = {104, Part 1}, year = {1997}, month = {01/1998}, address = {San Francisco, CA}, abstract = {

Curtain walls are assemblies of glazings and metal frames that commonly form the exterior glass fa{\c c}ades of commercial buildings. Evaluating the thermal performance of the bolts that hold curtain wall glazings in place is necessary to accurately rate the overall thermal performance of curtain walls. Using laboratory tests and computer simulations, we assessed the thermal performance of several different configurations of bolts and glazings. Curtain-wall samples were tested in the infrared thermography laboratory at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California. Experimental results were compared to two-dimensional simulations approximating the thermal effect of the bolts using the parallel path and the isothermal planes calculation methods. We conclude that stainless steel bolts minimally affect curtain-wall thermal performance (approximately 18\%) when spaced at least nine inches apart, which is the industry standard. Performance is increasingly compromised when there is less than nine inches between bolts or when steel bolts are used. We also show that the isothermal planes method of approximating curtain wall thermal performance can be used with 2-D heat transfer software typical of that used in the window industry to give conservative results for the thermal bridging effect caused by bolts.

}, author = {Brent T. Griffith and Elizabeth U. Finlayson and Mehry Yazdanian and Dariush K. Arasteh} } @article {1804, title = {Simulating the Visual Performance of Electrochromic Glazing for Solar Control}, journal = {Journal of the Illuminating Engineering Society}, volume = {27}, number = {2}, year = {1997}, abstract = {

A new technology called electrochromic glazing promises to provide the building industry with a means to dynamically control the visual appearance and solar gain of windows. Electrochromic glazing is a technology which allows an otherwise ordinary looking piece of laminated glass to change tint with the application of a small electrical charge. Prototype electrochromic devices have been produced in sizes up to one square foot, however, manufacturers are several years away from producing glazing samples large enough to fill the aperture of a typical perimeter office. Tooling up for the production of large samples is prohibitively expensive unless some assurance of the marketability of these new electrochromic products can be demonstrated.

Electrochromic glazings defy traditional performance rating mechanisms because of the temporal dimension of their thermal and visual characteristics. Every electrochromic glazing assembly has an infinite number of states at which the thermal and visual appearance could be characterized. Furthermore, the rate at which the assembly changes between states is vital for a complete understanding.

}, author = {Charles K. Ehrlich} } @conference {1819, title = {Solar Heat Gain Coefficient of Complex Fenestrations with a Venetian Blind for Differing Slat Tilt Angles}, booktitle = {ASHRAE Symposium}, volume = {103, Part 1}, year = {1996}, month = {01/1997}, address = {Philadelphia, PA}, abstract = {

Measured bidirectional transmittances and reflectances of a buff-colored venetian blind together with a layer calculation scheme developed in previous publications are utilized to produce directional-hemispherical properties for the venetian blind layer and solar heat gain coefficients for the blind in combination with clear double glazing. Results are presented for three blind slat tilt angles and for the blind mounted either interior to the double glazing or between the glass panes. Implications of the results for solar heat gain calculations are discussed in the context of sun positions for St. Louis, MO.

}, author = {Joseph H. Klems and Jeffrey L. Warner} } @conference {1817, title = {Sol-Gel Deposited Electrochromic Films for Electrochromic Smart Window Glass}, booktitle = {International Symposium on Glass Problems, International Commission on Glass}, year = {1996}, month = {09/1996}, address = {Istanbul, Turkey}, abstract = {

Electrochrornic windows offer the ability to dynamically change the transmittance of a glazing. With the appropriate sensor and controls, this smart window can be used for energy regulation and glare control for a variety of glazing applications. The most promising are building and automotive applications. This work covers the use of sol-gel deposition processes to make active films for these windows. The sol-gel process offers a low-capital investment for the deposition of these active films. Sol-gel serves as an alternative to more expensive vacuum deposition processes. The sol-gel process utilizes solution coating followed by a hydrolysis and condensation. In this investigation we report on tungsten oxide and nickel oxide films made by the sol-gel process for electrochromic windows. The properties of the sol-gel films compare favorably to those of films made by other techniques. A typical laminated electrochromic window consists of two glass sheets coated with transparent conductors, which are coated with the active films. The two sheets are laminated together with an ionically conductive polymer. The range of visible transmission modulation of the tungsten oxide was 60\% and for the nickel oxide was 20\%. We used the device configuration of glass/SnO2:F/WO3/polymer/LizNiOxHy/SnO2:F to test the films. The nickel oxide layer had a low level of lithiation and possibly contained a small amount of water. Lithiated oxymethylene-linked poly(ethylene oxide) was used as the laminating polymer. Commercially available Sn02:F/glass (LOF-Tec glass) was used as the transparent conducting glass. We found reasonable device switching characteristics which could be used for devices.

}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert and Michael D. Rubin} } @article {1849, title = {Strain Related Phenomena in GaN Thin Films}, journal = {Physical Review B}, volume = {54}, number = {24}, year = {1996}, month = {12/1996}, pages = {17745-17753}, chapter = {17745}, abstract = {

Photoluminescence (PL), Raman spectroscopy, and x-ray diffraction are employed to demonstrate the co-existence of a biaxial and a hydrostatic strain that can be present in GaN thin films. The biaxial strain originates from growth on lattice-mismatched substrates and from post-growth cooling. An additional hydrostatic strain is shown to be introduced by the presence of point defects. A consistent description of the experimental results is derived within the limits of the linear and isotropic elastic theory using a Poisson ratio nu =0.23+/-0.06 and a bulk modulus B=200+/-20 GPa. These isotropic elastic constants help to judge the validity of published anisotropic elastic constants that vary greatly. Calibration constants for strain-induced shifts of the near-band-edge PL lines with respect to the E2 Raman mode are given for strain-free, biaxially strained, and hydrostatically contracted or expanded thin films. They allow us to extract differences between hydrostatic and biaxial stress components if present. In particular, we determine that a biaxial stress of one GPa would shift the near-band-edge PL lines by 27+/-2 meV and the E2 Raman mode by 4.2+/-0.3 cm-1 by use of the listed isotropic elastic constants. It is expected from the analyses that stoichiometric variations in the GaN thin films together with the design of specific buffer layers can be utilized to strain engineer the material to an extent that greatly exceeds the possibilities known from other semiconductor systems because of the largely different covalent radii of the Ga and the N atom.

}, doi = {10.1103/PhysRevB.54.17745}, author = {Christian F. Kisielowski and Joachim Kr{\"u}ger and Sergei Ruvimov and Tadeusz Suski and Joel W. Ager III and Erin C. Jones and Zuzanna Liliental-Weber and Michael D. Rubin and Eicke R. Weber and Michael D. Bremser and Robert F. Davis}, editor = {Joachim Kr{\"u}ger} } @conference {1815, title = {Sol-Gel Deposited Amorphous Tantalum Oxide and Niobium Oxide Films as Protonic Conductors}, booktitle = {Window Innovations 95 Conference Proceedings}, year = {1995}, month = {06/1995}, address = {Toronto, Canada}, abstract = {

In this work we report on the preparation of tantalum oxide and niobium oxide films by the sol-gel method for use as proton ion conductors in electrochromic devices. Measurement of the proton conductivity was derived from impedence spectroscopy measurements. The proton conductivity for Ta2O5 and NbO5 films was 4.6 x 10-6 Scm-1 and 3.2 x 10-7 Scm-1 respectively. The structural and chemical properties of the films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. These films were found to be amorphous and close to the stoichometry of Ta2O5 and NbO5 respectively. In order to estimate the compatibility of these sol-gel deposited layers as ion conductors for EC devices, we investigated tantalum oxide and niobium oxide films deposited on sputtered WO3 films. Charge balance and coloration characteristics were investigated during voltammetric cycling in a pH 2 liquid electrolyte. Spectral transmittance was measured for colored and bleached conditions. The photopic weighted transmittance change and solar weighted transmittance change were Tp=35.2\% - 21.8\% and Ts=75.7\% - 14.2\% for tantala films on tungsten oxide. For niobia on tungsten oxide the values were Tp=85.3\% - 35.2\% and Ts=75.8\% - 28.1\%.

}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert} } @conference {1816, title = {Sol-Gel Deposited Electrochromic Coatings}, booktitle = {Am. Optical Society, Technical Digest}, volume = {17}, year = {1995}, month = {06/1995}, pages = {344-347}, address = {Tucson, AZ}, abstract = {

Electrochromic devices have increasing application in display devices, switchable minors and smart windows. A variety of vacuum depition technologies have been used to make electrochromic devices. The sol-gel process offers an alternative approach to the synthesis of optical quality and low cost electrochromic device layers. This study summarizes the developments in sol-gel deposited electrochromic films. The sol-gel process involves the formation of oxide networks upon hydrolysis-condensation of alkoxide precursors. In this study we cover the sol-gel deposited oxides of WO3, V2O5, TiO2, Nb2O5 and NiOx.

}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert} } @conference {1855, title = {Structural and Optical Properties of Sol-Gel Deposited Proton Conducting Ta2O5 Films}, booktitle = {8th International Workshop on Glasses and Ceramics From Gels}, year = {1995}, month = {09/1995}, address = {Faro, Portugal}, abstract = {

Proton conducting tantalum oxide films were deposited by spin coating using a sol-gel process. The coating solutions were prepared using Ta(OC2H5)5 as a precursor. X-ray diffraction studies determined that the sol-gel films, heat treated at temperatures below 400 {\textdegree}C, were amorphous. Films heat treated at higher temperatures were crystalline Ta2O5. The solar transmission values (Ts) of tantala films on glass generally range from 0.8-0.9 depending on thickness. The refractive index and the extinction coefficient were evaluated from transmittance characteristics in the UV-VIS-NIR regions. The refractive index values calculated at λ=550 nm increased from n=1.78 to 1.97 with increasing heat treatment from 150 to 450 {\textdegree}C. The films heat treated at different temperatures showed low absorption with extinction coefficients of less than k=1 x 10-3 in the visible range. Spectrophotometric and impedance spectroscopic investigations performed on Ta2O5 films revealed that these films have protonic conductivity of 3.2 x 10-6 S/cm. The films are suitable for proton conducting layers in electrochromic (EC) devices.

}, keywords = {electrochromic devices, optical proterties, proton conductor, tantalum oxide}, author = {Nilg{\"u}n {\"O}zer and Carl M Lampert} } @article {1872, title = {Surface Temperatures of Insulated Glazing Units: Infrared Thermography Laboratory Measurements}, journal = {ASHRAE Transactions}, volume = {102}, year = {1995}, month = {12/1995}, abstract = {

Data are presented for the distribution of surface temperatures on the warm-side surface of seven different insulated glazing units. Surface temperatures are measured using infrared thermography and an external referencing technique. This technique allows detailed mapping of surface temperatures that is non-intrusive. The glazings were placed between warm and cold environmental chambers that were operated at conditions corresponding to standard design conditions for winter heating. The temperatures conditions are 21.1 {\textdegree}C (70 {\textdegree}F) and -17.8 {\textdegree}C (0 {\textdegree}F) on the warm and cold sides, respectively. Film coefficients varied somewhat with average conditions of about 7.6 W/m2 K (1.34 Btu/h ft2 {\textdegree}F) for the warm-side and 28.9 W/m2 K (5.1 Btu/h ft2 {\textdegree}F) for the cold-side. Surface temperature data are plotted for the vertical distribution along the centerline of the IG and for the horizontal distribution along the centerline. This paper is part of larger collaborative effort that studied the same set of glazings.

}, author = {Brent T. Griffith and Daniel Turler and Dariush K. Arasteh} } @conference {1874, title = {Switchable Glazing: Science and Technology of Smart Windows}, booktitle = {Society of Vacuum Coaters 38th Annual Technical Conference }, year = {1995}, abstract = {

Electrically activated switchable glazing and their use as smart windows and other large-area applications are discussed. Electrochromic devices are compared to dispersed liquid crystals and dispersed particle glazing systems. A selection of device structures and performance characteristics are compared. A discussion of transparent conductors is presented. The characteristics of prototype and commercial devices from commercial and university labs in Japan, Europe, Australia, and USA are covered. A discussion of the future of this technology is made including areas of necessary development for the realization of devices in excess of 1 m2.

}, author = {Carl M Lampert} } @conference {1801, title = {Simulating the Energy Performance of Holographic Glazings}, booktitle = {13th SPIE International Symposium on Optical Materials Technology for Energy Efficiency and Solar Energy Conversion}, year = {1994}, month = {04/1994}, address = {Freiburg, Germany}, abstract = {

The light diffraction properties of holographic diffractive structures present an opportunity to improve the daylight performance in side-lit office spaces by redirecting and reflecting sunlight off the ceiling, providing adequate daylight illumination up to 30 ft (9.14 m) from the window wall. Prior studies of prototypical holographic glazings, installed above conventional view windows, have shown increased daylight levels over a deeper perimeter area than clear glass, for selected sun positions. In this study, we report on the simulation of the energy performance of prototypical holographic glazings assuming a commercial office building in the inland Los Angeles climate.

The simulation of the energy performance involved determination of both luminous and thermal performance. Since the optical complexity of holographic glazings prevented the use of conventional algorithms for the simulation of their luminous performance, we used a newly developed method that combines experimentally determined directional workplane illuminance coefficients with computer-based analytical routines to determine a comprehensive set of daylight factors for many sun positions. These daylight factors were then used within the DOE-2.1D energy simulation program to determine hourly daylight and energy performance over the course of an entire year for four window orientations.

Since the prototypical holographic diffractive structures considered in this study were applied on single pane clear glass, we also simulated the performance of hypothetical glazings, assuming the daylight performance of the prototype holographic glazings and the thermal performance of double-pane and low-e glazings. The results of our analyses show that these prototypical holographic glazings did not save significant electric energy or reduce peak electricity demand compared to conventional energy-efficient window systems in inland Los Angeles office buildings, mainly because of their low diffraction efficiency. Finally, we address various design and implementation issues towards potential performance improvement.

}, author = {Konstantinos M. Papamichael and Liliana O. Beltran and Reto A. Furler and Eleanor S. Lee and Stephen E. Selkowitz and Michael D. Rubin} } @article {1837, title = {Spectrally Selective Glazings for Residential Retrofits in Cooling-Dominated Climates}, journal = {ASHRAE Transactions}, volume = {100}, year = {1994}, abstract = {

Spectrally selective glazings can substantially reduce energy consumption and peak demand in residences by significantly reducing solar gains with minimal loss of illumination and view. In cooling-dominated climates, solar gains contribute 24{\textendash}31\% to electricity consumption and 40{\textendash}43\% to peak demand in homes with single pane clear glazing{\textemdash}standard practice for residential construction built before the implementation of building energy efficiency standards. The existing residential housing stock therefore offers a prime opportunity for significant demand-side management (DSM),but the energy and cost savings must be weighed against retrofit first costs in order for the technology to achieve full market penetration. Using DOE-2.1D for numerical simulation of building energy performance, we quantify the energy and peak demand reductions, cost savings, and HVAC capacity reductions using spectrally selective glazings for five cooling-dominated climates in California. The cost-effectiveness of various material and installation retrofit options is discussed. Glazing material improvements for retrofit applications that are needed to achieve a prescribed cost savings are also given.

}, keywords = {deserts, domestic, energy conservation, Glazing, housing, modernising, subtropics, usa, windows}, author = {Eleanor S. Lee and Deborah Hopkins and Michael D. Rubin and Dariush K. Arasteh and Stephen E. Selkowitz} } @techreport {1783, title = {Savings from Energy Efficient Windows: Current and Future Savings from New Fenestration Technologies in the Residential Market}, year = {1993}, note = {

A version of this report was presented at the\ 4th Global Warming International Conference. Chicago, IL, April 5-8, 1993.

}, abstract = {

Heating and cooling energy lost through windows in the residential sector (estimated at two-thirds of the energy lost through windows in all sectors) currently accounts for 3 percent (or 2.8 quads) of total US energy use, costing over $26 billion annually in energy bills. Installation of energy-efficient windows is acting to reduce the amount of energy lost per unit window area. Installation of more energy efficient windows since 1970 has resulted in an annual savings of approximately 0.6 quads. If all windows utilized existing cost effective energy conserving technologies, then residential window energy losses would amount to less than 0.8 quads, directly saving $18 billion per year in avoided energy costs. The nationwide installation of windows that are now being developed could actually turn this energy loss into a net energy gain. Considering only natural replacement of windows and new construction, appropriate fenestration policies could help realize this potential by reducing annual residential window energy losses to 2.2 quads by the year 2012, despite a growing housing stock.

}, author = {Karl J. Frost and Dariush K. Arasteh and Joseph H. Eto} } @conference {1800, title = {Simulating the Daylight Performance of Fenestration Systems and Spaces of Arbitrary Complexity: The IDC Method}, booktitle = {3rd International Conference of the International Building Performance Simulation Association, Building Simulation 93}, year = {1993}, address = {Adelaide, Australia}, abstract = {

A new method to simulate the daylight performance of fenestration systems and spaces is presented. This new method, named IDC (Integration of Directional Coefficients), allows the simulation of the daylight performance of fenestration systems and spaces of arbitrary complexity, under any sun, sky and ground conditions. The IDC method is based on the combination of scale model photometry and computer-based simulation. Physical scale models are used to experimentally determine a comprehensive set of directional illuminance coefficients at reference points of interest, which are then used in analytical, computer-based routines, to determine daylight factors or actual daylight illuminance values under any sun, sky and ground conditions.

The main advantage of the IDC method is its applicability to any optically complex environment. Moreover, the computer-based analytical routines are fast enough to allow for hourly simulation of the daylight performance over the course of an entire year. However, the method requires appropriate experimental facilities for the determination of the Directional Coefficients. The IDC method has been implemented and used successfully in inter-validation procedures with various daylight simulation computer programs. Currently, it is used to simulate the daylight performance of fenestration systems that incorporate optically complex components, such as Venetian blinds, optically treated light shelves and light pipes.

}, author = {Konstantinos M. Papamichael and Liliana O. Beltran} } @conference {1810, title = {Skylight Energy Performance and Design Optimization}, booktitle = {Windows in Building Design and Maintanence}, year = {1984}, month = {06/1984}, address = {Gothenburg, Sweden}, abstract = {

Proper skylight utilization can significantly lower energy requirements and peak electrical loads for space conditioning and lighting in commercial buildings. In this study we systematically explore the energy effects of skylight systems in a prototypical officesbuilding and examine the savings from daylighting. We used the DOE-2.1B energy analysis computer program with its newly incorporated daylighting algorithims to generate more than 2000 parametric simulations for seven U.S. climates. The parameters varied include skylight-to-roof ratio, shading coefficient, visible transmittance, skylight well light loss, electric lighting powersdensity, roof heat transfer coefficient, and type of electric lighting control. For specific climates we identify roof/skylight characteristics that minimize total energy or peak electrical load requirements.

}, author = {Dariush K. Arasteh and Russell Johnson and Robert Sullivan} }