Glazings for the 21st Century - Windows and Daylighting Group

821st Century Glazings ...(continued from page 1)Fenestration Facts“Avariant of the liquidcrystal display technologyused in wristwatches is nowserving as a privacy glazingfor new windows. Averythin layer of liquid crystalsis sandwiched between twotransparent electricalconductors on thin plasticfilms and the entire packageis laminated between twolayers of glass. When thepower is off, the liquidcrystals are in a random andunaligned state. Whenpower is applied, the electricfield in the devicealigns the liquid crystalsand the glazing becomesclear in a fraction of a second,permitting view inboth directions.”F A L LW I N T E R1 9 9 7Residential WindowsJohn Carmody et al1996LAWRENCE BERKELEYNATIONALLABORATORYENVIRONMENTALENERGYTECHNOLOGIES DIVISIONBUILDING TECHNOLOGIESPROGRAMWINDOWS & DAYLIGHTINGGROUPtime failure as well as to diagnoseand correct device problems(see page 5).Thin Film DepositionProcessesProcess modification for developmentof improved low-emittanceand solar control coatingscan be achieved through the useof advanced plasma technologydeveloped at LBNL. Anewtype of constricted glow-dischargeplasma source was recentlyselected for the prestigiousR&D 100 Award. Inventedby LBNL researchers AndreAnders, Mike Rubin, and MikeDickenson, the source was designedto be compatible with industrialvacuum depositionequipment and practice. Constructionis simple, rugged, andinexpensive. The source can operateindefinitely over a widerange of chamber pressure withoutany consumable parts suchas filaments or grids. Among theuses of the source are densificationof coatings for greater durability,crystallization at low temperaturesfor increased reflectivityor electrical conductivity, enhancementof reactivity to producean otherwise unstablephase or increase depositionrate, and control over composition.Several of these sourceshave been fabricated for specificuses by glazing manufacturers.LBNL will assist these manufacturersto optimize the sourcecharacteristics and to developnew coating types. Recently, alinear configuration was successfullytested. Consisting ofan array of miniaturized versionsof the original source, thislinear source is extendible to adeposition system of any width.International Collaborationon Optical MaterialsLBNLstaff continue to participateactively in several internationalforums under the auspicesof the International EnergySimulation tools, such as these RADIANCE ray tracing images, comparevisibility of a computer screen with conventional clear glass (lower left),tinted glass (lower right), and electrochromic glass (top left), using two differentcontrol strategies.Agency (IEA). LBNL led thesubtask on Chromogenics underIEATask 18 which concluded inMarch. Switchable glazing technologiessuch as liquid crystalsand thermochromics, as well aselectrochromics, were investigatedand compared. Asurveywas made of the companies involvedworldwide and the statusof their technology. Test methodsand results were comparedfor a variety of small sampletypes and some large electrochromics.Energy performanceof these technologieswas evaluated in another subtaskled by Bob Sullivan ofLBNL. Reports were producedon various specific technologiesand a final report will be availablelater this year. One newstudy used DOE-2 to evaluatethe performance of angle-selectiveprototypes developed byProf. Geoff Smith of the Universityof Technology at Sydney.(See the regular update onIEATask 18 on page 2).Materials CharacterizationStudiesCharacterization of these newglazing materials is an importantpart of our research. Structuraland compositional analysisis performed using a variety offacilites available at LBNL.These techniques range fromstandard techniques such as x-ray diffraction, or less commontechniques such as Nuclear ReactionAnalysis for detection oflithium in electrochromics, toexotic and unique applicationsof atomic resolution electronmicroscopy or the syncrotron atLBNL's Advanced LightSource. Amore complete listingand description of these generalmaterials science capabilitiesmay be found on LBNL's website, http://www.lbl.gov. Opticaland thermal characterization ofwindows are of particular importanceto our energy efficiencyprogram, so we maintainspecialized facilites in theseareas. Thermal facilites werehighlighted in previous issues.The Optical CharacterizationFacility for glazing is describedin detail in a separate article onpage 6.ContactMike Rubin(510) 486-7124 Fax (510) 486-6099e-mail: MDRubin@lbl.gov