Glass, daylighting and lighting
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GLASS TECHNOLOGY LECTURE NOTES Glass, daylighting and lighting (COMBINING ENERGY EFFICIENCY WITH AESTHETIC APPEAL USING ADVANCED OPTICAL MATERIALS) Geoff Smith Applied Physics and Institute of Nanotechnology g.smith@uts.edu.au UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 1 GLASS TECHNOLOGY LECTURE NOTES Science of energy efficiency and engineered spreading in light diffusing materials “Eliminate” backscattering Small average deviation of ray per particle intersection Easily cast, extruded or injection moulded Colour dependence of spreadng weak UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 2 GLASS TECHNOLOGY LECTURE NOTES Science of energy efficiency and engineered spreading in light diffusing materials “Eliminate” backscattering Small average deviation of ray per particle intersection Easily cast, extruded or injection moulded Colour dependence of spreadng weak UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 3 GLASS TECHNOLOGY LECTURE NOTES Courtesy Skydome Skylight Systems UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 A skylight with special solar control glazing and angular selective mirror light pipe for catching low angle daylight. 4 GLASS TECHNOLOGY LECTURE NOTES Glazing and skylights in buildings Thermal comfort heating dominated climate - insulation cooling dominated climate - solar heat gain temperate ( Sydney) - control both Daylight too intense, usefulness a distribution issue View important Skylights : Solar intensity (Io cosθi, θi = angle of incidence) much higher than a window UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 5 GLASS TECHNOLOGY LECTURE NOTES SOLAR, VISIBLE AND NEAR IR Spectral Zones 2.0 2 /nm) 1.8 UV VIS NIR NIR Most important AM 1.5 Solar Spectrum Less important 1.6 1.4 Photopic Response of the Human Eye 1.2 1.0 0.8 0.6 0.4 0.2 0.0 300 500 700 900 1100 1300 1500 1700 1900 2100 2300 2500 Wavelength (nm) UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 50% of incident solar energy is at wavelengths longer than 700 nm which we do not need for daylighting or vision. 6 GLASS TECHNOLOGY LECTURE NOTES UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Australia has 8 different climate zones - each requires different energy efficient building designs. 7 GLASS TECHNOLOGY LECTURE NOTES Warm climate spectral engineering in a window or skylight Need to handle solar spectrum as follows : Transmit visible for light and view (preferably with low glare) Block NIR component ( to reduce solar heat gain) and ideally (but more important in a cold climate) have low thermal emittance that is low R in thermal or black body IR λ > 2.5 µm to ~ 30 µm UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 8 GLASS TECHNOLOGY LECTURE NOTES Heat gain in absorbing windows U also affects SHGC since it involves absorbed heat in window finding its way inside, plus direct transmitted solar energy SHGC = Tsol + AsolU/ho Asol= solar absorptance ho = external surface heat loss coefficient NIR reflecting windows will have SHGC and Tsol close together and stay cooler than those which absorb (as do most windscreens) External conditions such as wind speed and outside temperature UTS Applied Physics alter h and hence impact of absorbed energyIEAust/IEEE 2005 & Instituteoof Nanotechnology Heat entering a building from the sun via glazing is in two parts; directly transmitted solar energy and solar energy first absorbed then thermally transmitted by convection or radiation. 9 GLASS TECHNOLOGY LECTURE NOTES Low e pyrolytic(tin oxide) glass and multilayer AR coated silver Note both of these Reflect NIR solar While nanoparticle doped layers absorb it. SHGC affected by absorption and re-radiaiotn UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Existing systems which allow in light and block some NIR radiation. 10 GLASS TECHNOLOGY LECTURE NOTES Solar and visible transmittance These are the two most important parameters in assessing window energy performance and are defined as follows in terms of the spectral transmittance T(λ) of the window, S(λ) the normalized Air Mass 1.5 (AM1.5) solar energy spectrum, and the Normalized spectral sensitivity of our eyes Y(λ ) Tsol = Tvis = ∞ ∫ dλS(λ )T(λ ) 0 ∞ ∫ dλS(λ )T(λ )Y (λ ) 0 These give total solar energyand visible light energy getting in once actual solar flux on window is known. Daylight in (see next slide) UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 The calculation that is used to compare different window materials for lighting gain and solar thermal control. 11 GLASS TECHNOLOGY LECTURE NOTES Luminous efficacy and energy efficiency Lumens through a window L = K m A ∫ dλS( λ )T( λ )Y( λ ) Km = 683 lW-1,the luminous efficacy at the peak photopic eye response wavelength of 555nm, S(λ) is the spectral solar energy flux density distribution on the window and Y (λ) is the eye’s photopic respon se function. S olar heat gain through a window Φ in = [ SHGC ] ∫ dλS( λ) UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Energy efficiency in lighting is measured by luminous efficacy(light quantity units = lumens, energy Watts) . SHGC is the solar heat gain coefficient. S is the measure of solar energy flux density at wavelength lambda. 12 GLASS TECHNOLOGY LECTURE NOTES Solar blocking versus visible transmittance UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Balancing light gain and heat gain - a compromise approach is usually needed. 13 GLASS TECHNOLOGY LECTURE NOTES Thin film solution for daylight transmittance plus solar blocking via NIR reflectance Each film ~ 18 to 20 nm thick 18 to 20 nm of Ag normally blocks all light but transmittance is induced by the high index coatings either side Thin Film stack TiO2 silver TiO2 Glass substrate In practice products use a double or triple stack (6 or 9 layers) forUTSbest results. Applied Physics IEAust/IEEE 2005 & Institute of Nanotechnology A basic vacuum coated system for solar control with daylight - usually a little more complicated than that shown above, but uses same principle- produced in large sputtering lines e.g. at G.James in Qld. 14 GLASS TECHNOLOGY LECTURE NOTES Laminate foils doped with nanoparticles for cheap solar control glazing in cars and buildings (a) ( b) ( c) Glass layer nanopart icle d oped po lymer layer UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Different configurations of glazing showing how nano-particles can be incorporated, in laminate, in a polymer foil on the surface or in a bulk polymer skylight. 15 GLASS TECHNOLOGY LECTURE NOTES UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Photo of PhD student Stefan Schelm with samples of laminate with different concentrations of LaB6 nanoparticles 16 GLASS TECHNOLOGY LECTURE NOTES Underlying science Surface plasmon resonance in conducting nanoparticles Dipole moment on a sphere has an absorption resonance at frequency defined by Rl[dielectric constant(ε)] = -2(ε of host) Very strong ( high Q) and narrow band As conductivity drops resonant wavelength increases Thus NIR resonances need weaker conductors than gold, silver and TiN. UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Metals have unusual dielectric properties at NIR wavelengths and some also at visible wavelengths ( a negative dielectric constant!) - result is small particles can resonantly absorb incident radiation very efficiently at a particular wavelength range. 17 GLASS TECHNOLOGY LECTURE NOTES Tsol and Tvis for different concentrations of special conducting nanoparticles 0.9 Tsol Tvis 0.8 0.7 0.6 0.5 Laminated glazing with LaB6 nanoparticles in PVB layer 0.4 0.3 0.2 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 concentration (wt%) UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Transmittance versus nanoparticle concentration ( note it is very small in a 0.7 mm thick laminate layer ). Impact on light (top blue curve ) and heat gain( red curve) . + on right plot is where a car windscreen has to be above visually. 18 GLASS TECHNOLOGY LECTURE NOTES Light distribution systems Diffusers for luminaires Diffuse skylights Light pipes which continuously emit Signs, displays, data projectors, “neon” replacement “Piping” of daylight in solid light guides UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 19 GLASS TECHNOLOGY LECTURE NOTES TRIMM spheres and mixing rod UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Light deviation in large clear polymer particles with close refractive index to their host polymer - in a sidelighting rod or a light mixing rod, deviation per encounter is small - so total is easily engineered. Programs can calculate the total deviation - walls keep it in until deviation gets big enough. 20 GLASS TECHNOLOGY LECTURE NOTES “Supersidelight” doped polymer UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Continuously illuminating supersidelight flexible polymer made in a one step process by TRIMM doping can achieve combination of transport and sidelight to any distances from a few cm to 30 metres; set up shown is for measuring output as a function of distance from source . 21 DIS Sup PLAY Elim erside Refrig dow inates light li erator t per nsizes >5 flu with lightin ex g lam o c p re ompr rolam ternal plac esso p ch LE r, > a ed 50W nges, D’s sav ing s GLASS TECHNOLOGY LECTURE NOTES UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 A display fridge lit not with a fluoro tube but with a superside lit polymer in which source is at end and can be external to fridge using light guide(fibre optic) principles to save much thermal energy gains from the lamps currently used and if done with Leds can last 10 years. 22 GLASS TECHNOLOGY LECTURE NOTES Beam White Light from LED’s Colored light in TRIMM mixer White light out UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Mixing colours homogenously and energy efficiently to produce new colours including white for novel LED based lamps- colour lighting with no filters and many colour options ! 23 GLASS TECHNOLOGY LECTURE NOTES UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 A prototype new generation white light lamp using colour mixing principles. 24 GLASS TECHNOLOGY LECTURE NOTES Clear rod mixer UTS Applied Physics & Institute of Nanotechnology TRIMM doped rod mixer IEAust/IEEE 2005 Mixing and colour uniformity mapped on right .vs. unmixed on left. 25 GLASS TECHNOLOGY LECTURE NOTES Solar Related Options Direct - windows, skylights, translucent walls Indirect - flexible light pipes PV power + lamps - solar cells , energy efficient lamps Various hybrids of above UTS Applied Physics & Institute of Nanotechnology UTS has developed some of these, Why are they best at present costs ? IEAust/IEEE 2005 26 GLASS TECHNOLOGY LECTURE NOTES Fluorescent solar concentrator UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 The new daylighting system developed at UTS and currently being commercialised in Sydney, Australia. 27 GLASS TECHNOLOGY LECTURE NOTES Measuring LSC-light pipe performance UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Measuring performance - note light is coupled into clear light guides for remote delivery anywhere in a building - only short guide lengths shown in this special experiment here, but can be many metres (to 20 at least) distant. 28 GLASS TECHNOLOGY LECTURE NOTES UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 Schematic of one type of domestic installation - product coming available late next year from Fluorosolar Systems Pty Ltd - a start up company in Sydney; a web site will soon available for lodgment of interest. 29 GLASS TECHNOLOGY LECTURE NOTES CONCLUSION NOVEL POLYMERS AND NANO BASED MATERIALS ARE OPENING UP A WHOLE NEW RANGE of COST EFFECTIVE ENERGY EFFICIENT OPTIONS IN BUILDING SYSTEMS with exciting and attractive new aesthetic features and design options THANK YOU UTS Applied Physics & Institute of Nanotechnology IEAust/IEEE 2005 30
