BEARS | SinBerBEST Translucent Panels: Construction, Light Transmission and Thermal Analysis

Khalid M. Mosalam I Baofeng Huang I Núria Casquero-Modrego I Jaume Armengou I Sing-Ping Chiew Supported by: Funded by:

Motivation and Overview Main Objectives  Optimal utilization of daylight for the façade system can Tasks Research Addressed reduce the carbon footprint and enhance the working efficiency of the indoor environment. 1. Translucent concrete panel prototype  Develop a daylight transmitting translucent concrete construction 1. Concrete selection structural panels for building façades. 2. Light transmission tests of the translucent 2. Optical fiber selection and spatial concrete panel arrangement Compared to traditional electric lighting system, daylight is 3. Light transmission simulation of the optical 3. development and construction more energy efficient and healthy for human beings as it fibers procedure contains full spectrum of the sunlight. The IR spectral band 4. Light concentration analysis: 4. Light transmission test setup and light could be filtered or used to generate heat or electricity, while the  Convex lens for light collection simulation transmission property description other bands could be filtered selectively and then guided into  Compound parabolic concentrator for light 5. Numerical modeling for light buildings. collection simulation transmission simulation 5. Thermal insulation analysis of the 6. Light collection section Due to existence of the optical fibers, the novel translucent translucent concrete panel 7. Thermal insulation property description concrete panel permits some light to be transmitted through to the indoor environment.

Translucent Concrete (TC) Panel Translucent Concrete Panel Details Light Transmission Tests Construction Process Specimen Details: Experimental Setup: Test Setup Volume ratio of the optical fibers = 5%  7 in.7 in.0.5 in. foam panel  7 in.7 in.7 in. white & black Instrumentation: Diameter of the optical fibers = 0.079 in. (2 mm) foam-board boxes  Light meter Clear distance of the optical fiber = 0.229 in.  Incandescent lamp (250 W)  Camera: Canon EOS 5D Mark IIL  2 mm Optical Fibers (OF) Number of pre-drilled holes = 1600 Distance between neighboring holes = 0.308 in. Wire mesh 1 in.×1 in. Wire Mesh Lamp Foam panel Mortar mix: Light meter Drilling Holes in Installing the Form Setup Holes Distribution Acrylic Panel Optical Fibers Vulcan sand passed through #8 sieve Type I/II cement Foam-board box Type F ADVA 190 super plastisizer

1.00 VMA 362 viscosity modifier

0.90 Black Box

) 2 0.80 White Box Details of Optical Fiber Optical Fiber 0.70 Property Value Finished Form Before Mortar Placement Placing Mortar Finished Specimen 1% 2% 2.5% 3% 4% 5% 0.60 Core Material Polymethyl-Methacrylate Resin Cladding Material Fluorinated Polymer White Box 0.50 Core Refractive Index 1.49 0.40 Refractive Index Profile Step-index 0.30 Numerical Aperture 0.50 0.20 Number of Fibers 1

1% 2% 2.5% 3% 4% 5% (W/m Intensity Light 0.10 1840 – 2080 µm Core Diameter Wire Mesh Arrangement 0.00 Cladding Diameter 1880 – 2120 µm Black Box (not to scale) 0 2 4 6 Approximate Weight 2.8 g/m OF Volume Ratio (%) http://i-fiberoptics.com/fiber-detail.php?id=110&sum=90 Form Removal TC Panel Light Transmission Showing Images of Objects Optical Fiber Simulation Light Concentration of Convex Lens Compound Parabolic Concentrator (CPC) Software package: TracePro 72 Software package: TracePro 72 Software package: TracePro 72 Optical Fiber Details: Convex Lens: Rays of light CPC: A 2D concentrator designed to concentrate light onto the r Light rays edge of a receiver. This basic principle can be used to design Diameter: 2 mm Optical fiber non-imaging devices. Its generalization is the “ edge-ray Focal length: 50 mm Optical fiber Cladding: 0.2 mm principle” and is the basis of non-imaging optics. Grid source Diameter: 38 mm θ Core: 1.8 mm Properties: Lens thickness: 3 mm θ Focal point –Source at “infinity” Light loss due to Grid Light Source: –Planar input and output apertures W/m² Material: Glass 1 0.95 bending of the fiber –Perfectly transmits light up to ± 0.9 Y θa 0.85 Grid boundary: Annular Grid Source Simulation 0.8 Grid Source Irradiation 0.75 0.7 Light rays 0.65 X 0.6 Convex lens h Y 0.55 Grid pattern: Circular X 0.5 Grid Source Modeling 0.45 0.4 Grid Source 1 Optical 0.35 Flux per ray: 0.1 Watts Bending of 0.3 0.25 0.2 fiber CPC fiber 0.15 0.1 a 0.05 No polarization 4.5×107 W/m2 a’ 0 Fiber bending will lose light

7 2 Φ 3.16×10 W/m 1.0×107 W/m2 θ θ Operation Mechanism

Convex Lens

Polar ISO Candela Distribution Light Transmission in the Irradiation Map for Exit Flux CPC and Fiber Academy of Sciences San Francisco – Roof Level - (Architect: Renzo Piano) (Concentration efficiency (Concentration efficiency is Total Irradiance Map for the Smoothed Plot Contour Plot higher than fibers only) higher than convex lens) Incident Flux

Thermal Flux Analysis Software package: COMSOL Multi Physics 4.2 Technical details: 120o Heat transfer time: 4 hours 20o Conclusions Temperature difference: 100o Temp. concrete fibers mesh Environmental Temperature: 20o variation 1. Translucent concrete (TC) can represent an energy Future Goals Concrete properties efficient solution as a material for building envelop Properties Values 5% volume ratio Note: 273K=0o Density 2300[kg/m3] 2. Construction of TC panel is feasible Thermal conductivity 1.8 [W/(m*K] 1. Active sun tracking system Sun at 12 pm Heat capacity at constant pressure 3800 3. Daylight transmission properties of the TC is × implementation ×Sun at 1 pm Young's modulus 25e9 [Pa] controlled by the volume ratio of the fibers Coefficient of thermal expansion 10e-6 [1/K] 2. Optimal design of CPC Possion's ratio 0.33 5% volume ratio 4. Light collection property of the TC can be Fiber properties 5% volume ratio CPC & 3 in. thick 3. CPC spatial arrangement in the TC panel Properties Values 3 in. thick improved by utilization of convex lens and CPCs. fiber Density 891.7[kg/m3] fibers Concrete 4. Daylight collection of CPC and fibers Thermal conductivity 0.15 [W/(m*K] Daylight simulation 5. Light concentration efficiency of CPC can be Heat capacity at constant pressure 5000 5. Thermal insulation performance Young's modulus 7e10 [Pa] optimized by changing its 3D shape. Possion's ratio 0.16 Temperature variations: Midpoint of Thickness optimization of TC panel Sky 6. The bending of the fiber should be minimized as it dome affects the light transmission performance model 7. Thermal insulation performance of the TC panel is 5% volume ratio 2.5% volume ratio No fibers affected by the concrete material, thickness of the 1.5 in. thick 3 in. thick 3 in. thick Sunlight irradiance at 1 pm panel, and volume ratio of the optical fibers. Concrete Solid panel Concrete

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