Optical Air Traffic Control Tower Blinds – AR762

The Optical Properties Of The Leeuw Ltd – Reflex-Rol (UK)

Sample AR762

M.G. Hutchins

Solar Energy Materials Research Laboratory

Sonnergy Limited

Report Nº 09/313

December 2009

Contents

  1. Introduction
  2. De Leeuw Reflex-Rol (UK) Blind Sample
  3. Experimental procedures
    3.1. Measurement of Spectral Transmittance and Reflectance – 3.2 Measurement of Infrared Spectral Transmittance and Reflectance

1 – Introduction

The Solar Energy Materials Research Laboratory of Sonnergy Ltd undertakes ultraviolet, visible and infrared spectral optical properties measurements of materials for a wide range of industrial clients. The Laboratory is approved by the Ministry of Defence to perform measurements in compliance with Defence Standard DS0023/1 ‘NATO Infra Red Reflective (IRR) Green Colour for Painting Military Equipment’ (1), The laboratory operates in accordance with ISO 17025 for which compliance is being sought (2). Spectrophotometric instruments are serviced annually by  the respective manufacturers. All measurements are made in accordance with recognised international procedures and instruments are calibrated using traceable reference standards. The Laboratory participates regularly in proficiency tests and interlaboratory comparisons for the measurement of optical properties (3, 4, 5, 7). Sonnergy serves as the Chair of the European Union Cool Roofs Council Technical Committee (6) with responsibility for recommending measurement test procedures for product certification, is a full member of the International Commission on Glass Technical Committee 10 ‘Optical properties of glass and coated glass products’ (7) and provides the European representative for the peer review of optical properties spectral data for inclusion in the International Glazing Database (IGDB) (8) administered and maintained by the Lawrence Berkeley Laboratory, USA.

In this report measurements are presented of the total and diffuse near-normal hemispherical spectral reflectance and transmittance of the AR762 sample supplied by De Leeuw Ltd Reflex-Rol (UK) for the wavelength range 280 – 2500 nm. From these measurements integrated ultraviolet, visible and solar optical properties are calculated in accordance with accepted international standard procedures (9).

The total near-normal hemispherical spectral transmittance and spectral reflectance was measured for wavelength range 2.0 – 1.80μm using a Bruker IFS 66 Fourier transform spectrometer with a gold integrating sphere reflectance/transmittance accessory. Reflectance measurements were made for both sides of the sample. From these measurements the spectral absorptance was determined. The integrated emissivity was then calculated by weighting the spectral absorptance data with a 283K blackbody spectral distribution using the recommended procedure of EN 12898 (10,11).

The European Standards EN 14501 and EN 13363-1 (12, 13, 14) are used to calculate values of the total solar energy transmittance, gtotal, shading coefficient and shading factor, Fc, for complex glazing employing a fully closed internal blind in combination with the default glazing of each respective standard.

From the measured spectral optical properties data, an ASCII text file has been prepared which conforms to the format as required for the British Blinds and Shutters Association (BBSA) SHADE shading device optical properties database (15, 16).

2 – De Leeuw Reflex-Rol (UK) Blind Sample

The De Leeuw Reflex-Rol (UK) sample submitted for measurement is identified in Table 1.

Sample No.Sample NameSample Colour
AR762Reflex Rol (UK) AR762Dark Blue
Table 1. Identification of the De Leeuw Reflex-Rol (UK) blind sample.

3 – Experimental Procedures

        3.1 Measurement of Spectral Transmittance and Reflectance
  • Measurements of near-normal hemispherical spectral transmittance, τ(λ), and spectral reflectance, ρ(λ), were made using a Perkin Elmer Lambda 900 spectrophotometer using the PELA 150 integrating sphere accessory. Measurements were made over the spectral range 280 – 2500 nm (UV/Vis/NIR) to enable calculation of the integrated ultraviolet, visible and solar optical properties.
  • Total near-normal hemispherical spectral reflectance measurements were made with the sample mounted on the rear sample port of the 0.15 m diameter PELA 150 integrating sphere. The basic experimental configuration is shown in Fig.1. Calibration was made using 2 Labsphere Spectralon white reflectance standards (17). The measurement procedures were performed in accordance with EN 14500 and CIE 130 (18, 19).
  • For measurement of the total near-normal hemispherical spectral transmittance, τn-h(λ), the blind sample is located at the sample entrance port of the integrating sphere (Position A) and the rear sample mounting port (Position B) is covered with a white reflectance standard.
  • For measurement of the near-normal diffuse spectral transmittance, τn-dif(λ), the blind sample is located at the sample entrance port of the integrating sphere (Position A) and the rear sample mounting port (Position B) is left open (uncovered) to enable any direct component of the transmitted light to exit the sphere through this port.
  • For measurement of the total near-normal hemispherical spectral reflectance, ρn-h(λ) the blind sample is located at the rear sample mounting port (Position B) of the integrating sphere and the sample entrance port (Position A) is left open (uncovered).
  • For measurement of the near-normal diffuse spectral reflectance, ρn-dif(λ) the blind sample is located at the rear sample mounting port (Position B) of the integrating sphere and the integrating sphere specular reflectance exit port cover located at Position C is removed to allow the regularly reflected component to exit the integrating sphere.
  • spectral transmittance and reflectance
    Figure 1. Experimental configuration for the measurement of spectral transmittance and reflectance (UV/Vis/NIR) using the PELA 150 integrating sphere reflectance accessory. (D1: Photomultiplier detector; D2: PbS detector) 

    Experimental configuration for the measurement of spectral transmittance and reflectance (UV/Vis/NIR) using the PELA 150 integrating sphere reflectance accessory.
    (D1: Photomultiplier detector; D2: PbS detector) 

  • 3.2 Measurement of Infrared Spectral Transmittance and Reflectance
  • Measurements of total near-normal hemispherical spectral transmittance and  reflectance in the range 2.0 – 18.0 µm were made using a Bruker IFS 66 Fourier transform spectrometer using a 0.2 diameter diffuse gold coated integrating sphere reflectance attachment. A globar source and potassium bromide (KRr) beamsplitter combination were employed. The signal level inside the integrating sphere was detected using a wall mounted liquid nitrogen cooled mercury cadmium telluride (MCT) solid state detector with 3 x 3 mm² detector area.
  • For transmittance measurements the sample was mounted to cover the entry port of the integrating sphere and irradiated with a beam at normal incidence.
  • For reflectance measurements the sample was mounted on the rear sample port of the integrating sphere and irradiated with a beam at 10ºangle of incidence. Reflectance measurements were made for both sides of each sample. 
  • The system was calibrated using two diffuse gold reflectance standards (20) and a bare gold mirror calibrated to a traceable NPL gold mirror (21).

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