Laminated glazing with coloured reflection and high solar transmittance suitable for solar energy systems

Abstract

Laminated and etched glazing unit for architectural integration of solar energy systems comprising a substrate delimited by two main faces and a multi-layered interference filter also delimited by two main faces, one main face of said substrate being adapted to be in contact with an incident medium, the other main face being in contact with a main face of said interference filter, the other main face of said interference filter being adapted to be in contact with an exit medium; said incident medium having a refractive index n_inc=1, said substrate having a refractive index n_substrate defined as follows: 1.45≦n_substrate≦1.6 at 550 nm, and said exit medium being defined as follows 1.45≦n_exit≦1.6 at 550 nm; and wherein said unit is designed in such a way that the following requirements are met: 1a) The saturation of the colour, given by C*_ab=√(a*)²+(b*)², according to the CIE colour coordinates L*, a* and b* under daylight illumination CIE-D65 is higher than 8 at near-normal angle of reflection, except for grey and brown. 1b) The visible reflectance at near-normal angle of reflection R_vis is higher than 4%. 1c) The variation of the dominant wavelength λ_MD of the dominant colour MD of the reflection with varying angle of reflection Θ_r is smaller than 15 nm for Θ_r<60°. 1d) The total hemispherical solar transmittance at near-normal incidence is above 80%.

Description

FIELD OF THE INVENTION[0001]The invention deals with coloured laminated glazing suitable for solar energy systems offering architectural integration of solar energy systems, e.g. as solar active glass facades.DEFINITIONS[0002]Direct Transmittance[0003]If parallel beams of radiation incident on a surface, an interface, or a specimen result in transmitted parallel beams, the transmittance is considered as direct. This is the case e.g., for flat surfaces or interfaces.[0004]Diffuse Transmittance[0005]If parallel beams of radiation incident on a surface, an interface, or a specimen result in a more or less wide angular distribution of transmitted beams, the transmittance is considered as diffuse. This is the case e.g., for rough surfaces or interfaces, or for specimens of granular structure.[0006]In general, the diffuse transmittance depends on the angle of incidence and the wavelength X of the radiation. If the angle of incidence is not explicitly mentioned, commonly normal incidence i...

AI Technical Summary

Benefits of technology

[0052]A diffusive surface treatment is applied on the outer surface of the coloured laminated glazing. The glass substrate can either be extra-white float glass or solar roll glass. Extra-white float glass presents the advantage of having a better flatness and will be preferred for facade applications. Both types of glass are also commercially available with a wide variety of textures and patterns applied on the outer surface. This kind of glass can be used in order to add some relief and get closer to tiles appearance in case of roof applications.

[0053]The etching treatment is applied in order to create diffuse light transmittance which reinforces the masking effect of the coloured filter. It also presents the advantage to create mat surfaces often desired by architects and to prevent glare effects.

Problems solved by technology

In order to ensure a maximal efficiency of the solar energy system, the substrate has to present a high solar transmittance, thus limiting the possibilities to solar roll glass, extra-white float glass (very low iron-content) or polymeric materials such as polyethylene terephthalate (PET), polyethylene naphtalate (PEN), fluorocarbon polymer (PFA, FEP, ETFE, PTFE .

The surface flatness is also a critical issue, especially for facade applications.

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