https://orcid.org/0000-0002-9954-3480
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Abstract
As a basis for further development of the BPS computer software, a method for simulating the characteristics of buildings with grating smart windows is proposed. This novel smart technology provides annual autoregulation of light and solar transmission due to an optical filter with two thin-film gratings located on window surfaces to adapt to the Sun’s trajectory and achieve angular-selective transmission. The previously developed methods for calculating the filter parameters are modified and on their basis new equations for the BPS software are obtained, which differ from the existing ones, unsuitable for grating smart windows due to their distinctive properties. The fundamentals of BPS for a building with such smart windows are considered in detail in order to select the individual parameters of grating windows for all rooms where they are needed. Calculation methods are validated by numerical simulation of the transmittance, sDA, ASE, DGP and by illuminance measurements.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
All data, models, and code generated or used during the study appear in the submitted article.
Nomenclature
| A | = | solar azimuth [°] |
| Aw | = | window azimuth [°] |
| B | = | angle between normal to window and line from observer to source [°] |
| C | = | sky factor of window |
| c1 | = | width of transmissive strip of input gratings [mm] |
| c2 | = | width of non-transmissive strip of input gratings [mm] |
| c3 | = | width of transmissive strip of output gratings [mm] |
| c4 | = | width of non-transmissive strip of output gratings [mm] |
| D | = | distance between observer and source [m] |
| DGP | = | daylight glare probability |
| DHI | = | diffuse horizontal irradiance [Wh/m2] |
| DNI | = | direct normal irradiance [Wh/m2] |
| EDHI | = | diffuse horizontal illuminance [lx] |
| EDNI | = | direct normal illuminance [lx] |
| EGHI | = | global horizontal illuminance [lx] |
| Eh | = | horizontal daylight illuminance [lx] |
| Ev | = | vertical illuminance at eye [lx] |
| Fw | = | area of window [m2] |
| F | = | total area of room surfaces [m2] |
| GHI | = | global horizontal irradiance [Wh/m2] |
| Hw | = | window height [m] |
| h | = | solar elevation [°] |
| kapp | = | angular coefficient of approximated trajectory |
| ktan | = | angular coefficient of tangent to trajectory |
| L | = | zenith luminance [cd/m2] |
| Ls | = | luminance of source [cd/m2] |
| Lsky | = | sky element luminance [cd/m2] |
| Lw | = | luminance of window [cd/m2] |
| n | = | refractive index of glass |
| P | = | Guth’s position index |
| R | = | average reflectance of room surfaces |
| Rc | = | average reflectance of surfaces above horizontal through window centre |
| Rf | = | average reflectance of surfaces below horizontal through window centre |
| s | = | distance between gratings [mm] |
| sΣ | = | total thickness of all panes of window [mm] |
| tmin | = | time with required minimum transmittance [h] |
| Ww | = | window width [m] |
| α | = | difference between solar and window azimuths [°] |
| αa | = | natural absorptance of glass [mm−1] |
| γ | = | slope angle of filter's gratings [°] |
| Δ | = | shift between traces of input gratings on output gratings surface [mm] |
| Θ | = | incidence angle [°] |
| Θav | = | average incidence angle [°] |
| Θc | = | characteristic angle of filter [°] |
| Θn | = | refractive angle corresponding to incidence angle [°] |
| θ | = | projection of incidence angle to plane orthogonal to gratings orientation [°] |
| ρ | = | ground albedo |
| σ1 | = | angle from vertical of plane containing source and sightline [°] |
| σ2 | = | angle between sightline and line from observer to source [°] |
| τ | = | theoretical transmittance |
| τav | = | average transmittance |
| τcor | = | corrected transmittance |
| τchr | = | transmittance of chromogenic strips |
| τd | = | diffuse transmittance of window |
| τmax | = | maximum theoretical transmittance |
| τmin | = | minimum theoretical transmittance |
| Ω | = | solid angle of sky view [sr] |
| ωs | = | solid angle of source [sr] |