Out of the Blue - SageGlass...400 500 600 700 Wavelength [nm] 0.0 0.2 0.4 0.6 0.8 1.0 Normalised...
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400 500 600 700 Wavelength [nm] 0.0 0.2 0.4 0.6 0.8 1.0 Normalised transmittance V (λ) Tvis = 62% Tvis = 20% Tvis = 2% Tvis = 6% More informa+on can be found in J. Mardaljevic, R. Kelly Waske<, and B. Painter. Neutral daylight illumina+on with variable transmission glass: Theory and valida+on. Accepted for publica+on in Ligh+ng Research and Technology. Conclusion It seems reasonable to speculate that a view containing panels of blue +nted EC glass will be acceptable to occupants (on sunny days) provided that the illumina+on spectrum contains a significant component of sunlight, i.e. a small propor+on of the panels are set to clear. Theore.cal model and field measurements A general matrix formula+on was developed to determine the spectrum that would result from any combina+on of +nted and un+nted panes. This model predicted that the spectral transmission curve of one clear pane combined with a number of fully +nted panes is much closer to the curve for the clear state than that for the full+nt state. To validate this theory, a set of field measurements was taken of daylight spectra in one of the case study rooms from a number of different viewing posi+ons under six different combina+ons of +nted and un+nted panes at different levels of +nt. Figure 3 shows that the measured spectra (blue curves) compare very well with the spectra predicted by the theore+cal model (red curves) for each combina+on. Note that the theore+cal spectra use the standard illuminant D55. The vector, R, indicates the combina+on being tested, e.g. the vector [3 0 0 5] indicates three panes in the clear state, five panes in the fully +nted state, and no panes in either of the intermediate states. (There are a total of eight panes in the room where the measurements were carried out.) Acknowledgements The EC windows in this study were supplied by SAGE Electrochromics Inc., a whollyowned subsidiary of SaintGobain Recherché. Can electrochromic windows deliver neutral daylighting? Out of the Blue Figure 1 Electrochromic glazing Electrochromic (EC) glazing changes +nt in response to a small applied voltage. It can enable users to control glare from windows with less or even no reliance on window blinds or external shading devices. The ability to control +nt dynamically can give users more access to daylight and a con+nuous view through the window, whilst decreasing energy consump+on through the reduc+on of cooling loads and electric ligh+ng usage. John Mardaljevic Loughborough University, Loughborough, UK [email protected] Ruth Kelly Waske< Ins+tute for Energy & Sustainable Development (IESD), De Mon_ort University, UK ruth.waske<@email.dmu.ac.uk Birgit Painter Ins+tute for Energy & Sustainable Development (IESD), De Mon_ort University, UK [email protected] The De Mon?ort University Case Study A case study focussing on the long term user experience of EC glazing was undertaken. The study involved two adjacent offices in a university campus building occupied by faculty support staff. The original windows were replaced by EC windows in 2012. The EC windows in the case study are divided into zones so that different sec+ons of window can be controlled independently (Figure 1). Hypothesis A key finding of the case study is that occupants preferred to leave the window panes in their eyeline un+nted, except when direct sun was visible through those panes. To explore this in more depth, a hypothesis was put forward: The glazing under study is capable of four states: Clear (T vis = 62%), fully +nted (T vis = 2%), and two intermediate states (T vis = 20% and 6%). Figure 2 shows the normalised spectral transmission curves of each state. The EC glazing takes on a blue appearance when +nted, with a deeper colour in the fully +nted condi+on. When +nted, the view to outside remains sharp, albeit darkened. Data from IGDB files supplied by SAGE Electrochromics Inc. If at least one pane is leI un.nted, the resultant spectrum of daylight in the room is similar to that when none of the glass is .nted. Figure 2 Figure 3 Further research More work is needed to explore how the measured spectra relate to the subjec+ve experience of occupants. A procedure using the FarnsworthMunsell 100 Hue Test has been piloted, and this indicates the poten+al for a more in depth study of colour percep+on under different EC window condi+ons. R = [ 3 5 0 0] 300 400 500 600 700 800 Wavelength [nm] 0.0 0.5 1.0 1.5 Spectral power [normalised] CCTmean = 5211K : CRImean = 92 Tvis = 0.36 : Pclear = 65% Theory [D55] Measured 21-221 rmean = 0.972 R = [ 3 0 5 0] 300 400 500 600 700 800 Wavelength [nm] 0.0 0.5 1.0 1.5 Spectral power [normalised] CCTmean = 5243K : CRImean = 93 Tvis = 0.27 : Pclear = 86% Theory [D55] Measured 31-331 rmean = 0.977 R = [ 3 0 0 5] 300 400 500 600 700 800 Wavelength [nm] 0.0 0.5 1.0 1.5 Spectral power [normalised] CCTmean = 4970K : CRImean = 93 Tvis = 0.25 : Pclear = 94% Theory [D55] Measured 41-441 rmean = 0.980 R = [ 1 0 0 7] 300 400 500 600 700 800 Wavelength [nm] 0.0 0.5 1.0 1.5 Spectral power [normalised] CCTmean = 4800K : CRImean = 94 Tvis = 0.09 : Pclear = 81% Theory [D55] Measured 41-444 rmean = 0.906 R = [ 0 3 0 5] 300 400 500 600 700 800 Wavelength [nm] 0.0 0.5 1.0 1.5 Spectral power [normalised] CCTmean = 6845K : CRImean = 87 Tvis = 0.09 : Pclear = 0% Theory [D55] Measured 42-442 rmean = 0.971 R = [ 0 0 3 5] 300 400 500 600 700 800 Wavelength [nm] 0.0 0.5 1.0 1.5 Spectral power [normalised] CCTmean = 11557K : CRImean = 84 Tvis = 0.03 : Pclear = 0% Theory [D55] Measured 43-443 rmean = 0.974 1 or more panes in the clear state None in the clear state
Transcript of Out of the Blue - SageGlass...400 500 600 700 Wavelength [nm] 0.0 0.2 0.4 0.6 0.8 1.0 Normalised...
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400 500 600 700Wavelength [nm]
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Tvis = 62%
Tvis = 20%
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Tvis = 6%
More informa+on can be found in J. Mardaljevic, R. Kelly Waske
