Hi Amir,
A student in our group has tried the same (setting exterior shading surface transmittance through EMS) and had the same difficulties. I haven’t tried this myself but I believe (maybe you can test if I am correct) the following might have be associated with your problem:
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From the engineering reference within ShadowCalculations object (access through HB shadow par withing energysimPar): ‘TimestepFrequency is required to capture changes in shading transmittance.’
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I recall from the students project that she still had troubles even with this setting applied. I suspect (but am not sure) not that the ShadowCalculations take place before the runPeriod (or at lest before the predictor calling moment) . She also noticed that the only way to get any recognisable affect was through a predefined schedule. If this is true then changing transmittance of an exterior shading object through EMS might be impossible.
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Also check this part from the input output reference:
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“Two choices are available here: SimpleSkyDiffuseModeling and DetailedSkyDiffuseModeling. SimpleSkyDiffuseModeling (default) performs a one-time calculation for sky diffuse properties. This has implications if you have shadowing surfaces with changing transmittance (i.e. not all opaque or not all transparent) during the year. The program checks to see if this might be the case and automatically selects DetailedSkyDiffuseModeling if the shading transmittance varies.”
I would say, make sure your initial schedule varies because else the program might still use the simple model which computes a one-time calculation (and therefore overwriting a schedule will have no effect). -
From the students project she concluded some more behaviour leading from varying transmittance exteriod shading that seemed unusual. When scheduling this, she also saw some unexpected behaviour of daylighting controls within EnergyPlus (I have not looked into this in detail, so this is just a heads-up).
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From your other post I conclude that you are trying to model electrochromic glazing. Using energyPlus’s built in models for electrochromic glazing seems more straight forward. Attached you will find a GH definition with an EMS script added through additional strings. This one acuates an exterior shade but you change the number set by ShadeIsOn to switch an electrochromic window to a darker or lighter state (see EMS application manual). You will have to find a way to implement an electrochromic window in HB or overwrite the idf afterwards (maybe add the whole fenestration surface into the additional string).
20190322_Tsk56prtCref_HB_EP_Example.gh (990.3 KB)
Kind regards,
Samuel