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calculate dynamic SHGC for Electrochromic glazing

asked 2017-07-17 04:57:44 -0500's avatar

updated 2017-07-17 07:31:13 -0500

hi, i want to calculate SHGC on energy plus hourly for example in 21 july to analyse the switching states from light to dark or how to calculate the solar gain and divided by the incident solar radiation under standard conditions to calculate SHGC

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answered 2017-07-17 16:33:48 -0500

If you are using the WindowMaterial:GlazingGroup:Thermochromic object for switching between light and dark tints in one window surface, then according to this section of the Input Output Reference discussing the output variables available ...

The overall properties (U-factor/SHGC/VT) of the thermochromic windows at different specification temperatures are reported in the EIO file. These window constructions are created by EnergyPlus during run time. They have similar names with suffix “_TC_XX” where XX represents a specification temperature.

There is an example file called ThermochromicWindow.idf that uses this object. If you run a simulation and examine the EIO output file, then you will find a line that specifies SHGC for each reference temperature defined by the Optical Data Temperature input field.

This data in the EIO file is only calculated once while processing model inputs, not every timestep. You could manually calculate SHGC at each timestep using the window surface output variables Surface Window Transmitted Solar Radiation Rate and general surface output variable Surface Outside Face Incident Solar Radiation Rate per Area (multiplied manually by the window surface area).

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Thanks for your answer, I want to check about something... I measured the SHGC by dividing the output variables as you suggested but the average is about 0.25 but in EIO it is 0.41. By reading about SHGC, found that the direct gain portion is the solar energy transmittance, while the indirect is the fraction of solar energy incident on the glass that is absorbed and re-radiated or transmitted through convection indoors. How to measure this in-direct solar radiation ????'s avatar  ( 2017-07-17 22:33:56 -0500 )edit

There are also the output variables Surface Window Total Glazing Layers Absorbed Solar Radiation Rate and Surface Average Face Conduction Heat Transfer Rate. I would try to use a Thermal Radiation output variable for the re-radiated component.

Aaron Boranian's avatar Aaron Boranian  ( 2017-07-18 10:12:39 -0500 )edit

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Asked: 2017-07-17 04:57:44 -0500

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Last updated: Jul 18 '17