Hi Samuel,
Le 1 sept. 2018 à 05:21, 'artcygne@xxxxxxxxx' artcygne@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> a écrit :
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First, itâ??s a great and very thorough answer.
I was going to say to use a Daylight Sensor for this, but just for the exercise, here's another potential proxy:
* thereâ??s a built in variable that tells you if the Sun is up (SunIsUp)
* you could implement a time delay by adding an interval variable to record the CurrentTime (fractional hours) at which sun is up, then check if current hour is greater than this + 2 for eg
I think something like this should work:
IF SunIsUp
 IF (TimeSunIsUp == 24)
   SET TimeSunIsUp = CurrentTime
 ENDIF
Â
 IF (CurrentTime >= TimeSunIsUp + 2)
   !- Close blinds
 ENDIF
ELSE
 SET TimeSunIsUp = 24 !- A value so high it's outside of the range of possible CurrentTime
 ! Open blinds
ENDIF
??
Sent from a mobile device, please excuse the brevity.Julien Marrec, EBCP, BPI MFBA
Owner
Direct:Â +33 6 95 14 42 13
Website:Â www.effibem.com
Le 1 sept. 2018 à 05:21, 'artcygne@xxxxxxxxx' artcygne@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> a écrit :
Thank you very much for your detailed explanation, I'll explore the methods you suggest and hopefully someone else can also contribute with other possible solutions.Thanks againStephOn Friday, 31 August 2018, 10:56:38 pm AEST, samuel.vries.de@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:ÂHi Steph,Â
It sounds like you are trying to implement Reinhart's manual blind control model. A student in our group recently stumbled across the same problem. We solved it by using daysim/Radiance to obtain solar Irradiance hitting the work plane throughout the year and inserted that into EnergyPlus as a schedule which we referenced using EMS. We made sure that we only measured direct solar irradiance by setting all the diffuse global Irradiance values in the EPW to 0 and setting the number of ambient bounces to 0 (-ab 0).ÂAn easier route however would be to just use the built in Reinhart models/blind logic capabilities that are implemented in Daysim and Honeybee (in our case we were trying to do some other very specific things which made this route impractical). You can use these to obtain a blind position schedule and reference this directly in EP.ÂAs for trying to obtain an input variable for the Reinhart model using only EnergyPlus, we considered the following options (none of them are ideal):Â
- Using 'Surface Window Transmitted Beam Solar Radiation Rate' and dividing this by the window's area. Problem is, this is on a vertical surface so you would have to cosine correct it using the horizontal profile angle. Also at the work plane is not really the same at directly behind the window.Â
- Using illuminance values at the work plane from EP's daylighting model and converting them back using EP's output Luminous Efficacy. Problems with this are that the split between diffuse and direct illuminance at the daylight sensor point is hard to obtain. Also you have to weigh your output using the spectral properties of the window as the luminous efficacy EP reports is outside whilst the sensed illuminance is inside.
Concerning the two only EP options it's good to note that the 50 W/m2 is a proxy. I understood that Reinhart found that this value corresponded with the moment that the sun becomes visible through the clouds. So I believe the value itself is not empirically derived. I believe rather it's a rationally deducted value based on the empirical knowledge that users pull down the blinds when the sun becomes visible and keep them down for the rest of the day. So in case you want to keep things simple; you could argue that using transmitted beam solar radiation rate', with a threshold that corresponds with a moment when the sun becomes visible, is in line with the original intent of the model.ÂI am still interested to know if anyone has alternative suggestions. Maybe there's more suited routes that we did not think of.ÂFinally as for the other two output variables your asking about:Â(Output:Variable,*,Surface Inside Face Interior Windows Incident Beam Solar Radiation Rate per Area,hourly; !- Zone Average [W/m2]This is for an internal window. So radiation going through a initial window and then hitting another one (as in a conservatory for instance).ÂOutput:Variable,*,Surface Inside Face System Radiation Heat Gain Rate per Area,hourly; !- Zone Average [W/m2]This one will also include radiation from other surfaces (walls, ceiling) in your model. Also it will include the absorptance of the surface itself:I guess you could try to use an internal surface as a sensor using 'Surface Inside Face Solar Radiation Heat Gain Rate per Area'. This however is an average for the entire surface so you would have to make a small measuring surface inside your floor. Also this includes both direct as well as diffuse and you have to weigh by the solar absorptance of the surface (or set it to 1). Also it isn't the same as on the work plane either.ÂKind regards,Samuel
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Posted by: Julien Marrec <julien.marrec@xxxxxxxxx>
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