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Re: [TRNSYS-users] Climate reference year: illuminance

Joke,
 Illuminance is a measure of luminous flux and it measured in lux (1 lux = 1 lumen/m2). Luminous flux is related to total radiation energy but is modified to account for the sensitivity of the human eye to certain wavelengths. To get from ambient lux to illumination in a zone you need to calculate the efficacy of the skylights and/or windows. Its not hard to get some examples of how to calculate that for some regularly spaced, single sided illumination sources (like evenly spaced skylights or roof monitors) but it gets hard when you have many light sources. For that, I think you might need to look at some daylighting software like Radiance or DaySim and then you might import the hourly illumination using Type9 and make your lighting decisions based on what is available.
Best,
 David


Joke De Beuckelaer wrote:

Dear Trnsys-users,

 

I’m looking for a method to define the illuminance (lux) in a zone. The purpose is to know when people put on the lights in a space.

 

I thought to use an output of type 89b: TMY2 Data Reader.

 

But I don’t find some explination about some outputs. So I don’t know for sure what the difference is between the output ‘direct normal illuminance’ and ‘global horizontal illuminance’.  Or does anyone suggest to use another output or method ?

 

Further when I plot these outputs the results seem to be extremely low : the maximum value over one year is 935illuminance for the direct normal illuminance and 970illuminance for the global horizontal illuminance.

 

To end a question to be sure : the unity illuminance is equal to lux ?

 

 

 

Thanks in advance,

  Joke De Beuckelaer   
  project engineer

 


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