[TRNSYS-users] Radiation in lux

[David Bradley]

Werner,
  lux (or lumens/m2) is a measure of luminous power as opposed to a 
measure of "pure" radiative power. A measure of pure radiative power 
weights all wavelengths of the radiation equally whereas measures of 
luminous power account for the fact that the eye is more sensitive to 
visible light wavelengths. There is certainly a relationship between the 
amount of solar radiation amount and the luminous radiation called the 
luminous efficacy. I have seen methods for calculating the luminous 
efficacy of certain window and skylight configurations but there is also 
a luminous efficacy associated with the atmosphere. If you run one of 
the TMY2 sites from the US, and look at the output for illuminance and 
solar radiation, you can divide one by the other and see what the 
general magnitude of the luminous efficacy is.
That was probably more informative than helpful...
Cheers,
 David


keilholz, werner wrote:
>
> Dear TRNSYS users,
>
>  
>
> I just ran into a weather data file with solar radiation data in 'lux'.
>
>  
>
> Now, that's even worse than the usual kj/hr.m^2... Illuminance (in lux 
> or cd/m^2) is a different dimension than Flux (in W/m^2), but one 
> might think there should be some relation between the two.
>
> Is there a way to compute (diffuse?) radiation from it?
>
>  
>
> Thanks,
>
> *Werner Keilholz**
> *TIDS / IIL / Ingénieur
>
> *Centre Scientifique et Technique du Bâtiment
> *84 avenue Jean Jaurès - Champs-sur-Marne - 77447 Marne-la-Vallée Cedex 2
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