[esp-r] Re: again about Radiance (Gian Luca Brunetti)

[Gian Luca Brunetti]

Dear Marco,
thank you for the link to the paper by Janak. I knew it: my intention 
stems from it.

I had presented my thoughts about this intention in two posts sent to 
the list in attachemt in August from my phone.

Considering that the mailing list archive strips the attachmnents from 
the messages and just for completeness, I'll re-past them at the end of 
the message.

But also, I now realize that text was full of annoying charactes that 
make it appear like a blurb (if it isn't). Moreover, since then I have 
focused and simplified my view a bit. So I'll try here to re-formulate 
the idea shortly.

The aim is to take into account the effects of reflections caused by 
external solar obstructions in solar gain calculations. And the 
assumption is that, as sustained in the Janak's paper, irradiation 
levels may be obtained from illuminance levels.

I'd like to try the effect of a program (and thus I'd like to try write 
it) performing the following operations, by receving as input a .shd 
file name and a .cfg file name.

a) Computing through Radiance the mean illuminance for each interior 
surface for each hour and each month that have been calculated in the 
.shd file for insolation, assuming that obstructions are black bodies 
(this by temporarily appying a fictitious material to them);

b) Computing the same thing, but for obstructions with their true 
material assigned.

c) Modifying the original insolation values in the .shd file (which were 
indeed calculated assuming osbstructions as black bodies) accordig to 
the ratio between the values obtained in step a) and the values obtained 
in step b) for each surface (probabily through the filter of other 
corrections factors and threshold values).

That is very likely much easier to be said than done, but I am very 
curious about it. The difficulty to me obviously resides mostly in the 
Radiance part.

Best regards

Gian Luca


Politecnico di Milano
Dipartimento BEST
via Bonardi 11
20133 Milano
tel./fax 02 2399 5750



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2 August message 1

Thank you for the reply.=0AFor technical reasons, my message will be=
  in two parts.=0AI was already considering trying to write a utility=
  program to resize insolation values with some proportionality to the=
  illuminances obtained through Radiance. I saw in a paper by Janak=
  (2003) that an acceptable correlation has been verified between=
  predictable irradiance and predictable illuminance.=0AThe program=
  would do the following things.=0Aa) computing the mean illuminance=
  for each interior surface for each time step through Radiance,=
  obtained by considering obstructions as black bodies and taking into=
  account just the direct sky component\;=0Ab) same as above, but=
  using the intended absorptances of obstructions\;=0Ac) increase the=
  insolation fractions obtained through ish by keeping fixed the=
  highest one and increasing the others with some proportionality to=
  the difference between a) and b), with some threshold. I think that 
the main limitations of the program would be the=
  following:=0A- it would underestimate the increase of insolations=
  values in the case that even the gain of the most insolated surface=
  turns out to be increased by the reflections due to obstructions,=
  since that value is kept fixed to scale all the others\;=0A- nothing=
  would be done to take into account the irradiation increase due to=
  the reflections caused by the obstructions due to the sky diffuse=
  component\;=0A- the computations would just regard interior surfaces=
  and not exterior ones.=0ABest regards=0Agian luca brunetti
END:VNOTE

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2 August message 2

I think that the main limitations of the program would be the=
  following:=0A- it would underestimate the increase of insolations=
  values in the case that even the gain of the most insolated surface=
  turns out to be increased by the reflections due to obstructions,=
  since that value is kept fixed to scale all the others\;=0A- nothing=
  would be done to take into account the irradiation increase due to=
  the reflections caused by the obstructions due to the sky diffuse=
  component\;=0A- the computations would just regard interior surfaces=
  and not exterior ones.=0ABest regards=0Agian luca brunetti
END:VNOTE