[esp-r] Re: Questions regarding optical properties of interior surfaces in ESP-r

[Jon Hand]

Answers below ::
________________________________________
From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk] On Behalf Of Sébastien Brideau [sebastien.brideau at gmail.com]
Sent: 03 December 2012 21:58
To: esp-r at lists.strath.ac.uk
Subject: [esp-r] Questions regarding optical properties of interior surfaces    in ESP-r

Hi all,

I am wondering how ESP-r treats solar radiation on surfaces by default.  Is the normal absorptivity used at all incident angle, or is there a default directional curve that is used to reduce the absorptivity at higher angles of incidence? Is there a way to input directional properties for solar absorptivity on an interior surface?

::Initial absorption is by angle-of-incidence (I think Paul Strachan would be a good person to answer this in detail).  Surfaces are treated
as diffuse.  There are no mirrors in ESP-r.  If you define surfaces floating in a room (e.g. back-to-back polygons) then they are
included.  

::If you have not done a shading/insolation analysis the direct sun entering the room is treated as a diffuse source, if you have
done an insolation analysis then the direct sun entering is directed to specific surfaces.

Also, how are solar radiation reflections treated?  It is my understanding that only one reflection is considered.  Is that correct?  Is the reflection considered diffuse, or specular?  Is there a way to change that default setting?

:: direct radiation entering the room becomes diffuse when it hits the first surface and then the process
iterates to distribute the solar to the other surfaces in the room by area and absorptivity.  Reflection
is diffuse.  In the code one might perhaps alter the tolerance setting which determines how many 
diffuse bounces but otherwise the process is automatic.

Prof Clarke's book includes further descriptions of the solar process.  There are also comments
in the source code esrubld/solar.F.

-Jon Hand

Thanks for any help.

Sébastien Brideau
sebastien.brideau at gmail.com<mailto:sebastien.brideau at gmail.com>