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Re: [EnergyPlus_Support] Daylighting:Simple
The simple daylighting algorithm was inherited from the BLAST
program. It puts the burden on the user to determine how much of the
visible sunlight entering the space can be used to offset artificial
lighting. Here is some additional explanation from the BLAST manual
with some minor editing.
Mike
-----------------------------
The DAYLIGHT statement is used if artificial lighting levels may be
reduced at certain times in the zone to take advantage of natural
light ("daylighting"). BLAST uses the parameters specified in the
daylight statement in the following manner. For each hour of the
simulation:
Daylighting = (Beam Usable) + (Diffuse Usable)
Where:
Daylighting = The amount of usable solar lighting that replaces
artificial lighting up to the maximum amount specified by the PERCENT
REPLACEABLE entry in the LIGHTS statement.
Beam Usable = (Visible beam radiation entering zone) x (PERCENT
BEAM USABLE) x (Schedule value)
Diffuse Usable = (Visible diffuse radiation entering zone) x
(PERCENT DIFFUSE USABLE)
The Beam/Diffuse entering the zone is based on the glass
transmissivity and shades, and the part of total radiation used in
the calculation only includes the visible spectrum. The schedule on
beam radiation simply allows the user flexibility in modeling angle
dependent obstructions within the zone. For example, a skylight
located far above a workspace may cast a direct beam into the work
space during one part of the day, and be completely obstructed during
another part.
The user supplied percentage of beam and diffuse account for the non-
angle dependent aspects of natural lighting. For example, a room that
is "black" to the visible spectrum should be specified with a low
percentage of usable beam and diffuse.
On 19 Sep 2002, at 14:15, alexander.beisteiner@xxxxxxxxxxxxxxxxxx wrote:
> Dear Sir/Madam
> Studying the Input/Output Reference some fields in the
> Daylighting:Simple object are unclear: 1. Schedule for Fraction Beam
> Usable What can such a table look like, respectively are there any
> schedules in the example files. Does the schedule depend on the window
> orientation and shades? 2. Fraction Beam Usable The idf example in the
> manual suggests 0.35 as value. What does this figure mean and on what
> does it depend. 3. Fraction Diffuse Usable In the example a value of
> 0.60 is given. Again, what does it mean and on what does it depend?
>
> Regards
> Alexander Beisteiner
>
> ----------------------------------------------
> Alexander Beisteiner
> Forschungs- und Technologietransfer
> Pinkafeld GmbH
> Steinamangerstrasse 21
> 7423 Pinkafeld
>
> Tel.: 0043/3357/45370-1324
> alexander.beisteiner@xxxxxxxxxxxxxxxxxx
> http://www.fh-pinkafeld.ac.at
>
>
>
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