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RE: [EnergyPlus_Support] Perez direct/diffuse spliting model
The Perez model is not used in the subhourly weather data in
the Weather Converter.
At 12:34 PM 11/2/2016, 'Edward G. Lyon' eglyon@xxxxxxx
[EnergyPlus_Support] wrote:
I agree it probably has
something to do with my sensor recording a pre-dawn or twilight solar
input when in fact the sun was not up. That would spike the direct beam
and not simply assign the input reading to a global solar. Since I
was inputing 10 minute weather data, I saw it more often?
Ned Lyon, P.E. (MA, WV)
Staff Consultant
SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct
617.285.2162 mobile
781.907.9009 fax
www.sgh.com
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From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[
mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Wednesday, November 02, 2016 2:20 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Perez direct/diffuse spliting
model
Ned,
Your mention of "odd calculations around dawn and sunset at
times" may be related to my observation in 2013 that the sun
position calculated by the WeatherConverter was off an hour compared to
another source (see plots from Nov 13 2013 e-mail sent to the EnergyPlus
Team. Base data was ASHRAE IWEC weather file for London, WC2 is
recalculated Dir Nor using the same Global Horizontal. Notice that
the source GHI and DNI are symetrical, while the WC2 DNI is not and more
spiky.
![[]](txtrrq2WTiz1J.txt)
![[]](txtdYOR4Mvb9j.txt)
If the sun position is inconsistent with the recorded data, you will tend
to see spikes at sunrise and sunset hours, as the model tries to adjust
for an abnormally high or low amount of solar for the amount of time the
sun is above the horizon at those hours.
Joe
Joe
Huang
White Box Technologies,
Inc.
346 Rheem Blvd., Suite
205A
Moraga CA
94556
yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx
http://weather.whiteboxtechnologies.com for simulation-ready weather
data
(o)
(925)388-0265
(c)
(510)928-2683
"building energy simulations at your
fingertips"
On
11/2/2016 8:45 AM, 'Edward G. Lyon'
eglyon@xxxxxxx [EnergyPlus_Support]
wrote:
-
- Read the documentation about defining a custom input file. You
can read a text file using a definition array and the converter will do a
split using whatever additional information you give it. Note that
you should review the file generated. I have had some odd
calculations around dawn and sunset at times, but then I worked with sub
hourly data as well. Pasting into an existing .epw file format will
not give you the conversions.
-
- Ned Lyon, P.E. (MA, WV)
- Staff Consultant
- SIMPSON GUMPERTZ & HEGER
- 781.907.9000 main
- 781.907.9350 direct
- 617.285.2162 mobile
- 781.907.9009 fax
- www.sgh.com
-
Send Files
- From:
EnergyPlus_Support@xxxxxxxxxxxxxxx
[
mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
- Sent: Wednesday, November 02, 2016 10:58 AM
- To:
EnergyPlus_Support@xxxxxxxxxxxxxxx
- Subject: Re: [EnergyPlus_Support] Perez direct/diffuse spliting
model
-
-
- Thank you Linda for the repply. I used the Weather Converter utility.
Actually I modified an existing epw file by inserting my own values for
global radiation and inserted zero values for the direct/diffuse
components. When I converted the file I found out that energyPlus
replaced the zero values with the value 999. Any help with this?
- Regards,
- Kostas
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Posted by: Linda Lawrie <linda@xxxxxxxxxxxxxx>
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