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Re: [EnergyPlus_Support] Advice on combining measured weather data to form a complete EPW file
At 08:59 AM 6/23/2015, lewisza1@xxxxxxxxxxxxx
[EnergyPlus_Support] wrote:
I recently posted a question
regarding obtaining measured weather data for the creation of EPW files,
but since looking at the options, our project group would like to ask
some advice on assimilating the data that we have found. To briefly
describe our current situation, we have managed to obtain privately
measured data from a site (apprx. 3 miles from model site) operated by
colleagues at Cardiff University providing air temperature, RH, global
solar irradiance (w/s), global illuminance (kLux), diffuse illuminance
(kLux), wind speeds, and precipitation every five minutes (much higher
granularity than necessary). We feel that this data is preferable to use
over Cardiff IAP weather station due to the close proximity. We see a few
problems with this data though:
1. There are data gaps (42
days unaccounted for throughout the 2014 year long
period)
For this missing data, we that convert data most often just try a
duplicate of a good day near the missing day.
2. We only have global
irradiance, global illuminance, and diffuse illuminance as lighting data
and are
afraid
that this is insufficient for lighting. (We don't have diffuse or direct
irradiance).
As suggested by Joe Huang in the group, I have had a look at the STRANG
database, which has been able to provide me with the direct irradiance at
the site coordinates through satellite data. My assumption is that it
would be suitable to just subtract direct irradiance from the already
measured global irradiance in our data set to obtain diffuse irradiance,
and thus our lighting
If it is direct horizontal irradiance, yes. if it is direct normal,
no. plus you still need direct normal. (Global - direct
normal does not equal diffuse, you need a factor of solar
altitude)
The EnergyPlus weather converter can split the global irradiance into
direct normal and diffuse horizontal (which are needed by the EnergyPlus
program).
issue would be sorted. Is this
an appropriate measure? The IDS database did not seem to have the
necessary solar data recorded (but perhaps my knowledge of the database
is too limited).
As for the 42 days of data gap, would it be suitable to substitute in
Weather Underground (Or IDS) Data from Cardiff IAP (apprx. 30 miles away
from site) combined with the STRANG data to compensate?
Yes, most probably or the technique I alluded to earlier.
And finally, since the data set
we are utilizing does not provide every variable utilized by EnergyPlus
in the EPW, would it be suitable to substitute this more accurate weather
data into a TRY file of the Cardiff region to ensure compatibility with
EnergyPlus?
Up to you. The weather converter for EnergyPlus can again help you
with that.
You can also sum your 5 minute precipitation to an hour and use
that.
Apologies for all of the
questions, but this is my first time creating a weather file from
multiple data sources, and I am unsure whether my outlined process has
any glaring issues.
Let me know (privately) if I can help you further with any EnergyPlus
Weather Converter questions.
Linda
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Posted by: Linda Lawrie <linda@xxxxxxxxxxxxxx>
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