What does Summer condition day mean? Can I use a summer condition day weather profile to do a simulation representing a whole summer?

asked 2015-08-28 02:28:36 -0600

Dr. Fan
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updated 2015-08-28 08:34:00 -0600

I need a weather profile to test the solar air heater's performance in summer. I know EnergyPlus provide the typical year' s weather profile, but if I use the whole summer weather file to test the solar air heater's performance, the computation takes quite a long time.

Is there a typical summer day weather profile for a specified plate so that I can use one day's weather data to do the simulation representing the whole summer period?
I noticed EnergyPlus provides designday condition profile which is a ddy type profile. Can this file be used as a typical day for my simulation?
If so, in the ddy profile for the summer design day, there are 5 or 7 conditions that can be chosen, so which one should I choose?

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Hi @Dr. Fan. Did you mean "specified place" rather than "specified plate"? Also, I've split the questions out so that answerers can respond to them, and added tags that people might be monitoring - in particular you should always include the software as a tag as lots of people get notified whenever an EnergyPlus is asked.

Jamie Bull ( 2015-08-28 02:48:16 -0600 )edit

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I would definitely NOT use a summer design day profile (DDY) for a typical summer day, because the DDY represent near-extreme conditions reached for 0.4% or 1% of the time over an entire year. What you could do is to identify a typical summer day from the weather data, e.g., with the average daily conditions over the hottest month, etc., and just run that day in your simulation. But, besides saving some computational time, there are no other advantages and you'll just have a kinda average result and defeat the whole advantage of doing annual simulations.

Joe Huang ( 2015-08-28 21:47:10 -0600 )edit

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answered 2015-08-28 09:41:00 -0600

Jamie Bull

flag of United Kingdom of Great Britain and Northern Ireland

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updated 2015-08-28 11:22:52 -0600

EnergyPlus lets you enter a RunPeriod object (link) which defines the period of simulation. If you are only interested in a specific period (for example summer design day) you can set the RunPeriod to that.

You may also want to run for a longer period to show the effect of a longer period of hot weather. A good start might be the extreme summer week which you can find at the bottom of the .stat file for your location. Here's an example from Gatwick, UK.

 - Typical/Extreme Period Determination

 - Summer is Jun:Aug
       Extreme Summer Week (nearest maximum temperature for summer)
       Extreme Hot Week Period selected: Aug 17:Aug 23, Maximum Temp=  31.30°C, Deviation=|12.677|°C
       Typical Summer Week (nearest average temperature for summer)
       Typical Week Period selected: Jun 29:Jul  5, Average Temp=  16.36°C, Deviation=| 0.115|°C

The typical summer week will give you typical performance (closest to the average summer temperatures in the EPW) while the extreme summer week (covering the maximum temperature in the EPW) will give you the system performance under the greatest stress. Which you choose depends on what you're trying to find out.

Depending on where you got your weather file (.epw), you may find the .stat file in the same place. If you can't find it then you can use the WeatherConverter program that ships with EnergyPlus to generate it. It should be in the EnergyPlusV8-3-0\PreProcess\WeatherConverter directory. Select your EPW, set the output to "Statistics report on input file", tell it where to save it, and then hit convert.

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thank you for your answer. i think what you said about the typical summer week is what i am looking for,as its temperature or radiation or someting else is nearest average temperature for summer. and one more question is where can i find this .stat files. Thank you

Dr. Fan ( 2015-08-28 10:08:49 -0600 )edit

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answered 2015-08-28 09:31:26 -0600