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Weather File of Past Year (2018)

asked 2018-12-15 10:04:06 -0500

Gregory gravatar image

updated 2018-12-17 08:01:26 -0500

Dynamic simulations are totally new to me and I did not had any eduction about it, everything I know about it is from the internet and trail and error with energyplus, so please do not blame me if I say stupid things.

For my masterthesis I have to perform a simulation of a passive school building nearby Antwerp, Belgium (51°09'53.1"N 4°24'20.2"E) in EnergyPlus. The building is already built and I have access to the as-build plans (almost all the information about how the building is built). In order to create an energy model that approaches reality I installed nine dataloggers that measure the dry bulb temperature and relative humidity for the periode (21th of september 2018 until ...), so i can adjust the model to reality. The only part that is missing to create the model is a weather file (epw) of 2018.

My question: Where can I find a weather file (epw) of 2018, not a design year, but real measures (for the airport of Deurne or Brussels (within the radius of 30-50 miles))? I found a lot of websites (e.g. with several weather files, but I am not sure which one I need to download/buy.

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answered 2018-12-16 19:32:07 -0500

rafael.alonso gravatar image

Normally, it is common practice to leave an extra datalogger outdoors while you are performing the measurements. Then you can replace the recorded temperature in a common EPW with that recorded by you datalogger - only for model calibration purposes.

To further approximate the "created EPW", you can look for a station nearby that records solar radiation and replace it as well. A good ressource is, where you can get some hourly weather data, depending on the location. In your case, it should also be a good place to get outdoor temperature - keep in mind that sometimes temperature varies a few degrees from the closer station to your specific location, due to urban microclimates.

A third option, similar to what Aaron mentions, is trying to get the 2018 AMY - Actual Meteorological Year for that location, which is widely discussed here

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The third option seems most appropiate to save some time. Hopefully it is available at the internet.

About the first and the second option, is it allowed to copy and past data in an existing weather file? As far as I know there are fysical relationships between the variables, so it will probably result in a weather file that is not valid or even not fysically possible?

In the meantime I will also place a datalogger outside.

Thanks for the help!

Gregory gravatar imageGregory ( 2018-12-17 13:23:50 -0500 )edit

Maintaining physical relationships of weather data while creating an AMY file can be done in Elements. This is a free tool that asks if you change an air parameter (dry-bulb, wet-bulb, etc.), what other parameters to hold constant to not violate physics (>100% RH, e.g.). This is also applied to solar radiation data (beam, diffuse, and total). Elements allows you to alter weather data in a spreadsheet-like fashion, then save the data as *.epw format to use with EnergyPlus. DISCLAIMER: the company I work for created Elements.

Aaron Boranian gravatar imageAaron Boranian ( 2018-12-17 14:07:44 -0500 )edit

I used to open the epw in excel, and adjust the variables for a certain period, so that I could calibrate the model before running it with a "regular EPW". Even if it is not perfectly accurate - it served to calibrate the model to a certain degree of accuracy.

Only recently I found ELEMENTS, which is actually quite handy to do the same task, but maintaining the relationships between variables.

rafael.alonso gravatar imagerafael.alonso ( 2018-12-19 21:46:45 -0500 )edit

answered 2018-12-16 16:47:14 -0500

If you didn't know already, EnergyPlus uses weather files ending in *.epw that are defined in a specific EnergyPlus Weather format. This format is similar to how a TMY file is organized, and you will likely need to create the *.epw file yourself from the raw measured weather data (like what you found at White Box Technologies).

There have been multiple posts on Unmet Hours about converting measured weather data into a usable weather file for building energy model simulations. The best place to start is here, which has great resources within the answers as well as links to other related posts.

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In the meantime I already found this topic. However, thank you for the help.

Gregory gravatar imageGregory ( 2018-12-17 13:08:50 -0500 )edit

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Asked: 2018-12-15 10:04:06 -0500

Seen: 151 times

Last updated: Dec 16 '18