Hello,
I am trying to create a weather file from hourly data I have in a spreadsheet (Excel format). I saved the data as csv and opened it in the weather tool. I made sure that the units and time intervals are correct.
For the radiation data – the units in my file are Watt/m2, and in the weather tool the units are Wh. This shouldn't really matter, if I understand correctly, as for 1 hour intervals they should be equivalent. I don't have direct radiation data, only global and diffuse.
The problem starts when I view the data – the graph for direct radiation doesn't match the data I have. In the raw data the peak global radiation is just under 1000 Watt/m2, but in the weather tool the graph for direct radiation shows values over 4000 Watt/m2. As for diffuse radiation – the graph shows values lower than the raw data (highest value around 250 Watt/m2 as apposed to 450 Watt/m2).
All the other parameters (temp', RH, etc.) look fine.
I'd appreciate your help very much!
Lilach.
| Attachment | Size |
|---|---|
| Tel Aviv climate data.zip | 412.37 KB |
global and diffuse to beam radiation
Hei
I experienced exactly the same problem.
Though, as Global = diffuse + direct
You can provide Direct and Diffuse
where you calculate Direct = Global - diffuse
Ecotect refers to direct and beam without specifying clearly.
Any comment from SQU1?
Beam beiing at a right angle if I understand well.
Anyway beam, direct or diffuse are less than global except if you play with mutiple reflections....
Xavier
Sustainable Design
Solar Rad
Lilach,
I had a look at your wea file and the excel file.
You have a problem indeed here, whereas your data in Ecotect does not match those of your excel file.
You direct radiation should = Global - diffuse. However, your direct in .wea file are much too high.
You need to create a separate column in the excel file and do a simple formula with substraction to get the direct radiation data in there, then when you import in Weather tool, you can assign proper column.
One way to quickly see your data in weather tool is to go under hourly data and then "edit hourly data" button.
Best,
Olivier
Direct radiation
The usual direct radiation used in simulation tools is "direct normal". It is not true that it is equal to Global (horizontal) - Diffuse (horizontal). You need to take the sun position into account.
the Global - Diffuse gives you Direct (horizontal), to get direct normal you need:
Direct (normal)= Direct (horizontal) /
SIN (solar_height)
Linda
EnergyPlus Development Team
Direct Rad
Thanks for pointing this out Linda,
I was always under the impression that the weather file was simply "calculating" the direct horizontal from the global horizontal and diffuse horizontal only, since many record are made on horizontal collectors (while others are synthetic values) and total radiation can be calculated with just global and diffuse horizontal radiation (i.e. Klein algorithm amongst others - yes, recall the long hand calculations...).
Now that you point out that the weather file actually presents the normal direct radiation, it sure makes a big difference once the data is in the simulation software.
I should have caught this by just looking at the TMY2 manual...
Thanks,
Olivier
Although I know that
Although I know that ecotect/weathertool always refers to direct beam radiation radiation shouldn't it be possible to use only diffuse horizontal and global horizontal insolation from meteonorm data for input? From the location and timezone weathertool calculates the sunpath and sholud therefor be able to calculate direct beam radiation itself. But if I do that peak beam radiation reaches almost 3 kW/m² so something must be wrong.
I attached the file I took the weather data from. When importing the data I ignored the G_Bh column.
Thanks for help