[solved] [urgent] error probably related to wrongly written IDF file on the class of SizingPeriod

Replies to This Discussion

Permalink Reply by Chris Mackey on July 23, 2016 at 5:13am

Grasshope,

Thanks for the detailed explanation.  At the least, I can put in an extra check in the Run Simulation component to see if the ddy file is incomplete and, if so, we just size the system using the extreme periods in the weather file like we did before I made the change.  I should also say that there is a check for this right now but it doesn't catch your case.  If you remove the ddy file from the epw folder, you should see that the Run Simulation component works fine.

To add the extra check in the Run Simulation component and to make sure that I catch your case correctly, I am going to need the ddy file that is next to the epw file on your system.  If possible, it would also be great to have the epw you are using.

Right now, your GH file works for me because I am running it with one of the EPW files from the DOE website.  Once I get the ddy file, I can make sure that it is fixed.

-Chris

Permalink Reply by Chris Mackey on July 23, 2016 at 5:15am

Also, with regards to OpenStudio, we will do a stable release within the next 2 weeks.  In the release notes, I will be clear about this transition.  We will update the install instructions and I will update all of my example files once we do the release.  I know that the transition may be a bit rocky but trust me that it will pay off in the end!

Permalink Reply by Grasshope on July 23, 2016 at 6:52am

Thank you very much, Chris!

Somehow, I cannot reproduce the error I reported now... strangely...

Nevertheless, here are the original EPW and DDY files for Singapore downloaded from energyplus.net for your reference. Originally, I only have the EPW file in my system for simulation.

I think it is not fair to you to take a lot of time to change the code of the Run Simulation component to suit for a particular weather file that may or may not generate error. So, maybe we can just follow your suggestion to use the Export to OpenStudio component from then on?

Thanks, again!

Attachments:

• SGP_Singapore.486980_IWEC.epw, 1.5 MB
• SGP_Singapore.486980_IWEC.ddy, 28 KB

Permalink Reply by Grasshope on July 23, 2016 at 7:14am

... sorry, again, here is the problematic DDY file generated during one of the error run, and it is way smaller than the orginal DDY file downloaded from energyplus.net.

Chris, hope this can help to identify the source of problem in the Run Simulation component. 

Thank you very  much!

Attachments:

• SGP_Singapore.486980_IWEC.ddy, 5 KB

Permalink Reply by Chris Mackey on July 23, 2016 at 5:37pm

Grasshope,

Thanks for posting all of the information and I understand why it's probably not the best idea to post the ddy file here.  I can get it from the EnergyPus Yahoo group.  Generally, it appears as if this Singapore ddy was made for a much older version of EnergyPlus and I'll have to add in some code to sense this and update it to recent standards.

I'll try to add this code in now and then post back here.

-Chris

Permalink Reply by Chris Mackey on July 23, 2016 at 5:55pm

Actually, I can't find the shorter ddy file in your image on any website.  There's no Meteonorm file for Singapore that I can find on the E+ Yahoo group and the Singapore file from the DOE (energyplus.net or EPWMap) is in the correct format.  Can I ask what your source is for this ddy file?  I am beginning to think that this issue might not affect users unless they somehow have really old ddy files.  If I know your source, this will help me understand the urgency of this extra check.

-Chris

Permalink Reply by Grasshope on July 23, 2016 at 10:48pm

Dear Chris, thank you!

The following might be what I did previously:

1. There are a few default weather files for USA cities in the In the C:\EnergyPlusV8-4-0\WeatherData folder. So, I put the Singapore EPW file there, only the EPW file, not the DDY and STAT files for Singapore downloaded from energyplus.net.

2. After opening the GH demo file posted earlier, I select this Singaproe EPW file and run the simulation using the Run EPlus Simulation component.

3. I got the error, and a new DDY file of Singapore was generated in the same folder where the EPW file is put which is the "shortened" DDY one I posted above. So, this shorter ddy file was generated in the process while the error was happening.

However, I have to admit that I cannot reproduce the error and the "shortened" DDY file for Singapore in the scenario described above any more, strangely ....

So, maybe I shall pause my question here until I identify the situation to reproduce the error.

Meanwhile, may I confirm with you that the EPW, DDY and STAT files for a particular city shall always be put together in the same folder just as those in the C:\EnergyPlusV8-4-0\WeatherData folder?

Thank you, again!

Permalink Reply by Chris Mackey on July 24, 2016 at 12:07pm

Grasshope,

I definitely agree that it was better to wait to respond.  I should have finished all that I was planning to do with the DDY files before sending you the responses yesterday.  It took most of my day but I just finished making sure that the "Run Simulation" Component and the "OpenStudio" Component use the same method for sizing the HVAC system.  Here are the two recent commits in which this change was made:

Fixed Up AutoGen of DDY File

Added Function For Absence of DDY

The new sizing method involves first checking if there is any ddy file and, if there isn't one, I derive a ddy frile from the EPW data and ASHRAE standards.  This use of the ddy is better than sizing the system by running the model through the extreme weather file periods (what we were doing previously).  Sizing with the ddy results in fewer unment hours and it can be used for large HVAC systems as well as the ideal air system.

I tested the new Run Simulation and OpenStudio components in a range of cases but, if you could update your components and confrim that they work for your Singapore file, that would be great.

Thanks again, Grasshope!

-Chris

Permalink Reply by Grasshope on July 27, 2016 at 2:25am

Dear Chris,

Thank you very much for your hard work to update the components which work fine now!

I noticed that the ddy file generated by the Run Simulation or the Export to OpenStudio components, in the case when only the EPW file is present, is different from the original ddy file downloaded from energyplus.net, at least for the Singapore EPW file. (both files attached)

The image attached shows the difference btw the original and the generated ddy files in terms of variables such as Maximum Dry-Bulb Temperature, Humidity Condition Type, Wetbulb or Dewpoint at Maximum Dry-Bulb, Barometric Pressure, Wind Speed, Wind Direction.

May I ask if these differences matter in the simulation, especially when using Ideal Loads Air System? 

Will you recommend to always put the original ddy and epw files side by side in the same folder when conducting simulation?

Thank you!

Attachments:

• SGP_Singapore_generated.ddy, 9 KB
• SGP_Singapore.486980_IWEC.ddy, 28 KB

Permalink Reply by Chris Mackey on July 27, 2016 at 6:37am

Hi Grasshope,

Glad that everything has been running smoothly.  To answer your question:

Yes, the original ddys issued by ASHRAE are different than those that are generated by the Energy Simulation components.  However, they are very close to each other and my inference as to why they are not perfectly equal is that the ddys for ASHRAE/DoE are likely built using all of the collected weather data over the (at least) 18 years that a weather station has been recording data.  In contrast, the Energy Simulation components use the same statistical methods but on just the data with in the epw, which is just one year (albeit a 'typical' year statistically).

You should keep in mind that what E+ is trying to do with the ddy file and autosizing of the HVAC is mimic the process that an engineer undergoes to size specify your building's HVAC system and there can be variations in techniques for sizing the HVAC just as there can be differences between the weather in an epw and that which a building actually experiences once it is built.  Still, it's probably safe to say that, if an engineer has a ddy file that is issued by ASHRAE, they will probably use that to size the system instead of a ddy file generated just from the epw.  As such, it's a good idea to include the ddy file next to the epw if you have it as this is closer to what an engineer might do.

All of this said, in the cases that I tested, the minor differences between the ASHRAE ddy and that generated by the Energy Simulation components had a negligible effect on the resulting heating and cooling values out of E+. I was often able to get the heating energy to match down to the kWh and the cooling energy matched within 1-2%.  The cooling sizing is off because the Sky model for radiation used by AHSRAE  in the ddy files (ASHRAEtau method) requires some information not contained in the EPW. Instead, I use ASHRAE's simpler ClearSky model at the highest solar intensity. As a result, the function here oversizes the cooling system by small amount (1-2% as mentioned previously).

-Chris

Permalink Reply by Grasshope on July 27, 2016 at 8:15am

Thank you very much, Chris, for the detailed clarification!

We shall use the ddy file came with the epw file from energyplus.net as suggested.

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