Extract more than energy use data from meter output?

asked 2020-12-08 11:23:24 -0600

mattkoch
1071 ●10 ●8

updated 2020-12-14 15:40:16 -0600

I am trying to extract monthly meter data, either via the BCL ExportMetertoCSV reporting measure or from the eplusout.mtr file via the ReadVarsESO.exe approach discussed here https://unmethours.com/question/12199....

Either way works, but I only get the energy use in [J]. Yet, at least the eplusout.mtr file - on the same line as the energy use (know as "Value") - also lists "Min", "Day", "Hour", "Minute", "Max", "Day", "Hour", "Minute", which I believe may be useful for demand estimates. I do not know if these "additional" data also show up in the eplusout.sql file, so that ExportMetertoCSV might access them, but either way, how DO I access these additional data?

Yes, I know that theoretically a meter only reports summations for [J], but these "additional data" DO show up in the eplusout.mtr file, so they must have some meaning and use?

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answered 2020-12-14 14:55:55 -0600

mattkoch
1071 ●10 ●8

I have switched from output meters to output variables and timeseries. The power (not energy) time series for a run at 4 time steps (15 min) are well suited to extracting both demand and usage. So, I just put out the variables I want at the Timestep reporting frequency, then I read them back through SQL, total them up and slice and dice them into months. The point here is that I can combine any loads into any sub-meters as I need them. One could also impose demand windows, but the utility I am working with right now just picks the maximum of each month.

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I did not fully understand the reporting features of EnergyPlus. Several posts on Unmet Hours set me straight. The way I am addressing this now is as follows. 1) Review the eplusout.mtd file and search for the line "For Meter=Electricity:Facility [J], ResourceType=Electricity, contents are:". The (many) meters listed below that line collect all the elelctricity there is. 2) Select the desired meters from this list and put them in a "Meter:Custom, SubmeterName", Electricity, whereby SubmeterName can be to your liking. 3) Create an "Output:Meter, SubmeterName, Monthly".

mattkoch ( 2021-01-14 09:59:21 -0600 )edit

To add the results to the EnergyPlus standard HTML report, 4) create an "Output:Table:Monthly, Electricity Usage, 3, Submeter, SumOrAverage, whereby the last two entries can be repeated as many times as there are submeters. This will generate a table with monthly energy in [J] per submeter. 5) Create an "Output:Table:Monthly, Electricity Demand, 3, Submeter, Maximum, whereby the last two entries can be repeated as many times as there are submeters. This will generate a table with monthly demand in [W] per submeter.

mattkoch ( 2021-01-14 10:02:54 -0600 )edit

The word "Maximum" was the key revelation to me. It finds the time step per month with the highest energy usage and divides it by the length of the time step. So for example, if that time step had 3.6 GJ or 1 kWh and was 15 min or 0.25 h long, the demand would be 1 kWh/0.25 h = 4 kW. I believe this is also the way a real utility meter calculates demand, which is very nice - the folks at EnergyPlus really know their stuff! - So, in summary, my initial approach of using output variables not only was wasteful, but it also was EXTREMELY slow, as the SQL files are LARGE. Now its is very FAST.

mattkoch ( 2021-01-14 10:13:02 -0600 )edit

As a bonus, if you want kWh instead of J in the EnergyPlus Report, you need to modify OutputControl:Table:Style to have a second line (after the one that says "HTML") that says "JtoKWH". By, the way, I am implementing all of what is discussed here as an EnergyPlus measure within OpenStudio, so do not forget the ";" instead of a "," at the end of each object. There may be a way of doing this as an OpenStudio measure, but I don't have the time for that right now.

mattkoch ( 2021-01-14 10:17:22 -0600 )edit

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