Inconsistent Hourly Results Hot Water

asked 2023-02-17 10:19:32 -0500

updated 2023-02-20 11:09:34 -0500

13830 ●76 ●24 http://bigladdersoftware.com/

I'm extracting the hourly run period consumptions from several simulations and I'm getting inconsistent results between the Energy Plus HTML report and the hourly output.

I'm pulling: Output:Variable, *, !- Key Value Water Heater NaturalGas Energy, !- Variable Name Hourly; !- Reporting Frequency

When i sum the hourly output I'm getting 20% less energy than the HTML report for Water Heating Energy Consumption. What am I doing wrong or is there a simulation error? I checked the output units in Wh to Therms and i'm finding the mismatch. I would have expected these two values to be the same.

Services used: Open Studio Application 3.5.1 Energy Plus 22.2.0 DView: Windows 64

I upload 4 files to github that could help recreate the error, they are all from the same simulation. https://github.com/SDonohueRI/Energy-...

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I believe i found the energy difference i was looking for in the .mdd file.

Annual Building Utility Performance Summary (in the .html file) shows:

For Meter=WaterSystems:NaturalGas [J], ResourceType=NaturalGas, EndUse=WaterSystems, contents are: 600 GAL WATER HEATER - 600 KBTU/HR:Water Heater NaturalGas Energy 600 GAL WATER HEATER - 600 KBTU/HR:Water Heater Off Cycle Parasitic NaturalGas Energy 600 GAL WATER HEATER - 600 KBTU/HR:Water Heater On Cycle Parasitic NaturalGas Energy

As i understand this the end-use consumption for natural gas for water systems is the sum of these three.

Shannon Donohue ( 2023-02-22 13:14:32 -0500 )edit

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answered 2023-02-20 02:49:28 -0500

Keigo
3699 ●1 ●43 ●21 https://www.linkedin.c...

updated 2023-02-20 02:59:07 -0500

I ran your model.

Natural Gas End Use for Water Systems in the html file: 1192GJ

Sum of the Output:Variable "WATER HEATER:Water Heater NaturalGas Energy" in the csv file: 1192GJ

They are the same.

image description

You might be looking at wrong table in the html file or wrong Output:Variable.

Note that your Simulation Settings are ON for both "Run SImulation For Sizing Periods" and "Run Simulation For Weather File Run Periods". You don't need to run simulation for sizing periods if you only want to know the annual simulation result. You might accidentally sum up 8760hours of annual simulation result + (24hours * 7days) of sizing simulation results, but if that's the case, the energy you manually sum up would be slightly larger than the energy shown in the html file.

Anyway, the simulation seems to be running correctly. Please check the result again.

P.S.

Please also clarify whether you want to know the energy for Service water heating (Domestic hot water) or Space heating. I assumed the former. "Hot Water" in your title could be misleading.

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Thank you for rerunning this. I added some comments to my original posting. It looks like in my model the water system energy consumption is adding in parasitic energy consumption. I would have expected that energy would be accounted for in the Water Heater energy consumption. Does this appear correct to you?

Shannon Donohue ( 2023-02-22 13:17:25 -0500 )edit

Water Heater NaturalGas Energy includes Off Cycle Parastic NaturalGas Energy.

Keigo ( 2023-02-22 19:42:26 -0500 )edit

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answered 2023-02-22 13:11:16 -0500

Shannon Donohue
9 ●1

I believe I found the answer in the .mdd file. I believe this would be different for every run.

The Annual Building Utility Performance Summary (html) includes Water Heater Off and On Cycle Parasitic Energy. I pulled this below from my .mdd file.

For Meter=WaterSystems:NaturalGas [J], ResourceType=NaturalGas, EndUse=WaterSystems, contents are: 600 GAL WATER HEATER - 600 KBTU/HR:Water Heater NaturalGas Energy 600 GAL WATER HEATER - 600 KBTU/HR:Water Heater Off Cycle Parasitic NaturalGas Energy 600 GAL WATER HEATER - 600 KBTU/HR:Water Heater On Cycle Parasitic NaturalGas Energy

As i understand it, the total Water System: Natural Gas energy consumption is the Water Heater Natural Gas Energy plus the on and off cycle parasitic losses. I believe I had been missing those meters.

This is a little confusing because I would have assumed the parasitic energy would already be included in the Water Heater's Natural Gas Energy?

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Inconsistent Hourly Results Hot Water

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Inconsistent Hourly Results Hot Water