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EnergyPlus™ is a whole building energy simulation program that engineers, architects, and researchers use to model both energy consumption and water use in buildings.
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Thermal Energy Storage Example File Strange Behavior #7219

Open mldichter opened 5 years ago

mldichter commented 5 years ago

Issue overview

I was trying to figure out what all the controlling objects do in the example file IceStorage-Series-ChillerUpstream.idf and came upon some strange behavior.

A little background. The plant side of this loop has a pump, chiller, and ice tank. The demand side has a pump and ONE water coil. There is a common pipe between them.

On the night of 3/12 and 3/13, the water coil is not cooling, the ice tank has charge, the ice tank has no flow through the ice tank part, the pump on the demand side is off, the pump on the plant side is on, and the chiller is chilling.

Also, the inlet temperature of the chiller is 7.283012856 and the outlet temperature is 7.22 during its midnight cooling, so not very much cooling at all.

What is going on? All I can imagine is that the chiller is chilling the heat from the pump that's running as the only water coil on the demand side is not providing cooling. Here is a google drive link to the files. All I did to the original file was change the run period and the output variables.

Something is wrong. The example file, the TES object code, or both.

15519789963481591

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mldichter commented 5 years ago

There is similar behavior with the IceStorage-Series-ChillerDownstream.idf example file.

wrong

mldichter commented 5 years ago

The IceStorage-Parallel.idf example file also does not behave correctly. Sometimes the chiller is on all the time and not cooling anything or charging the ice tank.

weekend

RKStrand commented 5 years ago

@mldichter I'm taking a look at this issue and I'm not sure this is actually a TES problem. In the first example you showed (ChillerUpstream, which I also ran locally), the TES is actually scheduled OFF during March. That explains why the end fraction keeps going down with no attempt to charge the system back up. So, then the question is: is the chiller not operating properly or is there something going on with the primary-secondary simulation (or input) or the pump operation. The chiller is consuming power but not providing much cooling--like you said, it's basically cooling off the pump heat. I haven't tracked down the problem yet, but I agree at this point that the results for these three files don't look right.

mldichter commented 5 years ago

@RKStrand What I ended up doing is making two plant loops. One with a frictionless pump that's always on, chiller, ice tank, and 100% effective heat exchanger. The other loop has the same heat exchanger, real pump, and demand objects. Controlling the charging and discharging of the ice tank becomes much easier since that loop is always flowing.