Re: [EnergyPlus_Support] Capabilities and modules of EnergyPlus

[Linda Lawrie <linda@xxxxxxxxxx>]

At 01:48 PM 1/7/2003, lengjing lengjing wrote:
>I wonder if there is a complete list
>of models (or modules) of EnergyPlus for different
>types of equipment related to building simulation.

Maybe not a complete list.  Several of the papers that can be viewed at the 
main web site (www.energyplus.gov) have tables comparing the 3 programs 
(EnergyPlus, BLAST, and DOE-2) but I don't think we've compiled a complete 
list.  Perhaps if you ask in the "area" you are looking for, we can give 
some specifics.

>Does EnergyPlus have all the modeling capabilities of
>and inherit all the equipment models from DOE-2 and
>BLAST?

That is our goal but not quite achieved yet.  On the other hand, in some 
areas EnergyPlus goes far beyond what either DOE-2 or BLAST could do.

>  For example, I heard that DOE-2 has a
>refrigerated case equipment model that can be used to
>calculate the case load as well as its contribution to
>the space AC load for supermarket simulation. Does
>EnergyPlus have this?

I believe this is on our development list but not fully incorporated yet.


>Is there any validation of E+ for humidity control and
>simulation with the predictor-corrector algorithm?

Are you familiar with the testing that EnergyPlus has undergone?  Specifics 
on the test comparisons to analytical tests and with other programs are 
again available from the main web site.

>How's thermal mass/furniture modeled in E+?

Thermal mass is modeled through the conduction transfer function method 
that we use and then interacts with the heat balance of the zones in the 
building.  This is documented in various places.  Furniture, if needed for 
the model, would be included as an "internal mass" object.

>Is it
>possible to obtain the transient thermal responses of
>the indoor air and building structure at startup and
>shutdown?

Yes, though not exactly sure what you are requesting.

>  Is 15 minutes still the minimum time step
>that can be used for predictions of temperature,
>humidity and building load?

Still?  15 minutes has never been the minimum time step for simulation 
though it is the recommended time step for non-HVAC models.  Most of our 
HVAC models use 10 minute time steps.  Note that we also have two FAQ 
questions dealing with Time Step:


Q: [Time Step] What is the difference between the TimeStep indicated in the 
TimeStep in Hour object and the "variable" timestep indicated in the HVAC 
simulation (ref. Engineering Documentation)?

A: The TimeStep In Hour object specifies the "basic" time step for the 
simulation.  This is used in the Heat Balance calculation as the driving 
time step.  When the HVAC portion of the simulation begins it's solution 
for the current time step, it uses the basic time step as its maximum but 
then can reduce the time step, as necessary, to reach the solution.

The technical details of the approach are explained in the 
<EngineeringDoc.htm>Engineering Documentation, under "Integrated Solution 
Manager".

Users can see the effect/actual HVAC time step used if they select the 
"detailed" option on an HVAC report variable (e.g. Zone/Sys Air Temp).  To 
contrast, the "Zone" variables will only be reported on the Heat Balance 
time step (e.g. Mean Air Temperature).

Q: [Time Step] Time steps recommended in E+ is 4 for non-HVAC and 6 for 
HVAC calculations. Does it mean using time step of 1 will cause E+ to 
diverge or sacrifice the accuracy?

A: Actually, 4 or 6 Time steps per hour are necessary for the HVAC 
calculations.  The heat balance simulation will give reasonable results at 
1, 4, or 6 Time steps per hour.

Note that the Time Step value must be evenly divisible into 60 -- therefore 
is limited to:

1,2,3,4,5,6,10,12,15,30,60



>Thank you very much in advance for your help.

You're welcome.  I think many of your questions may be answered in our 
documentation which comes with the program -- again available for download 
(free of charge) from the main web site.


Linda

EnergyPlus WebSite: http://www.energyplus.gov
Owner: EnergyPlus_Support list
Member: EnergyPlus Development Team



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