[EnergyPlus_Support] Re: dynamic vs. steady state (E+ significantly under predicting energy demands)

["Joe" <joebater@xxxxxxxxx>]

Thankyou all for your replies - some very interesting pointers to papers and the indication of the sensitivity to solar.  I have gone back to the steady-state weather information and rechecked these and also found a rather annoying user (me) error in setting output variables.  Now the results are aligned to within 25% at it's worst and 3% at it's best.  Thankyou all again!

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, oscar hernandez <oscarhernandez_81@...> wrote:
>
> Hello,
> 
> It's normal. The objectif of a steady state simulation it's to see what happens on extreme conditions, fox ex, in winter, no occupation, no sun, lowest temperature, etc... you can know the power of your equipement (boiler, chiller, etc). You simulate the coldest day and the hotest day.
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> A dynamic simulation it's to know the behaviour of the building, when there are people, lights, equipements, etc.... the systems power and loads are lower than steady simulation, as you said 25-40% are normal values.
> 
> You can't compare theses simulations, steady simulation gives the real power systems and dynamic gives you the opportunity to optimise your building.
> 
> good luck!  
> 
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: direzionecontraria@...
> Date: Sat, 27 Oct 2012 14:53:40 +0000
> Subject: [EnergyPlus_Support] Re: dynamic vs. steady state (E+ significantly under predicting energy demands)
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> I cannot answer, but utilization factor of heat gains has a great important in semi-steady state methods.
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> Try to read the following articles:
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> https://lirias.kuleuven.be/bitstream/123456789/204376/1/Whole+Building+IX+Comparison+of+steady-state+and+dynamic+building+energy+simulation+programs.pdf
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> http://www.sciencedirect.com/science/article/pii/S0378778806001861
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> With Regards a
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> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Joe" <joebater@> wrote:
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> > does anyone have any idea why discrepancies between E+ and simple steady state calculations, e.g. Q = U.A.dT, are so severe?  despite it being a dynamic modelling approach you'd think that in the long term (e.g. a year) the two methods would have a reasonable harmony, instead I'm often finding 25-40% under-prediction in E+ compared to steady state for some simple buildings...
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> > is there a recommended report for building fabric heat losses?
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> > best regards and thanks in advance for any advice
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> > j.
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