[Equest-users] Scale modeling

[Stefano Moret]

Dear Karen,

Thanks for your quick reply.
I've done plenty of simulation runs, which basically covered different types of buildings, of different sizes, in different locations.
Of course different parameters grow with different laws, and if lighting wattage is strictly related to the building area, heating/cooling loads are influenced by the lateral surfaces and perimeter zones. This makes perfectly sense, and it was somehow what I expected to see.

Said that, let me explain a little better my question: when I write about different results, I can probably show the point with an example. I take a 5x5x3m building with one skylight on the top (4% SRR) and I get certain values for lighting and HVAC loads. Then I simulate the same exact building with 50x50x6m dimensions, with 4% SRR for skylight, and I get lighting and cooling increasing by a factor of 100, heating by a factor of 10. I also have real data for this larger building, and I simulated it in Energyplus as well, and both these comparisons confirmed that heating and cooling should grow in a similar way in a temperate climate.
So my question is, since I want to keep the model simple, especially on the HVAC side, which are the most important variables in Equest which might lead me to more consistent results without bringing excessive complexity into the model. Of course I'm not looking for a unique building which could be valid for all cases, but I'm caring about model consistency and validation.

Thanks,
Stefano

From: Karen Walkerman [mailto:kwalkerman at gmail.com]
Sent: Monday, April 09, 2012 2:18 PM
To: Stefano Moret
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Scale modeling

The short answer is that every building is different, and there is no "typical" model that will fit them all.

As you mentioned, the ratio between lighting/cooling/heating changes depending on the size of the building.  I'm willing to guess that this is because the core zones that have very little need for heat get much larger in relation to the perimeter zones.  Also, the building energy needs will change depending on orientation and global location.

I would suggest that you take a slightly different approach - try to come up with values that are representative for different types of spaces.  You might do say:

1.  A perimeter office space with XX% glazing (run for North, East, South and West exposures)
2.  A core office space with no skylights
3.  A core office space with XX% of roof area as skylights
4.  A core manufacturing space???
5,6,7....

Run each model in the applicable climate.  Then, if you have an office building that is 70% core and 30% perimeter space, you'll have a better understanding of the building.  This is still a very rough approximation, but should get you farther than trying to model one "typical" building.

--
Karen


On Mon, Apr 9, 2012 at 4:57 PM, Stefano Moret <smoret at ucdavis.edu<mailto:smoret at ucdavis.edu>> wrote:
Dear all,

I've recently played around quite a bit with E-quest to simulate the effect of dynamic fenestration on building energy consumption.
For these simulations I've been using a very simple office model with a skylight on the top as a test-bed for my calculations (with default system for HVAC and daylighting controls with dimming for lights) but, observing the values I'm obtaining in output, I see that the values I obtain for lighting, cooling and heating consumption make sense relatively, i.e. if compared to themselves in different conditions, but are sometimes of totally different order of magnitude if compared to each other (lighting/cooling loads are often much higher than heating, by orders of magnitude), especially when scaling up the model to bigger sizes. This way, it's very difficult to see the effect of a variable change on the total energy consumption.

I know the model I'm using is very idealized, but is there any variable that I can act on in order to obtain a model which has energy consumption values more similar to a real building? For example, is there a "suggested" size of the building that gives better results? Or maybe simulating a single room in a large building gives more realistic results than the single room alone?
My point is that I would like to have a model whose results in scale might be consistent when applied to bigger buildings.

Thanks for your hints and suggestions,
Stefano

--

Stefano Moret
California Lighting Technology Center<http://cltc.ucdavis.edu/>
University of California, Davis
633 Pena Drive
Davis, CA 95618
530-747-3846<tel:530-747-3846>
smoret at ucdavis.edu<mailto:smoret at ad3.ucdavis.edu>


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