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[TRNSYS-users] Fwd: Re: COOLING PEAK LOAD CALCULATION

Dear Juan,

The following paper could help you:

"Uncertainty in peak cooling load calculations"
Energy and Buildings, Volume 42, Issue 7, July 2010, Pages 1010–1018"
The paper uses the Monte Carlo method to deal with the inherent uncertainties that occur in peak cooling load calculations. Using this approach you do not need to make "hard" assumptions on the value of the input variables. Instead, you just propagate their uncertainties through the building model and get a probability distribution for the cooling load. With this distribution, it is easier to inform a decision based on the desired safety margin.
The paper does not deal with the uncertainty in the weather conditions, although it could be included. The easiest solution would be to repeat the calculations for one design day (or week) for each season or month. 

I can provide you an author copy of the paper if you need it.

Best regards,

Fernando Domínguez
University of Malaga (Spain)



-------- Original Message --------
Subject: Re: [TRNSYS-users] COOLING PEAK LOAD CALCULATION
Date: Wed, 03 Oct 2012 12:06:46 -0500
From: David BRADLEY <d.bradley@tess-inc.com>
To: JUAN FRANCISCO BELMONTE TOLEDO <JuanF.Belmonte@uclm.es>
Cc: "trnsys-users@cae.wisc.edu" <trnsys-users@cae.wisc.edu>

     Juan Francisco,
This is a very good question to which there are as many valid responses 
as there are responders. My feeling is that traditional methods for
sizing cooling equipment lead to very over sized equipment and the
energy inefficiency that comes with it. Traditional sizing involves a
steady-state, worst-case scenario when all the equipment is on, all the
lights are on, and all the people are in the building. Some tools also
do not account for zone adjacencies; they compute the worst case
assuming that all zones are thermally isolated from each other. There is 
no credit for thermal mass and no credit for shading. That is obviously
going to give you the greatest possible cooling load. There are lots and 
lots of other justifiable methods, some of which you mention. What I
have done in the past is to look at what the peak cooling load is under
a number of these methods (with normal building operation during an
average weather year, including shading, excluding shading, during an
"extreme" weather sequence of days, during a "design day" that repeats
itself. From multiple tests, you can get an idea of how sensitive the
peak cooling load is. You can then do some experiments of limiting the
available cooling power in order to see how badly you miss your target
cooling temperature. If the overshoot is small, then under sizing the
equipment a little bit will create energy savings and the comfort
penalty will not be great. With all that information, it is then
possible to do an informed sizing the cooling equipment.
 Best,
 David

On 10/3/2012 04:44, JUAN FRANCISCO BELMONTE TOLEDO wrote:


Dear users.
Any idea how to make a good cooling peak load calculation with trnsys, 
in a similar way as max. heat load calculation does in trnbuild?.

I mean hipothesis about Solar radiation (What values we must consider
and where we can find them), temperature (we consider a sinusoidal
wave shape -as EnergyPlus does- or constant value, ...).., in which
months we must simulate (for example i´ve found many building with
higher values in September due to the Sun is lower and they had a lot
of windows,.. ), , tmy files should not be used because are average
values, or yes...etc.

thank you.
Regards.

_

JUAN FRANCISCO BELMONTE TOLEDO
Universidad de Castilla-La Mancha (Spain) _

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