[TRNSYS-users] COOLING PEAK LOAD CALCULATION

[David BRADLEY]

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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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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