[Bldg-sim] District Thermal System

Craig Simmons craig at greenengineer.com
Thu Aug 7 06:47:20 PDT 2008

Hi May,

I interpret the update differently. It does not state that the capacity must
be the same, only that the efficiencies must be the same. I believe it is
expected that you create a virtual onsite plant sized to replace the loads
normally covered by the DES. The virtual plant must have the same
efficiencies as the actual plant, but not the same capacity.  In addition
you must implement a calculation or approximation to account for losses in
the distribution system. I believe that the statement "the DES central plant
itself shall always be modeled as a total, entire unit" is to prevent the
model from combining the virtual plant (to cover DES loads) with any
supplementary onsite plants that may exist. I don't think it is intended
that you model the DES at its actual capacity.

Anyone else have a different opinion?

Craig Simmons

The Green Engineer, LLP
Sustainable Design Consulting
50 Beharrell Street
Concord, MA 01742
t: 978/369-8978
craig at greenengineer.com

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-----Original Message-----
From: May Xu [mailto:may.xu at hok.com] 
Sent: Tuesday, August 05, 2008 10:20 PM
To: Jeff Haberl; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] District Thermal System

Hi Jeff, 

Thanks, I found many useful information there, it is a very good
resource! However, I didn't get relative answers regarding my question,
which is about the simulation rule updated by USGBC recently about the
district thermal system. Could anyone give me any suggestions?

Thanks a lot!


-----Original Message-----
From: Jeff Haberl [mailto:jeffhaberl at tees.tamus.edu] 
Sent: Tuesday, August 05, 2008 11:36 AM
To: May Xu; bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] District Thermal System

The Laboratory has spent quite a bit of time modeling the thermal plant
on the Texas A&M Campus with good success. Unfortunately, we ended up
using some rather complex, interacting loop models with chiller on/off,
staging algorithms, etc.
We have a number of papers and thesis on this at our web site
"www-esl.tamu.edu" look under publications.
8=! 8=) :=) 8=) ;=) 8=) 8=( 8=) :=') 8=) 8=) 8=?
Jeff S. Haberl, Ph.D.,
P.E.............................jhaberl at esl.tamu.edu
Ph: 979-845-6507
Department of Architecture.......................Lab Ph: 979-845-6065 
Energy Systems Laboratory.......................FAX: 979-862-2457 
Texas A&M University..............................77843-3581
College Station, Texas, USA.......................URL: www-esl.tamu.edu
8=/ 8=) :=) 8=) ;=) 8=) 8=() 8=) 8=? 8=) 8=) 8=) 


From: bldg-sim-bounces at lists.onebuilding.org on behalf of May Xu
Sent: Mon 8/4/2008 4:53 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] District Thermal System

Dear All,


I'm now working on a project using Districted Heating System provided by
a municipal system. The municipal system is working for a very large
areas providing steam for about hundred buildings. And my building is
one of them.


According to the latest update issued by USGBC
(https://www.usgbc.org/ShowFile.aspx?DocumentID=4176), the modeling will
be implemented by two steps. My question is about Step-2 (Aggregate
Building/DES Scenario).  In step-2, the energy source of Proposed
Building is virtual on-site chiller representing upstream DC system. The
document also issues "The DES central plant itself shall always be
modeled as a total, entire unit." My understanding is that it requires
to model the central plant with the full capacity that is able to
provide heating for all of buildings in whole district. However, if
doing so, the energy consumption of the proposed building may be quite
quite high, since it includes the energy consumption of the whole
heating plant!! But my building is only one of the 100 buildings that
are heated by the central plant.  It is weird and  I don't think it is
what USGBC asked for. Does anyone know what shall I do for the proposed
building in Step-2? 


Thank you.

May Xu,  LEED(r)AP
Project Engineer - Sustainable Design

Suite 3705A, Ciro` s Plaza,
388 Nan Jing West Road,
Shanghai, 200003, PRC  

Tel:  (86 21) 6334.6181 ext. 2230 
Fax: (86 21) 6334.6182

www.hok.com <http://www.hok.com/>  
www.hokasiapacific.com <http://www.hokasiapacific.com/> 

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