[BLDG-SIM] [Campus Chilled Water] eQUEST: Central Chiller for Baseline?

[Fred Porter]

Jon, Bill, Sam, et. al.;

For LEED EA Cr1, and EPACT analyses, the method should be Appendix G
Performance Rating, not Chapter 11 Energy Cost Budget. Appendix G  has
its own tables and sections, which lay out the "Baseline."

 

Comparing campus CHW costs with electric cost for DX seems to be what
App G requires if you are modeling dorm rooms with fan coils, but this
raises a host of problems with extra costs (CUP amortization and O&M)
which may be included in CHW rate but not in the DX system's electric
rate. But an ill-considered CIR re-iterated that's how it should be
done. This method appears to conflict one of the prime directives of
baseline and budget comparisons: 

 

G2 SIMULATION GENERAL REQUIREMENTS

G2.1 Performance Calculations. The proposed building

performance and baseline building performance shall be calculated

using the following:

(a) the same simulation program,

(b) the same weather data, and

(c) the same energy rates.

 

I think there are proposals to allow accounting for just the energy
costs embodied in the CHW, however the ones I've heard of would also
require "modeling" a portion of the campus CUP and distribution system
even though it is outside the scope of the project and associated CDs
(which was a limiting prime directive of any code-centered building
simulation). USGBC does already recognize that for cogen CUPs.
(https://www.usgbc.org/ShowFile.aspx?DocumentID=1354 ). I bet the EA Cr1
reviewers are allowing modeling of campus CUP, under the "existing HVAC
systems" clause, expanded in scope from the CIR that allowed modeling of
a portion of a new high school and part of the associated chiller plant.
The LEED ref guide for EA Cr1 vaguely refers to using the "existing HVAC
system, such as a central plant on campus…" in a paragraph that is
sandwiched between two other paras specifically about baseline
definitions, so it appears to be discussing baseline model system
definition. However, the referenced text in ASHRAE applies only to the
proposed building model.

 

I think App G should return to the ECB methodology for building
heat/cool source (CHW vs. CHW, steam vs. steam) in all cases, but LEED
should have a separate (easier) EA Cr1 points scale for campus
CUP-served buildings. Maybe combined with a separate "LEED for CUPs"! 

 

Sorry if this isn't helpful.  I guess folks disagree about what a fair
revision to this would be. If anyone wants to comment to ASHRAE on
Appendix G, now is the time. Go to
http://www.ashrae.org/technology/page/331#672 and download the 90.1-2007
Addendum R zip file under Oct 12-Nov 26 public review. This includes
forms and instructions for suggesting specific changes. Below is the
forward to the addendum:

 

FOREWORD 

This addendum changes Informative Appendix G Performance Rating Method
into a Normative Appendix. Additionally, some language has been modified
to make the Appendix Enforceable. 

Please note that the entire content of this Appendix is open for public
comment as the entire Appendix is changing from Informative to
Normative. 

Note: In this addendum, changes to the current standard are indicated in
the text by underlining (for additions) and strikethrough (for
deletions) unless the instructions specifically mention some other means
of indicating the changes. In addition, the remainder of the text is
open for public comment.

 

Do we need a separate mailing list for baseline (LEED, ASHRAE, EPACT,
IRS, GGHC, Labs21!) banter? Is this what building simulation has come
to? This is what my lunch break has come to.

 

--

Fred W. Porter, B.S., LEED A.P.
Senior Engineer
Architectural Energy Corp., Boulder CO

 

  _____  

From: Jon Evans [mailto:jevans at sustaineng.com] 
Sent: Thursday, October 18, 2007 3:03 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] [Campus Chilled Water] eQUEST: Central Chiller for
Baseline?

 

Sam and others,

 

I have a follow-up question related to your response on 9/25 to
purchased chilled water and LEED modeling. 

 

I have a baseline building using ASHRAE 90.1 System 1 (PTAC Units). The
proposed building is using campus chilled water and fan coil units or
water source heat pumps.  Do I use electric as the source for the PTAC
cooling, or the campus chilled water? Using campus chilled water with
PTAC units is not a realistic option, but it seems like 90.1/LEED
requires this (Table 11.3.2A in 90.1-2004)- would USGBC consider this
fuel switching?

 

Also, as a general survey, what are the going rates for campus chilled
water and steam?  I have seen ~$0.70/therm chilled water (generated by
absorption chillers) and $0.35/therm for steam for a college dormitory.
I think these rates will vary by campus and end use.

 

Thanks for your guidance in advance.

 

-Jon 

  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Sam
Mason
Sent: Tuesday, September 25, 2007 8:31 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] eQUEST: Central Chiller for Baseline?

 

Yoko,

In note 5 under Table 11.3.2A, 90.1-2004 says for systems using
purchased chilled water, no chillers shall be modeled and CHW costs
shall be determined using the adopting authority’s utility rates.  For
both the baseline and proposed buildings, you would not include central
chillers and instead use purchased chilled water.

 

Sam

 

--
Sam Mason
Atelier Ten
sam.mason at atelierten.com
  

  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Yoko
Matsuyama
Sent: Monday, September 24, 2007 8:09 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] eQUEST: Central Chiller for Baseline?

 

Hi, everyone,

 

I am modeling a building that is served chilled water from a central
chiller, and the building doesn't have any individual chiller. 

I am wondering if  the baseline model (by ASHRAE 90.1-2004) should
follow ASHRAE specified "type and number of chillers" (TABLE G3.1.3.7,
ASHRAE 90.1-2004) depending on building conditioned floor area, or it
should be modeled with a Central chiller as proposed/designed model.  

 

Thank you for your help

 

 

YM 

Graduate Mechanical Engineer

 
 
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