[Bldg-sim] District Thermal Energy in LEED

Minu Agarwal Minu.Agarwal at BuroHappold.com
Fri May 8 07:03:21 PDT 2009


I too would vote for Option A. I have a somewhat similar grey area
scenario:

 

In a district cooling system with electric heating ASHRAE 90.1 prior to
the DES memo would have had the baseline be district cooling with
electric heating in step 1. The DES memo document irrespective of fuel
types available on site requires the baseline to be district cooling and
fossil fuel boiler in Step 1. ASHRAE 90.1 says baseline system must be
selected based on the heating source (and floor area and building type
etc) (See G3.1.1). There is a clear conflict here and I have not found
documentation on who supersedes what. 

 

 

Minu Agarwal  LEED AP

Building Physicist, CoSA Solutions

 

________________________________

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of David S
Eldridge
Sent: Wednesday, May 06, 2009 3:38 PM
To: bldg-sim at lists.onebuilding.org; bldg-rate at lists.onebuilding.org
Subject: Re: [Bldg-sim] District Thermal Energy in LEED

 

To make a long story short, I vote Option A except that a portion of
your proposed fuel usage will be low-cost or free trash, and the
baseline will use only coal, per "Exception to G2.4" in 90.1.

 

Read on at your own peril...

 

Paul, I agree with most of what you've said.  In the definitions section
of 90.1 they do include coal as a fossil fuel, so the intention of
ASHRAE at least was to include coal among the fuel options. 

 

I think you have an opportunity in the selection of the fuel source if
the proposed plant is hybrid for coal and trash.  If you did have a
coal/trash-fired plant, then would you be treating the trash portion as
on-site "renewable" fuel source in EAC1 and EAC2?  (90.1 "Exception to
G2.4") In that case you would run both models, but the trash would be
free in the proposed design and the baseline would use coal alone as the
standby source.  That would be your gain in overall DES plant
performance.

 

Coal plant efficiency-wise, I think you are left with using the
documented efficiency of your actual plant that you suggest in Option A,
but taking credit only for the cost of the trash.  The default
efficiencies presented in the DES memo don't seem to apply to baseline
boilers, they rely on 90.1 for the baseline plant configuration.  If
your plants were instead hybrid with natural gas and trash, then you
would use Chapter 6 for plant efficiencies.

 

You don't mention if you think the coal plant equipment in place would
be more efficient than any other coal plant.   If that isn't a point of
emphasis, I would suggest taking the cost of trash and calling it a day.

 

Otherwise you'll need a CIR to have the USGBC approve a natural gas
baseline boiler plant, but I'm not sure that the intent of the DES memo
is to make a comparison against a typical boiler plant, or else the memo
could have been simplified to say that.  The USGBC seems to have gone
out of the way to use fuel source as specified by 90.1 rather than
compare against typical.

 

On the other hand, maybe they are just waiting for a CIR to come through
to edit the guidance...90.1 does rely on Section 6.4 for baseline plant
efficiencies, assuming that a DES would use the purchased heating
method G1.1.1 which helped lead to this whole guidance memo in the first
place...Good Luck!

 

David

________________________________________________________________________
____________________________________________

 

David Eldridge, PE

LEED(r) AP, HBDP


Grumman/Butkus Associates | 820 Davis Street, STE 300 | Evanston, IL
60201 | Ph: (847) 328-3555, ext 224 | Fax: (847) 328-4550

 

Energy Consultants and Design Engineers
________________________________________________________________________
____________________________________________

 

 

 

 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul Riemer
Sent: Wednesday, May 06, 2009 1:28 PM
To: 'Seth P. Spangler'; bldg-sim at lists.onebuilding.org;
bldg-rate at lists.onebuilding.org
Subject: Re: [Bldg-sim] District Thermal Energy in LEED

 

Seth, Sam, and Eric, 

Thank you for weighing in.  I should not have used the word 'plant'.  So
please allow me to restate my question. 

I know the Step 2 baseline boilers are on-site, but what fuel type and
what efficiency?

 

Appendix G prohibits fuel switching and I cannot find anything in the
DES guide that counters that, so on one hand I think I need the same
fuel type which means options A or B.

If I chose option A, I have no savings potential and just distribution
losses so no heating side reason to do Step 2.

If I chose option B, I am choosing a code efficiency for a natural draft
coal/trash fired hot water boiler.  A piece of equipment so far outside
the mainstream, I assert that any statement of code efficiency is
arbitrary.

 

Appendix G also requires me to use a boiler efficiency from Ch 6, so on
the other hand, I want to choose gas so I can get a code efficiency
which is option C.

If I choose option C, the savings will be strongly dependent on the
modeled price differential between coal/trash and natural gas.  This is
the savings projects really achieve and why they use coal/trash fired
district plants.

 

The difference between these options may well be the maximum allowed
differential of 4 EAc1 points.

 

I eagerly anticipate any other responses and the forthcoming DES Guide.
(Did I miss the public comment period?)

 

Paul Riemer

 

 

From: Seth P. Spangler [mailto:sspangle at rmf.com] 
Sent: Wednesday, May 06, 2009 12:46 PM
To: Paul Riemer; bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] District Thermal Energy in LEED

 

In the Step 2 model for the baseline, you DON'T use the same district
energy system used in the proposed.  Instead, you use on-site boilers of
the type specified in ASHRAE 90.1 Tables G3.1.1A and Tables G3.1.1B.

 

Interestingly enough, this is a contradiction from what is stated in
paragraph G3.1.1.1 of 90.1, but USGBC has clarified their intention in
soon to be released updates of the DES Guide.  

 

 

Seth Spangler, LEED(r) AP 

Design Engineer

 

RMF Engineering, Inc 

Ph: (843) 971-9639 ext:1497

Fax: (843) 971-9641 

sspangle at rmf.com

________________________________

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul Riemer
Sent: Tuesday, May 05, 2009 4:12 PM
To: bldg-sim at lists.onebuilding.org; bldg-rate at lists.onebuilding.org
Subject: [Bldg-sim] District Thermal Energy in LEED

 

Fellow Modelers,

I would greatly appreciate any answers and comments on formulating a
submission and/or CIR.

 

I am working on a LEED project which is heated by steam from a coal
fired plant and is subject to the USGBC's District Thermal Energy
document https://www.usgbc.org/ShowFile.aspx?DocumentID=4176.

Should the baseline hot water boiler plant in the Step 2 analysis be:

A) a coal fired boiler with the proposed boiler efficiency since 90.1
does not address coal fired boilers,

B) a natural draft coal fired hot water boiler with an assumed code
efficiency since 90.1 does not address coal fired boilers,

C) a natural draft gas fired hot water boiler with the code efficiency
referenced in 90.1, or

D) something else?

 

Remember the metric is energy cost savings.

 

If you reread it, replacing the word 'coal' with 'trash', does your
answer change?

 

Thank you,

 

Paul Riemer

Dunham

 

 

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