[Equest-users] CHW loop process load
fiona.you at cn.bureauveritas.com
fiona.you at cn.bureauveritas.com
Sat Apr 6 22:26:03 PDT 2013
Hi James,
Thank you for your sharing. I am doing a district chilled water project at
present, your information is very useful.
I made the Baseline model with chillers and cooling towers as indicated in
Apppendix G. The proposed model is modeled with one air-cooled chiller with
average efficiency+piping loss.
One thing I am not clear is what's the chiller curve like in your model?
Because it is hard to set curves as a constant value. For example, a
chiller's EIR curve should be a quadratic curve, how do you make it into a
constant value?
Best Regards!
游超 Fiona You
高级LEED咨询师 Senior LEED Consultant
必维国际检验集团 工业与设施事业部 Bureau Veritas Industry &
Facilities Division
中国上海市浦东新区陆家嘴软件园 8/F Building No.8 Pudong
Lujiazui Software Park,
峨山路91弄120号8号楼8楼 邮编: 200127 No.120, Lane 91, E Shan Road,
Shanghai 200127, P.R.C.
Tel: +86 21 6886 0643 Ext.8557 Fax: +86 21 6886 1421
Mobile: +86 180 1750 1596
Web : www.bureauveritas.cn (CHN) | www.bureauveritas.com (Global)
P Save a tree. Don
’t print this
e-mail unless it is
really necessary
James Hess
<JHess at tmecorp.co
m> To
Sent by: Adam S <adam.scherba at gmail.com>
equest-users-boun cc
ces at lists.onebuil "equest-users at lists.onebuilding.org
ding.org "
<equest-users at lists.onebuilding.org
>
2013-04-06 03:36 Subject
Re: [Equest-users] CHW loop process
load
Ref
Those are good questions.
Answer to 1st question = yes
Answer to second is the following:
To be practical about this and simplify the modeling, we create a constant
efficiency air cooled chiller to simulate the default DESv2.0 plant.
The EIR is entered equal to 0.839 kw/ton, which equates to 4.4 COP + 5%
losses.
This represents the energy usage of the plant chillers, plant pumps, and
cooling tower.
We further create and apply performance curves that keep the EIR the same
versus load and temperatures. In other words, Avg EIR = Max EIR = Min EIR =
the EIR we enter into eQuest.
It's easier to do this with an air cooled chiller because then you don't
have to worry about a cooling tower and tower water pump in the model.
This approach is simple and it works. I've used it on several LEED projects
involving district chilled water systems.
We probably give up some savings with this approach, but it's a lot of work
to correctly model the actual performance of an actual CHW system in
accordance with DESv2.0. If this isn't in our modeling scope of work, we
use the stipulated efficiency route.
Hope this helps.
P.S. The stipulated efficiency approach does not work out well when
modeling heating water and steam systems because the default efficiency
numbers for those systems are pretty bad. That's not the case with chilled
water, at least if you are comparing to a Baseline based on air cooled
equipment. If the building was big enough to require chilled water as a
baseline, this approach will not work that well, and you would have to
pivot to a new approach. Comparing the stipulated efficiency against a App
G Baseline water cooled chiller plant would probably result in little to no
savings in the cooling equipment category.
Thanks!
Regards,
JAH
On Apr 5, 2013, at 1:51 PM, "Adam S" <adam.scherba at gmail.com> wrote:
Do you interpret the USGBC guidance for baseline district energy
systems to be 4.4 COP + 5% losses averaged over the year? Meaning
that the chiller in your model should be modeled with a better EIR so
that the average annual COP calculated using the PS-C report is 4.4?
Their use of the term "average efficiency" seems a bit vague.
Thanks,
-Adam
On Fri, Mar 29, 2013 at 3:24 AM, James Hess <JHess at tmecorp.com>
wrote:
I definitely agree with that suggestion, versus reinventing the
wheel. Our experience with the RMI tool is that it works. There
seems to be a quirk regarding a little shifting due to DST, but
that’s a very small thing in the grand scheme of things. I want to
say we tested it and the annual average value coming out of eQuest
was ~ 99.3% of the average input value. Close enough! J
Also, I don’t know if you are modeling the other buildings because
a GBCI reviewer said you had to do that (assuming this is a LEED
project) in order to ensure that correct part load ratios on the
chillers operating profile are appropriately accounted for. I got
that sort of comment on a recent project and my response was
something to the effect of … I could do that, but since we aren’t
getting paid by the owner to model buildings outside of the project
scope just to make the chiller modeling more accurate, instead I
will just use the default efficiency allowed by the DESv2.0
guidelines for water cooled chiller plants à 4.4 COP + 5% losses =
~ 0.839 kW/ton on average.
That saved a lot of time with that change because if you do that,
you don’t have to model any other buildings served by the system.
If you are comparing against air cooled equipment for the Baseline,
you still get a decent amount of savings. I probably left some
savings on the table because the plant had high efficiency VFD
water cooled chillers, and VFDs on the pumps and cooling tower.
I’m positive that the annual efficiency was much better than 0.839
kW/ton, but (the way I look at this) we have to balance the level
of effort on energy modeling versus the fees we are getting for the
modeling.
Hope this helps! J
Regards,
JAH
James A. Hess, PE, CEM, BEMP
Energy Engineer
TME, Inc.
Little Rock, AR
Mobile: (501) 351-4667
From: equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] On Behalf Of Javed
Iqbal
Sent: Thursday, March 28, 2013 1:55 PM
To: Kimberly Wiebe
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] CHW loop process load
You should use RMI tool to generate schedule which will eventually
gives you schedule in INP format.
Here is the link to download it..
http://www.rmi.org/Content/Files/EMIT1.4.zip
On Thu, Mar 28, 2013 at 1:41 PM, Kimberly Wiebe <
Kimberly.Wiebe at burohappold.com> wrote:
Hello,
I am modelling a central cooling plant that serves many buildings
on an college campus. For some buildings I am building the geometry
and inputting internal gains. For other buildings I have annual
8760 cooling load profiles. If I want to add these annual cooling
load profiles to the CHW loop as process loads, would I have to
make 365 day schedules (and 52 weeks)? If so I will write some sort
of text generator out of an excel file and paste in the .inp, but
before I do want to see if there was any other way.
Thank you,
Kim
Kim Wiebe
Direct: +1 310 945 4813
kimberly.wiebe at burohappold.com
_______________________________________________
Equest-users mailing list
http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
To unsubscribe from this mailing list send a blank message to
EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG
--
Javed Iqbal, LEED AP, CEA
Energy Analyst
_______________________________________________
Equest-users mailing list
http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
To unsubscribe from this mailing list send a blank message to
EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG
_______________________________________________
Equest-users mailing list
http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
To unsubscribe from this mailing list send a blank message to
EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG
"This message contains confidential information.
To know more, please click on the following link: http://disclaimer.bureauveritas.com"
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20130407/92c04238/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 51443022.jpg
Type: image/jpeg
Size: 4108 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20130407/92c04238/attachment-0002.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: graycol.gif
Type: image/gif
Size: 105 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20130407/92c04238/attachment-0006.gif>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: pic01560.gif
Type: image/gif
Size: 1255 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20130407/92c04238/attachment-0007.gif>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ecblank.gif
Type: image/gif
Size: 45 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20130407/92c04238/attachment-0008.gif>
More information about the Equest-users
mailing list