[Equest-users] CHW loop process load

Adam S adam.scherba at gmail.com
Fri Apr 5 11:50:55 PDT 2013


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****
>
>  ****
>
>
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>
>
> ****
>
> ** **
>
> -- ****
>
> ** **
>
> ** **
>
> Javed Iqbal, LEED AP, CEA****
>
> Energy Analyst ****
>
> ** **
>
> ** **
>
> ** **
>
> ** **
>
> ** **
>
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