[Equest-users] Reply： The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007
Nicholas Caton
ncaton at catonenergy.com
Sun May 24 06:53:22 PDT 2015
I received some similar review language very recently suggesting 80%
efficiency is expected at all/most part load conditions for the baseline
boiler…. Similar context in that case with the boiler rarely operating
near full load.
My comment has other issues that would cloud the topic at-hand, but here
is truncated version:
“…Furthermore, the average boiler efficiencies in the Baseline PS-C output
reports, calculated by dividing the boiler energy consumption by the annual
boiler heating energy generated was… [approximately 5% lower than the
nominal efficiency input & documented]. Revise the baseline boiler
efficiency to 80% and revise the boiler curve for the Baseline case as
necessary to have an average efficiency that is near 80%. Provide updated
PS-C reports for the Baseline confirming that the average baseline
efficiency is near 80%.”
This is the first time I have run into commentary checking up on PS-C’s
output at all, and I’m using the same library curves as always for typical
baseline boilers.
I believe the PS-C discrepancy is explained both by the non-flat library
curve and by the boiler’s default start-up loads, in combination.
Here is the default library curve – it is (roughly, but not quite) linear:
[For those unfamiliar, the Y-axis is a unitless multiplier]
If I’m not mistaken, this curve serves double-duty: it simultaneously
applies the hourly PLR to the full capacity (as either input or auto-sized)
and also accounts for increased HIR (lower efficiency) as the PLR drops.
My understanding in equation form:
Energy Consumed (for the hour) = (Boiler full capacity as input/autosized)
* (Boiler nominal HIR input @ full load) * HIRf(PLR)
If all of that is true, a perfectly “flat efficiency” curve, returning your
nominal input HIR at all efficiencies, would therefore be Z = X. That’s
plotted above for reference with a light/thin line.
Even with such a “flat efficiency” curve applied to a test-case, PS-C’s
outputs still suggest an annual equivalent HIR higher than the nominal
input. Zeroing out the startup/standby inputs as well is required to get
PS-C to report your nominal HIR = annual fuel / annual load:
I think the correct response (which perhaps I’ve mostly composed above) is
to demonstrate the causes (library curve shape, startup/standby defaults),
and to assert these are all appropriately applied to the baseline boiler,
though *none of this is regulated by 90.1* to the best of my knowledge so
it might be relatively shaky territory.
I would wager 90% of all eQuest baseline boilers submitted to GBCI to date
probably don’t mess with the library curves or standby/startup inputs, but
that’s pure speculation on my part.
Has anybody ever tried to explain/justify the default boiler curve and
default startup/standby inputs? Do we know where those defaults come from?
~Nick
*NICK CATON, P.E.*
*Owner*
*Caton Energy Consulting*
1150 N. 192nd St., #4-202
Shoreline, WA 98133
office: 785.410.3317
www.catonenergy.com
*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
Behalf Of *???
*Sent:* Sunday, May 24, 2015 5:34 AM
*To:* Julien Marrec
*Cc:* equest-users at lists.onebuilding
*Subject:* [Equest-users] Reply： The problem of minimum equipment
efficiency requirement of Ashrae 90.1-2007
Hi,Julien
I understand his meaning is keep a constant efficiency and I know the
flat efficiency in equest is a curve that is y=x, but I can't confirm if a
constant efficiency is Ashrae 90.1-2007's original intent.
------------------
*Yongqing Zhao*
*Changsha Green Building & Energy Saving Technology CO.,LTD*
NO.438,Shaoshan Road,Changsha,Hunan,China
Telephone:13574805636
Email:zhaoyongqing1987 at 126.com
503271081 at qq.com
------------------ 原始邮件 ------------------
*发**件人**:* "Julien Marrec";<julien.marrec at gmail.com>;
*发**送**时间**:* 2015年5月24日(星期天) 晚上8:19
*收件人**:* "赵永青"<503271081 at qq.com>;
*抄送**:* "equest-users at lists.onebuilding"<equest-users at lists.onebuilding.org>;
*主**题**:* Re: [Equest-users] The problem of minimum equipment efficiency
requirement of Ashrae 90.1-2007
Hey,
He's saying that you need to make sure that the curve boiler-fPLR gives you
a constant efficiency. As far as I remember, the default atmospheric curve
from equest is like this.
Don't be confused by "flat". A flat efficiency curve is when you plot
efficiency=f(PLR). In equest, it should be a curve that is y=x
Look at the curve you used.
Best,
Julien
Envoyé de mon iPhone
Le 24 mai 2015 à 11:27, "赵永青" <503271081 at qq.com> a écrit :
I get the energy model comments from LEED reviewer as following:
The narrative response indicates that the Baseline boiler has been modeled
utilizing operating performance curves and a boiler HIR of 1.25. However,
since the boiler operation HIR is based on the performance curves, the HIR
is less than 1.25 in the part-load condition, which is inappropriate.
Revise the Baseline boilers to include a flat efficiency of 80% for all
part-loads. Provide eQuest input files or screen shots verifying the boiler
efficiency has been modeled as required.
<545E22AD at FA528147.9F996155>
However, I can not understand it very much. The minimum equipment
efficiency requirement(80 % Et) of Ashrae 90.1-2007 should be base on full
load condition.Why the LEED reviewer raise such a question?Any insight is
appreciate!!
Thanks
------------------
*Yongqing Zhao*
*Changsha Green Building & Energy Saving Technology CO.,LTD*
NO.438,Shaoshan Road,Changsha,Hunan,China
Telephone:13574805636
Email:zhaoyongqing1987 at 126.com
503271081 at qq.com
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