Dear all,
When simulating district cooling for LEED, a virtual plant is required to be added to the proposed building, according to the "Treatment of District or Campus Thermal Energy in LEED V2 and LEED 2009 ? Design & Construction".
The efficiency of the virtual plant is obtained through modeling if the district cooling system is new.
The "Treatment of District or Campus Thermal Energy in LEED V2 and LEED 2009 ? Design & Construction" said, "Apply measured or estimated load profiles as ?process loads? to reflect the estimated total loads on the district energy plant".
My question is:
What is the estimated load? If the district cooling system provides cold to any other buildings that are not in the LEED certificate scope, how can I get the estimated load?
Regards,
Esmi
First off, I have no idea...
But I would start with the load profile of a building representative of
the median or average age of the buildings on the system, even if I had
to build the model. Then I would apply that to the central plant,
scaled up to the capacity of the central plant, or where you think the
capacity factor falls. If I was doing this in Energy Pro, which I use
most often, I might build a "typical" model building and add it to the
model of the proposed building (all being heated and cooled by the
central plant), with an appropriate multiplier to use up the capacity of
the central plant, minus the new proposed building, on a design day. I
would then consider leaving those "bogey buildings" in the model as I
proceeded forward. Perhaps (just perhaps) calling them "existing" might
allow the software to ignore them for the LEED calculations.
You could also find out what other buildings are on the system, and
model those. Probably more accurate than just a "typical building". If
you modeled all the buildings being provided heating and cooling by the
central plant, that would be a pretty good way to go.
But, like I said, I have no idea.
Robert Wichert P.Eng. LEED AP BD&C
I would agree with that.
I would recommend informing your client that you can either do Option 1 of the USGBC DESv2.0 guidelines (i.e. plants modeled as neutral between baseline and proposed via stipulated rates), or using the stipulated efficiencies for Option 2.
Otherwise, I would recommend informing your client that modeling the entire district system just to estimate the plant efficiencies (i.e. includes buildings outside the scope of the current project), with the goal of getting more EAc1 points for the project, will result in you asking for additional fee because this is additional work on your part, potentially a lot of additional work. I think this is a very reasonable approach.
Regards,
James A. Hess, PE, CEM, BEMP
If your client actually meters the chilled water usage at the buildings and
allocates the charges to each facility for the cost of producing chilled
water you can use that information and just set the model up in baseline
and proposed building like any other metered utility with a cost per btu,
Kbtu, ton-hours, etc. There would be no need to model a central plant at
all in this case.
I believe the rule is that the proposed building has to be less than 50% of
the load on the central plant. You would need to verify that in the LEED
documentation.
--
M. Dennis Knight, P.E.
Esmireta,
It has been awhile since I modeled a central plant for a LEED project, so you'll have to verify my comments.
After applying a CHW meter and a Steam Meter to your CHW Loop and HW Loop respectively, a new Central Plant can be modeled in either of the following ways:
1) Using efficiencies per section 2.4.1.2.3 Default Efficiencies and applying them to your meters, or
2) Using efficiencies per the design specifications and applying them to your meters.
I don't remember ever seeing a 'process load' that must be applied to the plant. I'm sure some else will chime in a correct me if I'm wrong. Have a great day!
Thanks,
David Griffin
I would agree with that.
I would recommend informing your client that you can either do Option 1 of the USGBC DESv2.0 guidelines (i.e. plants modeled as neutral between baseline and proposed via stipulated rates), or using the stipulated efficiencies for Option 2.
Otherwise, I would recommend informing your client that modeling the entire district system just to estimate the plant efficiencies (i.e. includes buildings outside the scope of the current project), with the goal of getting more EAc1 points for the project, will result in you asking for additional fee because this is additional work on your part, potentially a lot of additional work. I think this is a very reasonable approach.
Regards,
James A. Hess, PE, CEM, BEMP
Dear community,
I?ve just finished some LEED Energy Modelling for a building in Sao Paulo and I came across some results that made me a bit sceptical. I would greatly appreciate your thoughts on the matter.
Description of the model:
Our proposed building has 30% less Energy Demand than the Baseline building.
The proposed building uses a fan coil system with minimum fresh air provision. The baseline model utilises a PFP VAV system (no.8 according to ASHRAE classification).
Fresh air flow rates between Baseline and Proposed buildings are the same ? i.e. around 7.5l/s/p.
Both Buildings have heat recovery and similar SFPs.
The proposed building uses a rather mediocre Air Cooled chiller ? COP of 2.8 - whilst the baseline building uses a highly efficient Water Cooled Chiller ? COP of 5.5.
The problem:
The proposed building?s auxiliary energy Consumption is around 80kWh/m2, whilst the Baseline?s auxiliary energy consumption is around 400kWh/m2 ? i.e. 500% more. Does this sound normal? What kind of auxiliary energy consumption (kWh/m2) is reasonable for a VAV system with PFPs doing 7.5l/s/p fresh air? Of course there will be some recirculation from the economiser, but can this justify 5 times more energy spend on auxiliary?
Regards
Ioannis Rizos