Hello Everyone,
I am currently modeling (Design Builder) a building which essentially consists of a mix of laboratories and office spaces. This building is supplied by a District heating (Steam) and cooling (chilled water) based on thermal energy coming from a nearby factory (I have no info on the production and distribution equipment).
Based on the LEED reference guide page 363 (Project type variations) I decided to follow Option 1, Path 1 – ASHRAE 90.1-2010 Appendix G, which states that I have to model both the proposed and baseline designs using purchased energy.
The building has 5 floors and 25000 - 150000 ft2, so the baseline HVAC system type is System 5 – Packaged VAV with Reheat, which per G3.1.1.3.3 is replaced by system 7 – VAV with Reheat.
From this point I model all the Downstream equipment the same in both designs, Baseline and Proposed.
Please correct me if I made anything wrong till here.
I would like to ask:
1
How do I determine the Energy Rates for this case? May I use the following formulas that were used for LEED previous versions?
Chilled water rate: $/MBTU = Virtual Electric rate * 71;
Steam: $/MBTU = Virtual Fuel rate * 1.59 + Virtual electric rate*3;
And what are the Virtual rates? May I use a flat annual averaged electricity and natural gas rates available in the market operator website for my country?
2
Is there a maximum number of points or any points floor if I follow this path (not considering upstream equipment)?
Thank you in advance.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
June 22, 2018 - 11:01 am
The DES guidance for LEED v4 projects is now contained within the Reference Guide. The chilled water formula did not change but the steam factor is 1.81 instead of 1.59 (1.59 is for hot water).
Here is the part of Option 1, Path 1 from the DES where the virtual rate is discussed.
All virtual DES energy rates must be identical in the baseline and proposed cases. If tariffs or rates are not available from the district plant serving the project, such as for campus or military plants, calculate the rates based on the virtual electric and fossil fuel rates from the model.
If a flat rate structure, in which the cost per unit of energy is the same throughout the year and there are no demand charges, is being used for all energy sources, then those flat rates become the virtual energy rates for the project.
If all energy rate structures are not flat, a preliminary run of the Option 1 baseline case energy model must first be completed to identify the virtual electric and fossil fuel rates for the project. For this preliminary run only, the rate for the DES-supplied energy may be left blank or entered as any value.
Once all the virtual energy rates are known for electricity and fossil fuel, calculate the virtual DES rates for both the baseline and proposed case per the values in the minimum energy performance calculator provided by USGBC.
The point floor and ceiling has been removed.
Greenlab
Green Lab6 thumbs up
June 22, 2018 - 11:31 am
Thank you for your help Marcus.
Maya Karkour
EcoConsulting871 thumbs up
January 31, 2020 - 3:21 am
Hello,
I am using Option 1 as well for my project. However, my thermal modeling software does not allow me to model purchased chilled water directly. I still need to model a chiller, and the source of electricity for the chiller would be purchased electricity. My understanding is that I should model the chiller with a COP of 1.0 so that the DES plant is neutral (for both baseline and proposed). Can you please confirm if this is correct, or if I should use a more reasonable/realistic COP?
Thanks!
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
January 31, 2020 - 11:44 am
Sounds right. You are not accounting for the efficiency of the chiller when modeling purchased energy. Make sure the same value is used in the baseline.
Antonio Galicia
January 18, 2022 - 10:13 am
Hello
I am using "Path 2. Comprehensive system energy simulation" to achieve this credit. I understand that this path does not need to comply with the no exceed requirement about the 2.5%- annual energy output in the pumping energy consumption. I only need to find out that my proposed DES plant shows an annual energy savings improvement of at least 10% over a DES plant with minimally efficient requirements.
Could you please help me to confirm if this is correct?
Tyler Thumma
7GroupLEEDuser Expert
60 thumbs up
February 17, 2022 - 10:22 am
I am not aware of the requirements you're referring to. Could you provide more information about where they are found?