[Bldg-sim] District Thermal System

[Julia Beabout]

I just finished my first DES project (not submitted yet, though) and have a couple more in the works.  

I agree with the interpretations below especially with respect to Step 2 and the utilization of the DES purchased rates as an acceptable means of reflecting the prposed/actual central plant's efficiency in the proposed energy model.  Although, the DES purchased rates should reflect/be adjusted for the items Karen mentions.  Additionally, I'd recommend confirming that the DES rate includes all the central plant's bits and pieces.  The maintenance costs should also be extracted from the DES rate if possible.  (The DES document seems to clarify that the maintenance costs do not need to be included.  So, if those can be extracted that will be more of an apples to apples comparison with the baseline model and work in your proposed model's favor).  

In my estimation, the above method provides the most expedient, realistic and accurate method of determining the central plant's efficiency.  The trick is that that info is not always available - especially in a campus situation.  So, in that case you may need to use one of the other methods of modeling the central plant discussed in the DES document: other metering data, modeling of the central plant equipment, etc.  However, sometimes even this data can be hard to come by and/or is not within the project's ability or budget to determine or model.  So, in that type of situation, the default central plant efficiency values provided in the DES document could be used.  





----- Original Message ----
From: Karen Walkerman <kwalkerman at gmail.com>
To: Eric Youngson <ericy at pae-engineers.com>
Cc: bldg-sim at lists.onebuilding.org; bldg-rate at lists.onebuilding.org
Sent: Tuesday, September 9, 2008 3:08:28 PM
Subject: Re: [Bldg-sim] District Thermal System


I am also in the middle of a DES project at the moment.  The way that I interpreted Step 1 and 2 is as follows:

Step 1:

Baseline: all downstream (on-site) equipment, envelope components, etc, as in Appendix G.  heating and cooling is purchased from a DES system.
Proposed: all downstream (on-site) equipment, envelope components, etc, as designed.  Heating and cooling is purchased from a DES system.

Step 2:

Baseline: all equipment is modeled as on-site.  Boilers and Chillers are to be modeled as designed in Appendix G.  Utility rates are to be local utility rates
Proposed: building is to be modeled as built.  Heating and cooling is purchased from a DES system, energy costs must take into account DES production and transmission losses.

In my opinion, the vocabulary in Table 1 is confusing, but the guidelines on pages 5 and 6 seem pretty clear.  Am I on the same page as everyone else here?

Thanks,

--
Karen
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