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District Cooling in ASHRAE Energy Cost Budget Method

asked 2024-06-28 16:29:04 -0500

Srecko Curkovic's avatar

updated 2024-07-01 12:14:09 -0500

I'm working on a baseline building energy model in IES VE 2023 following ASHRAE 90.1-2016 Energy Cost Budget Method. Per ECB, my baseline system should be System 6 (heating: water-source heat pumps connected to a water loop served by boilers and water coolers; cooling: DX). The proposed model includes district cooling (water-cooled chillers + cooling towers). What are the ECB guidelines regarding district cooling? Do I need to model the baseline cooling plant same as in the proposed model? Or do I simply model DX cooling as listed for System 6? If I have DX cooling, do I use electricity rates or purchased chilled water rates from the proposed model?

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answered 2024-07-01 06:30:24 -0500

updated 2024-07-01 06:36:30 -0500

There are not a lot of details in the Energy Cost Budget Method section of 90.1-2016, but two of the footnotes to Table 11.5.2-1 Budget System Descriptions provide some information:

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and

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and they both reference 11.4.3, which discusses steam and chilled water here:

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For System 6, since it uses direct expansion cooling, as shown in 11.5.2-1, I think there is no other way to interpret the baseline except that it uses a normal direct expansion water source heat pump, as described in footnote g.

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Based on this, you model an entire water source heat pump system as the baseline as if it were not a district system at all. Since it is a heat pump, you would use an electric rate for the baseline for the fluid cooler, and presuming there is no boiler in your proposed design, you would use fossil fuel for that.

This is just my opinion on interpreting this for your situation, and it is not official at all. If you want to get an official or unofficial interpretation from ASHRAE, see

https://www.ashrae.org/technical-reso...

But it is not the fastest process.

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Thank you, that all makes sense!

Srecko Curkovic's avatar Srecko Curkovic  ( 2024-07-01 13:14:24 -0500 )edit

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Asked: 2024-06-28 16:29:04 -0500

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Last updated: Jul 01