Cooling fuel type - ASHRAE 90.1 - 2004

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Hello,
I posted this a couple of days back but perhaps wasn't specific enough.

I am modelling a hotel in Iran for a US NC project and they will be using absorption chillers to satisfy 100% of the cooling load. I will be using ASHRAE 90.1 2004 to create the reference building, however I don't see any reference for the cooling fuel type. It is clearly stated in ASHRAE 90.1 - 1999 that the cooling fuel types will be the same in the proposed and reference building, but this is not stated in 90.1 - 2004. Does anyone have any experience modelling absorption chillers and if so, where is it stated that the cooling fuels should match.

Any assistance you could provide is much appreciated

Thank you

Macintosh, Richard's picture
Joined: 2011-10-02
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Richard,

I assume your building falls under System # 7 or 8 where chilled water
is the Cooling Type. In ASHRAE 90.1-2004 Appendix G section G.3.1.3.7,
it states that electric chillers shall be modeled in the baseline
building independent of the proposed building chiller type.

Sam Mason

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Does anyone know the rationale behind ASHRAE's change from matching fuel
types in 1999 to only using electric on 2004?

COPs of absorption chillers are typically below 1.0, so even if a
"renewable" fuel such as solar thermal is used (and deducted from the
EAc1 cost), it may be difficult to reduce cooling consumption compared
to electrically operated chillers in the reference building. Has anyone
been able to get any benefit from using absorption chillers?

It seems that the use of a hypothetical reference building as the
foundation of 90.1 performance comparisons, often favours very typical
HVAC systems. Perhaps the intent of 90.1 is to increase efficiency of
conventional systems, but using the "reference building" approach as the
basis of LEED and other programs does not often reward innovative HVAC
designs. A better approach may be to mandate specific energy intensity
targets rather than % improvement over a reference building.

This absorption chiller issue fits nicely into the recent discussion
regarding the performance of LEED buildings. One of the recent analyses
of the NBI study found that although Silver/Gold/Platinum LEED building
use less site energy than comparable CBECS buildings, they use the same
amount of source energy, possibly indicating a fuel switch/favouring to
electricity. The use of absorption chillers would reduce the source
energy and the load on the current electricity grid, which is a double
benefit since new generation capacity often comes from gas and coal
power plants, thus increasing the GHG emissions at the source and
downstream. However, absorption efficiencies are considerably less, so
that may even things out in the end.

Luka

Matutinovic, Luka's picture
Joined: 2011-09-30
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