[Bldg-sim] Bldg-sim Digest, Vol 209, Issue 2
Samuelson, Holly
hsamuelson at gsd.harvard.edu
Fri Apr 11 14:27:50 PDT 2025
Hi Jason,
Regarding modeling the efficiency of equipment...
It depends on whether you're modeling a specific system for a specific building project, or if you're trying to model generalized performance, for example for research. I'll comment on the latter scenario. For generalized research purposes, where we don't know the exact heat pump system and configuration, my team has found that energy simulation results are too sensitive to many of the heat pump details in the energy model. Therefore, to avoid our results being overly-specific to one heat pump model and configuration we've done one of the following two things.
1.
We've output the annual heating and cooling demands from tour energy model, then applied the heat pump heating or cooling COPs in a spreadsheet. We've found the COPs from a published study with realized, weather-dependent, COPs (from representative climates and buildings)
2.
We've also done this with hourly performance, based on realized, weather-dependent COPs at different temperatures from representative field studies. For interpolation, we've calculated the maximum possible COP (based on the Carnot Cycle) for each time step, then scaled those values down to something more realistic, based on the results from the published field studies.
Hope this helps.
Best,
Holly
[A black and white letter h Description automatically generated]
Holly Samuelson
Associate Professor of Architecture
Harvard University | Graduate School of Design
www.hollysamuelson.com<http://www.hollysamuelson.com/>
Unless otherwise noted, I do not expect a reply outside your normal working hours.
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From: Bldg-sim <bldg-sim-bounces at lists.onebuilding.org> on behalf of bldg-sim-request at lists.onebuilding.org <bldg-sim-request at lists.onebuilding.org>
Sent: Thursday, April 10, 2025 4:00 PM
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Subject: Bldg-sim Digest, Vol 209, Issue 2
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Today's Topics:
1. How do you model minimum and high efficiency DX cooling and
heat pump equipment? (Jason Glazer)
2. Re: How do you model minimum and high efficiency DX cooling
and heat pump equipment? (chris.malcolm.yates at gmail.com)
----------------------------------------------------------------------
Message: 1
Date: Thu, 10 Apr 2025 08:28:44 -0500
From: Jason Glazer <jglazer at gard.com>
To: bldg-sim at onebuilding.org
Subject: [Bldg-sim] How do you model minimum and high efficiency DX
cooling and heat pump equipment?
Message-ID: <bf88e843-c541-47e9-9462-0ff92a23c74a at gard.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
I just posted a question on unmet hours:
https://unmethours.com/question/101487/how-do-you-model-minimum-and-high-efficiency-dx-cooling-and-heat-pump-equipment/
"I?m trying to get an understanding of the practice of
modelers when comparing minimum efficiency and
high-efficiency DX equipment and heat pumps for different
applications. I know that detailed performance data is
sometimes difficult to get. How successful have you been in
trying to get detailed performance data from vendors? If you
can?t get data like that, how do you model the equipment?
How do you model the indoor fan? If you know it is
multispeed, how do you figure out those details? What if all
you have is the AHRI data (EER/EER2, SEER2/IEER, COP at
17/47, capacities, full load/intermediate/minimum airflows)
what assumptions do you have to make? What performance
curves do you use? If you can get data from the
manufacturer, what assumptions do you still need to make? Is
it different for residential size equipment than commercial?"
If you can respond to this email or post a response on
unmethours, I would appreciate it.
Thanks
Jsaon
--
Jason Glazer, P.E., BEMP, GARD Analytics, ASHRAE 209 chair
Admin for onebuilding.org building performance mailing lists
------------------------------
Message: 2
Date: Thu, 10 Apr 2025 15:47:12 +0100
From: <chris.malcolm.yates at gmail.com>
To: "'Jason Glazer'" <jglazer at gard.com>, <bldg-sim at onebuilding.org>
Subject: Re: [Bldg-sim] How do you model minimum and high efficiency
DX cooling and heat pump equipment?
Message-ID: <000801dbaa27$72659cf0$5730d6d0$@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Hi Jason,
I asked this question over a decade ago to a couple of different suppliers in the UK. What intrigued me was the very high efficiency that suppliers (e.g., Mitsubishi, Daikin) quoted - figures that we just plugged into building code calculations. Based on these figures it seemed like a no-brainer to just rip out centrifugal chillers and replace them with acres of DX systems! My enquiries came to little. The only interesting thing that I got (from a Danish academic) was that the market was very Germany-centric which resulted in SEER & COP being established at what seemed like, for the UK at least, quite extreme temperature bins.
The impression I got is that, locally, there is some design experience within the sales teams but it's limited to sizing. The best I got back in terms of energy was something along the lines of "we've got some boffins over in Japan, we can try asking them."
I don't doubt that they have some very clever people. Are they clever enough to get centrifugal-like performance out of a scroll compressor? I don't know. Reading your message, it's interesting to see that maybe the US market is subject to the same "black box" issues!
Good luck. I'll keep an eye on this thread and Unmet hours.
Cheers
Chris
-----Original Message-----
From: Bldg-sim <bldg-sim-bounces at lists.onebuilding.org> On Behalf Of Jason Glazer via Bldg-sim
Sent: 10 April 2025 14:29
To: bldg-sim at onebuilding.org
Subject: [Bldg-sim] How do you model minimum and high efficiency DX cooling and heat pump equipment?
I just posted a question on unmet hours:
https://unmethours.com/question/101487/how-do-you-model-minimum-and-high-efficiency-dx-cooling-and-heat-pump-equipment/
"I?m trying to get an understanding of the practice of modelers when comparing minimum efficiency and high-efficiency DX equipment and heat pumps for different applications. I know that detailed performance data is sometimes difficult to get. How successful have you been in trying to get detailed performance data from vendors? If you can?t get data like that, how do you model the equipment?
How do you model the indoor fan? If you know it is multispeed, how do you figure out those details? What if all you have is the AHRI data (EER/EER2, SEER2/IEER, COP at 17/47, capacities, full load/intermediate/minimum airflows) what assumptions do you have to make? What performance curves do you use? If you can get data from the manufacturer, what assumptions do you still need to make? Is it different for residential size equipment than commercial?"
If you can respond to this email or post a response on unmethours, I would appreciate it.
Thanks
Jsaon
--
Jason Glazer, P.E., BEMP, GARD Analytics, ASHRAE 209 chair Admin for onebuilding.org building performance mailing lists
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