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RE: [EnergyPlus_Support] Comparable Comfort

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Subject: RE: [EnergyPlus_Support] Comparable Comfort
From: "Andy Tindale" <andy@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 14 Dec 2005 22:42:28 -0000
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Rick/Rory,

I wondered whether the Low Temp Radiant System:Hydronic system which allows
Temperature control type to be OPERATIVE could be used to condition
buildings to equivalent comfort conditions? The Operative temperature
control type senses the average of the air and mean radiant temperatures so
presumably is capable of maintaining a fixed operative temperature.  I guess
it would also depend on whether the heating/cooling systems you are trying
to model could be accurately represented by a low temperature radiant
system. Perhaps you could approximate a purely convective system by giving
your radiator components low emissivity and high convective heat transfer
coefficients.

Andy Tindale
DesignBuilder Software

-----Original Message-----
From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]On Behalf Of Rick Strand
Sent: 14 December 2005 20:04
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Cc: Mike Witte
Subject: Re: [EnergyPlus_Support] Re: Comparable Comfort

Rory:

Your question is an interesting one.  I have done similar work in the past
using IBLAST (a predecessor of EnergyPlus) in that I was trying to achieve
equal comfort for both a radiant and a forced air system.  Due to the
distinct differences between these two system types, there are different
thermostatic settings that are required to maintain the same level of
comfort.  I ended up doing the "brute force" method that you
discussed--varying thermostatic settings in different input files to
achieve similar levels of comfort between the two system types.  This is
certainly a possibility for your study, but as you point out, this is
fairly time consuming.  I was not able to find any other alternatives at
the time and thus don't have any better suggestions to offer.

To answer your other questions, it is fairly likely that you should see
"effective temperature" controls in EnergyPlus within the next year.  The
effective temperature is simply defined as some user specified combination
of mean air temperature and mean radiant temperature such as ET = (x)(MAT)
+ (1-x)(MRT) where x is defined by the user.  Such controls would allow you
to come close to achieving equal comfort for various cases by factoring in
both radiant and convective contributions to thermal comfort.  The radiant
systems in EnergyPlus already allow some alternate controlling schemes
(x=0, X=0.5, and x=1.0 in the above equation).

Regarding whether it is possible to control the building to PMV=0, this is
not something that is planned for EnergyPlus and there are not any
buildings I am familiar with that even try to implement such a control
scheme.  In theory, all buildings should achieve acceptable PMV levels but
thermostatic settings are usually based on achieving a particular air
temperature.

This information probably does not help your situation, but I hope that it
at least sheds some light on what is possible and what has been done in the
past.

Rick Strand
EnergyPlus Development Team Member

At 10:07 AM 12/14/2005, you wrote:

>Hello
>
>I am an enginnering masters student in University College Dublin.
>I am about to start a series of simulation studies relating to
>thermal mass in office buildings.
>
>I am hoping to asses the energy perormance of a naturally ventilated
>office building as a function of different construction types (of
>increasing weight). Each construction will have the same U-value.
>
>In order to properly rank the annual energy perfomance provided by
>the different constructions I feel that I should try and normalise
>out the comfort conditions experienced in each case. ie. I would
>like each building to be equally comfortable before comparing the
>buildings associated energy perfomance.I will probably measure
>annual comfort using a PMV or PPD index, (possibly "PMVhrs Too Hot"
>and "PMVhrs Too Cold").
>
>At the moment I am looking at winter time heating perfomance, and as
>expected the "PMVhrs Too Cold" is increasing with increasing thermal
>mass, mainly as a function of the low radiant temperatures which are
>experienced following a period of night-setback. I can normalise
>for "PMVhrs Too Cold" by manually using different dry bulb
>temperature setpoints prior to simulation, untill comparable heating
>comfort results are produced, but this is taking a long time.
>
>Does anybody know if there is a better way to do this?
>
>Can radiant temperature setpoints be used instead of dry-bulb
>temperature setpoints in E-plus?
>
>Or would it even be possible to control a buildings heating system
>so that a PMV of zero is always acheived?
>
>I would be interested to know if this would be technically possible
>and if anybody has tried to do something similar in the past.
>
>Best Wishes
>
>Rory Walsh
>Energy Research Group
>University College Dublin
>
>
>
>
>
>
>
>
>
>
>The primary EnergyPlus web site is found at:
>http://www.energyplus.gov
>
>The group web site is:
>http://groups.yahoo.com/group/EnergyPlus_Support/
>
>Attachments are not allowed -- please post any files to the appropriate
>folder in the Files area of the Support Web Site.
>
>EnergyPlus Documentation is searchable.  Open EPlusMainMenu.idf and press
>the "search" button.
>
>Yahoo! Groups Links
>
>
>
>

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References:
- Re: [EnergyPlus_Support] Re: Comparable Comfort
  - From: Rick Strand

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