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[EnergyPlus_Support] Re: Ground temperature of Singapore
Hi Group,
I would like to post a recommendation Dr. Ooi sent to me privately. For me, THIS is the answer I was looking for. An easy and systematic way to find the ground temperature for unconditioned buildings. I think Dr. Ooi will not mind me sharing this email:
--------------------------------------------------------------
Hi,
For indoors that are not conditioned, you can use the 12 monthly average ground temperatures in the stat file, which is one of the 3 files that comes with the download of .zip weather file. These IWEC weather files are available for Singapore and, i believe Sweden too.
Enter these 12 temperatures for Jan...Dec fields in the Site:GroundTemperature:BuildingSurface object.
Of course there is daily fluctuation of temperature, but for the ground, this is not much
For buildings that are not conditioned, there is no need to use the Slab utitlity.
Hope this helps
ooi
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In case anyone doesn't know, Dr. Ooi has done a lot of research on EnergyPlus ground temperatures. He has written a paper on it and is the author of the EneryPlus excercises "3D heat transfer with ground" for introducing ground modelling.
So I open it up to the Yahoo Group to decide if this is CASE CLOSED for ground temperatures for unconditioned buildings. Or we can discuss Dr. Ooi's recommendation and compare it to your own methodology.
I looked into the STAT monthly averages, they are supposedly the 0.5 m depth ground temperature. Although when I tried calculating that using the Hillel (1982) method, I got a slightly different result.
Ryan
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Joe Huang wrote:
>
> made a typo, meant to write 16C (60F), not 13C.
>
> Joe
>
> On 1/20/2013 11:08 AM, Joe Huang wrote:
> > Ryan has said that those previous runs with Slab were done with the
> > default indoor temperatures which were very low (13C for winter, 18.3
> > for summer) and appropriate only for buildings in northern climates.
> > Since the building is naturally ventilated, a more appropriate indoor
> > temperature would be simply the outdoor air temperature, in which case
> > you would probably see the same ground temperatures as on the weather
> > file. Further iterations between E+ and Slab can be done, but that
> > would definitely a 2nd or 3rd order effect.
> >
> > Joe
> >
> >
> > On 1/19/2013 11:45 PM, jeannieboef wrote:
> >> Your itteration approach is correct. I don't believe high accuracy is
> >> needed for the deltaT over the slab, as the small error is only
> >> impacting on a small chunk of energy transfer over the entire
> >> envelope. if the space above is conditioned this makes things easier.
> >>
> >> Post an example of your unbelievable results. Corrispond them also
> >> with Dr. Li as he has practiced energy modelling in Singapore. You'll
> >> have to check some older posts for the contact details.
> >>
> >> Sent from my iPhone
> >>
> >> On 19.01.2013, at 03:37, Linda Lawrie
>> > wrote:
> >>
> >>> If you don't enter the indoor temperature, you will likely have
> >>> unrealistic results.
> >>>
> >>> You have not given your problem to the helpdesk == this is a user=user
> >>> forum.
> >>>
> >>> Rule of thumb - make your ground temperature -2C from your indoor
> >>> temperature. I believe this is stated in the aux programs document if
> >>> you choose not to believe the calculations from the slab program.
> >>>
> >>> On 2013-01-18 19:32, academicryan wrote:
> >>> > Hi Linda I have read that section at least 4 time trying to
> >>> > understand it. I still don't really understand it very well but I'm
> >>> > pretty sure its simply telling me to use the Slab program in the
> >>> > EnergyPlus Utilities.
> >>> >
> >>> > I've mentioned that the Slab program gives unrealistic results. What
> >>> > I particularly don't understand about the Slab is why there is an
> >>> > input for monthly averaged indoor temperature. This means I need the
> >>> > indoor temperature to calculate the ground temperature. But to
> >>> > simulate the indoor temperature, I need the ground temperature. This
> >>> > seems like an impossible chicken/egg scenario of which one comes
> >>> > first. I've even read somewhere I'm supposed to start with an
> >>> > arbitrary indoor temperature and keep doing this chicken/egg cycle
> >>> > until both ground and indoor temperatures converge and stabilise.
> >>> > This
> >>> > seems really silly and tedious but maybe that really is what I'm
> >>> > supposed to do?
> >>> >
> >>> >
> >>> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> >>> , Linda Lawrie wrote:
> >>> >>
> >>> >> Read the auxiliary programs document on Ground heat transfer with
> >>> >> EnergyPlus. Look at the EPW file ground temperatures as well (which
> >>> >> are
> >>> >> not suggested for the Site:groundTemperatures values)
> >>> >>
> >>> >> On 2013-01-18 18:49, academicryan wrote:
> >>> >> > Update: *EnergyPlus developer please respond*
> >>> >> >
> >>> >> > OK I now know how to calculate soil temperature as a function of
> >>> >> > depth from Hillel, 1982.
> >>> >> >
> >>> >> > Essentially his equation says that at 0 m depth, monthly average
> >>> >> soil
> >>> >> > temperature is the monthly average air temperature plus 1�°C. This
> >>> >> is
> >>> >> > basically a sine wave. With increasing depth, the soil temperature
> >>> >> > gets closer to the annual mean air temperature plus 1�°C.
> >>> >> >
> >>> >> > NEW QUESTION: Is this what
> >>> >> 'Site:GroundTemperature:BuildingSurface'
> >>> >> > wants? i.e. 0 m depth soil temperature. Or some other depth? Or
> >>> >> some
> >>> >> > other 'ground temperature' altogether?
> >>> >> >
> >>> >> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> >>> , "academicryan" wrote:
> >>> >> >>
> >>> >> >> Can somebody please help me do a very simple task.
> >>> >> >>
> >>> >> >> Calculate/find the monthly ground temperature for Singapore. To
> >>> >> >> clarify, this is the input for the
> >>> >> >> 'Site:GroundTemperature:BuildingSurface'.
> >>> >> >>
> >>> >> >> ------
> >>> >> >>
> >>> >> >> Extra info - I've already tried the Slab utility, it comes up
> >>> >> with
> >>> >> >> very unbelievable results. Calculating some months below 17�°C
> >>> >> when
> >>> >> >> Singapore air temperatures never drops below 21�°C.
> >>> >> >>
> >>> >> >
> >>> >> >
> >>> >> >
> >>> >> > ------------------------------------
> >>> >> >
> >>> >> > Primary EnergyPlus support is found at:
> >>> >> > http://energyplus.helpserve.com or send a message to
> >>> >> > energyplus-support@
> >>> >> >
> >>> >> > 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 currently allowed but be mindful that not everyone
> >>> >> > has a high speed connection. Limit attachments to small files.
> >>> >> >
> >>> >> > EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf
> >>> >> under
> >>> >> > the Documentation link and press the "search" button.
> >>> >> > Yahoo! Groups Links
> >>> >> >
> >>> >> >
> >>> >> >
> >>> >>
> >>> >
> >>> >
> >>> >
> >>> >
> >>> > ------------------------------------
> >>> >
> >>> > Primary EnergyPlus support is found at:
> >>> > http://energyplus.helpserve.com or send a message to
> >>> > energyplus-support@...
> >>> >
> >>> > 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 currently allowed but be mindful that not everyone
> >>> > has a high speed connection. Limit attachments to small files.
> >>> >
> >>> > EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under
> >>> > the Documentation link and press the "search" button.
> >>> > Yahoo! Groups Links
> >>> >
> >>> >
> >>> >
> >>>
> >>
> >
>
------------------------------------
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