RE: [EnergyPlus_Support] Re: Ground temperature of Singapore

Hi, Karen

Your suggestion is good and has been tried by us, adding a basement zone below the house.

The problem is the definition for material "soil" or "earth".

With a concrete floor, the material is usually air, sand, small stone, large stone, and then earth. Depending on drainage, the top portion is usually dry.

The floor is actually not in contact with the "ground". I suggested to Dr. Ooi the use of the simple transmission line model powered from both ends. The far end voltage is unknown, the near end can be measured.

In the thermal case, I suggested to cover a section of the floor area to cut off the heat flow, (open the switch for the current) and record the the temperature with time. Using the simple RC model similar to the CTF wall, the measured value was around 25.5°C and his measured temperature at the similar depth outside the building was 27°C.

In the EPlus Earth Tube example, there are four conditions for the earth on the top and the bottom of the tube, because the difussivity can change.

Dr.Ooi's nanny house extension is 440mm above ground. How do you model this space? and how to maximize this for location Melbourne, Australia?

I have suggested to Dr. Ooi that the use of monthly average number for simulation will never produce a good result for every day of that month.

Natural ventilation is a different class of research. To the American people, this is going back to the stone age.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: kwalkerman@xxxxxxxxx
Date: Tue, 22 Jan 2013 10:01:22 -0500
Subject: Re: [EnergyPlus_Support] Re: Ground temperature of Singapore

One additional suggestion: As this is a naturally conditioned building, you are likely interested in the thermal mass affects of the ground. One way to take this into account is to bring some of that ground into the yearly EnergyPlus simulation by including it in your underground wall construction. For example, if your underground wall construction is, in reality, 6" of concrete, you would model the construction as:

UWALL, !-Name

2 foot Earth, !- Outside Layer

6 in Concrete; !-Inside Layer 1

Keep the ground temperature as the undisturbed ground temperature. This will allow the earthen layer to store and release heat to the building or ground, depending on the simulation parameters.

Karen

On Mon, Jan 21, 2013 at 7:16 PM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

Hi, Ryan

You should post the full paper by Dr. Ooi for the group, if he does not object.

Dr. Ooi may be responding to your specific questions in the short reply below.

The ground temperature data are in the .stat file with the TMY data for both Sweden and Singapore.

However, Sweden is seasonal and building requires heating in Winter. There is no heating requirement in Singapore.   Naturally vented building has no HVAC equipment    So please read with care.

The suggestions in my previous post was also not completely explained, because only the latitude was used for the cosine law without saying why. The profile was due to the tilt of the earth axis, from the obiting plane which gives the Summer and Winter conditions. I simplified the calculation by using the difference which has two variables.

For detailed research, one looks at many other factors as well, such as ocean current direction, the relation of the location on the land mass, wet and dry raining seasons, etc.   Dr. Ooi researched on many of these and may not have included all of them in the published paper.

There is no one simple rule for multi location use.   Changing the name of the topic will not get you a quick answer.

When you are designing a lake side Summer cottage in Canada do you really need to simulate it with annual TMY?

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: azianzheep@xxxxxxxxx
Date: Sun, 20 Jan 2013 19:53:04 +0000
Subject: [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

----------------------------------------------------------

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

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