Re: [EnergyPlus_Support] diffuse solar

On Mon, Feb 1, 2010 at 1:17 PM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

Hi, HuJia

I noticed that you are very interested in finding the various fields in the weather file.

My former student Mr. Ooi KB, in a PhD program now, is very interested in findint out how to use:

Global horizontal, HIR, Cloud cover, ODT and RH, to get the Direct Normal and Diffused Horizontal fields in the EPW.

He can get those five sets of data from the Kuching Met. Station for his work in East Malaysia. However, he does not know how to divide the Global into the Direct Normal and Diffused horizontal, which the EPlus use for simulation..

Dr. Li

P.S. for Linda. Do you have any sub-routine in Fortran or any programming language, to generate these two missing fields in EPW. (Direct normal and Diffused Horizontal from Global horizontal, HIR, Cloud cover, ODT and RH)

He passed on the sub-routine from ticket #2013 for me to solve his ground surface temperature calculation. [EnergyPlus #2013]: Basement outside surface temperatures. I am studying it and see whether all the data are available, to run it as a C++ program.

What he really nead is the correct solar radiation level through the windows, so that the simulated and the measured room temperature can match.

He tried measring the DIrect Normal using a Pyranometer. Because the spectrum of this device is wider, the measured value was about 30% higher.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: hujia06@xxxxxxxxx
Date: Mon, 1 Feb 2010 10:53:00 -0500
Subject: Re: [EnergyPlus_Support] diffuse solar

Thank you, Dr. Li

Yes, it follows time shift using formula (PDF 1994) for temperature varibales. But I also find some variables like Diffuse Solar does not follow the rule: hourly point values reported are not the same as the hourly value in weather file in timestep interval .report.

yes, I try to set up TimeStep = 4, in an hourly interval report, the value is the average. In a time step report, the output is unchang

On Mon, Feb 1, 2010 at 7:53 AM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

I think, these minor time shift and averaging appears with other variables as well.

For example, the outside dry bulb temperature listing at the output is unchanged at the hourly points when using timestep as listing interval (same as the EPW hourly value). When listed as in a hourly interval report, the value is the average of the preceding hour, which is slightly different from the original list value in the EPW.and is the same as the half hour points of the time step listing.

I have a feeling that this is done by the post processor using the ESO in time steps, and not at the simulation time.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: hujia06@xxxxxxxxx
Date: Sun, 31 Jan 2010 20:06:15 -0500
Subject: [EnergyPlus_Support] diffuse solar

Hi, all

In EnergyPlus, when timestep = 4, the diffuse solar in weather file is different from the output at the same hour. For example, in weather file, at 9:00, the diffuse solar is 58, while in the output, 58 appears at 8:30. This rule seems different from interpolation mentioned in help ref.

In calculating Daylight Factor, EP ref. mentions it uses hourly DF and then interpolate the two hour DF to calculate the DF at time step in one hour. So when calculating Daylight Factor, the Energyplus adopts which hour values of Diffuse and direct Radiation in the Outputfile? Does EP use 58 (at 8:30 in the output), or use value at 8:00 in output (average values at 7:30 and 8:30, which are corresponding to 8: 00 and 9:00 in the weather file respectively) ? .

Thanks in advance,

jia

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