I beg to differ.���� EnergyPlus needs the
two solar components, but it does not do any climate-related
calculations beyond interpolating for subhourly timesteps.
There is a���� weather converter program that comes in the EnergyPlus release (PreProcess/WeatherConverter/weather), but when I tested it out six months ago I found it didn't do the direct/diffuse split correctly.���� I brought this to the attention of the EP Team, but did not receive any meaningful response.
Researchers have worked on direct/diffuse split models for 30 years or more.���� The industry standard, in the US at least, is the Perez Model developed by Prof. Richard Perez of SUNY (Perez, Ineichen et al 1990, "Modeling Daylight Availability and Irradiance Components from Direct and Global Irradiance", etc.). The difficulty of the Perez Model is that it's quite complex, making it hard to implement and get right.���� According to its documentation, the EnergyPlus weather converter applies the Perez Model if the input weather only contains total global horizontal, but I recommend that users check the results because for me it was returning direct normal radiation that was not believable.
For my weather work, I've written a Fortran program that uses the Perez Model, as well as two other simpler models developed in Japan (Watanabe, Gompertz Function) and in the end went with the Gompertz Function Model because of its simplicity (Zhang, Lou, and Yang 2004, "A New Method to Separate Horizontal Solar Radiation into Direct and Diffuse Components", ISESAP).��������
Marco,���� I would be happy to share that program, but you would still have to calculate the solar altitude angle, which is not a trivial thing.���� Alternatively, the Gompertz Function Model is so simple that you can code it up yourself in about 15 lines of code (note caveat on the solar altitude angle, though).���� Lastly, if this is just a one time need, you can send me your total global horizontal,���� and I can return to you the direct and diffuse.���� Don't expect immediate turn-around, though.
Joe
Joe Huang ������������
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx
http://weather.whiteboxtechnologies.com for simulation-ready weather data
http://www.whiteboxtechnologies.com
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
On 11/1/2013 7:41 AM, ooi_kb3@xxxxxxxxxxx wrote:
There is a���� weather converter program that comes in the EnergyPlus release (PreProcess/WeatherConverter/weather), but when I tested it out six months ago I found it didn't do the direct/diffuse split correctly.���� I brought this to the attention of the EP Team, but did not receive any meaningful response.
Researchers have worked on direct/diffuse split models for 30 years or more.���� The industry standard, in the US at least, is the Perez Model developed by Prof. Richard Perez of SUNY (Perez, Ineichen et al 1990, "Modeling Daylight Availability and Irradiance Components from Direct and Global Irradiance", etc.). The difficulty of the Perez Model is that it's quite complex, making it hard to implement and get right.���� According to its documentation, the EnergyPlus weather converter applies the Perez Model if the input weather only contains total global horizontal, but I recommend that users check the results because for me it was returning direct normal radiation that was not believable.
For my weather work, I've written a Fortran program that uses the Perez Model, as well as two other simpler models developed in Japan (Watanabe, Gompertz Function) and in the end went with the Gompertz Function Model because of its simplicity (Zhang, Lou, and Yang 2004, "A New Method to Separate Horizontal Solar Radiation into Direct and Diffuse Components", ISESAP).��������
Marco,���� I would be happy to share that program, but you would still have to calculate the solar altitude angle, which is not a trivial thing.���� Alternatively, the Gompertz Function Model is so simple that you can code it up yourself in about 15 lines of code (note caveat on the solar altitude angle, though).���� Lastly, if this is just a one time need, you can send me your total global horizontal,���� and I can return to you the direct and diffuse.���� Don't expect immediate turn-around, though.
Joe
Joe Huang ������������
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx
http://weather.whiteboxtechnologies.com for simulation-ready weather data
http://www.whiteboxtechnologies.com
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
On 11/1/2013 7:41 AM, ooi_kb3@xxxxxxxxxxx wrote:
Energyplus splits the global radiation to direct and diffuse. You may try to measure diffuse by shading your sensor from direct solar radiation
Would be nice to see your measured results. The relationship between the 'Normal' and 'horizontal' components are given in the documentation
����
---In EnergyPlus_Support@xxxxxxxxxxxxxxx, <energyplus_support@xxxxxxxxxxxxxxx> wrote:
Hi all,
I am trying to calibrate energyplus model for my research and I obtained some weather data from local Meteo station. Most of the parameters are being measured at the building itself, but radiation is taken from nearby official meteo station. In meteo station only global horizontal radiation is being measured. When I converted epw file for my city���� to csv I saw that there are 3 columns about radiation: global horizontal (already have), direct normal and diffuse horizontal. I know I need some additional info in order to obtain the last two, but I do not know which (I assume it is the cloud cover). The station does not have perheliometer for diffuse radiation measurement. Are there any software for calculating various radiation components from known global horizontal radiation?
Sincerely
Marko
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