Chris,
Not sure how far to follow this thread on EnergyPlus_Support, but I have a question on your tests of the Z-H Model. Did you use the single set of coefficients developed in 2000 (and described in my 2001 ASHRAE paper), or the 23 sets of coefficients assigned by a location's Koeppen Climate Classification developed in 2010 for the IWEC2 project (and described in the Final Report for RP-1477)? I'll send you the link to the Final Report in a separate e-mail.
Joe
Joe Huang White Box Technologies, Inc. 346 Rheem Blvd., Suite 108D Moraga CA 94556 yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx www.whiteboxtechnologies.com (o) (925)388-0265 (c) (510)928-2683 "building energy simulations at your fingertips"
On 11/9/2012 11:27 AM, cgueymard wrote:
Like Joe, I feel flattered too because of how things are connected: STRANG calculates the clear-sky irradiance with my SMARTS spectral radiative transfer code, which formed the basis of the REST2 broadband model, itself at the root of the new ASHRAE parameterized model. The latter made its debut with the 2009 HOF, as Joe mentioned. Note, however, that the 2009 model has now been updated and improved in anticipation of the 2013 HOF, which will also have more world stations than in 2009.
My own tests with the Z-H model showed it was not accurate (and sometimes unreliable) in climatic areas away from its intended "comfort zone" (i.e., parts of Asia). This is most probably because it is purely empirical. Based on that experience, I can confirm Joe's comments.
Outside of ASHRAE's weather stations and linked irradiance information, it is still possible to obtain hourly clear-sky irradiances with the REST2 model. Its input atmospheric data are gridded, and available globally over the world.
Chris
--
Chris A. Gueymard, PhD
Solar Consulting Services
P.O. Box 392
Colebrook, NH 03576, USA
Florida's Office:
Tel. (386) 402-8949
http://www.SolarConsultingServices.com
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Joe Huang <YJHuang@...> wrote:
>
> Although I feel flattered by the mention of the Zhang-Huang Model, I need to add three
> caveats to its use.
>
> The Zhang-Huang Model, developed by Dr. ZHANG Qingyuan of Tsukuba University in Japan and
> yours truly, is a multi-linear regression model that estimates the solar as a function of
> cloud cover, temperature change over the past three hours, wind speed, and relative
> humidity, bounded by what someone earlier called a "sanity check" of no more than 0.8 *
> extraterrestrial solar.
>
> 1) Although other researchers and I have found that the Z-H Model produces a good match to
> measured data on an aggregate basis, such as annual or monthly totals, while working on
> the IWEC2 files, I found that the Z-H Model often produced uneven hourly profiles when the
> data would suggest otherwise, such as for a clear day with no clouds. To overcome this
> problem, I now use the new ASHRAE Clear Sky Model afterwards to adjust the hourly solar
> profiles coming out of the Z-H Model. This procedure was incorporated for the IWEC2
> files, but I am still not finished working on it.
>
> 2) Make sure that the raw weather data contains cloud cover (or opaque cover)
> information. If not, using Z-H will produce a weather file as if there were never any clouds.
>
> 3) Because of first caveat, I would not recommend using the Zhang-Huang Model as a Clear
> Sky Model. The new ASHRAE Clear Sky Model (2009), simplified from a detailed model by
> Chris Gueymard, is far superior, although getting the inputs might present problems if the
> location is not among the stations in the ASHRAE HOF.
>
> Joe
>
> Joe Huang
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
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.
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe
__,_._,___