[Equest-users] Purpose of a DESIGN-DAY CLIMATE input?

[Joe Huang via Equest-users]

I think this is a case of DOE-2 still using an older procedure for the solar portion of 
the design day calculation.  Prior to 2006, ASHRAE used a relatively crude ASHRAE Clear 
Sky Model to determine the hourly profile of solar radiation for the design day.  That 
model assumes there are different sky conditions for different latitudes, etc.  In 2006, 
ASHRAE TC 4.2 (Climatic Information) carried out a project to develop an entirely new 
ASHRAE Clear Sky Model that's a parameterization of a detailed solar model developed by 
Chris Gueymard.

It would be nice if DOE-2 incorporates the new ASHRAE Clear Sky Model, which isn't 
terribly hard, but would take work. Besides, I'm under the impression that the vast 
majority of DOE-2 users don't do design day calculations but rather let the program 
autosize the equipment anyway!

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 11/29/2016 9:43 AM, Nicholas Caton via Equest-users wrote:
>
> I have a question concerning doe2/eQUEST DESIGN-DAYs.
>
> One of the keywords for DESIGN-DAY confuses me:  CLIMATE.  I have not been able to find 
> this documented in the current doe2 reference manual or 2.1A engineering manuals.
>
> It appears the CLIMATE keyword can accept one of three inputs:  “SUBARCTIC,” 
> “MIDLATITUDE,” or “TROPICAL.”  The default is MIDLATITUDE and does not appear to 
> reference anything else.
>
> So I have a few questions:
>
> 1.What is this input used for? Does it help to determine solar angles during design day 
> calculations?  Does it affect how other DESIGN-DAY inputs are interpreted?
>
> 2.Since one of the options is named “MIDLATITUDE,” my best guess is this is trying to 
> establish in a loose sense which slice of the globe the weather station is located at 
> for solar angle purposes.  From that guess, I googled the topic for a bit 
> <http://www.lat34north.com/cities/CitiesLatitude.cfm> and came up with this framework:
>
> a.SUBARCTIC latitudes are > 66.5 or < -66.5  (Inside the Arctic circles – experiences 
> days of complete daylight/darkness)
>
> b.TROPICAL is between -23.5 and 23.5 (Tropic of Capricorn/Cancer – experiences the sun 
> traversing directly overhead)
>
> c.MIDLATITUDE = everywhere else
>
> 3.I struggle however with the concept of a DESIGN-DAY input based on latitude, where
>
> a.The latitude is already a part of the weather file required for every simulation… and 
> pulling the exact latitude would be more accurate anyway (I confess here I have never 
> studied solar pathing in great depth – the problem may be simpler than I realize?).
>
> b.These bands alone don’t give you enough information to know when you’re in the lower 
> hemisphere (where solar angles based on the day/month would be flipped)
>
> c.This leads me to question whether there’s a (meaningful) difference in solar angles 
> experienced for loads calculations when you use the weather file instead of DESIGN-DAY 
> inputs.
>
> d.Alternatively, maybe the latitude IS pulled from the weather file for solar angle 
> purposes so I’m completely on the wrong path as to the purpose/intent for the CLIMATE input.
>
> Can anyone set me straight on this topic?
>
> ~Nick
>
> *Nick Caton, P.E., BEMP*
>
> Senior Energy Engineer
> Energy and Sustainability Services
> Schneider Electric
>
> 	
>
> D 913.564.6361
> M 785.410.3317
> E nicholas.caton at schneider-electric.com <mailto:nicholas.caton at schneider-electric.com>
> F 913.564.6380
>
> 	
>
> 15200 Santa Fe Trail Drive
> Suite 204
> Lenexa, KS 66219
> United States
>
> cid:image001.png at 01D189AB.58634A10
>
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