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Re: [EnergyPlus_Support] Re: Fwd: AW: TRY-Daten Strahlung um Zeitpunkt? => JA !


Sorry, made a mistake, should have written "move the building location EAST by 7.5 degrees (== 0.5 hour solar time) to "catch up" to the solar data entered in European Convention (-0:30h to +0.30h).

Joe
Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
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On 4/9/2014 3:37 PM, Joe Huang wrote:
>  I had not planned to say anything more on this topic, but then hit upon a very simple solution - just move the building location west by 7.5 degrees (== 0.5 hour solar time).   Just be sure to insert an explanation in the IDF so that 5-10 years down the road someone (including yourself) think that you've made an input mistake.
> 
> Joe
> 
> Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx";>yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx</a>
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://weather.whiteboxtechnologies.com";>http://weather.whiteboxtechnologies.com</a> for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
> 
> On 4/9/2014 11:27 AM, Joe Huang wrote:
>>  Jean,
>> 
>> I want to expand a little more about the term "time offset" used in the WeatherConverter to avoid any possible misunderstandings (please note #3 in particular):
>> 
>> 1) US time convention on solar is from -1:00h to 0:00h, i.e., the previous hour, while the European convention is from -0:30h to +0:30h, i.e., around the hour (assuming hourly notation just for simplicity).
>> 
>> 2) Because of the US time convention, all US simulation programs, including EnergyPlus, calculate the sun position at  -0:30h,  which in EnergyPlus is called a "time offset".   As far as I know, this time offset is hardwired and cannot be changed.
>> 
>> 3) For weather files that follow the European convention, the "time offset" should be 0, rather than -0:30h.
>> 
>> 4) The "time offset" can be changed in the WeatherConverter, but it would only have an effect if the source weather lack solar data,  in which case WeatherConverter calculates the solar based on the sun position.  If the source weather  contains solar data,  WeatherConverter will simply pass them through to the EPW.
>> 
>> Joe
>> Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx";>yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx</a>
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://weather.whiteboxtechnologies.com";>http://weather.whiteboxtechnologies.com</a> for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
>> 
>> On 4/9/2014 10:02 AM, Joe Huang wrote:
>>>  
 Jean, others,
>>> 
>>> It's nice to know that I wasn't crying wolf, but I'm confused whether adding an offset (or actually it should be removing the default offset of  -0.5 hour) to the EnergyPlus WeatherConverter would do anything at all if the files already contain total horizontal and direct normal radiation, which they no doubt do.   As far as I know, the WeatherConverter will use the offset only when it has to do solar calculations when either solar component is missing.  If the German TRY2010 files already have solar, you're stuck with the -0:30/+0:30 convention used in their creation.
>>> 
>>> That doesn't mean the solar in the files are wrong, just that they're a half-hour early compared to the internal clock EnergyPlus uses to calculate the solar position.  Ideally, EnergyPlus would also allow users to change the time offset when it runs, but I haven't heard yet whether that's possible.  If not, then you would have to shift the solar on the weather files by a half hour to get it in sync with EnergyPlus.  If the raw data are subhourly, this would mean rebinning the solar data.  If all you have are the hourly solar data, this could be done by simple averaging the data from adjoining hours and using the time of sunrise and sunset to  apportion the solar for those hours.  
>>> 
>>> OR, you can decide to not change anything and tolerate the half-hour difference between the clock on the weather file and that in EnergyPlus.
>>> 
>>> Joe
>>> 
>>> Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx";>yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx</a>
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://weather.whiteboxtechnologies.com";>http://weather.whiteboxtechnologies.com</a> for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
>>> 
>>> On 4/9/2014 8:29 AM, <mailto:marais.jean@xxxxxxxxxxxxxx>marais.jean@xxxxxxxxxxxxxx wrote:
>>>> Joe was right. Therefore german TRY2010 data must be "adjusted" radiation-wize by the -.5hr adjustment when using the weatherconverter.
>>>> 
>>>> Mit freundlichen Grüßen- Sent from my iPhone (excuse the brevity)
>>>> i. A.
Jean Marais
b.i.g. bechtold
Tel.   +49 30 6706662-23
>>>> Begin forwarded message:
>>>> 
>>>>> From: Krähenmann Stefan <<mailto:Stefan.Kraehenmann@xxxxxx>Stefan.Kraehenmann@xxxxxx>
>>>>> Date: 9. April 2014 16:07:58 MESZ
>>>>> To: "<mailto:marais.jean@xxxxxxxxxxxxxx>marais.jean@xxxxxxxxxxxxxx" <<mailto:marais.jean@xxxxxxxxxxxxxx>marais.jean@xxxxxxxxxxxxxx>
>>>>> Subject: AW: TRY-Daten Strahlung um Zeitpunkt? => JA !
>>>>> 
>>>>>  

>>>>> Sehr geehrter Herr Marais,

>>>>>  

>>>>> für den TRY-Zeitraum (1988 bis 2007) liegen die Strahlungsmessreihen als Stundensummen (der diffusen und der Globalstrahlung) in Wahrer Ortszeit (WOZ) vor (Stundensummen bis WOZ). In Abstimmung mit dem Strahlungs-Know-How-Center am RKB Hamburg und der Fa. CEC in Potsdam, die mit der Berechnung der TRY beauftragt war, wurde entschieden aus den jeweiligen Stundensummen die mittlere Strahlungsintensität (Stundensumme/3600 s) in W/m² zu ermitteln. Bei der zeitlichen Zuordnung der mittleren Strahlungsintensität wurde davon ausgegangen, dass grob gesprochen die WOZ-Stunde etwa bei MEZ-30 min beginnt und bei MEZ+30 min endet. Daher entspricht die mittlere Strahlungsintensität etwa dem zur vollen Stunde MEZ zu erwartenden Wert. Das genannte Vorgehen führt allerdings zu Ungenauigkeiten, da aufgrund der Zeitgleichung die Zuordnung WOZ zu MEZ über das Jahr um ca. +/- 15 min variiert und der zeitliche Verlauf der Strahlungsintensitäten nicht immer symmetrisch über die Stunde verläuft. Besonders deutlich wird dies bei Sonnenauf- und -untergang. Hier kann es durch das o.g. Verfahren dazu kommen, dass für die Stunden MEZ bereits eine Strahlungsintensität angegeben wird, obwohl die Sonne noch gar nicht auf- oder bereits untergegangen ist. In solchen Fällen, wurde die Solarstrahlung dann auf 0 W/m² festgesetzt.

>>>>>  

>>>>> Mit freundlichen Grüßen

>>>>> Stefan Krähenmann

>>>>>  

>>>>>  

>>>>>  

>>>>> Von: Kaps Marcus [<mailto:Marcus.Kaps@xxxxxx>mailto:Marcus.Kaps@xxxxxx]
>>>>> Gesendet: Mittwoch, 9. April 2014 08:47
>>>>> An: <mailto:%27stefan.kraehenmann@xxxxxx>'stefan.kraehenmann@xxxxxx'
>>>>> Betreff: TRY-Daten Strahlung um Zeitpunkt?

>>>>>  

>>>>>  

>>>>>  

>>>>> Von: Marais.Jean [<mailto:marais.jean@xxxxxxxxxxxxxx>mailto:marais.jean@xxxxxxxxxxxxxx]
>>>>> Gesendet: Mittwoch, 9. April 2014 08:22
>>>>> An: Offenbach Klima
>>>>> Betreff: TRY-Daten Strahlung um Zeitpunkt?

>>>>>  

>>>>> Sehr geehrte Damen und Herren,

>>>>>  

>>>>> Es ist voll bekannt das fast alle Länder (außer Amerika), die Strahlungswerten um den Zeit entspricht, d.h. -0.5hr Timestamp +0.5hr. Ist das für die TRY-Daten auch so?

>>>>> B  Direkte Sonnenbestrahlungsstärke (horiz. Ebene)             [W/m²]   abwärts gerichtet: positiv

>>>>> D  Difuse Sonnenbetrahlungsstärke (horiz. Ebene)               [W/m²]   abwärts gerichtet: positiv

>>>>>  

>>>>> Mit freundlichen Grüßen

>>>>> 
>>>>> i. A.

>>>>> Jean Marais

>>>>> B.Eng (Mech)

>>>>> <http://www.usgbc.org/leed>>>>>> LEED Accredited Professional

>>>>>  

>>>>> <http://www.designbuilder-big.de/>>>>>> <image001.jpg>

>>>>>  

>>>>> 	
>>>>> b.i.g. bechtold

>>>>> INGENIEURGESELLSCHAFT MBH
>>>>> Keithstraße 6

>>>>> 10787 Berlin

>>>>> 	
>>>>> Tel.   +49 30 6706662-23
>>>>> Fax  +49 30 6706662-18

>>>>> <mailto:Marais.Jean@xxxxxxxxxxxxxx>>>>>> Marais.Jean@xxxxxxxxxxxxxx

>>>>> <http://www.big-gruppe.com/>>>>>> www.big-gruppe.com/tga

>>>>> 	
>>>>> Firmensitz: Berlin, Registergericht: Amtsgericht Charlottenburg, HRB 112242 B
>>>>> Geschäftsführer: Bernd Bechtold, Carsten Teichmann

>>>>> "The LEED® (Leadership in Energy and Environmental Design) Green Building

>>>>> Rating System is the nationally accepted benchmark for the design, construction,

>>>>> and operation of high performance green buildings."

>>>>> Other LEED descriptive copy may be found on the USGBC Web site: <http://www.usgbc.org/leed>http://www.usgbc.org/leed

>>>>>  




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