[Radiance-general] Experience implementing gendaylit with physical inputs (-G: direct - horizontal irradiance and diffuse - horizontal irradiance)

[Jan Wienold]

Hi Kyle,

I can confirm, that the delta-T sensor delivers very good and accurate 
values. Problematic is just sun-rise and sun-set.

In case you have only the global horizontal iilluminance, the Erbs model 
is the most accurate one (but still the error could be huge). This model 
is implemented in the current version of gendaylit (-E option). you 
could also see the error and spread of the data in our presentation at 
the last radiance workshop:
http://www.radiance-online.org/community/workshops/2013-golden-co/sprenger_wienold_gendaylit.pdf

If you can afford the sensor, I would go for the delta-T. We used it in 
several projects and also did comparisons with a tracking pyrheliometer.

Jan



On 04/10/2014 09:10 AM, Axel Jacobs wrote:
> Hi Kyle,
>
> check out the SPN1 and BF5 from Delta-T:
>
> http://www.delta-t.co.uk/product-category.asp?div=Meteorology%20and%20Solar 
>
>
> Very neat, but I have not used them myself.
>
> If you prefer to use two instruments and shading ring instead, you'll 
> need to correct for the shading ring:
>
> Rawlins F, Readings CJ (1986) The shade ring correction for 
> measurements of diffuse irradiance under clear skies. Solar Energy 
> 37:407–416
>
> Steven MD, Unsworth MH (1980) Shade-ring corrections for pyranometer 
> measurements of diffuse solar radiation from cloudless skies. Quart J 
> Royal Meteorol Soc 106:865–872
>
> Painter HE (1981) The shade ring correction factor for diffuse 
> irradiance measurements. Solar Energy 26:361–363
>
> Regards
>
> Axel
>
> On 10/04/14 01:29, Christoph Reinhart wrote:
>> Hi Kyle,
>>
>> Your approach is valid. Depending on what your plan to do with the data,
>> you can also use just global horizontal irradiance and use the Reindl
>> (or another separation model) to model direct and diffuse components. I
>> have used Reindl extensively in the past with satisfactory results. For
>> validation work using two sensors is of course preferable. You can use
>> the gen_reindl.exe command in Daysim to convert a time series of
>>
>> month day hour global-irradiance
>>
>> into a Daysim weather file.
>>
>> Best,
>>
>> Christoph
>>
>> *From:*Kyle Konis [mailto:kskonis at gmail.com]
>> *Sent:* Wednesday, April 9, 2014 8:08 PM
>> *To:* Radiance general discussion
>> *Subject:* [Radiance-general] Experience implementing gendaylit with
>> physical inputs (-G: direct - horizontal irradiance and diffuse -
>> horizontal irradiance)
>>
>> I am curious if anyone has experience to share regarding the generation
>> of skies with gendaylit using physical sensor data as input.
>>
>> I would like to monitor sky conditions at a building rooftop site and
>> plan to collect direct - horizontal irradiance and diffuse - horizontal
>> irradiance using Licor pyranometers.
>>
>> Both sensors will be oriented horizontally. The first will be unshaded
>> and record global horizontal irradiance.
>>
>> The second will have a shadow band applied and will serve to record
>> diffuse horizontal irradiance.
>>
>> I will then subtract the diffuse-horizontal contribution from the global
>> horizontal value to obtain an estimate of direct-horizontal irradiance.
>>
>> I wanted to confirm that this is an appropriate approach, as well as to
>> see if anyone has an alternative (better) idea, that does not involve a
>> pyrheliometer.
>>
>> Best,
>>
>> -Kyle
>>
>> -----------------------------------------------
>>
>> Kyle Konis, AIA, Ph.D
>> Assistant Professor
>> School of Architecture, WAH 204
>> University of Southern California
>> Los Angeles, CA 90089-0291
>> http://arch.usc.edu/faculty/kkonis
>> -----------------------------------------------
>>
>>
>>
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>
>
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-- 
Dr.-Ing. Jan Wienold
Head of Team Passive Systems and Daylighting
Fraunhofer-Institut für Solare Energiesysteme
Thermal Systems and Buildings
Heidenhofstr. 2, 79110 Freiburg, Germany
Phone: +49(0)761 4588 5133 Fax:+49(0)761 4588 9133
jan.wienold at ise.fraunhofer.de
http://www.ise.fraunhofer.de

In office:
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