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Topics: Shading Effect on Solar Energy
#1

Dear Professionals I have a small query that would be the distance between the rows on a flat roof(bipv)to avoid shadow of the first array on the array behind it?(in India)
12-29-2013 03:34 PM
Top #2

Inter-row spacing is different for different geographical coordinates. It can be easily calculated using solar geometry formulas. Factors affecting the inter-row distance are Angle of tilt
Declination
Latitude
Hour Angle
PV panel length
12-29-2013 06:07 PM
Top #3
Dear Mr. Sandeep,
Thank you very much for your kind reply. I read a book and the author suggested that the distance between the rows should be 3.5 times of the module height to avoid the self shading effect. Can you please provide me the formula which you have mentioned?

Regards,
12-29-2013 08:32 PM
Top #4
You can do an onsite test by placing a stick on the roof and track the length of the shade at 9 o clock morning and 6 o clock evening...
12-29-2013 10:43 PM
Top #5
12-30-2013 01:07 AM
Top #6
@Nirmal: The sun is at the lowest position during winters and that too on a particular day when the declination is -23.45. According to the method you mentioned one has to wait for that particular day and time in order to plan the system such that it does not face self shadowing.
12-30-2013 03:35 AM
Top #7
Dear Sandeep,
This is my email-id : prasad.arulraj@hotmail.com
12-30-2013 05:47 AM
Top #8
If the array was in Bangalore (or on the same latitude) your ideal angle for the modules would be around 21 degrees from horizontal and you will need approx 0.75 x module height between frames. i.e. for a 1m wide module at 21 deg the height is around 0.35m so distance between frames 0.26m. Here in the UK we need much greater distances because of the low angle of the sun in winter. I hope this helps.
12-30-2013 08:32 AM
Top #9
...You could also install east/west no worries about shade and much more
Energy produced as you can install double the amount of modules
Sometimes up to 3 times more, it depends on the walkway in between the rows.

Hesting up of the modules is also way less as the modules doesn t face straight
The sun, by that energy production can be the same as southfaced during the
Whole year.

Angle is mostly 10_1d degree

Cheers
A
12-30-2013 11:16 AM
Top #10
Prasad: For south-facing flat-panels NABCEP suggests three times the vertical projection of the adjacent row to avoid inter-row shading, with the minimum distance lowering as one approaches the equator. In some cases tilting panels to 15 degrees below "latitude-tilt" affects production by a small amount --NREL data in San Francisco, Ca (37 deg North) shows average daily harvest is reduced from 5.4 kwh/m2/day to 5.3 kwh/m2/day (1.85% less) if the panels are 15 degrees below latitude-tilt. In Tampa, Fla, (28 deg North) the radiation changes from 5.3 to 5.2. I wonder if your harvest-optimal inter-row spacing won't bring added expense in horizontal construction -- longer wiring or support structures. And a lower panel profile may be better for wind loading but worse for rain loading or catch more debris. A 3:1 ratio may impact roof utilization, considering 1.85% doesn't seem that great a reward. BTW doesn't BIPV "hug" the contour of the structure?