HELP WITH PV CONFIGURATION

[josealjim]

Hi guys,
I have to design a solar parking for the company im working with. The building is in front of the parking so it will be shaded after noon during 3 months a year.
Click image for larger version.


The height difference between the first module and the last is about 2.5 meter so the panels distribution will be in 13 stages with a difference in height of 15cm. It will lead to a 2 different directions shading, one from the stages(whole year) and the other from the building(3 monts)

The first configuration I have simulated is filling up each stage with modules utilizing the total stage area



When I consulted some people they told me to avoid the shade generated by the height difference between stages, otherwise the diodes would be damaged quickly. According to their advise I simulated another configuration, leaving a 50 cm gap between stages and setting them in landscape in order to lengthen the diodes life as much as possible.



System description:
-234 modules (Canadian Solar CS6P-250P, 250 W). Each module has 3 Schottky diodes (one per 20 cells)
- Inverters: Leonics Apollo GTP-4000TL (P). 15 KW x 4 units. 2 MPPTs with a voltage range 380v-800v


I have contacted Canadian Solar technical department but is difficult to get an answer so I hope you could give me your opinion and help.

- Despite leaving the 50 cm gap between stages, there will be a bit of shade after 17-17:30 (less than 250 W/m2). I dont think it will affect the diodes life but anyway tell me please if im wrong.
- I assume that the diodes life will be shortened by the 3 months shade from the building. Looking at the iso-diagram and configuration, Do you think it will become a problem? I would not like to damage any module or change any diode before 10-15 years.
- Any suggestion to extend and improve the life of the modules/diodes?


THANK YOU IN ADVANCE

 

[Smart $]

...Any suggestion to extend and improve the life of the modules/diodes?

Interconnect panels ("modules") in parallel as much as possible. Arrange panels (assuming rectangular) inline with shading, i.e. so shade crosses the least number of panels at any point in time. Correlate series-interconnected panels as best possible with panel shading.

PS: Welcome :thumbsup:

 

[Zee]

What angle are the panels tilted at?

 

[BillK-AZ]

Interconnect panels ("modules") in parallel as much as possible. Arrange panels (assuming rectangular) inline with shading, i.e. so shade crosses the least number of panels at any point in time. Correlate series-interconnected panels as best possible with panel shading.

Think this suggestion through carefully. If there are more than two modules in parallel, fusing is needed to protect each module string per the UL listing. This is impractical in a large array with parallel connections. The fuse protects both cells (hot spot effect) and the bypass diodes. In a normal series string a single fuse protects all the modules in the string from over current from parallel strings in the event of problems in a string such as shadows and broken cells.

PV modules and their bypass diodes are designed to accommodate the effects of shading. The hot spot testing that is part of PV module qualification tests for this.

If your PV supplier will not warrant PV modules exposed to shading, find another supplier.

I recently had the first level warranty claim processing person reject a claim because photos showed some shading from trees in the array area. A quick complaint to the company management, pointing out that the installation instructions made no such requirement and referring to the hot spot test resulted in a quick claim acceptance.

You should consider micro inverters and module level control such as Solar Edge to mitigate the effect of shadows on the non-shadowed portion of the system. Use of many string inverters instead of a central inverter may give better results.

 

[Smart $]

Think this suggestion through carefully. If there are more than two modules in parallel, fusing is needed to protect each module string per the UL listing. This is impractical in a large array with parallel connections. The fuse protects both cells (hot spot effect) and the bypass diodes. In a normal series string a single fuse protects all the modules in the string from over current from parallel strings in the event of problems in a string such as shadows and broken cells.

...

I wasn't saying connect them all in parallel. I was referring to the parallelling of series-connected strings.