PV system in shading conditions

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.
Attachment not found.

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

Attachment not found.
Attachment not found.

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.
Attachment not found.
Attachment not found.

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

waynefromnscanada

Re: PV system in shading conditions

Welcome to the forum "Josealjim",
If the panels are properly designed and wired together in the final project, shading will not damage either the bypass diodes, nor the solar cells.
That said, any panels mounted in areas that are shaded, will be a waste of money as they will produce next to no power. Even partial shading of a panel can almost totally kill it's output, making it all but useless until, when, or if it ever receives full sun.
Knowingly installing solar panels in a shaded area is sort of like heading out on the highway to cross the country, knowing in advance you have little fuel in the tank, and no money to purchase more fuel. Both projects are bound to fail.

Ralph Day

Re: PV system in shading conditions

Why not mount the panels on the building roof?

solarix

Re: PV system in shading conditions

You need to look into controlling each module individually in order to minimize the impact of shading. This can be done by: 1) using micro inverters on each module like Enphase to manage it individually, 2) using a distributed inverter like Solar Edge which has an optimizer on each PV module but still uses a central inverter, and 3) using optimizers such as Tigo - just on the PV modules which have the shaded problem. Each approach has its pluses and minuses, all cost more than a basic GT inverter, but under shady conditions will be worth it.

josealjim

Re: PV system in shading conditions

Ralph Day wrote: »

Why not mount the panels on the building roof?

I suggested that option to the executives but they want the solar parking

josealjim

Re: PV system in shading conditions

waynefromnscanada wrote: »

Welcome to the forum "Josealjim",
If the panels are properly designed and wired together in the final project, shading will not damage either the bypass diodes, nor the solar cells.
That said, any panels mounted in areas that are shaded, will be a waste of money as they will produce next to no power. Even partial shading of a panel can almost totally kill it's output, making it all but useless until, when, or if it ever receives full sun.
Knowingly installing solar panels in a shaded area is sort of like heading out on the highway to cross the country, knowing in advance you have little fuel in the tank, and no money to purchase more fuel. Both projects are bound to fail.

On this project, the payback is not a problem. It is to feel the local grid of Chiang Mai University. When you say that both configuration are bound to fail, are you talking about technical issues or profits?
Some expert told me that the two direction shade will short the diodes life. Do you agree with that? do you think that with the second config we will not have any technical problem?

THANKS

josealjim

Re: PV system in shading conditions

solarix wrote: »

You need to look into controlling each module individually in order to minimize the impact of shading. This can be done by: 1) using micro inverters on each module like Enphase to manage it individually, 2) using a distributed inverter like Solar Edge which has an optimizer on each PV module but still uses a central inverter, and 3) using optimizers such as Tigo - just on the PV modules which have the shaded problem. Each approach has its pluses and minuses, all cost more than a basic GT inverter, but under shady conditions will be worth it.

I also thought about that option but it makes it too expensive. Another issue is that it is gonna be a show case for investors and micro and optimizers are not popular here in thailand. Micro-inv are not approved by the authorities so we can not go for FIT. The important think is not to short the diodes life or damage the panels with the configurations posted. The PVSyst simulations give as shading losses: Irradiance loss (11.1%), Electrical loss due shadow (2.7%). The part that we could avoid with the micro or optimizers is that 2.7 %, Would that 2.7% make the installation worth?

thanks a lot

westbranch

Re: PV system in shading conditions

Sawatdee kraup. Why not use the portion of the car park that is in full sun and avoid the shade area.
Put the panels that would have been in the shade elsewhere, on the roof of a building?, and get the best PV output for all panels

SolInvictus

Re: PV system in shading conditions

If I understand correctly, why are you stair-stepping the PV panels in stages? Why not incline them all at the same angle and attach them together which prevents them from shading each other? Alternately, keep the PV panels level and make the support structure higher on one side than the other. Is this stair-stepping an architectural style demanded by the executives?

You are stuck with shading from the building, so the best you can do is point them in a direction that favors the shade-free times of the year.

josealjim

Re: PV system in shading conditions

SolInvictus wrote: »

If I understand correctly, why are you stair-stepping the PV panels in stages? Why not incline them all at the same angle and attach them together which prevents them from shading each other? Alternately, keep the PV panels level and make the support structure higher on one side than the other. Is this stair-stepping an architectural style demanded by the executives?

You are stuck with shading from the building, so the best you can do is point them in a direction that favors the shade-free times of the year.

Hi and thanks for your reply,

I suggested that option (same inclination, tied together avoiding the stage shade) but the civil engineer told me it would make the project much more expensive because the structure. Finally i pushed them and we are going for that solution, it is by far, the best one.

Thank you for your post

josealjim

Re: PV system in shading conditions

waynefromnscanada wrote: »

Welcome to the forum "Josealjim",
If the panels are properly designed and wired together in the final project, shading will not damage either the bypass diodes, nor the solar cells.
That said, any panels mounted in areas that are shaded, will be a waste of money as they will produce next to no power. Even partial shading of a panel can almost totally kill it's output, making it all but useless until, when, or if it ever receives full sun.
Knowingly installing solar panels in a shaded area is sort of like heading out on the highway to cross the country, knowing in advance you have little fuel in the tank, and no money to purchase more fuel. Both projects are bound to fail.

Thanks for your answer,

What do you mean with "properly designed and wired"?

The modules have the same slope and orientation, Then strings will follow the shade pattern in order to group it in the same string favoring full operational conditions in no-shaded areas.

Thanks in advance