Shading : yes, it does make a difference !

[series530]

There have been plenty of topics on the subject of shading - here's another one ... from my perspective

The original link had an issue - this one should work with more web browsers:

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[HPSauce]

Hmm, that looks like it could be interesting as I have serious shading during the winter months.

But ... the link doesn't take you to the full story.

 

[brspark]

HP click the links at the side.

 

[moggy1968]

there are no links at the side on my view.

I always recommend people move things like sky dishes and aerials.

have you considered things like the effect of bypass diodes. also the array works as a whole, not individual panels so a poorly designed system with cheap panels without diodes will suffer a lot more in shade than your sanyos. research looking at the output of individual panels is meaningless. you need to look at the array as a whole because thats how the majority of systems are configured. To be good science you would need to have a control system south facing without shade and then compare that to identical systems at the same tilt angle, azimuth angle etc with different shde conditions. Anything else is poor science, poor research and a purely anecdotal piece of evidence.

my guess though, is this is perhaps being a little picky. a bit of shade in the winter, when balanced over the whole of the year does it actually drop the output below expected levels. I suspect in most cases no, unless a complete muppett installed the system (and there are some out there unfortunately).

every one of my installations is producing in excess of 20% over predicted output. I talked a cutomer out of an installation 2 weeks ago because the shading was too much given that it was a small installation so had a relatively high price per Watt.

Use a good installer and you will do fine. Ask the surveyor some pertinent questions. does he know what he is talking about from a technical perspective or is he a salesman who knows nothing about the actual design of a system and just want his commission cheque?

 

[brspark]

I've got the above on mine and it allows me to read through it if i click them.

 

[Scooby]

Series, that's an absolutely cracking piece of work, and I'm sure it'll be invaluable to installers on here.

 

[HPSauce]

Well, I'm using IE8 here and there are no links on the side panel.
I've tried compatablity view as well.

More intriuging still when you can't see it.....

 

[brspark]

Just had a quick look and it's written in google chrome, you internet explorer lot have no chance. It's a secret.

 

[brspark]

PV Shading—

Introduction Our house lies SSW and is south west of London - about 30 miles from the centre. We enjoy an open vista The system consists of 14 Sanyo HIT250E01 panels arranged in a line just below the ridge of a chalet house. Panel 1 is far left and panel 14 is far right. Each panel is connected to an individual Enecsys micro inverter. This configuration means that each panel is individually MPPT controlled rather than relying upon a single or a dual MPPT tracker located within a central string inverter. The output of each panel is transmitted wirelessly to a gateway device and this gateway connects via the internet to Enecsys servers. The data is processed at Enecsys and is fed to a web page dedicated to this system installation. The user can interrogate this web page and see up to the minute energy harvest data. Output from this web page is included within the text. Photographs showing shading are compared against Enecsys harvest information from the web page. From this, conclusions are drawn and people considering PV can decide how to deal with the problem of shading.

There are a number of shading issues with this house: As the sun follows a path to the right of the photograph, during the summer months, it has sufficient height so that the property to the right does not influence the array to any great extent. As we get closer to the winter months, the sun, being lower, casts a shadow from the aerials and their chimney. This was very evident from the shading analysis. Furthermore, the chimney of our house causes a shadow when the sun is low. This was less evident from the shading analysis but, as we will see, is something of an issue during these tests. As the owner, I was far from convinced that these factors would be an issue prior to purchase. My installer convinced me that they were more of a problem than I thought. We will see, a little later, how much of an influence they are. We had to wait for inverters to become available. In the end, the project was completed in the first week of November. Thus, the hottest part of the year has passed but, hopefully, what is presented here, gives some idea of how shading affects harvest in the latter part of the year. Parallels can be drawn to the summer months. I hope to repeat these experiments as an addition to this document during the summer months. There are several stages in this analysis. One stage provides a reference baseline on a dull day. Another stage represents a day where there are sunny periods and, finally, times of bright sun shine. The data has been gathered over several days, at roughly the same times but with varying weather conditions. As the analysis is being done in November with a view to publishing reasonably quickly, the analysis cannot use a bright summer day. Hopefully, next year, data for such conditions can be gathered and added to the analysis.

 

[brspark]

Blank Link for dull day

http://beckiws.webspace.virginmedia.com/PV shading Publication_files/Page315.htm

http://beckiws.webspace.virginmedia.com/PV shading Publication_files/Page375.htm

[URL="http://beckiws.webspace.virginmedia.com/PV shading Publication_files/Page518.htm"]http://beckiws.webspace.virginmedia.com/PV shading Publication_files/Page518.htm

[URL="http://beckiws.webspace.virginmedia.com/PV shading Publication_files/Page617.htm"]http://beckiws.webspace.virginmedia.com/PV shading Publication_files/Page617.htm

Li[/URL]n[/URL]ks for story

 

[SolarCity]

Thanks for the information, Series. I'm surprised that the drops are so dramatic even from the television aerial. It'll be interesting to see what kind of effect the shading will have in summer.

Moggy, Series system uses micro-inverters so effectively the panels work independently of each other.

 

[moggy1968]

yes, I know!!!!!!
thats why I suggested this 'experiment' isn't refelctive of the situation in the majority of installations, as they use a single inverter. To be truly valuable as a piece of science useful to the majority of installations you would need to compare this system, but with a single inverter to an identical system without shading with the same azimuth, tilt etc.
looking at the piccies subsequently published it looks like your installer gave you very good advice as that chimney would cause significant problems on a single string single inverter set up

 

[SolarCity]

Got ya.

Micro-inverters give an interesting idea of exactly what each seperate panel is producing, which then shows exactly how much effect the shading will have. It is only bad science if you jump to the wrong conclusions from this data.

Personally I think it is a fascinating bit of data and I hope Series keeps us updated.

 

[moggy1968]

yep, fair comment, I don't have the advantage of seeing the data as I am using IE and can't use the links but yes, the key with all experiments is to understand the data, the lmitations of that data and draw only realistic conclusions from it.

there was once an experiment done to assess wether there was a link between the length of your lifeline on your palm and your actual life expectency. The research found there was indeed a link, the longer the lifeline, the longer the life expectancy of the person.
conclusion, palmistry is based on fact supported by this scientific data, until someone pointed out the lifeline was longer because the person was older and more wrinkly!!

 

[series530]

sorry everyone = web site design isn't my core business !

The document was written in Publisher 2003 but it seems that having grouped hyperlink boxes doesn't work properly with newer browsers. This version has been redone and seems OK with internet explorer.


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thanks to everyone who has broken up the links for better access.