How to know the efficiency of a single panel (or string) over a specific period of time?

UnhappyCustomer

So I'm thinking of installing solar panels on an area of the roof that only gets sun for a certain period of the year and I'd like to know if these panels would be cost effective.

I know suncalc.net but I can't see where I can retrieve the efficiency for just one panel. These panels would be 420 w each with microinverters

Do you know if there is any tool for this?

10-10-20

Using the European calculator, you insert the kWp as a decimal.

https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP

But yes, I don't see how you'd modify the horizon in that case to represent the obscured loss. Other tools do have that function. I'll keep looking.

10-10-20

Ah, you'd have to upload a horizon file:

An example is provided and it looks easy.

https://re.jrc.ec.europa.eu/pvg_download/userhorizon.txt

DC999

https://www.boards.ie/discussion/2058310331/how-to-know-the-efficiency-of-a-single-panel-or-string-over-a-specific-period-of-time

Some of us might have real stats from our setups.

What orientation is the roof? South, South West, West.

What type of shade?

I have a North West roof that is great from spring to end of Sept or into Oct. Then it hibernates for the winter. Sun doesn't hit it at all.

Or winter sun is too low to hit it. Or trees block the winter sun. Or, or...

What roof angle? As in normal roof. Flat roof...

Any other unshaded roof you can use as well as the shaded one? I have 5 panels on a flat roof. Others have used shed roofs.

UnhappyCustomer

https://www.boards.ie/discussion/comment/121011910#Comment_121011910

Thanks a million @10-10-20

This is the performance of the panels without having the shade in consideration.

South:

https://ibb.co/hmDtvyY

West:

https://ibb.co/P6QYbmj

However, I don't fully understand how to use the user-defined horizon.

As stated in the help text:

"In the file there should be one number per line, with each number representing the horizon height in degrees in a certain compass direction around the point of interest. The horizon height cannot be higher than 90 degrees, so if the file contains a value higher than that, it will be automatically replaced by 90."

The shade would need to have height and width apart from the degree of the shade? Also, it depends on the season of the year which I cannot see how we can establish that.

https://www.boards.ie/discussion/comment/121013247#Comment_121013247

There are details about my roof here: https://www.boards.ie/discussion/comment/121006197/#Comment_121006197

The roof is a cross so it is 1 east, 2 west (back and front) north and south.

The west back is partially blocked during the summer and almost completely during the winter. so I suppose string wouldn't be a good idea there but I am considering if it would even be worth the investment for microinverters

10-10-20

So the uploaded horizon is slightly complicated. From reading around you would calculate the visual horizon from the vantage point of the solar cells. In your case you would ideally sit yourself on the roof with a protractor and level. You'd use the level to establish a horizontal and then measure the angle of the tops of the trees for a set of points around the panels, for all 360 degrees. So you're only describing the obstacle by the angle which it reaches in the sky-view, hence you don't need to supply heights into the tool.

So let's say you had an open field and only one tree in the way and it was due-East of your panels, it was 60 degrees high (when viewed using the protractor), was 30 degrees wide, and the rest was a clear-sky view. You would then create a CSV file like this:

The 12 numbers in the above represent the 360-degree view in steps 30-degree rotations starting from 0-degrees North, showing the tree at 90 degrees (E), and that's also shown in the "Outline of horizon" below, as is the loss of irradiation between the hours of 06:00 to 08:30 in the sample month, June.

Then when you calculate your irradiance the tool will include the loss of the sun to the east (early morning sun) for all seasons, automatically.

UnhappyCustomer

https://www.boards.ie/discussion/comment/121016893#Comment_121016893

So if this is my gaff

https://ibb.co/n813h3x

it would be more or less this?

https://ibb.co/n6QpZTj

not sure about the height, the roof would be in parallel so not sure how it would look like the csv file

10-10-20

https://www.boards.ie/discussion/comment/121017211#Comment_121017211

OK, so you have the first part right.

Have a look at part 2 of this instructable:

https://www.instructables.com/Using-a-clinometer-to-measure-height/

Now visualise if you were to sit on your roof and see this view, and let's pretend that these mountains are trees really close by.

So for the first line in the CSV (due North) we would want to enter the angle of the top of that 'tree' off the horizon into the file. So in this case let's say that you used the protractor to work out that the very top of the tree was 70 degrees off the horizon. Then rotate the clinometer 30 degrees to face NNE, measure the height of the tree again, let's say it's 60 degrees high... the next is 40 high... and so on. Then keep repeating this for each 30 degree segment until you have recorded the whole skyview.

Make sense?

UnhappyCustomer

https://www.boards.ie/discussion/comment/121017270#Comment_121017270

I get you now! however, I would need to get on the roof, and calculate these measurements from the bottom of what a solar panel measures to have an accurate measurement, not counting the slope... which at the end of the day I'm not sure if it is THAT impactful if that makes sense?

EDIT: I think even if it were a string, it would reduce the performance of the whole thing just partially during a period of time during a particular season. Passed that, I think it would work well

10-10-20

https://www.boards.ie/discussion/comment/121017371#Comment_121017371

Yeah, I might have said earlier "looks easy", but in reality it's a pig of a job, and it gets more complicated with a string as the horizon view is different for every panel.

If I was you could look at going down the microinverter route and let the panels and the microinverters do their thing.

UnhappyCustomer

https://www.boards.ie/discussion/comment/121017455#Comment_121017455

What about string and optimisers on those panels "affected" by the shade of the roof? As I said I think they would be really affected during a short period of time during a particular season (spring mainly I'd say), although they could get very little sun during the winter and drag the other panels down...

To be honest this is driving me nuts... After all of this, it is still not clear that those additional panels could bring much more power. Also, the tree at the left is blocking a lot of sun

I'll talk to the provider and have a look at costs to see if the potential impact could be worth it.

10-10-20

I think that's your best bet as we can't visualise the roof well from here! Optimisers can't solve all of the shading problems on strings, that's why I like microinverters for complex roofs, such as my own.