In the dark about real-world shading

[bladerunnerpv]

Had a bit of free time recently to play with easy-pv 3D, so put together my house situ. As you can see (1st pic) , not the clearest of surroundings. (mine is the one with the red gable end and panels on the roof - gable end is approx S-facing, tall trees are to the west)

The roof lines to the south are not so bad,

The real irritation is the deciduous tall trees to the west which have an impact.

I reckon about 1/2 hr sunlight lost in mid October (see pix, roof ones are west-facing), but it also affects the summer as the sun transits much of the way across them, interrupting some evening generation, maybe 1-2hrs

In your experience of shading does this shading from trees look like a case where I'd really need and benefit from solar optimisers or enphase micro optimisers?

Or is it more likely not to be cost-effective, with Enphase at £150ea that's £1500 vs a £500 solis PV inverter, so it would need to regain £1000 over 10yrs to make it worthwhile, unless there was another benefit like making panel changes easier, or facilitating addition of 6x south facing panels at a later date

thanks for taking a look

 

[binky]

Once the leaves have dropped in Autumn, it will probably not make much difference. Even in summer, as they are a reasonable distance away, background irradiance will still be quite high. What really messes systems up is hard shading from objects close to the panels, like a chimney. So you need to calculate if losing a few hours of generation makes financial sense to spend the extra? Does your software show simulated outputs for different inverters/ micro inverters? PV-Sol, the software I had, would do that, but I don't think there's a free version available.

 

[bladerunnerpv]

Hi Binky, sorry for not following up on this previously.

1. Thanks very much for the tip about hard shading and re-assurance about trees.
It looks like I would get a little on the west side (pic1) mid-morning wintertime, this is mid-Jan 1030am


And from nearby buildings to the east side (pic2) early morning Feb, Mar, Oct, Nov . Not sure how well it shows on screen

 

[bladerunnerpv]

2. Does your software show simulated outputs for different inverters/ micro inverters? PV-Sol, the software I had, would do that, but I don't think there's a free version available.

I had a look at PV-Sol but the free version is quite limited and I didn't fancy setting aside £1500 for a trial version, even if they'd let me have one of course as non-company purchaser.

I dug bit further to see what was going on in EasyPV
I set up two separate models and ran them to see what happened.
i) East roof 10 panels, using two strings, upper 5 and lower 5, using a 4k inverter, 2 x MPPTs
ii) West roof 10 panels, using two strings, upper 6 and lower 4, using same inverter

I was a bit surprised by the results and decided to try contact easypv to understand more. They were very helpful with my queries and I thought I'd post it on the forum

It's worth noting now there are two separate tasks in easypv, a "performance task" and a "consumption task", it will make more sense later on.

Question to EasyPV:-

Hello
just trying to understand some results from easypv, wonder if you could advise please ?

I used the buildings task to make two separate systems
option 1 : east-facing array
option 2: west-facing array

I used the 3d horizon option in the performance task to determine the shading
[post email: anticipating the 3D sunpath would drive the panel generation and self-consumption results in the consumption task]

When I look at the consumption task, generation, daily option for May1st,
the generation profiles for option i) and option ii) both last from 5am to 7pm, maximum around noon
There is no apparent difference between the two options (east-facing and west-facing) at the start of the day or between the two at the end of the day
[post email: I was anticipating the East would be better in morning and less so in evening and vice versa for West]

Looking at the 3D model the east-facing array (option i) is shaded by about 4pm, the west-facing (option ii) is not

Yet the east-facing array (option i) is indicating generation at 4pm at the same magnitude as the west facing array and continuing well past 6pm.

Question :
Does easypv, using the 3D sunpath method, actually make a timed generation profile based on the panel/roof orientation and sun path?
Is the shading factor linked to the 3D sunpath, are the two parts connected together yet?

Option i) East (my ref Est Jnk 0A0x 435W 2x Sol 4k Giv 0kWh 26Sep23 3D2s1)
3D model 4pm [pic]


EAST Shading (using 3D option) for top row of panels (shading is part of the Performance Task)


EAST Generation (Generation graph is part of the Consumption Task)


Option ii) West (my ref Est Jnk 00Ax 435W 2x Sol 4k Giv 0kWh 26Sep23 3D2s1)
3D model 4pm [pic]


WEST Shading (using 3D option) (shading is part of the Performance Task)


WEST Generation (Generation graph is part of the Consumption Task)


Basically I was confused as to why an East-only facing array was indicating generation post 4pm ish when not directly illuminated, and similarly the West-facing was apparently generating at the start of the day

 

[bladerunnerpv]

Please note that as a courtesy I checked with easypv before posting their reply on a forum, they were happy for me to do so.
Frankly I'm amazed something like easypv this is available for free and I for one am grateful that it is. (there is a paid for option too)

Easy-pv's reply to my query....

"Essentially the performance task and consumption task can be seen as two separate methods of calculating self-consumption

While the consumption task does use the generation estimate found in the performance task, this is essentially the only datum it pulls.

The sun path models you create in the performance task are there to work out the shade factor, which is of course factored into the generation estimate calculation on the table, [my addition: the table in the performance task] it does not create a timed generation profile per se. In this way the performance task sticks very closely to the MCS method which it seeks to automate.

The generation profiles , and other data you see in the consumption task are based in an entirely separate set of data; this is extrapolated out using the annual generation estimate found in the performance task, and the consumption you enter, as parameters, to create all the graphs and models you see.

This means that although you don't get a completely specific generation profile in the consumption task, you do get estimates of both generation and consumption that are backed up by both MCS data and real-world data."


I had not noticed the extra step in the performance task, which moves it from this

to this



Conclusion
The Easypv 3D sun path functionality is used in generation estimates but not quite as I had anticipated/assumed...

If I've got my head around it correctly then...
The 3D sunpath is used for shade factor calculation, this shade factor is used in the MCS estimated annual output in kWh and thence the MCS Estimated PV self-consumption in the easyPV "Performance task"

The 3D sunpath is also used for shade factor calculation used in the easyPV "Consumption Task" but only as a global scaling factor for however the Consumption task calculates it's stuff.

It doesn't work out a time-dynamic shading factor for the "Consumption Task" based on the 3D sunpath (not yet at least anyways).

So my pre-conceptions were incorrect!

So I can't use it to work out a quantitative answer to my original puzzle as accurately as I would like (for free anyways)

The 3D sunpath does give me an idea of the shading factor though which is a big plus, and it does look like there will be further development of easypv, so I may be able to one day.

 

[binky]

Predicting outputs from the panels is relatively straight forward, and based on some quite comprehensive dates sets that date back decades. Most software is a little 'gloomy' ie underforcasts a bit, due to panels and inverters moving faster than software programmers. I used to use professional software, it was always interesting how different panels worked better with different inverters, but even then, the differences were mostly in the region of small percentages. Shading adds a whole new dimension to the differences, SMA would frequently outperform cheaper inverters, without the additional costs of microinverters or optimisers.

Consumption is a much harder thing to predict, there's several standardised MCS options, such as retired couple at home all day, or working couple with kids. Ultimately though, you really want to change energy demand to suit your generation/ battery charging, rather than just use energy like you used to. So consumption figures can only be 'guidance'. You should do better if you modify your energy consumption patterns.