What is the best way to overcome the problem of shade from a chimney?

[compmad1]

Hi, I want solar pv panels: a 4KW system. My roof is large and south facing, but shadow is cast by a rather large chimney.

Solar Edge power optimizers have been recommended by one company, but a different company has reservations about fitting this system because of the expense of scaffolding required if an optimizer needed to be replaced.

Even though the power optimizers have a 25 year manufacturers warranty, apparently Solar Edge are not confident enough about the reliability of their system to enable them to cover labour expenses etc.

I'd appreciate others opinions on Solar Edge power optimizers, and advice on any other effective solutions to the problem of shading.

My brother-in-law was not advised correctly about his new system --- lots of shade and panels connected in series. His system was not generating much electricity at all. His company are supposed to be fitting individual inverters on each panel now, but I don't know much about this.

I did not know anything about solar panels until a week ago, and would appreciate any advice at all. Thanks.

 

[wersolaruk]

We have had problems with two optimisers out of around 3-4k , solar edge paid us to change it. Depends on the relationship you have with your manufacturer, ours is pretty strong with solar edge.

 

[Deleted member 38070]

Solar edge systems are great, very well made, I've installed quite a few of them and I've never had a problem, the company are very helpful and I wouldn't think you'd have any problems with warranty. The monitoring system is also good, very informative, They're very good for maximum generation at different points of the day with various shading issues.. There is an evecsys system with uses an inverter for each panel. I personally prefer the solar edge system.

 

[FB.]

Any chance of some pictures? (maybe screenshot captures from google maps)

The shading might not be as bad as you fear and there are lots of clever tricks which could be used to get the best from the panels even if they suffer hard shadow at certain times of day.

 

[SolarCity]

We actually visited the OP this morning and discussed the options and we recommended that they post on this forum to get some impartial advice.

I'll design the system on PV Sol Expert tomorrow morning and post the layout on here. I personally don't think a Solar Edge system is required but won't know until I've tried a couple of designs.

It is interesting that Wersolar says that Solar Edge paid him to change the optimisers as this hasn't been our previous experience. Although a conversation I had earlier in the week with someone from the company suggests that this situation may change. To be honest, I think it is the very least that a company should do to back up their product.

Even with this back up, I am not convinced that Solar Edge would be the best option with the extra expense involved. It will be interesting to see what other installers' opinions are.

 

[wersolaruk]

I have made this clear with them that they need to make it more clear in there warranty statement, I said this was major negative point, they have a great USP in there product. I think you can't expect a full scaffold rig being paid for but a small donation maybe a benefit in the form of 100-200 pounds, we didn't receive a great deal other than two free optimisers but that was enough for me.

 

[whinmoor]

We like Solar Edge but tend to use it only when installing on three or more roof surfaces, not because of shading issues.

The online monitoring system is good once set up. It's great to be able to analyse each panel individually.

We haven't yet had a problem with Solar Edge so haven't needed to test their after-sales or warranty service.

 

[Gavin A]

Depends on the shading, but we'd usually use an SMA or Power One dual string inverter with full scan shading function, which works to use the panels bypass diodes to cut out the shaded cells and avoid the system getting stuck on a false peak.

The important thing to make this work is to design the system properly to ensure the shadow comes across the panels to maximise the use of the bypass diodes - ie not running across the short side.

It works pretty well, and saves around £1k vs microinverters / solar edge - takes a hell of a long time to make back that £1k from the 2-5% or so performance advantage I'd expect from microinverters vs the performance from these specific inverters if set up correctly.

Also worth bearing in mind that microinverters will only cut out one shaded string within the panel, if 2 out of 3 strings are shaded then it will function at the output of the shaded cells, so it doesn't actually deal with shading that well within the shaded panels, just prevents the shading from impacting on other panels.

 

[Geordie Spark]

What is the best way to overcome the problem of shade from a chimney?


Knock it down???

 

[UNG]

What is the best way to overcome the problem of shade from a chimney?


Knock it down???

That was my thought as well

 

[Geordie Spark]

That was my thought as well

Great minds think alike !

 

[jason121]

Enphase, 20 year warranty. they will change the inverter for you or pay you to do it. 24hr / 7 day monitoring, and alert status to the installer if one of the panels fails. Could improve performance by 12% versus string inverter. More money piece of mind for 20 years. Also low voltage DC on roof rather then 250v DC plus. Just a thought.

 

[SolarCity]

Okay, below are a couple of screenshots of our PV*Sol model for this project.

The roof faces just 10degrees off south and the two shading issues come from the chimney and the neighbouring property to the south.


I've placed some REC 260w panels in this design and laid them in the least shaded areas.

The chimney clearly gives the most shading but with the panels in this layout, most of the shading is cast on the lower row of panels.

This screenshot shows the shade cast on 13th October at 3pm.

I've tried a few different string configurations and I get a yield of 3,542kWh on a Power One 3.6. With a Solar Edge system, I get a yield of 3,627kWh.

The yield loss due to shading on the Power One option comes in at 6.9% and at 6% on the SolarEdge system. The extra yield on the Solar Edge system probably comes from the increased yield as mismatch penalties don't apply.

I would think that it would be a judgement call. Personally I am not a big fan of having too much electronic equipment on a roof and I would argue it should be avoided if possible. In this instance I would say that the shading cast on the roof doesn't warrant a SE system.

It'd be interesting to know others' thoughts.

 

[compmad1]

Any chance of some pictures? (maybe screenshot captures from google maps)

The shading might not be as bad as you fear and there are lots of clever tricks which could be used to get the best from the panels even if they suffer hard shadow at certain times of day.

Thanks for your help. I have attached a picture of our house from Google Earth. It is the house with the word 'Peveril' running across the front of it. Looking at the picture I have noticed some other shading as well, presumably from the house in front.

 

[SolarCity]

I have made this clear with them that they need to make it more clear in there warranty statement, I said this was major negative point, they have a great USP in there product. I think you can't expect a full scaffold rig being paid for but a small donation maybe a benefit in the form of 100-200 pounds, we didn't receive a great deal other than two free optimisers but that was enough for me.

If Solar Edge are so confident that their product is reliable, why don't they back their product with a FULL guarantee with the cost of scaffold and labour included? Why should an installer carry the cost of replacing someone else's product?

 

[FB.]

It'd be interesting to know others' thoughts.

Is it viable to have all the panels arranged in landscape as close to the ridge and/or as far to the right as possible? I reckon the roof is wide enough to take rows of six along the ridge and at least four per row on the unshaded right. The sun would have to be very low in the sky to affect those on the ridgeline.

 

[SolarCity]

Is it viable to have all the panels arranged in landscape as close to the ridge and/or as far to the right as possible? I reckon the roof is wide enough to take rows of six along the ridge and at least four per row on the unshaded right. The sun would have to be very low in the sky to affect those on the ridgeline.

Can only get 5 in a row in landscape and the layout receives more shading this way.

 

[FB.]

I'd stick with that layout then.

I would worry about an "upper" and a "lower" string because in autumn, winter and spring that chimney is going to play games with the leftmost five panels on the upper row.

If we number the panels 1-15, starting at the top left as #1, the top right as #9 and with #10 being the one on the bottom row closest the chimney, I think I'd have the eight on the right (6,7,8,9,12,13,14,15) on one MPPT and the seven on the left (1,2,3,4,5,11,12) on another.
I appreciate that #5 has less impairment than #12 and you might want the least-impaired panels on one string, but I think in the afternoons #5 will be more affected than #12 as the sun shines between the chimney and the neighbour's roof (your first image shows what I mean).

The second string is going to be a bit of a mess and rarely reach its full potential, but a scan function for optimum voltage should be able to keep it running close to three-quarters potential on sunny days (and no noticeable losses on the many cloudy days).

 

[SolarCity]

Actually, I think you'd be surprised. Which is why PV Sol is such an excellent piece of software.

You can try different string set ups and it will recommend a best option. No guess work. I've been trying to post a video to show you what I mean.

 

[Gavin A]

As I said before - Power-One probably split into 8 and 7, set the full MPPT scan function to 5 minutes, and maybe adjust the low voltage setting down to allow for lower string voltages on the shaded side when shading has knocked out a few of the strings within the panels.

string systems underperform badly in shaded conditions when the installer doesn't know what they're doing, and either spec an unsuitable inverter, or don't set it up properly.

As your numbers indicate, solar edge would likely outperform the power-one, but not really by enough to justify the extra expense in this situation IMO.