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Mixing Solar Panels


smurfdbn
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Good day all,

Current setup is 18 x 285w ArtSolar panels on garage roof facing slightly west of north.  Thinking of adding a few more panels on the side of the garage (vertical) to boost early morning and late afternoon, 2 strings due east and a string due west.

Artsolar don't offer the 285w any more but have 280w on offer - specs attached.  I think I can use the 280w panels with minimal effect but would really appreciate any thoughts from someone more knowledgeable than me.

Thanks in advance

PV 285 vs 280.jpg

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17 minutes ago, Speedster said:

Would these all feed to the same MPPT?

Hi Speedster

That's what i'm thinking.  My setup is Multiplus-II 5K/48v.  Strings are 3 series to SmartSolar MPPT 150/100

 

Edited by smurfdbn
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10 minutes ago, phil.g00 said:

I think they are close enough spec'd to give it a whirl.

I'd not not mix panels within the string, and if you are using different aspects or slopes, I'd try to group similar strings at the same aspect.

Other than that I'd say go for it.

Thanks Phil

All strings will be same specs panels - 6 strings of 285w panels and 3 strings of 280w

Original 6 strings are on the roof. The new one's will be vertically mounted on the side of the building so they will only have direct sunlight from mid to late morning

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57 minutes ago, smurfdbn said:

Thinking of adding a few more panels on the side of the garage (vertical) to boost early morning and late afternoon, 2 strings due east and a string due west.

This practice will become more common as theoretically it doesn't add to the noon peak, so you can get away with using the same MPPT.

I am considering toying with vertical mounted bifacial panels E/W for this very reason.

Power early and power late means a smaller battery, it's worth more than the unusable glut at noon when the batteries are charged.

It is also sometimes worthwhile considering  your battery type and its charging profile. Lead acid for example takes more juice early with a long tapering tail. In higher latitudes the day has to be made as long as possible with more power in the morning. Hugh Piggott of Scoraig wind has a recent blog about this. ( Scoraig is an isle in the North of Scotland).

Edited by phil.g00
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Oh, and one more thing. You might consider mounting the long ways on. This is because of the effect of shade of the roof eaves on a panel.

There are 3 strings of 20 cells in those panels. If you shade a single cell it knocks out the entire string and you have 2/3rds production.

If you shade another cell in the same string it makes no difference, however if you shade another cell in a different string you lose another 1/3rd of the power.

The cell stings run up and down the long length of the panel, so depending how you orientate the panels you can still be on 2/3rd power and the 1/3 power for quite a while longer as the shade of the roof eaves creep down the panel.

Every watt counts.

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5 minutes ago, phil.g00 said:

Power early and power late means a smaller battery, it's worth more than the unusable glut at noon when the batteries are charged.

Midday is sorted, we mostly getting more PV than we use, getting an extra kw or thereabouts at 8am is going to be really handy, keep the ladies of the house happy since I have instructed them to only start their work from 9 onward - didn't go down to well <g>

Going to go for it and monitor carefully - winter should be within limits, summer could be touch and go - if we get to close to the limits, can always disconnect a string, only use it for winter

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4 minutes ago, phil.g00 said:

Oh, and one more thing. You might consider mounting the long ways on. This is because of the effect of shade of the roof eaves on a panel.

I will be making a custom bracket to mount these so they will be well away from the eaves and this shouldn't be a problem but good to know, thanks

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Just clipped this of the web. Bifacial panels favour one side for production.

As you can see you really get away the adding panels and not having to add peripherals.

The expensive peripherals have to sized to deal with that noon peak. Panels are relatively cheap.

I have been an advocate of more panels and a longer day for a long time now.  Make those peripherals work a full day.

Plus when its overcast more panels beat less panels.

Regarding, custom brackets, yes that's how I started out, but they cost money too.    edit:( Your vertical brackets maybe exceptions).

I see pics of these perfectly tilted panels on expensive brackets, ( I did it too). However I found that tilting a panel casts shade behind it. That's an area I can't use.

Nowadays, I find it's faster (cheaper) and (probably?) more productive to have two panels at whatever roof pitch you've got, than 1 perfectly angled one. I say "cheaper" because remember I don't have to add peripherals.

I haven't run out of roof yet so, I'll spend the savings on even more panels.

I just monitor my MPPT's and string inverters and you'd be surprised how much extra PV you can squeeze in without exceeding any limits.

 

image.png

Edited by phil.g00
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10 minutes ago, phil.g00 said:

The expensive peripherals have to sized to deal with that noon peak. Panels are relatively cheap.

100%

The result i'm hoping to achieve is something similar to the pink and green curve in your pic

Thanks for your thoughts

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Just as a matter of interest, and to have the resources on the same thread:

https://www.researchgate.net/publication/241076784_Increasing_the_solar_photovoltaic_energy_capture_on_sunny_and_cloudy_days

This study shows that a perfectly tilted panel produces twice the power of a flat panel on a sunny day. So having two panels ( flatish/wrongly angled/tilted) instead of one sort of evens that out.

It also goes on to say that a flat panel produces 40% more than a perfectly tilted panel on an overcast day.

So two flat panels produce 80% more power than a perfectly tilted one when is overcast.

An overcast watt is worth far more than a sunny day watt.

 

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To mix and match panels, angles and orientation is the reason I decided to rather go for a few smaller MPPTs instead of one large one. 

So instead of one large SmartSolar MPPT 150/100, I have opted for the SmartSolar MPPT 100/20(48V) match to 4 panels. The SmartSolar MPPT 100/20 is about the cost on 1 solar panel. It does not have all the extra features like the current clamp of the more expensive models, but it does mean that I have a MPPT tracker for each 4 panels. As I have a bit more shade to contend with that was higher on my priorities.

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20 minutes ago, Louisvdw said:

To mix and match panels, angles and orientation is the reason I decided to rather go for a few smaller MPPTs instead of one large one. 

So instead of one large SmartSolar MPPT 150/100, I have opted for the SmartSolar MPPT 100/20(48V) match to 4 panels. The SmartSolar MPPT 100/20 is about the cost on 1 solar panel. It does not have all the extra features like the current clamp of the more expensive models, but it does mean that I have a MPPT tracker for each 4 panels. As I have a bit more shade to contend with that was higher on my priorities.

I think you're missing the point, the point is you can get more panels/MPPT regardless of the size of MPPT.

What is you could get 6 or 8 panels on that 100/20 MPPT and make more kWh/day?

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59 minutes ago, RikH said:

So if I understood it right; on the roof right now 6 strings of 3 in series right? Now you want to ad 3 strings of 3 right? And as @Speedster already asked: all on 1 MPPT?

Hi, yes.  The original 6 string are on the roof of our garage oriented NNW.  The plan is to add 3 strings mounted vertically on the side walls of the garage, 2 strings facing East (morning) and 1 string West (afternoon).

I realise that if all the strings were mounted on the roof at same angle etc, this would exceed the rating of my MPPT.

The thinking is that early morning, the East strings would be pushing out close to max while the Roof strings are only starting to "warm up".  As the East strings start to drop off, the main roof strings would pickup where they left off.

Pic taken at 9 am with PV sitting around 1.9 kw

My Panels 1.jpg

Edited by smurfdbn
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15 minutes ago, smurfdbn said:

I realise that if all the strings were mounted on the roof at same angle etc, this would exceed the rating of my MPPT

I don't think your historical data will bear that out.

Data trumps theory.

Like I said I've done this exercise many times and you will be surprised how how extra PV you can add before you clip.

How much clipping is acceptable is another debate as well.

 

 

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28 minutes ago, phil.g00 said:

don't think your historical data will bear that out.

Only had our system up since mid June so early days but from what i've seen so far, i'm inclined to agree

From what i've seen of our Winter figures, I could comfortably add another 2 strings on the roof and still be well within limits of my MPPT

Want to run the remaining "seasons" and look at the data - will then figure out if we can add more panels for different times of the year

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@smurfdbn,

Apologies I see from your profile this is a new system and you wont have any historical data. So it was an unfair challenge.

( I was just replying and I see your reply came in).

Yes, I was about to say that anecdotally I would expect to get another string on the roof and vertical panels and still not clip.

I started out like everyone else perfect tilts and theoretical limits.

Now I mix and match the strings of any direction and tilt so that I get the MPPT working all day, without clipping at noon.

Doubling the theoretical number of panels can sometimes be achieved, certainly an extra 30-50%

PV inverters for AC coupling are an interesting addition ( at least the 2 MPPT version I have is).

It has a 3kW max AC output, but can accept 2kW DC input on either MPPT, I can't remember how many E/W panels I got on that, but it was a lot.

I have been growing this system for a few years now down in SA for my family, I cant even remember how many panels there are any more.

I generally add a pallet a year when I am on annual holiday. There is a pallet waiting for me, but COVID put the kaibosh on me travelling. There might be 2 pallets to go up by the time I'm there.

 

 

Edited by phil.g00
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Max of the MPPT is 150V and 100 Amps if I understand that right. So yes you can ad more panels. Keep in mind that all panels in a string have to have the same orientation / tilt so what I see from the picture it should be ok.

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2 minutes ago, RikH said:

Max of the MPPT is 150V and 100 Amps if I understand that right. So yes you can ad more panels. Keep in mind that all panels in a string have to have the same orientation / tilt so what I see from the picture it should be ok.

Thanks Rik

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1 minute ago, phil.g00 said:

They absolutely don't. 

Excuse me but what don't they? Please be more clear about "mix and match to your hearts content" as well. Is this lack of understanding due to my English not being my native language? ;) 

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