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mohammedbera2

Panel (Array) ventilation

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22 hours ago, mohammedbera2 said:

 In south Africa  what's  the best angle  is 30°  OK  

Being  in nylstroom / modimolle  ?

Please  advise 

Here is is again, way back I posted all this on the forum.

http://solarelectricityhandbook.com/solar-angle-calculator.html

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According  to calculator I got

42° - 66°- 90° from vertical  

according to me that's 

48° - 24° - 0° from horizontal

48+24+0÷3 =24°

also have a NW facing  roof @15° 

Will  it make a big difference

NW  compared to  N  facing  

Or will it just  produce power latter 

 

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7 hours ago, mohammedbera2 said:

According  to calculator I got

42° - 66°- 90° from vertical  

according to me that's 

48° - 24° - 0° from horizontal

48+24+0÷3 =24°

also have a NW facing  roof @15° 

Will  it make a big difference

NW  compared to  N  facing  

Or will it just  produce power latter 

 

If you cannot mount it at 24 degrees, it would / might produce a little less solar energy. Ideally, your panels need to be perpendicular to the sun, i.e. "face" the sun at a 90 degree angle. But that isn't always possible, or (financially / physically) viable. 

On small systems, it doesn't always make financial sense to build / buy a solar tracker, for your panels to track throughout the day. And thus it is often cheaper to add upto 20% more PV, you can. For example, instead of using 12x 250W panel for 3000W, use 12x 300W panels instead to get 3600W. This will then help for the shortfall incase your panels are not aligned 90 degrees to the sun. 

 

If you look at larger commercial installations, most shopping centers have their panels mounted flat on the roof, and not at an angle facing the sun. The main reason for this is to cater for strong wind resistance on those open roofs. So instead of mounting at an angle, more panels are used. 

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10 hours ago, mohammedbera2 said:

also have a NW facing  roof @15° 

The roof pitch at 15' will make the system very effective in spring/summer/autumn, but less effective in winter - if anything I would prefer to see it the other way round (favoring winter), but it will probably make a difference of 5-10% over the year.

The NW pointing roof is similar situation - great in the early morning late afternoon, not so great in late afternoon early morning- probably 5% loss overall.

I dont think it makes financial sense to change any angles, if you are worried about losing 15% throughout the year then rather add 15% more panel area than try and change angles.

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5 hours ago, plonkster said:

..., go with NW.

In CPT that makes sense, seeing sun sets very late in summer.

But elsewhere, would it really have that much benefit, in like Nylstroom?

Which side do the summer rains come from, the ones that come late afternoon, IF that is still happening?

I would be more focused on winter in Tvl, as then one uses the most power.

For in Cpt, winter is a wee bit of a waste to focus on as it is rainy season, at least supposed to be, or overcast a lot.

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6 hours ago, plonkster said:

NW is much better than NE. If you can't get North, and you have to choose between NW and NE, go with NW.

 Was just thinking not sure if anyone  tried this:   I have  9 x320w panels

Going to be 3 strings of 3

what  if I put

3 to face NE @ 15 ° and ( front roof )

3 north and last @ 30°  ( on a frame )

3 to face NW@ 15° ( side roof)

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9 hours ago, pilotfish said:

The roof pitch at 15' will make the system very effective in spring/summer/autumn, but less effective in winter - if anything I would prefer to see it the other way round (favoring winter), but it will probably make a difference of 5-10% over the year.

The NW pointing roof is similar situation - great in the early morning late afternoon, not so great in late afternoon early morning- probably 5% loss overall.

I dont think it makes financial sense to change any angles, if you are worried about losing 15% throughout the year then rather add 15% more panel area than try and change angles.

Agreed. If he has enough roof space for more / bigger panels, go for it. You can easily scale upto about 60% more than the MPPT's range, permitted you stay within the VOC limits. 

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1 hour ago, The Terrible Triplett said:

In CPT that makes sense, seeing sun sets very late in summer.

But elsewhere, would it really have that much benefit, in like Nylstroom?

Which side do the summer rains come from, the ones that come late afternoon, IF that is still happening?

I would be more focused on winter in Tvl, as then one uses the most power.

For in Cpt, winter is a wee bit of a waste to focus on as it is rainy season, at least supposed to be, or overcast a lot.

Yes. The afternoon rays are much more intense than the early more sun rays

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52 minutes ago, mohammedbera2 said:

 Was just thinking not sure if anyone  tried this:   I have  9 x320w panels

Going to be 3 strings of 3

what  if I put

3 to face NE @ 15 ° and ( front roof )

3 north and last @ 30°  ( on a frame )

3 to face NW@ 15° ( side roof)

Can you take some pics of your roof?

 

If you can point North, mount them North.  

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2 hours ago, mohammedbera2 said:

 Was just thinking not sure if anyone  tried this:   I have  9 x320w panels

Going to be 3 strings of 3

what  if I put

3 to face NE @ 15 ° and ( front roof )

3 north and last @ 30°  ( on a frame )

3 to face NW@ 15° ( side roof)

If I remember correctly you have 2 Axperts therefore 2 MPPTs and should have panels facing in 2 directions rather than 3. All the panels on one MPPT should face the same direction and have the same tilt. I do know some of the solar pump installers face panels in two different directions on a single MPPT. Pump MPPTs are much more forgiving.

 

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3 minutes ago, The Terrible Triplett said:

My first thought: Any chance of a ground mounted array,

No chance at all -  2m from  boundary  and walls  and roof 4m high  

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7 hours ago, mohammedbera2 said:

Quick drawing  hope you will verstaan :wacko:

20180205_232246.jpg

String 1: NE facing roof top of "n" :)

String 2: NW facing roof "n's" right leg 

You will then have the best of both worlds - morning, midday and evening power generation!

My 2c

Mark

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7 hours ago, mohammedbera2 said:

Quick drawing  hope you will verstaan :wacko:

20180205_232246.jpg

In my opinion, it would work fine if you have all the panels on your North-West facing roof, i.e. the one on the left - permitted there's enough space. Early in the morning, say 7am, take a photo of that roof and see where the sun hits it. Then late in the afternoon, say 17:30, take another photo and see where the sun hits it. In winter it might be a different scenario though. 

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2 minutes ago, SilverNodashi said:

Early in the morning,

Left side of left roof is in shade  till about 8/9h

The top NE  has sun  (guessing )till around 15h00

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Just now, mohammedbera2 said:

Left side of left roof is in shade  till about 8/9h

The top NE  has sun  (guessing )till around 15h00

eish. Ok. The biggest problem you'll have with the West + East string, is that your roof doesn't face East or West either, so at some stage one, or both of those strings will probably get more shade than it should as well. And in Winter it would probably be a problem, depending on how low the sun goes in Nylstroom that time of the year. In which case you would need to add more panels to make up for the loss. 

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13 hours ago, The Terrible Triplett said:

In CPT that makes sense, seeing sun sets very late in summer.

But elsewhere, would it really have that much benefit, in like Nylstroom?

Most people leave home early so having lots of morning power not as good as being able to use a little more solar when you get back after work

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Seperate into 2 arrays as follows, depending on shading (assuming 2x MPPT as mentioned by @Chris Hobson) - the system will work great.

5a795e0f84f9b_Arraylayout.jpg.f620e3569dc10af7faf9f198010a1ac4.jpg

Most PV systems work hard in the morning to charge batteries etc, and then start to idle one batteries reach float, so that being the common case it makes sense to favour NE array if you had to pick one because you are likely to have excess capacity in the afternoon anyway.

 

Edited by pilotfish
additional info

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