PV Directions

[savage]

Hi,

Ok, so here by us in CPT, the ideal situation is to mount panels facing north, ideally, with about a 30 degree (odd) angle.... I have 10 x 300W panels, just about ready to go up (3KW)

My problem is that I do not have a lot of north facing real estate on the roof. I will be able to mount the 10 panels facing north, but it's really pushing it in terms of real estate, and no way to mount any additional panels in the future.

I know that if I mount all 10 panels facing north, I'm looking at 3KW generating capacity (under obviously optimal conditions that will never happen). What will happen if I mount 5 panels facing East, and 5 panels facing West? Would this have significant implications in terms of generating capacity, or am I safe to presume that instead of 3KW, I will now be looking at +-1.5KW (generally speaking) generation capacity?

East / West facing, I can mount (and have real estate) for a serious amount of panels, so if I have to put up a few more, then so be it - it can be done.

I'm just really interested in how this will affect the PV panels in terms of power generation, and how it would affect the inverter considering the lower generation capacity from the PV array?

Anyone with some meaningful insights perhaps?

 

[P924]

Mount them facing north. If you do 5 west+east, you will get half the output half the time, so left with 1/4th of what you would get facing north. (Well perhaps slightly more, but in that region). Also, you would need an inverter with 2 mppt controllers to get the most out of 2 strings.

There are websites that will calculate the energy generated if you put in the angles.

 

[oober]

Hi,

Ok, so here by us in CPT, the ideal situation is to mount panels facing north, ideally, with about a 30 degree (odd) angle.... I have 10 x 300W panels, just about ready to go up (3KW)

My problem is that I do not have a lot of north facing real estate on the roof. I will be able to mount the 10 panels facing north, but it's really pushing it in terms of real estate, and no way to mount any additional panels in the future.

I know that if I mount all 10 panels facing north, I'm looking at 3KW generating capacity (under obviously optimal conditions that will never happen). What will happen if I mount 5 panels facing East, and 5 panels facing West? Would this have significant implications in terms of generating capacity, or am I safe to presume that instead of 3KW, I will now be looking at +-1.5KW (generally speaking) generation capacity?

East / West facing, I can mount (and have real estate) for a serious amount of panels, so if I have to put up a few more, then so be it - it can be done.

I'm just really interested in how this will affect the PV panels in terms of power generation, and how it would affect the inverter considering the lower generation capacity from the PV array?

Anyone with some meaningful insights perhaps?

Rather mount the ten panels you have now all facing north. Then when you add more panels get another charge controller and mount them in the other direction.

 

[savage]

Mount them facing north. If you do 5 west+east, you will get half the output half the time, so left with 1/4th of what you would get facing north. (Well perhaps slightly more, but in that region). Also, you would need an inverter with 2 mppt controllers to get the most out of 2 strings.

There are websites that will calculate the energy generated if you put in the angles.

Hmpf! I was thinking 1/2 generation, but you are right! I will be 1/4 Also didn't even think about two charge controllers that would be required. Just looked at the specs for the inverter I'm using too, and if I split the 10 panels to 2 strings (one east / one west) I won't meet the min required DC voltage on the array (so I would immediately need more panels to up the voltages)...

So yes - not ideal, but I don't have a choice. 10 in series for one string - all north facing. Will just have to get creative with the rest. I'm putting up 10 in series now, but mid to long run I want two strings of 12 each, which is pretty close to max what the inverter can safely accomodate....

ARGH WTF did I have to build my braai on the North side of the house, and not the South side! Have almost 10m2 of prime north facing real estate on brand new IBR roof... The damn chimney casts a shadow over the roof the entire day long

 

[P924]

Hmpf! I was thinking 1/2 generation, but you are right! I will be 1/4 Also didn't even think about two charge controllers that would be required. Just looked at the specs for the inverter I'm using too, and if I split the 10 panels to 2 strings (one east / one west) I won't meet the min required DC voltage on the array (so I would immediately need more panels to up the voltages)...

So yes - not ideal, but I don't have a choice. 10 in series for one string - all north facing. Will just have to get creative with the rest. I'm putting up 10 in series now, but mid to long run I want two strings of 12 each, which is pretty close to max what the inverter can safely accomodate....

ARGH WTF did I have to build my braai on the North side of the house, and not the South side! Have almost 10m2 of prime north facing real estate on brand new IBR roof... The damn chimney casts a shadow over the roof the entire day long

Actually, I am wrong. It is half the output half the time x2. So it is around half (slightly more than half in most situations. But your controller needs to be able to handle it.

 

[Gallderhen]

Generally speaking, how difficult would it be to mount panels on a steel-plate of sorts thats mounted on a pole secured to the house, at 30 degree angle facing north? (in a 3x3 + 1 grid)

-G-

 

[thehuman]

Why dont you angle the pannels with brackets . Will cost more but can make mounts out of aluminium maybe .
What system this . Bateries or grid tied

 

[savage]

Hybrid system. Going to be using the InfiniSolar 3KW Plus inverter... If the 5KW is available on the market by the time I purchase, I'll more than likely opt for the 5KW unit instead of the 3KW unit.

If I have to start building custom mounts and frames and what not, then I may just as well opt for Solar Trackers and guarantee max. yields. Am currently looking into that and sending off some emails to a few suppliers. Not cheap, but not unaffordable either.

 

[thehuman]

How I understand a string all the pannels need to have about the same amount of exposure to the sun . If one pannel is in shade the whole string is comprised

 

[oober]

Hybrid system. Going to be using the InfiniSolar 3KW Plus inverter... If the 5KW is available on the market by the time I purchase, I'll more than likely opt for the 5KW unit instead of the 3KW unit.

If I have to start building custom mounts and frames and what not, then I may just as well opt for Solar Trackers and guarantee max. yields. Am currently looking into that and sending off some emails to a few suppliers. Not cheap, but not unaffordable either.

Will be interesting to find out how much these trackers go for and how easy they are to install on a roof. Lots of DIY videos out there.

 

[thehuman]

Also maybe look at smaller micro grid tie inverters for expansion

 

[P924]

Also maybe look at smaller micro grid tie inverters for expansion

It would be cheaper to buy 3 infinisolar inverters. The 5kW version has 2 mppt controllers, IIRC the 3 kW also does, but I'm not sure about that.

 

[savage]

It would be cheaper to buy 3 infinisolar inverters. The 5kW version has 2 mppt controllers, IIRC the 3 kW also does, but I'm not sure about that.

2KW, 3KW, and 3KW Plus only has one MPPT Controller. 5KW and 6KW has two. This is according to the datasheets...

The 5KW and 6KW is still in a testing phase, it hasn't been released for sale yet as far as I am aware, but it will apparently become available shortly.

 

[itareanlnotani]

Your setup is going to be based largely on controller size.

What's the largest voltage it can do, and whats the largest amp rating it handles.
Datasheet here [ http://www.voltronicpower.com/oCart2/files/brochure/InfiniSolar_DS.pdf ] for the plus says 500v DC / 18A

Look at the datasheet for the panels and check the open voltage rating for the panels (VoC). I think your's are 43.3v open voltage / 8A, so calculate max voltage based off that. 10 x 43V = 430V so well under the max voltage. You only have one input on that inverter, so I'd do one string of 10 panels in series.

I wouldn't bother with solar trackers. It only makes sense as a solution if you're space constrained.
Typically adding more panels is cheaper than a tracker system, so has better RoI.

That inverter doesn't give you much headroom to expand though, which may be an issue.

 

[savage]

I wouldn't bother with solar trackers. It only makes sense as a solution if you're space constrained.

In terms of north facing roof space... Trust me, I'm constraint. Significantly.

 

[itareanlnotani]

Don't forget about the angle also;

As a rule of thumb, if the main loads are in winter months when solar availability is reduced, tilt angles should be more vertical (approximately equal to latitude plus 15°) to maximise exposure to the low winter sun.

If major loads are cooling and refrigeration the tilt angle should be reduced (approximately latitude minus 10°) to maximise output during summer.

For grid connect systems the summer optimum angle should be used to maximise annual output of the modules. A directly East or West facing panel will never operate at better than 85% of its rated output.

Preference should be North if possible, then West.

http://solargis.info/pvplanner/ should help.



As a real life example:

Mine are at NE (50 degree's +-) and on an angle of 30degree's as our roof is structured that way. Out of our 16 mounted panels (300W panels), we get about 4KW peak looking at the historical figures over the year. Thats less than its theoretical 4800W max, but its still more than we use.

Right now its sitting at 500v +-5 @ 5.5a at 11:30am for 2.7KW +-
I also have shading which doesn't help (chimneys).

We generate about 25KW a day on average at the moment.


I'll be comparing this soon as I've installed 6 of the same panels in a new location for an offgrid setup in due north quite soon (have the panels mounted, need to make some secure mounting for the inverters as its on a plot)