I have 15 x JA Solar 265W panel and have connected 12 only so far

There is a Voltage Open Circuit (VoC) of 37.95V and VMPP of 30.92V
I have an Axpert 5kVA which has a maximum VoC of 145Vdc

Am I correct to say no more than 3 in series per array?

With the spec only use 12 or possible to use all 15 (5 arrays of 3 panels each) as the inverter will limit 3000W input?

Many thanks

13 hours ago, mervinpearce said:

Am I correct to say no more than 3 in series per array?

Yes 100%

13 hours ago, mervinpearce said:

I With the spec only use 12 or possible to use all 15 (5 arrays of 3 panels each) as the inverter will limit 3000W input?

In Australia and the US it is common to overspec ones panels. Here it is rarer. @Sidewinder I think overspeced by 25% and had no problems. I think one can go to about 30%.

Yes, definitely no more than three in series per string though.

I'd go for 5 strings though, it is especially useful if you have more than one aspect/direction for your panels.

 

3 minutes ago, phil.g00 said:

I'd go for 5 strings though, it is especially useful if you have more than one aspect/direction for your panels.

 

I would only have panels facing different directions  if you have more than one SCC.

Actually, that is a common misconception.

True, you shouldn't have different tilt/ direction panels in the same string.

To have an entire parallel string at a different tilt or direction to another string is perfectly acceptable, even desirable.

In fact, East/West string combinations compliment each other by allowing for more panels and a longer solar production day for a given size SCC.

 

 

1 hour ago, phil.g00 said:

In fact, East/West string combinations compliment each other by allowing for more panels and a longer solar production day for a given size SCC.

An East West array is great, an idea that eminates from Germany in about 2012, and you can connect them to a single SCC with some provisos (which are hard to meet in a domestic situation perfect East West orientation being one of them).

Yes, I have read that German article.

It mentions exactly 15 degrees tilt at perfect E/W alignment.

But if you read the article with the knowledge that anything less than 15 degrees tilt and you would lose the effect of rain helping with self-cleaning, you would interpret it differently to the writer.

Perfect E/W is preferable because it allows for an equal number of strings in each direction.

But basically a parallel string is at full voltage, without the oomph to provide current at with very little light, but it doesn't create a current restriction for a parallel string in full sunlight.

So its a lot more flexible than that article makes it out to be.

So you can mix and match 3 : 2 strings depending on your roofs orientation.

For the best tilt angle much steeper that 15 degrees is actually preferred. It basic trigonometry,  ( lets assume we are at equinox on the equator, for a moment, but shades of this logic apply at every latitude.)

If the tilt were say 45 degrees they both east and west they each panel would present half their area to the sun at midday. 

So you could  almost double the amount of panels per charger and maximise your generation throughout the day.

I say almost because the sun is actually stronger at midday. Some experimental testing has shown this tilt to be closer to 60 degrees to double the amount of panels.

 

thank you

I see the tilt calculator here in SA (East rand) says 88 degrees at the moment

@mervinpearcePlease make a reference to your source and the detail of your calculations.

Edited December 12, 20187 yr by phil.g00

1 hour ago, mervinpearce said:

thank you

I see the tilt calculator here in SA (East rand) says 88 degrees at the moment

i.e 12 degrees in normal speak. I suppose I must accept that different parts of the world measure the other angle.

 

1 hour ago, mervinpearce said:

thank you

I see the tilt calculator here in SA (East rand) says 88 degrees at the moment

Yes, and it changes as the seasons change - which is why something like isn't always fully achievable everywhere. I prefer to work with winter based angles, then you have more the sufficient energy in summer.

OR, if you can afford it, and have the space, a tracker would be better.

I have a 4 season tilt which cost about 100 bucks and a reminder on Outlook to change the panels. I can do it as it needs a bit of labour.

1 hour ago, phil.g00 said:

@mervinpearcePlease make a reference to your source and the detail of your calculations.

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

@mervinpearce

The tilt difference wasn't really my point.

My point was a pair of bigger east facing string coupled with an equally large West facing string, makes more usable power throughout the day than a string optimised throughout the day. (More kWh's per inverter).

I refer to an PV inverter without batteries, over the day you start to produce power earlier and for longer than optimally tilted North facing panel.

North facing panels, per panel will produce more power, but its in the form of a peak at midday.

East - facing panes are less efficient, so you add more panels up to the inverter's capability, and skew that power peak towards the morning, West facing panels you do the same.

At Midday you are in the valley, between the two power peaks, but because you have more panels there is still enough of both East and West strings combined to match an optimally sized string of North facing panels.

The aim is with an equally -sized inverter is that you can achieve a longer solar day, and if you have a base load, that you are trying to match it all day, rather wasting a peak of power around noon, and not being able to match the demand in the morning or afternoon.

Think of it as being a tracker but made out of fixed panels.

I attach examples from that site that illustrate the energy available from North facing panels as opposed to East and West facing panels all at the same tilt.

The tilt I selected  was the year round optimal for North facing panels. My point is independent of changing the tilt angle throughout the year.( Although, it doesn't exclude doing that as well).

For a given size of inverter, the lesser production of E & W panels is an indication the numbers of panels in the string can be increased.

What the diagram don't indicate is that the E & W energy is available at two different times of the day, morning and afternoon respectively.

 

 

22 hours ago, mervinpearce said:

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

Thanks, this topic is very informative, i have one pole mount panel that is facing NE for now although my roof is East West.

 

23 hours ago, Chris Hobson said:

i.e 12 degrees in normal speak. I suppose I must accept that different parts of the world measure the other angle.

 

Assuming 100 degrees in a right angle?? 🙂

18 hours ago, Thunderdolt said:

Assuming 100 degrees in a right angle?? 🙂

You got me there - I see it was one in the morning.

On 2018/12/12 at 11:25 AM, mervinpearce said:

88 degrees at the moment

Sounds a bit high to me. If you were living between Keetmanshoop and Mariental or somewhere in Botswana I might believe it :-)

Here in the Karoo it was 5° but I made it 10° so that the panels would self-clean.

A true north panel would be perpendicular to the sun at noon only a few degrees off flat at East Rand latitudes in December.

 

 

 

58 minutes ago, phil.g00 said:

A true north panel would be perpendicular to the sun at noon only a few degrees off flat at East Rand latitudes in December.

You guys are right. I am way-overestimating the radial distance from the Tropic of Capricorn (which is actually just a few degrees north of here given that the sun is 8 light-minutes away :-) ).

 

1 hour ago, plonkster said:

given that the sun is 8 light-minutes away :-) ).

You're lucky it was an hour late in Ireland this morning.

9 hours ago, plonkster said:

Sounds a bit high to me. If you were living between Keetmanshoop and Mariental or somewhere in Botswana I might believe it :-)

I will measure with a glass ball to check the burn pattern