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KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178

Posted: 08:11am 27 Jun 2010

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Saw Peak AC of 2340W delivered to grid!
Not bad considering inverter rated at max 2.2KW!

Array 1 with array 2 in the background
Peaked at over full rated output of the panels (1850W) at 1925W to the grid.

Lightning rod

Additional earth stake (i know I know should have run a cable but didnt have one big/long enough hence through the roof sheets at 0.001Ohms to ground)

Proud owner

Schematic for next owner / anyone who has to work on it

Pretty happy with 9KW for today as was cloudy, peaks were for the few minutes the sun poked its head out.

Luck favours the well prepared

VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 08:46am 27 Jun 2010

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Hi Karl

Good results for winter looks like a good job I hope you encourage a few more to have a go at doing it themselves.

All the best

Bob

Foolin Around

neil0mac
Senior Member

Joined: 26/12/2009
Location: Australia
Posts: 210

Posted: 08:57am 27 Jun 2010

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KarlJ said

Saw Peak AC of 2340W delivered to grid!
Not bad considering inverter rated at max 2.2KW!

Peaked at over full rated output of the panels (1850W) at 1925W to the grid.

Pretty happy with 9KW for today as was cloudy, peaks were for the few minutes the sun poked its head out.

Results look impressive.

Question(s), though.

1. Was the over watts during the cloudy or sunny periods? (Bearing in mind that diffuse light can reportedly be 'up to' 30% more intense?)

2. With small sunny breaks and/or overcast conditions, were there any indications of possible high temperatures in the system (panels or inverter? Probably not. Worth keeping an eye on - with records?

3. If over production is (more or less) the norm, what about panel degradation (browning)? It would be a pity if panel life was shortened appreciably.

4. Seeing you have two systems in different orientations, monitoring them both for sun angle vs. output could be a worthwhile exercise for others to see?

KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178

Posted: 07:18am 03 Jul 2010

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Yep.
1. as the sun pokes its head out from behind the clouds power goes up up up.
2.Panels will be at low temp -(no problems) inverter as 80% of the time making well under rated output the other 20% of the time has no problems (so far touch wood)

3. Over production definitely NOT the norm, norm is more like 65% of panel rating.
browning -from what I can see out at the university is going to happen (a little and some are worse than others) but takes 20 years+ and by then I'd say 95% of the panels at the test facility are well and truly stuffed. (thin films look remarkably good though)
The most beautiful panel I've ever seen, glass both sides etc etc.
brand new one in the foyer of my building awesome.
one in the paddock- been there 5 years, looking very tired indeed!!! Mainly corrosion inside the panel around the links that are adjacent to the output connections.

4. math there is really simple.
take total production today 3pm was
47KW north facing 1850W panels
60KW NW facing 2590W panels

so 47 / 1850 x 2590 =65.8

=9% knockdown for NW over north assuming nothing is lost in the oversize array or in running a lower voltage (230-250VDC) at 7-8A vs 330-360V at 4-5A both exactly 9.3m of 6.0mm cable.

This is pretty consistent with what i've read with 30% knockdown for east/west facing. -better in fact than I thought.

Thus my "expert" opinion 2590W on a 2KW CMS is no problems whatsoever and has
-regardless of the boost/buck circuit required to pop it up to 250V.
very similar levels of efficiency to a single higher voltage string.

When I have accumulated enough stuff (and another $2500), I'll be taking down the Nth facing array to re-configure it and adding another 4 panels on some wicked racking arrangement to get them facing North!

In fact thinking of it right now -probably not worth the wicked racking on adjacent W facing roof just add 4 panels to the pergola adjacent on the NW face and cop a small loss from having parts of a string on two (22.5deg) different faces.

Luck favours the well prepared

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