Let me see what you are saying. Because higher voltage is produced with panel size efficiency is increased.
What about the other factors? I understand that cells will be closer together if on one panel thus higher efficiency. This is mostly due to loss of area because of the frame. Efficiency is the wattage presented from the sun vs. Output wattage. i.e. The conversion ratio.
What you are not putting out there is the rest of the equipment. Let's say we need a controller that will handle that 300 watt VOC of about 60 volts. That makes for a more expensive controller. Because it is human to cut corners we put a cheap PWM controller on the panel rather than an MPPT controller.
All in one move we have dumped 1/3 (48/60) of the panels output. We now can forget the efficiency of the panel because the system is inefficient.
Same system with panels having lower efficiency coupled with the MPPT controller will out perform the better panel.
The conclusion is panel efficiency is the smallest factor in the solar array. Wire loss is big but based on voltage not watts. Conversion creates loss and throwing away power the way PWM controllers do is a crime.
Used panels that have discoloration will lose efficiency. Mono crystalline panels have the highest efficiency the market will bear the cost for. Only the goods on satellites produce more power.
Kevin
In general, efficiencies go way up with size.
Bigger panel in watts = much less lossses as % of power produced.
The low-voltage DC power is pretty inefficient - so try to minimise DC
wires as much as possible.
Also, always, panels used to get better quite fast , until 2015 or so.
Older panels are very much less efficient, in terms of % of power produced.
So, second hand panels are likely to be much less useful than new ones.
So;
Get the biggest panels by watts You possibly can.
A 330W panel, vs 3x100W panels .. the difference might be several 10 of
% in losses.
Modern panels, best, have about 20% efficiency. Sunpower, usa.
Typical modern panels, china made, are about 16-18% (20-21% at cell level).
Almost all panels, by volume, today are made in china.
They are all generally excellent, and getting better by about 1%
efficiency, and 0.01$ / watts production cost, year/over.
Current production costs are about 0.39$ / Watt, and retail for around
0.54 €/watt, in the EU, 22% VAT included.
The top 5-6 chinese manufacturers make about 90% of all the panels in
the world (in plants all over the world).
(TSL, YNGLI, CSUN, some others).
Only other major manufacturer left is FSLR, with less effficient CdTe
cadmium telluride iirc (ie different process) panels used in mostly
large-scale installs.
And sunpower SPWR.
All data is in public year end and quarterly filings with SEC.
Most panels are about a std size, so more watts = newer, better panel.
When mounting the panels, try to get an airgap under them.
Cooler panels = more power.
Difference can be 10%, or more.
Also, internal temps will get higher, if you have a black roof,
absorbing lots of heat.
Hth.
--
-hanermo (cnc designs)
Posted by: Kevin Pemberton <pembertonkevin@gmail.com>
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