How to find a quality solar module
When it comes to sloar panels, the main criteria considered most
often is nominal efficiency factors or the price per Watt peak.
These are of course two important criteria - but, from a long-term
perspective, simply not enough.
After all, solar installations must last for 25 years. And they
will, provided they are installed correctly, and are of good
quality. But how do you actually recognise good quality in a solar
panel?
For David McCallum, General Manager at Conergy Australia, quality
panels must fulfill three criteria: They must be high-yield, solid
and safe.
The solar cells themselves are responsible for the yield factor.
Innovative cell designs can deliver efficiencies of 16 to 23
percent, depending on material and processing effort.
The market is currently dominated by cells with two metallic
collector contacts on the upper side - 'busbars'. Some manufacturers
print three busbars instead of two onto their solar panels to allow
for more efficient dissipation of the generated power.
David McCallum sees definite benefits in improved power
distribution: "Three busbars help to reduce contact resistance
between the cells. The result is increased and more consistent
module efficiency."
McCallum, also believes that combined with suitable cell connectors,
the use of three busbars provides more reliability in terms of power
generation.
He and his colleagues favour bypass diodes when it comes to module
manufacturing. "They function like a protection switch for the
cells. If, for example, foliage should shade individual cells, the
bypass diodes will channel away power, thus protecting the shaded
cells. Once sunlight is no longer impeded, the bypass diodes switch
back to their original mode, and the module will once again work at
full capacity," explains McCallum.
Even the highest yield is of little use if the module doesn't last
for its projected 25-year lifespan. The production process must lead
the way into the right direction.
Premium quality components, like specialist solar glass and a robust
frame, provide the necessary protection for the fragile cells.
But even for solar glass, the choice is endless: Smooth,
unstructured, micro-structured, heavily structured or even specially
coated glass is on offer. Each and every glass type is designed to
conduct as much sunlight as possible into the solar module.
Conergy's General Manager explains: "Heavily structured glass types
tend to attract contaminants, which over time will lead to a
decrease in the module's capacity."
The module frame stabilises the solar module, and protects both the
glass and the cells. The most robust frames are those made from
anodised aluminium. They are much more scratch-resistant than coated
frames."
McCallum also warns about possible hazards due to hollow enclosures:
"Frames should not have any hollow enclosures, as these could
collect water, which can then turn to ice in the winter in
Australian’s cooler climates. As a result, the frame could buckle or
even burst."
In summer, contaminants like pollen or dust will find no adhesion,
which means that moss growth can be avoided. Contaminant of that
type can be particularly critical, as they will permanently shade
cells, which will result in a significant loss in module capacity –
and in consequence in output of the entire solar installation.
The safety aspect is one of the most important criteria to bear in
mind when shopping around for solar modules. McCallum therefore
advises users to pay particularly close attention to the junction
box. Faulty construction or poor workmanship can, under certain
circumstances, create a fire hazard for the entire solar plant.
"I generally advise against clamp, plug or screw connections. These
could easily come undone or corrode if installed improperly. The
resulting arc could cause the junction box to catch fire." Instead,
he recommends molded junction boxes made from non-flammable plastic
with soldered connections.
These are moisture-protected and vacuum-sealed, providing a maximum
of safety. Solar module manufacturers offer many safety options:
Warranties, certifications, and positive capacity tolerances.
The actual scope of services provided, is determined individually by
each manufacturer. A warranty period of five years for solar modules
should be the absolute minimum offered.
McCallum also recommends: "If the solar modules will be deployed in
regions with severe weather conditions, customers should look for
additional certifications, like ammonia resistance, or for special
certifications regarding corrosion-resistance if the solar modules
will be installed in coastal regions."
Source:
www.pacetoday.com.au