ReNew
Technology for a
sustainable future
Issue 124 : Energy monitoring
special feature
HIGH-TECH
SHACK
Set for the
international stage
Cool competition
Winter PV testing
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Issue 124 July–September 2013
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DIY: biochar benefits + build-your-own
solar HWS; The basics: how solar panels
work; Electric bikes: winning the race
Window & Film
Buyers Guide inside
Cool competition
Winter performance figures
Colin Dedman updates his popular PV testing to include new panels and those that
had previously only had a run in summer. The results are interesting!
THE RESULTS of my solar PV panel testing
were published in ReNew 118 and 119. At that
time the top-performing panel, at least under
summer conditions, was the Panasonic threelayer model VBHN235SE10 (formerly known
as the Sanyo HIT-N235SE10).
I have now tested the Panasonic panels
under winter conditions, as well as panels
from Winaico, with a remarkable yield
performance that had me double-checking
the calibration of my equipment. Is there a
new king among the panels tested so far?
Winter energy yield scores
As explained in detail in the previous articles,
the yield score is a measure, under real-world
conditions, of the energy yield relative to the
rated nameplate power. The higher the yield
score, the more the panel exceeds nameplate
power rating. Previous test results showed a
clear correlation with the cost of the panels,
with the high-end brands tending to produce
more power for a given nameplate rating.
Summer test results in ReNew 118 showed
the Panasonic HIT panels comfortably
outperformed the competition with an energy
yield score of 108.5%. As shown in Figure
1, the Panasonic panels lose a little of their
edge in winter, although they still score an
above-average yield of 104.5%. The reduction
in winter wasn’t a surprise, as the Panasonic
panels have an unusually low temperature
coefficient of power, so the power drops
off less at high summer temperatures. In
summary, the Panasonic HIT panels provide
exceptionally high energy yield relative to the
stated nameplate power, especially under hot
summer conditions.
However, the newly tested Winaico
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ReNew Issue 124
polycrystalline panels set the proverbial cat
among the pigeons, with a record-breaking
yield performance of 108.8% under winter
conditions. Further, as the temperature
coefficient is similar to most other panels,
it seems likely that a similar score will be
achieved in summer. This is an impressive
performance, with the result that they provide
significantly more power than you pay for.
PV panels always contain some spread
in performance as a result of normal
manufacturing tolerances. Just to make sure
that the Winaico panels tested were not ‘lucky
freaks’, I obtained the factory flash test results
for the two panels that I tested, as well as for
all panels imported in the previous month.
The flash test performance of the two panels
that I tested was very close to the average of
the previous month’s imports, suggesting that
the unusually high energy yield performance
reported here is typical of these Winaico PV
panels, and not just due to good luck.
Energy density score
The energy density score is a measure of the
real-world energy yield relative to the area
of the panel, which is especially important
when roof area is scarce. It can also reduce
installation cost, because fewer panels and
less mounting hardware are required for a
given amount of installed power.
As shown in Figure 2, the Panasonic HIT
o Figure 1. Winter yield performance.
renew.org.au
panel retains the crown in this category with a
remarkable score of 133%. This is a direct result
of the high-tech three-layer construction (HIT,
or Heterojunction with Intrinsic Thin layer,
is a recent advance in panel technology that
combines the best features of both crystalline
and thin-film panels), which ‘catches’ more
photons per unit area of panel.
Among the conventional panels, Winaico
scores above average at 105.4%, and
provides the highest energy density of any
polycrystalline panel tested so far, due to
its energy yield significantly exceeding
nameplate power. Polycrystalline panels
have traditionally had lower energy density
(efficiency) compared to monocrystalline
panels, but the results show little difference for
modern panels. Sunpower is another company
producing very high efficiency panels and it
would be interesting to test them in the future.
o Figure 2. Energy density, or output per unit of surface area.
Warranty score
Details of how the warranty score is calculated
are given in ReNew 118. Note that Solarfun is
now known as Hanwha and the Sanyo HIT
is now a Panasonic panel. Their warranties
have been recently upgraded, and it is the
upgraded warranties that are charted here.
Referring to Figure 3, Winaico and Solarfun
score well, mainly on account of a 12-year
materials/workmanship warranty, compared
to the general industry standard of 10 years.
In addition, Winaico offers as standard a twoyear insurance period covering the entire PV
generation system, including panels, inverter,
wiring, mounting system and so on, against
damage or failure from almost any possible
cause. Also covered is financial loss due to
unexpected loss or reduction in electricity
production for almost any reason. If total peace
of mind is important to you, then it is worth
looking at the details on the Winaico website.
For those who have never heard of Winaico
(I hadn’t), they are a high-end PV panel
supplier with their head office in Germany
and manufacturing in Taiwan. Quality and
reliability are their stated priorities and this
appears to be reflected in their above-average
warranty and performance.
Warranty details often change, so be sure
to check for current warranty details with the
manufacturer or distributor.
The best PV panel?
There is no such thing as the ‘best’ PV panel.
A premium panel with above average
energy yield score provides the satisfaction
of knowing that, for a given nameplate rating,
your PV installation will produce more power
than the guy’s down the road using cheaper
panels with a lower yield score.
If obtaining the most power for the
lowest initial cost is your top priority, then
it will be hard to beat the cheaper Chinesemanufactured panels, even allowing for the
fact that the cheaper brands tend to overstate
rated power. However, keep in mind that
panel manufacturers who overstate the rated
power output may also take shortcuts in other
areas that affect reliability and longevity.
If roof area is scarce, then ultra high efficiency
panels (those with a high energy density score)
provide a real benefit and are worth considering.
How much weight should be attached to the
warranty is a matter of personal preference.
Hopefully the test results presented here
will assist in choosing the PV panel best
suited to your own budget and priorities. S
o Figure 3. Warranty performance.
renew.org.au
ReNew Issue 124
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