Issue 124 July–September 2013 AU $7.95 NZ $8.95 www.renew.org.au

Window & Film Buyers Guide inside

DIY: biochar bene"ts + build-your-own

solar HWS; The basics: how solar panels

work; Electric bikes: winning the race

Issue 124 : Energy monitoring

special feature

ReNew Technology for a

sustainable future

Cool competition Winter PV testing

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38 ReNew Issue 124 renew.org.au

Cool competitionWinter performance !gures

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 three-

layer 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

coe[cient of power, so the power drops

o\ 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

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

coe[cient 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

signi]cantly 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 `ash test results

for the two panels that I tested, as well as for

all panels imported in the previous month.

The `ash 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 Issue 124 39renew.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-]lm 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 signi]cantly exceeding

nameplate power. Polycrystalline panels

have traditionally had lower energy density

(e[ciency) compared to monocrystalline

panels, but the results show little di\erence for

modern panels. Sunpower is another company

producing very high e[ciency panels and it

would be interesting to test them in the future.

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 o\ers as standard a two-

year 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 ]nancial 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 o[ce in Germany

and manufacturing in Taiwan. Quality and

reliability are their stated priorities and this

appears to be re`ected 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 Chinese-

manufactured 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 a\ect reliability and longevity.

If roof area is scarce, then ultra high e[ciency

panels (those with a high energy density score)

provide a real bene]t 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 2. Energy density, or output per unit of surface area.

o Figure 3. Warranty performance.