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6) CHINESE PRODUCT IS RUBBISH
The myth here is that apart from Trina,
Yingli and Suntech, everything out of China
is cumbersome, performs badly and will be
up for warranty claims within a few years of
being installed.
Let’s remember that Chinese inverter
manufacturer Growatt is the company that has
the largest share of the Australianmarket when
it comes to inverters. They had some issues
in a prior run of inverters that got swapped
out under warranty, as you should expect, yet
everyone in the industry seems to be using
that done and dusted story from the past as a
model (but poor) case study of why Chinese
inverters and other products are no good.
There’s also a bit of irony in the
rubbishing of all Chinese inverters because,
as I’ve discovered, Growatt inverters for
instance have better power monitoring
than some of the leading brands, with five
minute interval data available showing the
performance of the array or arrays attached
to each individual MPPT (this stands for
maximum power point tracking – it is
essentially the computer smarts of the
inverter which optimises the power output
from a group of panels given varying sun
conditions). Some well-known German brand
inverters can’t give you monitoring of each of
your arrays though their manufacturers have
promised it’s coming .... so is Christmas.
7) YOU SHOULDN’T PUT ON
MORE PANEL CAPACITY THAN
THE OUTPUT OF YOUR INVERTER
(OVERSIZING IS BAD)
Let’s be straight – it’s better economics
to oversize the amount of panel capacity
relative to the inverter. All systems should
be oversizing 150% panel capacity to
inverter output. Unfortunately, the Clean
Energy Council (CEC) guidelines undermine
good solar system economics. They
currently only allow 133% oversizing of
arrays, after which you forgo eligibility for
the government STC rebate.
However, provided you are prepared to do
the project in two passes, claiming the STC
rebate only for that capacity up to 133% of
the inverter capacity, this is entirely legitimate.
Most importantly it can be done safely and
within electrical codes and regulations.
Yet, what’s even more ridiculous is that
many installers come up with arbitrary
constraints that they’ll only do 15%
oversizing on the north. Others even
incorrectly claim that you’re not allowed
to oversize and it wouldn’t get past the
electrical inspector/authorities.
Oversizing changes production over the
day from a bell curve to a table top (much
like an intermediate power station) which is
better for solar owners by maximising self-
consumption, but also customers without
panels and the network operators.
8) THE ELECTRICITY NETWORK
DISTRIBUTOR WON’T ALLOW
OVERSIZING BEYOND THEIR
INVERTER SIZE LIMIT
Wrong again for most network distributors.
Yes, Ausnet in Victoria has this stupid rule and
they should hire some electrical engineers
with competence to help them out. But
Citipower/Powercor, Jemena and United
Energy in Victoria all allow oversizing, as do
network operators in WA, SA, Queensland as
well as some distributors in NSW.
So if distributor Jemena says you can
have a 10kW capacity inverter installed on a
single-phase then as long as it’s compliant
with Australian Standard 4777 you can
attach panels with capacity of 13kW, 15kW
or even more. Also by not going beyond a
10kW inverter you slip in under their rule of
automatic pre-approval
9) FRAMES SHOULD BE USED TO
ENSURE PANELS ARE OPTIMALLY
TILTED TO THE NORTH
No, this is old thinking. Adding the cost of
20 or 30 cents per Watt to a system that costs
$1.00 per Watt so the the panels are ideally
tilted to eek out every bit of output from a
panel is a complete waste of money. With the
exception of completely flat roofs where build-
up of dirt and grime will be a real problem,
flat racking is the go. If space permits, you
could instead install 30%more panels for the
same price as using tilt framing. Better to install
more panels than frame – because that creates
economies of scale and brings the cost of
panels down in the future!
10) YOU CAN’T SPLIT ARRAYS ON
DIFFERENT INCLINATIONS
Yes, it can be done. Sure there is a loss of
output (in technical speech, a cosine loss
leading to voltage mismatch dynamics
because of different MPPTs within the series
strings) but this must be balanced against
other benefits in, say, reduced installation
cost and the ability to fit more panels on a
roof. The CEC guidelines say a maximum
of a 5% difference in inclination, yet most
installers won’t even do that. In reality the
guideline should be scrapped or increased to
a higher figure more like 15%, as long as the
consequences are understood and explained
to the customer and the economics of
a larger system outweigh any losses per
capacity invested.
PLEASE BURY THESE MYTHS FOR
EVERYONE’S BENEFIT
By burying these myths, Australians will be
able to buy a lot more solar panels, benefiting
from economies of scale and availability of
roof space. Electricians on the other hand
who get on board can make a healthy living
helping Australians realise their dream of
more solar panels; the environment benefits,
the nation’s grids don’t have to max out close
to their peaks anymore and customers will
be ready for their next purchase of energy
efficiency, more solar and batteries.
Myths aren’t good for solar, good for
customers or good for installers – so let’s bust
and bury them.
MatthewWright is executive director
of Zero Emissions Australia, technical director
at Efficiency Matrix.