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E L E CT R I C AL CONNE CT I ON
S P R I NG 2 01 5
THE SHADOW
The panel game
T
he maintenance of domestic
solar photovoltaic systems is a
neglected area.
It’s an area in which a business-like
approach to householders might give
a skilled person the chance to render a
service and make some money.
On the economics – other than
‘grandfathered’ feed-in tariffs of about
60c/kWh – a 12-panel installation will
potentially earn about $600 a year, or
reduce the energy bill by that much.
Battery storage could substantially
increase these savings. Based on a
period of 20 years, the savings for a
non-storage system are about $12,000,
but with a drop in installation efficiency
this would come down dramatically.
The owners might imagine themselves
doing the planet a favour, but they would
not be doing that very effectively or see
an economic benefit.
A check-up every two years might
be annualised at $150 for labour, and
installations more than four years in
service would be candidates.
PV panel and inverter efficiency
is the main aspect to consider. PV
panels degrade, and manufacturers’
specifications state the fall in efficiency
over time. The inverter does not degrade
slowly over time, but it can suddenly
lose conversion efficiency. Householders
wouldn’t be aware of this, except maybe
when the electricity bill arrived.
Other problems that can occur with
grid-tie inverters may require grid voltage
monitoring, as inverters are allowed to
operate only within a voltage range of 204V
to 268V. This is a particularly nasty problem
in relation to the upper voltage limit, when
inverters cut in and out because of voltage
spikes. It is an ’unseen’ problem in that the
inverter is sound but little or no energy is
being fed back to the grid.
This is not directly a service problem.
However, by doing a test on an installation
– particularly one in a street of PV
installations where the problem
is likely to be prevalent – a contractor
can alert the owners to contact their
energy distributor.
Sudden failures are quickly checked by
testing the inverter’s AC output. Failure
or degradation of the DC link is usually
because of the electrolytic capacitor.
There’s not much to be done on the spot,
but the inverter can be returned to the
authorised service depot.
Panels sometimes degrade faster than
expected. Thin panels are more subject
to induced degradation than thick panels.
Voltage across the cells with respect to
the grounded frame causes a drift of
sodium ions in the protective glass and
affects cell performance.
Testing all this is ‘hairy’, but doing a
rooftop inspection, armed with a DC
tongue tester, will allow the DC power to
be measured and can put the owners of
the PV installation at ease that the panels
are doing their job.
On the other hand, the failure of
some cells on a panel may be apparent.
Timely replacement of a panel or panels
is very important and can be subject
to renewable energy certificates being
available to discount the panel cost.
In summary, the combination of a DC
test and AC output test, of themselves not
difficult to perform, will indicate the basic
health of the PV installation.
Maintaining solar systems can
be a good source of business
and customer peace of mind,
writes
The Shadow
.
with
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