[RFI] SOLAR INSTALLATION PROS/CONS

[Carter, Michael]

Bob,

I developed and taught for 15 years a university-level
engineering course on renewable energy systems
design, which was principally devoted to PV systems
design.  Here are some recommendations if you're
evaluating PV for your own use - getting neighbors
to regard the RFI issues with the same degree of
seriousness is a much stickier wicket.

1) Sacrifice some overall conversion efficiency by
using a single central inverter (if your array isn't
so large as to require paralleled inverters).  Do
NOT be sold on the use of microinverters (solar optimizers)!
The microinverters do increase overall system conversion
efficiency, but at the expense of adding typically
one microinverter per PV module.  That multiplies
the RFI by the number of PV modules.  The microinverters
enable use of smaller wire gages and standard interconnect
bus voltage (240 VAC) to the array junction box, and that
was (and even more so now is due to copper prices) a significant
cost-savings by not requiring custom array designs (number
of modules per string and number of paralleled strings)
and heavier interconnect wire gages.

2) A single central inverter has MPPT (maximum power point
tracking), which is also the principal selling point for
the microinverters (each of which has MPPT to
extract maximum power from its PV module under
variable illumination and partial shading conditions).
The central inverter designs sacrifice some overall
efficiency because they can only compensate for
array-scale variability of the composite I-V curve
over temperature and solar irradiance, especially
non-uniform shading of the PV array.
A competent PV system designer will generate a
detailed site shading analysis for the array and will
qualify the design's power output over the course
of a year, then adjust the array design to ensure
the customer's needs are met.

3) Insist that the inverter selected by the installer
meet FCC Part 15, Class B radiated emission standards.
Go further and insist that the inverter meet
conducted RFI limits on both the DC and AC
sides.
Dave, W0LEV, is correct in that the FCC does not
specifically regulate PV system RFI emissions.
However, emissions from unintentional RF radiators
(e.g. switch-mode DC-DC or DC-AC converters) ARE
subject to FCC limits, and may be subject to FCC Part 18
limits as well.  I have read several web sources that
suggest that PV systems are exempt from FCC RFI
regulations, and this is NOT true.  The PV modules
generate DC, but the module and array interconnect
wiring makes wonderful antennas for the switch-mode
power converter signals if these are not filtered
adequately for both differential- and common-mode
signals at the switching frequency and its harmonics
(up to the 10th harmonic or so).

4) Ask your installer for references to other installations
done nearby within the past 2-3 years.  Take a portable
shortwave receiver and visit the sites during the
day and again at night.  Be sure that the installation does
not have a battery storage unit - the central inverter or the
battery unit itself (with self-contained inverter) will
continue to generate RFI at night using the stored battery
energy.

5) Contact the installer's preferred inverter manufacturer
and ask if an independent testing lab has measured both
radiated and conducted RFI.  Ask for those results if
available, and if not available, choose a different inverter
manufacturer.  Better yet, ask the manufacturer to hire
K9YC as a design consultant!

73,
Mike, K8CN



________________________________
From: RFI <rfi-bounces+mike.carter=unh.edu at contesting.com> on behalf of Robert T. Devine <rtdevine at comcast.net>
Sent: Sunday, May 23, 2021 3:32 PM
To: rfi at contesting.com <rfi at contesting.com>
Subject: [RFI] SOLAR INSTALLATION PROS/CONS

Caution - External Email




Looking for information from those that have experienced Solar Installations



Pro's and con's appreciated



Thanks



Robert T. Devine, KC6AWX

Manager, ARRL 6th District Incoming QSL Bureau



"Save a Life...Become an Organ Donor"

'Be kinder than necessary, for everyone you

meet is fighting some kind of battle.'



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