RFI

[Thos]

Hi there,

I have a project coming up that will require products to be very quiet with respect to RFI.

I have been out of the game for a few years now so I am not up to pace with current product.

I was among the installers on the wrenches list for several years - now in retirement - in theory.

I will need 4 systems with 1kW solar and a battery bank capable of delivering 1 kW for 8 hours to 50% DOD

The application will be for remote Ham radio.

Would appreciate advice on current best solutions.

Many thanks...

[qrper]

FYI

I too was worried about the RFI generated by the Classic controllers. So far, I haven't been able to hear the controller in any of my radios. I have yet to set up the spectrum analyzer to see what if any gunk it's producing. It's a case of good old fashion common sense.

Don't put the antenna feed lines close to the controller. Use coaxial cable if you can and not open line feed. Use a single point ground and ground the @*#& out of everything. There is a dc ground and a RF groundâ€"same thing but different!

One controller I had used in the past had so much junk on it I ended up sticking .01 caps (voltage rated high enough do they didn't pop!) across the PV input wires. A large 50kmfd cap was parallel on the battery side. Think I may have even stuck a few .01 across that line, too.

Ferrite cores might be needed, but that will be location dependent.

You didn't mention if you're running the radios directly across a 12 V buss or if the buss is 48 V and you're inverting. Those high frequency inverters are God awful bad when it comes to RFI.

Location, location, location! If possible, place the antennas as far away from the controller as possible. Line loss will not be as much of an issue if you have a S-20 noise level.

Not much help, but that's all I have with the limited info you mentioned in your post. Keep us all up to date

73
I'm mike, wb8vge

[Vic]

Hi Thos,  welcome to the Fourm.

Very briefly,   in general,  MPPT Charge Controllers create the greatest RFI signal levels at the lowest end of the frequency range.  For Hams,   this would be on 160 & 80/75 Meters.   Diminishing in level for every octave increase in frequency.

Of course,  160  is generally useful when the sun is near or below the local horizon.   80/75 M  can be more impacted that 160,   but  …

The most pesky emissions from MPPT CCs are conducted on the cables that connect to the PVs and battery.

Common-Mode chokes can be effective for the HF frequencies,  when placed on these cables,   close to the CC.

Some recent discussion here:
http://midniteftp.com/forum/index.php?topic=4922.0

And,   look at the Link to the Wind-Sun Forum for a lengthy discussion.

More later,   73 GL,  Vic

[Thos]

Hello again,

Thanks for the responses.

In a past life I designed 9 solar powered cell sites for the Sydney/Brisbane motorway, they worked flawlessly for years until taken out by the Australian bush fires. They had no backup generators, we used what was Canon/Unisolar ASi panels because you could shoot at them and they still worked.

So vandal proofing will be an issue in at least two of the sites. (you cant control fire without large fire breaks)

Big picture wise, the radio will be in a grounded metal enclosure directly under the tower.

If I have the array some distance away along with the battery bank, inverter and propane backup and bring 230V back underground - I am thinking say 200 ft. Maybe this distance will be overkill if we manage the RFI from the inverter?

This by the way is a non-commercial operation supported by philanthropy to give global coverage for ocean sailors.

I will be looking for someone to step in to set the first one up in the US. Firstly however I would like open dialogue to ascertain the best possible options.

There are several such installs on the remote ham network in the North, maybe someone here was involved?

I am looking into registering the sites for marine as well as ham if possible. The target freq range will be 80 thru 10.

Since the earthquake in Nepal and the considerable role that ham played in bringing relief to a country cut off from the world, We will be well positioned to assist globally during such events.

So the target is very low noise floor. The sites will be un-manned.

Are we allowed to comment on any product range on this forum? There may be very quiet inverters/controllers available...

Greatly appreciate your thoughts.

Carl Emerson
ZL3CX

[boB]

Thos, comment away here !

We are pretty much familiar with most controllers and inverters but maybe not all that might be used in NZ.

80 through 10 meters will be bands to watch out for though.  The Classic itself has its highest RFI at around 40 MHz.

The switching frequency is around 25 kHz so you may hear "something" every 25 k.  But far enough away, and maybe 200 feet might be enough, and that EMI should come down a LOT.

The Classic did/does comply with FCC part B EMI but with a common mode ferrite on the power lines inside of the wiring compartment.  I think these were similar to #41 material ?  We just put all  3 or 4 wires (3 if common negative used) through the ferrite tube or toroid.

At thats distance, the PV might be the most worry because it can turn into somewhat of an antenna.

Common mode filtering and grounding should help a lot if it does turn into a problem.

I cannot use my HF radio here in Washington state at home anymore because of all of the neighborhood electrical noise.

Another way of reducing EMI from solar chargers at least is to use PWM type controllers (slower frequency) and just add more PV which some do.


You will want to put up the PV array in any case which may be the hardest part anyway and see how well or how bad ANY controller does in that scenario.
Maybe even a cheap Chinese controller just to see how much EMI you get at that distance.

I would LOVE to have a semi-remote site that is line of sight to my house to be able to use HF without EMI.  Maybe some day

[Thos]

OK excellent responses...

A few odd questions.

Long gone are the days of the democracy rack - the results were too embarrassing. I still have the raw data from the shootout in California... the results were gagged.

The issue is I would prefer again panels without glass if possible.

Are there ASi panels available these days that are up to the mark.

And how long did Say US64's from Unisolar perform to spec???

Cross brand testing I did yielded threatening phone calls. Is the industry still misguided regarding real world performance of current product. Label data meant very little when measuring real world power out over say 6 months. Degradation at temperature was a serious problem with major brands loosing 40% power in hot sun.

The Sydney Olympic Stadium was powered by 1100 Cannon ASi panels grid tied in the year 2000. I would love to know if the product lasted well - does anyone know?

[Vic]

Hi Carl,

As you know from your Solar design days,   MPPT Charge Controllers allow great latitude in choosing PVs,   due to their ability to use PV String voltages that are several times the battery voltage.

PWM CC,   need the PV input voltage to be a fairly small amount above the nominal battery voltage.   So choosing batteries and PVs are closely tied together.

Most MPPT CCs are not Emission tested on the DC input side,   below 30 MHz,   as the FCC Class B tests below 30 MHz are  ONLY done on cables that connect to the AC Grid.  The specified interface (the LISN) is a device that couples the AC line conductors to the Spectrum Analyser (or whatever is the emission test device).  Our CCs do not connect to the Grid,   so  no tests are done.  [FCC Part 15,   does state that  Unintentional Radiators,   may not create harmful interference,   but the definition of "harmful",  is subject to interpretation.   ALL,  IMO.

Here,   we do notice the birdies from MPPT CCs,   spaced at 25 KHz intervals,   on 75/80M.   Their intensity varies  with the amount of power that the MPPT CCs are producing.   Here,  we use Classics,   other MPPTs,   like the KID,  use a bit higher switching frequency,   which will increase the spacing of the birdies

Speaking of 80 Meters,   our antennas for this band are,   generally large,   and have a lot of capture area.   It can be difficult to locate a wire antenna far enough away from the PVs,   and sometimes the AC power conductors.

As boB suggested,  you might want to experiment with different CCs.   PWM  CCs are bound to be quieter than MPPTs.   But the top-notch MPPT CCs,   like the Classic (and KID),   have many,  many functions that are generally absent from PWM  CCs.

We are in the process of making some changes to one system,   here.  This will include trying some new Common Mode suppression on the PV in,   and the battery cables on a Classic.    Will see how much difference this makes we will see.

Know nothing of ASI PVs.   A neighbor had 40 US64s for many years,   and they did not seem to loose too much production vs time.   But did not run any tests.

Later,   73,   and have fun with this very beneficial project.   Vic   kilo six italy charlie 

[Thos]

Hi Vic,

From your comments I imagine with a beam up at at 70 feet and the Array,MPPT/inverter/propane generator 200 feet away in seperate shielded enclosure with seperate DC ground we will have a good start. The trick will be to find a good installer able to work in Texas who really knows what he is doing. I imagine we will have a fan dipole for the lower bands.

Incidentally are they still manufacturing passive solar tracking racks with refrigerant in the frame?

Carl E.

[ClassicCrazy]

Hi Vic,

From your comments I imagine with a beam up at at 70 feet and the Array,MPPT/inverter/propane generator 200 feet away in seperate shielded enclosure with seperate DC ground we will have a good start. The trick will be to find a good installer able to work in Texas who really knows what he is doing. I imagine we will have a fan dipole for the lower bands.

Incidentally are they still manufacturing passive solar tracking racks with refrigerant in the frame?

Carl E.

Looks like they do still make those trackers.
My neighbor has some that were installed in 2000 and they still work.
http://www.zomeworks.com/photovoltaic-tracking-racks/
Larry

[Thos]

Excellent Larry thanks...

[qrper]

Way back when I was a dealer for the Unisolar panels. They came with a lot of hype, and I did sell quite a few. For reasons unknown to many, they were sold off and then quietly went away.I don't know if they are even sold anymore.

One of the issued I knew of with the early US-24s were they delaminated. These were the panels that didn't have a aluminum frame around the active material but rather the substrate that the cells were stuck to was bent at 90º to form the frame. The idea of course was to eliminate the frame and thus save $$$ on production costs.

The idea was great, but in real world applications, it fell flat on its face. Unisolar ended up wrapping an standard aluminum frame around their  panels.

Unisolar also made a larger panel that was rated at 64 watts, The US-64. The first generation  had a plastic frame, and this first generation lost about 40% of their output within six months. Some out and out failed in the field. They later came out with a triple cell coating that helped dramatically with the lost of power. They rated the panels new at about 70ish watts knowing that after a few months they'd degrade to 64, and they'd hold there for decades.

I met Stanford Ovshinsky, the guy at the heart of Unisolar,  at his Troy Michigan solar research facility around 82 or so. Heck, I even gave a talk there, too. A brilliant mind to say the least.

Now you have to remember, this was the early 80s and solar panels were still $5-$7 a watt, and with Ovsinsky's thin film amorphous solar panel technology, anything that didn't move could be made into a solar panel.

That was a great time to be into photovoltaics. It was more magic than science! I remember way Back when, a group of long haired pot-smoking hippy type tree hugging green freaks all met in Washington state and started building DC to AC inverters. What an amazing time to be alive!

[Thos]

Yes for sure, I remember the days well. I got into RE in 1997.

I provided the electronic control for the 1kW Soma wind generator designed by Harold Ward from Canada.

I was the National distributer in NZ for Canon before the were bought by Unisolar.

I provided the solar for the first solo crossing of the Atlantic - rowing... We used US32's valcro'ed to either side of the boat to run the water de-salination unit.

I used US64's to run a chicken hatchery on the Solomon Islands. A cyclone ripped them off the roof and they tumbled down the road. The locals found them and put them back - the system continued to run beautifully.

There is a system still net metering after 20 years with 96 Unisolar EF2-60 roofing panels - No issues.

A hail storm with hail the size of golf balls hit Sydney and many Mono/Poly arrays were destroyed but the ASi panels were fine.

They were the days...

[Thos]

Hi Vic,

From your comments I imagine with a beam up at at 70 feet and the Array,MPPT/inverter/propane generator 200 feet away in seperate shielded enclosure with seperate DC ground we will have a good start. The trick will be to find a good installer able to work in Texas who really knows what he is doing. I imagine we will have a fan dipole for the lower bands.

Incidentally are they still manufacturing passive solar tracking racks with refrigerant in the frame?

Carl E.

Looks like they do still make those trackers.
My neighbor has some that were installed in 2000 and they still work.
http://www.zomeworks.com/photovoltaic-tracking-racks/
Larry

Larry - I looked at the website, they no longer make passive trackers - just powered models now.