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SOLAR POWER INVERTERS




 
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KB5MD
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« on: June 10, 2022, 12:43:17 PM »

Has anyone experienced RF noise being created by the inverters on solar panel arrays?  I have been approached about converting to solar panel power and am concerned to the possibility
noise from the inverters used.
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« Reply #1 on: June 10, 2022, 07:06:10 PM »

That is a legitimate concern.

I've helped locate some noisemakers, and a few have been domestic solar arrays.  Remedies are difficult after the fact unless it shows it is specifically Part 15 compliant in terms of radiation.

Buncha crap up & down the HF bands, varying as to array output.

If you go that way, make sure it is written into your contract they have to fix any RF noise problems affecting your ops.

Some outfits won't sell you anything if you voice that concern.

73DG
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« Reply #2 on: June 10, 2022, 08:31:50 PM »

That is a legitimate concern.

...If you go that way, make sure it is written into your contract they have to fix any RF noise problems affecting your ops.[/b]

Some outfits won't sell you anything if you voice that concern.

73DG

For sure!

in addition, some solar charging regulators often use switching regulators, but linear regulators are also available.

Inverters use an array of switching MOSFETS for conversion. Some are modified sine wave (actually a modified square wave) inverters, and some are designated as sine wave (sometimes referred to as a "true" or "pure" sine wave) inverter.

For the least amount of noise, I would choose the pure sine wave inverter.

Phil
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kg7bz
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« Reply #3 on: June 10, 2022, 11:22:08 PM »

Quote

For sure!

in addition, some solar charging regulators often use switching regulators, but linear regulators are also available.

Inverters use an array of switching MOSFETS for conversion. Some are modified sine wave (actually a modified square wave) inverters, and some are designated as sine wave (sometimes referred to as a "true" or "pure" sine wave) inverter.

For the least amount of noise, I would choose the sine wave inverter.

Phil

The "Sine Wave" is produced by high frequency PWM followed by low-pass filter or transformer. Not necessarily going to be any cleaner. All depends on how well filtered for RFI. My Outback Off-Grid system with heavy transformer makes plenty of RFI, luckily it's far away from my shack and I only use it for backup when the grid drops.

August KG7BZ
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« Reply #4 on: June 11, 2022, 08:48:10 AM »

My neighbor put in Grid-tied solar last year.  The Tech assured me it was filtered for RFI  No RFI experienced at my QTH.  The solar array is about 400 ft away. 
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« Reply #5 on: June 11, 2022, 10:55:31 AM »

I talked to my neighbor who is a manager at Ercot here in Texas....

Conversation moves to power grid reliability, and how the fossil fluid plants are being shuttered, and that includes natural gas plants.

In order to keep the grid afloat with rapidly changing conditions, they are relying more and more on artificial intelligence. If the frequency drops to 59.7hz (IIRC), an impending emergency

is about to happen due to the load exceeding the supply. The other way, a rise to 60.3hz suggests the supply exceeds the load. The EU has gone farther than us so far, and they see the issue

big time. My neighbor says Ireland is way too high on wind generation, and they have to dump excess power for free. Germany's plan to shutter all 12 Nukes is not a very timely situation. I

believe that the last two are scheduled to be decommissioned this year right as oil and NG are becoming increasingly expensive, and scarce. Imagine the economic powerhouse of Germany going dark. Wind and solar are only a partial solution.

My point, regarding solar on your home Roy, is to make it versatile such that you can maintain your homes electricity in case the grid goes down.

That means batteries, inverters, gasoline or propane or NG generators, whatever you can do options. A windmill would not hurt either!

We are spoiled, and the days of 24/7 affordable energy may be coming to an end.

Jim
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« Reply #6 on: June 11, 2022, 11:38:48 AM »

It's about time.  The atmosphere is suffering from all the CO2 emissions, like our Summers are three months longer than before.  The UV index has never been so high either.

It doesn't take much to see this happening for the first time in my 69 years here.

Voluntary compliance with alternative energy is great, but too slow.

Mandates are very unpopular, but they get the job done.

Solar out here is a great alternative, as the sun hammers us all but 4 or 5 days a year.

Panels are going in here at the Radio Ranch, for the greatest demand is during the day to run the HVAC. 

Greatly reduced grid tie for the rest.

73DG
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« Reply #7 on: June 12, 2022, 12:46:39 AM »

I just put a new roof on, and not going to nail or mount anything to it without written guarantees from the folks doing the nailing. It goes way beyond electrical noises for me. If that's not interesting or TL;DR then I understand.

My main comment is that I'm suspicious of company marketing claims for installed systems in lieu of measured facts because the panels absolutely degrade over time and have a lifetime to a 60-80% power that is about as long as the payment plan lasts. 15-25 years they say. Modern panels of high quality degrade about 1% per year. 20 years=82% output. But there are cheaper lower-tech panels being sold.

What is the benefit when the power dollars saved is no more than the price of the system? The system price is high compared to power output. Someone else is making all the loot on that deal. Might as well buy juice from the power company. I didn't mention inverter failures and timely servicing. Long term electric contract here is for 9.5 cents/kwh. By the time it ends I will have had time to finish saving up for work to increase the old home's R value.

How many square FT of panels needed to still have enough capacity after 15 years? Lifespan has been improved if you can believe the various reports but the degredation will be there.

The bypass/isolation diodes should also be MOSFETs, not diodes. The diode has a definite voltage drop, whereas a MOSFET has an Ohmic value, and also acts as a controllable switch if necessary during failure. Each panel ought have its own microinverter to get MPPT from that individual panel and so that any one failure has a smaller effect on system performance.

You never save money selling power back to the power company because 1.) the house is almost always using all of what the panels make in summertime because of HVAC, and 2.) the electric utility legally 'cheats' you in the way they buy power from you. They credit you a mere pittance per KWH, not the high rate they charge you. Some don't even pay anything, just take the juice.

The salespeople of the companies who did not want to let me see the entire contract have not had businesslike or technical answers and most just seemed to have made up stuff or parrotted brochure materials which were not pertinent to the questions asked.
There were no techincal specifications timely available, nor was there a daily capacity graph for my area including or based upon actual installations with the correct insolation (a U.S. government figure) and info about their inverters, as all are not alike though they have improved greatly over the years.

I guess they did not want to spend the time with me, and obviously they have too far many customers who are not asking questions except how soon the solar power installation can be done. Maybe I expect too much or am talking with the wrong people because there must be companies out there willing to address the noise, liability, power, and contractual concerns.
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« Reply #8 on: June 12, 2022, 01:18:49 PM »

I know that Lutron for instance, did manufacture lower EMI dimmers for 2-3X the price, so it is not out of the question that there may be manufacturing folks who are taking the steps necessary in the design.

But I would assume that they all radiate RF noise, so knowing how to mitigate is the backup plan.

Shielding and filtering at the source. And if that means locating the noisemaker, and offering help to that neighbor, I am afraid that is going to be the fastest approach.
Step 1: be nice and talk to your neighbors.  Smiley
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« Reply #9 on: June 12, 2022, 02:13:59 PM »

Sunny Boy is a great manufacturer.  They are rf silent.

What you want to do is find manufacturers that are EU compliant.  The EU doesn't put up with noisy crap.

BUT, as someone whose installed a LOT of residential solar, SMA (Sunny Boy) and Fronius are two great companies to deal with. And they are rf silent.

All wiring in bonded conduit.  Both ends!  Usually it's a plastic bushing at the solar end.  This makes a choke.
 
Twisting the 240 volt wires is also a good requirement.

Optimizers at the panels increase production and efficiency, especially when you have passing clouds, etc.  However, they are rf trash.

Having type 31 at the input to the conduits and the exit to the conduits will help as well.

I've worked on multi megawatt industrial projects and small residential.  Both have the ability to be quiet or just square wave generators.

Some panels have optimizers built in.  Avoid those like the plague!

I really like Enphase as well.  But the install gets somewhat expensive with all the type 31.  However, in a few months it pays for itself with increased output.

Let me know if you have any questions.  I've been out of it a few years so am not 100 pct hip on what's current.

--Shane
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K6IC
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« Reply #10 on: June 12, 2022, 03:17:36 PM »

YES, avoid "Optimizers", at all cost. They are switching,DC/DC converters. They are often used to comply with current Code,  and are an inxpensive way to do the requires PV Module-level of Rapid Shutdown.  Since Optimizers operate on the DC side of the process,  Part 15, Class B testing for Conducted Emissions begins at 30.0 mHz, and up, compliance with and testing for conducted emissions, is not required under Part 15.  (yes,  Part 15 does mention, that in general for non-intentional emitters,  they may not cause "Haarmful interference",  but this is probably something that needs to be determined by some Federal Coutt.
Conducted Emissions are defined as AC Line conducted emissions, using an FCC designated ACpower line interface (a "LISN").  This testing begins around 100, or 150 kHz, up to 30 mHz.

A number of Ham friends have Grid Tie systems, using Enphase Microinverters,  and they report that these are clean as a whistle.

Because Microinverters are connected to AC cables, at the PV level,  they need to pass Class B Conducted Emissions (actual) TESTING!

 ...   and so on,  IMO,  GL, Vic
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« Reply #11 on: June 15, 2022, 01:05:05 AM »

The "Sine Wave" is produced by high frequency PWM followed by low-pass filter or transformer. Not necessarily going to be any cleaner. All depends on how well filtered for RFI. My Outback Off-Grid system with heavy transformer makes plenty of RFI, luckily it's far away from my shack and I only use it for backup when the grid drops.

August KG7BZ

All inverters use PWM to control the output voltage, whether "modified" since wave or "pure" since wave, using class D, H-bridge circuits. The MOSFET switching transients produce EMI/RFI noise. The better the filtering and shielding the less switching noise one will receive.

One of the most quiet inverters I have is a pure sine wave 'medical' class inverter that is both well shielded and well filtered.

Solar panels with battery storage are great for areas such as the Southwest US or other sunny areas of a country, but suck for the northern tier states.  

Unfortunately, ideologues without much scientific training are pushing costly alternative energy sources as if it were a panacea to our future energy needs.

Alternative energy sources should be a personal choice without being mandated or forced, since the cause-effect relationship for climatic variations is very much equivocal.

Phil - AC0OB

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« Reply #12 on: June 15, 2022, 08:19:26 AM »

Using optimizers to meet code for an RSD system sure is an expensive way to do it.

RSD is basically a couple contactors. Optimizers are a lot of electronics.

I went to a house with RSD devi es in the attic.  Idiot installer had put them with the 500 volt string side, reverse polarity, to the 12 volt input side.  And yes, the 12 volt loop from the RSD pushbutton at ground level was hooked up to the 500 volt side!

This passed inspection since all the city inspector did was poke his head in the attic and ensure RSD boxes where there and conduit was going to them.

The installers where no slouched, but had never done solar.  Licensed Journeymen Electricians in California, having completed an apprenticeship program.

Cost the homeowner almost a grand to replace both RSD boxes and tum some new wiring.  Homeowner was also the owner of the contracting company.

Needless to say, I never brought that crew out for solar work.  This was my 1st job working for this company, figuring out why the owner still had an electric bill with 10kw of solar on his roof.


Those guys where great oilfield industrial electricians.  Idiots when it came to DC.

--Shane
WP2ASS / ex KD6VXI
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KB5MD
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« Reply #13 on: June 15, 2022, 05:48:19 PM »

I decided not to go solar.  It turns out the payments for several months
were going to be more than my electric bill is for those months. 
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« Reply #14 on: June 16, 2022, 09:21:13 AM »

I have gone back and forth with PV solar  and even thermal solar but bottom line is I don't want the equipment on my home.  I don't want anyone touching my home.  And of course there is the concern for EMI/RFI from a PV system.  I do have 2 neighboring homes that are about a tenth of a mile on either side of me that have PV systems.  They are silent at my QTH.  Don't know if they are quiet by design or distance away. I don't hear them, thankfully.  for now, the only RFI issue I have is with the wife's treadmill. Like to keep it that way.  Cheesy

If I were to do a PV system it would be off grid and stand alone. 
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« Reply #15 on: June 16, 2022, 09:22:32 AM »

delete this. not sure how I ended up with a dupe.
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Bob
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« Reply #16 on: June 16, 2022, 08:21:00 PM »

Shade structures are great.  They give you shade, dissipated rain, keep snow from hitting items underneath (I'd still use tarps).

They cost a bit more in the beginning, but can be placed where the tree canopy will interfere the least, etc.

I don't blame anyone for not wanting them on their roof.  Who knows what fast food restaurant the crew was working at last week.  The first crew I was put in charge of I had a 17 yr old dropout whom it was his first job and a commercial electrician.

--Shane
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« Reply #17 on: June 16, 2022, 09:08:11 PM »

There is quite a bit of grid tie solar going up around here. However, the co-op we have gives you nothing for payback and still have a base charge per month.  Only savings to be had is during sunny months. I have an energy efficient home so best case is likely $100-150 savings on the predominately sunny months. Almost nothing in the winter. Real hard to make it pay for itself at that rate and it does not solve the issue of rolling blackouts. That is what I have been thinking about. I am rural with all electric so no NG. No propane by choice.

I have a pair of electric dist. panels that I had installed when we built the house 12 years ago. A main panel and an emergency panel. All critical circuits and emergency lighting are on that panel (not AC). Let's call it panel2. I have used it probably 3-4 times since built, running a 6500W generator. Was always in the winter. That plus a whole house wood fireplace - worked good.

With gas being so high and the fear of frequent rolling blackouts (we are in the MISO region) was thinking of a different approach. Rolling blackouts in the summer would mean mostly sunny days and hot nights.

What I am thinking about is a dedicated inverter to run Panel 2 with enough PV to carry the loads during the peak of the day, with battery to cover the nights. Use the Panel 1 grid feed to run a battery charger to keep the batteries full if the PV cannot recover it daily to 100%. So panel2 is effectively off grid, in my opinion.

I would like to have AC on it. I have a WaterFurnace GeoThermal system so I am now looking to determine the peak power it needs and the average daily consumption to just run the system for AC only. On the furnace it shows a 1hp blower motor and a 1/10 hp load from the loop pumps. That does not sound like a heavy load. I think I have capacity on Panel 2 for that.

Now it may be a lot cheaper to just install a propane generator, but the run time costs are variable and subject to the market. A PV system would have higher up front costs but lower runtime costs.

My 2 cents.

John

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« Reply #18 on: June 18, 2022, 11:46:35 PM »

Using optimizers to meet code for an RSD system sure is an expensive way to do it.

RSD is basically a couple contactors. Optimizers are a lot of electronics.

  ...   WP2ASS / ex KD6VXI

Since the later Code seems to have gone to the requirement for RSD of individual PVs,  there are not too many inexpensive ways to do this.  MicroIinveters, and Optimizers on each PV module,  seemed to be the least expeisnive way to meet this new Code requirement, as I read it.

More and more, fairly simple things become more complex, and more highly-regulated.

FWIW,  all, IMO,   73  GL    Vic
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« Reply #19 on: June 19, 2022, 12:08:23 AM »

I've given more thought to our PV system design here.

I'm not going to arrange anything with our utility nor connect it to the grid. 

The lions' share of electrical demand out here is running HVAC devices. 

So, the PV output will be monitored to judge available load vs HVAC demand, and will switch to that load automatically only when able to do so.

The rest of the house and property will just get juice from the grid, no big deal.

Too much crap to go through with grid-tie systems. None of their business this way.

73DG
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« Reply #20 on: June 19, 2022, 08:02:40 AM »

Using optimizers to meet code for an RSD system sure is an expensive way to do it.

RSD is basically a couple contactors. Optimizers are a lot of electronics.

  ...   WP2ASS / ex KD6VXI

Since the later Code seems to have gone to the requirement for RSD of individual PVs,  there are not too many inexpensive ways to do this.  MicroIinveters, and Optimizers on each PV module,  seemed to be the least expeisnive way to meet this new Code requirement, as I read it.

More and more, fairly simple things become more complex, and more highly-regulated.

FWIW,  all, IMO,   73  GL    Vic


Agreed.

And this is one of the reasons I've always been a fan of Rnphase and a couple other micro inverter mfgs.

There is another company that has 4 panel inputs on its micro inverter.  Each input had MPPT and then they aggregate the DC and convert to 240.

Enphase, SMA, etc also offer island mode.  Island mode allows your solar system to operate with no 60 hz signal to sync to....  Enabling it to provide you with 240VAC during blackouts.  You just need a transfer switch.

I've also done the following.  Henry, in their rf generators, has a 240 to 120 xformer. This allows for 2 wire 240 or 208 to be stepped down and ha e a neutral for code compliant 120.

I used a pure sineeave inverter hooked to the battery in my work truck.  Fed that into the 120 volt of the transformer.  That gave me 240 volts.

Turn off the main panel to grid 200A breaker.  Feed the newly acquired 240 volt signal I to a dryer outlet.

BAM, we had 20kw of solar powered electricity.

Total amp draw from the truck was a couple amps. The inverters for the two solar systems don't take squat for sync.  As soon as they saw 240 volts they fired right up.

This trick also works with generators.  This allows inverters with no island mode to still power the house.  The only caveat is you need to be AT 60 hz or the inverters won't fire in most cases.

We have solar galore here on the island.  With over 300 days a year of blazing sun, it's a no brainer.  Only downside is the local utility doesn't pay for over production. 

Simple, put any overage into batteries and use it to run for free at night!

--Shane
WP2ASS / ex KD6VXI
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« Reply #21 on: June 20, 2022, 04:27:50 PM »

Has anyone experienced RF noise being created by the inverters on solar panel arrays?  I have been approached about converting to solar panel power and am concerned to the possibility
noise from the inverters used.

You betcha -- and one of the worst offenders is SolarEdge and their optimizers.  Someone a few doors down from me has one of these systems and it's basically destroyed most of the HF band during the daytime.  Got the local club involved, and then the ARRL -- who contacted SolarEdge about my situation.  SolarEdge has now committed to fixing the cheap, RF-spewing junk they installed down the street.  Fortunately the homeowner has been helpful.  If you don't complain, the manufacturers never fix it....
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