micro inverting verses string inverting vs no inverting ..

offgriddle

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OFTEN, when reading a post that a DIY forum member took the time to share, I find the need to read up on some of the terminology not only for reasons of plain curiosity but also for possible use with my own system.

I am aware of micro inverters and string invertors but have not allowed myself to think big enough to consider using them to improve the efficiency of my system.

I suspect that transporting voltage above 48vdc, and/or inverting to 120 or 240 AC most likely means electrical codes apply accordingly.

I like the idea of increased efficiency due to higher voltage when transporting current from the array to the SCC but have questions.
 
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nosys70

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micro inverter is a clever way to put any number of panels in parallel .
you can add 1 or 100 panels , it does not make a difference in the setup.
the only drawback , is you got many inverter (increased risk of having a bad one) , usually at an exposed location (under the panel) and high voltage in the wiring.
Added to that that is probably more expensive.
 

offgriddle

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micro inverter is a clever way to put any number of panels in parallel .
you can add 1 or 10 panels , it does not make a difference in the setup.
the only drawback , is you got many inverter (increased risk of having a bad one) , usually at an exposed location (under the panel) and high voltage in the wiring.
Added to that that is probably more expensive.
More components in more places, (often very hard to get to), and more costs, I see, thank you.
 

offgriddle

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Some can be put in your shed/garage...they do not need to be near/under/beside solar panels ( so, either have 5-10-20 feet of solar cabling from roof microinverter to house/garage/shed or have 5-10-20 feet of solar cabling from solar panel mc4's to microinverter that is in house/shed/garage [this way may require more mc4's and wire , but those are cheap to purchase and give one an easier go at, if ones microinverter malfunctions).

Or am i wrong in the above?
Well, I've not researched remotely locating micro invertors to a convienient location using short cables, but it sure would solve the problem of going to the panels on roofs and racks to access the microinvertors.
 

nosys70

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but then you negate the advantage of micro inverter not requiring thick wire for low volt/high amps.
really not a good solution since instead getting benefits , you cumulate disadvantage.
 

nosys70

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when you see the diameter of the metallic part of the MC4 , you know it is is very limited to a few Amps.
MC4 should be used only to connect panel to main wiring.
using MC4 to put panels in parallel is very suspicious IMHO.
The best is to use a busbar in a box and set 1 MC4 for 1 Panel.
unfortunately you find weird frankenstein MC4 coupling to put 4 panels in parallel .
Could work for 4x 50W panels, but if you use 4x 250W panel, expect problems
 

nosys70

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MC4 is UL approved for 20A, but you can expect that at 20A you really need a good MC4 , not a cheap china copy.
MC4 can accept 4-6mm2 so you can check what is 4-6mm2 able to support .
 

offgriddle

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My next set of panels i am gonna pop the back case off and see if i can remove cabling, if so I will then string 2 lines of either 8 or 10 gauge wire directly from solar panels to joiner box or microinverter or... ( in shed/enclosure... easier accessed). This will get rid of some or all mc4's.

I am not convinced that mc4 connectors either enhance or detract from the flow of dc current, what I have experienced tho is "more things added to something can increase the potential of problems".

I would like to see someone take a 10' wire, cut it every 1 foot then add mc4's at each cut then measure if there is any significant loss-- i doubt their would be significant loss, maybe 1-2-4 watts?????
I know from a matter of training and practical application that connector losses at high frequencies are a given and substantial enough to measure and calculate, (in db loss), when designing, building and maintaining RF systems.
The 50 and 60 cycle per second electrical power AC waveforms are much less active than the RF AC waveforms which cycle thousands, millions and billions of cycles in one second, so the loss characteristics are different.
IF a AC or DC connector is made of the same or superior metal as the wire and is of the electrically equivalent gauge or greater and is perfectly mechanically mated to the wire and has never experienced any arcing which causes resistance and creates losses via heat from carbon being created in the connection, then I'm guessing that the connector losses while probably still measurable, are negligible.
Each connection, however, is one more opportunity to create loss and mechanical vunerability, so, just like keeping wire lengths to a minimum, keep your connections to a minimum as well is my recommendation.
PS: I believe there are connector loss charts available somewhere.
 

DThames

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More components in more places, (often very hard to get to), and more costs, I see, thank you.
I have a ground mount system that I can walk under and easily access my micro inverters. If there is a failure, the entire system is not down, just some fraction. Proper planning and selection are important, as there is no single best solution, for all cases.
 

offgriddle

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A
I have a ground mount system that I can walk under and easily access my micro inverters. If there is a failure, the entire system is not down, just some fraction. Proper planning and selection are important, as there is no single best solution, for all cases.
Agreed.
I also like the fact that only the production of one panel is lost when one microinvertor malfunctions, shading is less of an issue and especially that you do not have to be a trapeze artist to access your panels!
 

offgriddle

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"Enphase" or "Cyboinverter" to name 2. I am more inclined towards Cyboinverter: "...2. A CyboInverter can connect to multiple solar panels that may be different in types, sizes, and sunlight orientations...." - i take this to mean if you have a hodgepodge of panels (145/230/245/300watt) it doesnt care (if you read the info differently let me know) and if you are running a 12v system all you would need is 3 panels connected to AC load(s) and 1 to your battery to keep er charging/charged.

The "CyboEnergy" site is quite unique.

GL.
I see, the ability to allow for varying panel wattage production is a nice feature, but perhaps the capability of individual microinvertors to successfully output power regardless of what the other panels are doing, is inherent because each panel acts as it's own stand alone power producer, regardless of the manufacturer brand of the microinvertor?
I'll check out the Cyboenergy site thank you. 😎
 
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offgriddle

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One can place Cyboinverters in their shed/garage/barn.... so no need for "Cirque de Soliel" actions on varying roof pitches!

Great info on their site, i liked the FAQ, "Overview" section under "Solution" headingand mostly the "Inverter Technology" under the "Technology" heading.

I havent seen anything with the qualities and abilities of this, yet.
Wow, learning quite a bit thanks. Did you know that, "Solar charge controllers claim that they have MPPT. When putting multiple solar panels together in series and/or parallel, the I-V (Current and Voltage) curve of the DC source will most likely have no single MPP (Maximum Power Point). Thus, the claimed Maximum Power Point Tracking (MPPT) in solar charge controllers can get stuck in a "local maximum power point" and unable to harvest the available solar energy.

Because CyboInverters has an MPPT for each solar panel, the partial shading problem is eliminated. In other words, one partially shaded panel will not affect the performance of other panels. This is an important feature that allows the off-grid CyboInverter to deliver AC power to the load reliably and smoothly"?
 

JeepHammer

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1. Redundancy.
Micro Inverter per panel allows for any panel/micro inverter to fail, be shaded, ect and NOT effect the rest of the production.
The issue is, they are VERY sensitive to overload, most micro inverter systems are 20% to 40% 'Over Paneled' to compensate.

2. Losses.
While full production/Full useage is quite efficient, anything you produce above & beyond usage is wasted entirely (Without Grid Tie).
You WILL need a 'Timing' source off grid, a battery powered inverter to produce the sine wave form so micro inverters can sync.
No 'Signal', no Sync, no power.
ANY glitch will take 10-30 minutes for inverters to sync.

3. You can't 'Mix & Match' micro inverters.
As far as I know, and I've been reading a lot about AC coupling, They only work with their same brand/type/model.
Several threads about replacing failed emphase (spelling?) brand with newer model and NOT working, buying 'Spares' wouldn't be a bad idea if you intend to live in the same house for 10 or 20 years.

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Every connector will eventually fail. Period.
The seal will dry out, the terminals will corrode, particularly conducting DC power.

NEC only recognizes 20 Amps through an MC4 connector, which I just ran onto myself...
A good, solid, sealed up splice will be there 20 years from now, and it's a small price to pay for 20 years of reliable service...
Particularly in harsh environments.

---------------------------------------------

Most bigger (whole house 240V) inverters support TWO STRINGS, and I just found out why from an installer with 15 years experience.

Most high powered strings are permanently mounted,
On a home, that's East *OR* West facing with peaked roofs, not flat warehouse roofs...
That means full power in the morning from the east facing string,
Leveling off around noon when sun isn't at optimum for east or west facing panels,
And full power again after noon sun for the West facing high voltage string.

Big SINGLE STRING inverters are almost exclusively used in solar fields where panels track the sun, or big, flat warehouse roofs where all panels are orientated the same way.
-----------------------------------------------

As long as AC is the king of power appliances, inverters will be needed, 'Ugly' or not.
With my remote strings, I'm simply going to plug in an AC inverter to contribute to the 'Common' 240 VAC lines and use AC power supplies/battery chargers directly off panel production.
No more of the uber costly Battery Charger combined units that don't like to charge *MY* specific kind of LFP batteries.
Power supply/battery charger set specifically for my LFPs and forget it, charger on a timer for peak sun so everything is producing when batteries charge and walk away...
Truly 'Plug & Play' with no chances of damaging my SPECIFIC LFP strings/banks, and I can add as many solar strings as needed to fully power everything with AC Coupling.

These are my retirement years, I don't want to mess with 'Managing' every detail every day, so I'm throwing some money/equipment at it for specifics with 10 or 20 year warranty stuff and going fishing! ;)
 
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JeepHammer

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Ok, I just found some things called " (AC Module) - Loom Solar 375 watt mono panel"-amps are not great...yet-there are others, looking good tho.

Form follows function...
25-30 years ago the power output from 'Consumer' panels was aimed at amperage since cell count was limited.

Now the commercial systems drive voltage up and keep amperage very low.
Suits me fine other than I have to make a switch-over from Parallel to Series wiring at the panels, and replace inverters to high voltage rather than high amperage, but at 20+ years old on some of my stuff, that change isn't a big deal since my stuff has lived WAY past it's expected life span anyway...

Now virtually everything is 'Transformer-less', that wasn't the case 30 years ago.

There is, and will always be, economy in scale.
There will always be reliability in redundancy.
While a 'Modular' (component) system is easier to service, and any one failed part can be replaced,
The integrated (all in one) systems are a little more efficient, but lack redundancy.

Technology has reached the point where discounting panel efficiency,
The inverters are 98-99% efficient with low amps/high volts, no battery power conversion losses in the middle...
Batteries are still the least efficient way to do things, but absolutely necessary if you intend to have power overnight.

Since 90% of my usage is in the daytime, a micro grid, converting high volt DC to AC is the most efficient route, but I still need a DAY OR TWO of batteries/generator since it's common not to see the sun for a day or two.
I want every WATT I can harvest when the sun shines, and in *MY* case, I think micro-grid tied inverters on high volt panel strings is the way to do it.

Everyone else will have to assess what they want/need, I can't answer those questions...
In 20 more years everything might be micro-inverter, or it may go another direction.
Keep in mind solar only went main stream in the US about 20 years ago, and the US invents most of the technology, so who knows where it will go in 20 years?
 
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Supervstech

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but then you negate the advantage of micro inverter not requiring thick wire for low volt/high amps.
really not a good solution since instead getting benefits , you cumulate disadvantage.
Why?
Each panel would still have its own microinverter, and single conductors from each panel... they are just longer, to feed the MI a bit further away...
 
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