Enphase field MTBF: M190: ~36 Years M215: ~316 Years M250: >357 Years

ltbighorn said:

It seems like you're preferring to cycle out units that still have warranty left on them for new units (characterizing it as "extending the warranty by X years"), but I presume that essentially sacrifices the warranty on the existing ones.

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You're right, it does sacrifice about 9.5 years of warranty on each unit that becomes a cold spare. (The M190s only came with a 15-year warranty while the newer units come with 25.) But I will point out that each time an M190 fails, it gets replaced by a new, fourth-generation unit that has no more warranty, but that likely has a 25-year life.

ltbighorn said:

What's your thinking behind that? Is it primarily a side-effect of trying to get more failure-prone M190s off your house roof, or is it also for its own sake?

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Getting them off my roof is the primary motivation. The MTBF of the original M190s is nearly 20X worse than that of the fourth-generation Enphase microinverters. Repairs on my roof are significantly more difficult than those done in the field, which are trivial.

ltbighorn said:

If not the former, then why keep so many spares right now, vs. buying them later?

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The issue is that the PV modules in the field are 72-cell units while the ones on the roof are 60-cell modules. The original M190s will work with either type of module, but the fourth-generation microinverters (including the M190IG replacements that Enphase is now shipping out) will NOT work with the 72-cell modules in the field. So I had a choice: spend the next 10 years replacing M190s on the roof one-at-a-time as they failed and end up with a dead field array after about ten years or purchase new, high-reliability inverters for the roof and create a stockpile of 72-cell-compatible microinverters that I can swap in as they failed. Since ALL of the M190s are likely to fail before ANY of the fourth-generation units fail, my stockpile of M190s will slowly be converted to fourth-generation M190IGs as Enphase replaces failures.

ltbighorn said:

Are you concerned that secondary supplies will dry up?

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Yes, but primarily for the 72-cell-compatible microinverters. 60-cell-compatible microinverters will be around for many years to come. The original M190s are both less reliable AND they have a shorter design lifetime. As a result, the quantity available is shrinking rather quickly. In addition, the quantity manufactured was significantly lower than the number of fourth-generation inverters. Sure, you can purchased used M190s on eBay, but why would anyone want to do that? Used Enphase inverters carry NO warranty, so you risk getting a unit that is dead or malfunctioning or will be soon. OTOH, I have been able to purchase NEW fourth-generation M215IGs with 24 years or more of warranty remaining on eBay. The last 16 NEW M215IGs I purchased were under $100 shipped!

As it stands, I currently have 37 original-style M190s (not counting the four that I sold show ever in the Mountain Array). 12 are in operation in the Field Array. Of those 12, 11 are currently malfunctioning but not badly enough to get Enphase to send replacement hardware. Enphase requires energy harvest over one week to be below 90% of their neighbors to warrant replacement. (I told my wife these have malfunctioning inverters been "put out to pasture". ) The 25 cold spares were all functioning properly when they were removed from service, so I know their condition when they go back into service.

The bottom line is that I am now very hopeful to get an additional 25-to-30 years out of all of the equipment that I currently have and With some good fortune, that will only entail a small number of future trips onto my roof.

Do you happen to know the failure mode of these offending units? By which I mean, have you taken one apart and looked for a smoking gun (or capacitor)? Just curious. If you find yourself in a bind, I wonder if you could repair them yourself. Maybe even find better quality parts if the problem is that Enphase cheaped out.

BTW, unrelated, but I had a second M215 fail on me last week. It started to sputter out in direct sun on Tuesday and Wednesday (still worked in the morning/evening). Then Thursday it finally gave up the ghost and quit for good. Time to call the installer back.

GetOffYourGas said:

Do you happen to know the failure mode of these offending units?

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No, I really have no idea beyond guesses.

GetOffYourGas said:

By which I mean, have you taken one apart and looked for a smoking gun (or capacitor)?

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No. All the failures have been under warranty, so they go back to Enphase as soon as they fail.

GetOffYourGas said:

Just curious. If you find yourself in a bind, I wonder if you could repair them yourself.

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No, these units are potted in epoxy. That makes repair practically impossible.

GetOffYourGas said:

Maybe even find better quality parts if the problem is that Enphase cheaped out.

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I seriously doubt Enphase used anything except the highest-quality components. Most likely any failures are due to solder joints failing due to thermal stresses.

GetOffYourGas said:

BTW, unrelated, but I had a second M215 fail on me last week. It started to sputter out in direct sun on Tuesday and Wednesday (still worked in the morning/evening). Then Thursday it finally gave up the ghost and quit for good. Time to call the installer back.

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I'm sorry to hear that. I have updated the spreadsheet to reflect this latest failure. This brings the MTBF for your M215s down to 36 years, which is significantly lower than the 57 years I am seeing for my M190s, even though my system is nearly one year older than yours.

I certainly hope your failure rate is just an anomaly, given all my efforts and expense to convert from M190s to M215s on my roof. Can you confirm that the M215s on your roof are the original ones with the ground wire attachment? I assume they are given the date your system was activated. All of the fourth-generation inverters I have installed incorporate the new insulated-ground feature and have a 48VDC maximum rating rather than the 45VDC that came on the original units.

RegGuheert said:

I certainly hope your failure rate is just an anomaly, given all my efforts and expense to convert from M190s to M215s on my roof. Can you confirm that the M215s on your roof are the original ones with the ground wire attachment? I assume they are given the date your system was activated. All of the fourth-generation inverters I have installed incorporate the new insulated-ground feature and have a 48VDC maximum rating rather than the 45VDC that came on the original units.

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I'm not sure how I would check this short of climbing up on the roof. It has been sunny and hot, so I'm not going to get a chance in the near future to comfortably do that.

I got my system turned on within a few months of a friend. His has 24x M215 microinverters, and he has had zero failures. He also had a much better experience with his installer than I had with mine. I was just joking with him that my contractor must have picked up the microinverters from the discount rack. Which is probably just the reject pile from his much more reputable contractor.

RegGuheert said:

The issue is that the PV modules in the field are 72-cell units while the ones on the roof are 60-cell modules. The original M190s will work with either type of module, but the fourth-generation microinverters (including the M190IG replacements that Enphase is now shipping out) will NOT work with the 72-cell modules in the field. So I had a choice: spend the next 10 years replacing M190s on the roof one-at-a-time as they failed and end up with a dead field array after about ten years or purchase new, high-reliability inverters for the roof and create a stockpile of 72-cell-compatible microinverters that I can swap in as they failed. Since ALL of the M190s are likely to fail before ANY of the fourth-generation units fail, my stockpile of M190s will slowly be converted to fourth-generation M190IGs as Enphase replaces failures.

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Ahhhh, OK. That all makes sense now. Thanks.

RegGuheert said:

OTOH, I have been able to purchase NEW fourth-generation M215IGs with 24 years or more of warranty remaining on eBay. The last 16 NEW M215IGs I purchased were under $100 shipped!

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Nice!

RegGuheert said:

I'm sorry to hear that. I have updated the spreadsheet to reflect this latest failure. This brings the MTBF for your M215s down to 36 years, which is significantly lower than the 57 years I am seeing for my M190s, even though my system is nearly one year older than yours.

I certainly hope your failure rate is just an anomaly, given all my efforts and expense to convert from M190s to M215s on my roof. Can you confirm that the M215s on your roof are the original ones with the ground wire attachment? I assume they are given the date your system was activated. All of the fourth-generation inverters I have installed incorporate the new insulated-ground feature and have a 48VDC maximum rating rather than the 45VDC that came on the original units.

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That's an interesting aspect, confirmed by Enphase as well. The models, even of the same generation, are constantly being revised, probably at times to improve the design, and especially now, to reduce the cost. Cost reduction is big on Enphase's road map, both in current generation and future generations, given their financial situation and the market as a whole. Is an M250 sold today substantially different than one sold a year ago, in terms of quality/longevity? We'll probably never know.

Now I need to dig out my ten year old Davis Vantage Pro2 weather station and see about setting it up again. Given it's 10 years old though, first order of business will be testing to see what condition it's in. I'm guessing I might end up needing to solder in some replacement super capacitors!

More compromises this time re: rain gauge and temperature sensor siting vs the old install location at a different address. Unfortunately due to rain shadows, I don't have a much better place to put the rain gauge than my roof, which is less than optimal, especially since it means having to drag the temperature sensor up there, unless I want to a cable running down from my roof to my backyard (I really don't).

Hmm... maybe they can fit an extra cat5e and cat3 run in the conduit. That would certainly be nifty...

ltbighorn said:

Hmm... maybe they can fit an extra cat5e and cat3 run in the conduit. That would certainly be nifty...

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It's possible but I believe the rule is the insulation on the low voltage wiring has to meet the same requirements as the "high" voltage. I've never tried to source cat5 that would be suitable for that so have no idea if it's feesisble. Maybe just consider zip tying the cables to the conduit? Cat5 is pretty easy to hide behind conduit so you'd barely notice it was even there.

GetOffYourGas said:

I'm not sure how I would check this short of climbing up on the roof. It has been sunny and hot, so I'm not going to get a chance in the near future to comfortably do that.

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No need to check. Enphase did not start shipping the M215IGs until AFTER the M250 was introduced in late 2013, so your system had to use the original M215s.

Given the 1) post up-thread showing the insides of an M250 with electrolytic capacitors inside along with 2) my discovery of Enphase' patent fillings indicating their new architecture which eliminates said electrolytic capacitors, 3) the significantly different electrical specifications, 4) your failures, as well as 5) Enphase' statement that all original M215s will be replaced by M215IGs upon failure, I'm starting to believe that, in spite of the enhanced 25-year warranty, the original M215s used a similar power stage architecture and the same control ASIC as the M190s, but were designed for the higher power level and to fit inside the new case developed for the new architecture that incorporated the Engage cabling system (which I really like!).

My guess is that the new cabling system was ready to go in late 2011 but that the ASIC to support the new power stage architecture took another couple of years to complete. So Enphase decided to bite the bullet and release the new product in 2011, including the 25-year warranty in spite of the fact that the first units still contained electrolytic capacitors which Nichicon would not warrant for more than 15 years.

That's not to say the original M215s are not more reliable than the M190s. Certainly Enphase have built in fixes to problems they found in the M190s, which is reflected in my MTBF data. But perhaps only the M250 and M215IGs will be able to survive for significantly more than 15 years. Time will tell.

GetOffYourGas said:

I got my system turned on within a few months of a friend. His has 24x M215 microinverters, and he has had zero failures. He also had a much better experience with his installer than I had with mine. I was just joking with him that my contractor must have picked up the microinverters from the discount rack. Which is probably just the reject pile from his much more reputable contractor.

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Likely the quality of the inverters is identical. However, if you look at my spreadsheet, you will see drastic differences in MTBF between one M190 system and another, even though they are the same vintage and geographically close. I have always wondered what caused these discrepancies. Certainly one possibility is that the architecture of the M190s makes the unit very sensitive to installation quality. For instance, if the ground is done poorly, then perhaps the units are more apt to failure. If so, the new M215IG grounding architecture may have served two purposes: simplify the installation AND make the units less vulnerable to failure due to any installer mistakes.

Anyway, this is all just conjecture on my part, but I have been trying to put together this puzzle ever since dsinned posted that picture of the innards of an M215.

QueenBee said:

ltbighorn said:

Hmm... maybe they can fit an extra cat5e and cat3 run in the conduit. That would certainly be nifty...

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It's possible but I believe the rule is the insulation on the low voltage wiring has to meet the same requirements as the "high" voltage. I've never tried to source cat5 that would be suitable for that so have no idea if it's feesisble. Maybe just consider zip tying the cables to the conduit? Cat5 is pretty easy to hide behind conduit so you'd barely notice it was even there.

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Hmm, good point. I'm guessing running alongside the powerline would also be pretty terrible for data transmission anyway, though the rain gauge signaling might be OK since it's just a basic reed switch signaling for a tipping bucket.

Unfortunately the conduit is on the other side of house from where I'd need to run to the ISS, but if I get desperate I can drape off behind the chimney without it being too visible. Fastening may be tricky though as I'm hesitant to drill extra holes in the exterior stucco for a telephone wire. It's super annoying that the Davis console only allows the wind signal to come from a non-ISS source, as I already will have a wireless transmitter up there with a board capable of transmitting the wind+rain gauges both, but the console would ignore it, unless I also put the temperature/humidity sensor up there. Ahhh, the challenges and compromises in urban weather station siting.

Makes me realize though that I should have them run at least one extra pair of 12 gauge in the conduit for future circuits. Then if I want or need something else up there (AC powered, or another solar string of sorts), I have some options.

ltbighorn said:

Makes me realize though that I should have them run at least one extra pair of 12 gauge in the conduit for future circuits. Then if I want or need something else up there (AC powered, or another solar string of sorts), I have some options.

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If the conduit is not too long or too thin or does not have too many bends, then you have the option of pulling more wires through it later.

RegGuheert said:

ltbighorn said:

Makes me realize though that I should have them run at least one extra pair of 12 gauge in the conduit for future circuits. Then if I want or need something else up there (AC powered, or another solar string of sorts), I have some options.

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If the conduit is not too long or too thin or does not have too many bends, then you have the option of pulling more wires through it later.

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Not sure how many bends they'll put before a junction box - it'd have quite a few if they try to run it straight from the roof through the garage to the main panel in one go, but I'd certainly add a couple boxes if I was doing it. I'm guessing it'll be doable later without too much insanity, just seems like for what can't be more than $50 in wiring and basically no extra labor, can probably save a fair bit of hassle should I ever need it. Though the only thing I can think of using it for right now is an AC-powered webcam (with powerline networking! ). Or roof-hung Christmas lights maybe. Am I being silly?

Hmm, could use some advice on tilt! Today my installer installed the mounts (reroofing is in progress). Next week the panels will come up.

He mentioned that he thought a 15-degree tilt would be optimal. I asked why. My own calcs with PVWatts and other formulas generally suggested a higher tilt, with 20 degrees seeming a reasonable floor. He said looking at the specific site, it'd optimize better for me in the summer and because of the hills to the south, I wouldn't benefit as much from the tilt during the winter.

Thing is, *if* PVWatts is right, 20 degrees does better than 15 degrees even in the summer. And annually. Stepping up to 25 degrees (vs 20) sacrifices a small amount of summer kWh (<10), for a larger number of winter hours (>60). Stepping up 30 degrees starts to sacrifice more summer (~30) for smaller amounts of winter hours (~45). This is for a April1-Oct31 "summer". If you figure a "short" E-6 yr2021+ summer of June1-Sep30, 20 degrees still returns more summer and annual kWh than 15 degrees.

Now, my installer has been to my site, PVWatts just knows "San Francisco", with SolarAnywhere data's grid box encompassing almost the entire city. Is my installer reasonably accounting for some PVWatts isn't? Should I heed his recommendation over a website that hasn't been 'on site'?

Some details of my location:

200 degrees azimuth, 37.7 latitude, ~700 ft elevation. No immediate shading. A bit higher elevation hills about a hills about a 0.5-0.75 miles to my east and west. I've included pictures. Roughly equal elevation hills to my south. To the north is a big hill -- including trees it rises ~200 ft vertically in ~200 ft horizontal distance. See picture for illustration of the SW view from the roof (ocean visible), and ESE. Pictures taken Nov 30 2015 @ 3:06pm. http://imgur.com/a/cQwqy

I'm just west of the major SF ridge line that holds back fog, but I'm also in the fog-shadow of hills to my east, so it's kind of like I straddle the border. Falls are clear, summers are a mix but it's common to have morning fog that burns off by ~11am, returning around sunset. Spring tends to be clear and sunny with occasional overcast. Winter is a mix of sunny and overcast.

Here's what PVWatts has to say, noting that the more granular weather data (SolarAnywhere) still considers basically all of SF as one region. TMY3 uses SFO airport, which is east of mountains and much lower lying.

For these purposes, summer is April1-Oct31 and winter is Nov-March.

Using SolarAnywhere data:
15 degrees: 5208 kwh annually, 3598 summer, 1610 winter
20 degrees: 5298 kwh annually, 3606 summer, 1692 winter. +90
25 degrees: 5357 kwh annually, 3599 summer, 1760 winter +59
30 degrees: 5387 kwh annually, 3570 summer, 1818 winter +30

Using TMY3 data:
15 degrees 5522 kwh annually, 3955 summer, 1567 winter
20 degrees: 5619 kwh annually, 3974 summer, 1645 winter +97
25 degrees: 5683 kwh annually, 3972 summer, 1711 winter +64
30 degrees: 5712 kwh annually, 3945 summer, 1767 winter +29

In all these situations, PVWatts estimates more annual kWh the steeper I go, though above 20 degrees it comes at a reduction of summer kWh for more winter kWh. Since summer kWh are typically more valuable, I figured 20 degrees was a reasonable stopping point. But of course, these are all using the same modeling assumptions.

Are there other tilt factors that should be taking precedence? Greater tilt for less dust? Less tilt for less wind uplift? We get decent winds some afternoons but nothing gale force (it's California after all), so hopefully wind/upforce isn't a factor in 15 vs 20. 1950s wood-framed house. While I don't have my weather station up, it seems like winds are generally from the southwest or west. Weather systems move in sometimes from the northwest but because of the higher hills to the north, I *think* their intensity is fairly well blunted.

So, should I insist on 20 degrees? More? Or might he be right about 15 degrees? Opinions/insights please!

ltbighorn said:

Not sure how many bends they'll put before a junction box

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The NEC requires no more than 360 degrees of bend between pull points (which need not be a junction box, it can be a C conduit body or a pulling elbow).

Cheers, Wayne

ltbighorn said:

He mentioned that he thought a 15-degree tilt would be optimal.

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According to Solmetric, 31 degrees of elevation is the optimum angle for SFO. 15 degrees will result in about 3.7% less production.

Note that shadows can be very long in wintertime, so be careful that your placements and tilt angles do not create shadows on the neighboring rows of panels.

ltbighorn said:

QueenBee said:

ltbighorn said:

Hmm... maybe they can fit an extra cat5e and cat3 run in the conduit. That would certainly be nifty...

Click to expand...

It's possible but I believe the rule is the insulation on the low voltage wiring has to meet the same requirements as the "high" voltage. I've never tried to source cat5 that would be suitable for that so have no idea if it's feesisble. Maybe just consider zip tying the cables to the conduit? Cat5 is pretty easy to hide behind conduit so you'd barely notice it was even there.

Click to expand...

Hmm, good point. I'm guessing running alongside the powerline would also be pretty terrible for data transmission anyway, though the rain gauge signaling might be OK since it's just a basic reed switch signaling for a tipping bucket.

Makes me realize though that I should have them run at least one extra pair of 12 gauge in the conduit for future circuits. Then if I want or need something else up there (AC powered, or another solar string of sorts), I have some options.

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If the conduit is in metal it will not be a problem at all though I would think being that it's just AC it probably ends up in PVC to reduce costs.

FWIW you could add a recepracle on the roof using the existing pairs.

wwhitney said:

The NEC requires no more than 360 degrees of bend between pull points (which need not be a junction box, it can be a C conduit body or a pulling elbow).

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Ah, they'll almost certainly have to install some extra pull points then, so I guess pulling later wouldn't be hard. Might skip the extra AC line for now then.

QueenBee said:

ltbighorn said:

Hmm, good point. I'm guessing running alongside the powerline would also be pretty terrible for data transmission anyway, though the rain gauge signaling might be OK since it's just a basic reed switch signaling for a tipping bucket.

Makes me realize though that I should have them run at least one extra pair of 12 gauge in the conduit for future circuits. Then if I want or need something else up there (AC powered, or another solar string of sorts), I have some options.

Click to expand...

If the conduit is in metal it will not be a problem at all though I would think being that it's just AC it probably ends up in PVC to reduce costs.

FWIW you could add a recepracle on the roof using the existing pairs.

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To clarify, I meant data transmission if I ran it inside the conduit instead of outside. I know they're going to use metal conduit (not sure if it's a code requirement here or not, but I've never seen PVC electrical conduit in use here).

I could add a receptacle on the existing pair, but as I'm having the enhanced generation & consumption metering installed, it'd throw off the measurements.

On the upside I found a way to do the rain gauge transmission wirelessly, so unless I decide to add a roof camera I don't have any urgent needs for roof receptacles. I have a camera mounted in the yard now for weather timelapses. It'd be neat to be able to see the panels, but it'd be facing their backside so I couldn't see the conditions on the front surface anyway. So not much point in the end.

RegGuheert said:

ltbighorn said:

He mentioned that he thought a 15-degree tilt would be optimal.

Click to expand...

According to Solmetric, 31 degrees of elevation is the optimum angle for SFO. 15 degrees will result in about 3.7% less production.

Note that shadows can be very long in wintertime, so be careful that your placements and tilt angles do not create shadows on the neighboring rows of panels.

Click to expand...

Good advice that I probably should have spent more time on! Between work emergencies all week, monitoring the reroofing, etc., I didn't get much time to look extensively into the self-shadowing issue. I found some basic guidelines and because of various details of how the rafters are laid out on my roof (and that I have plenty of room overall), my inter-row spacing seemed to exceed typical recommendations. It's ~84 inches.

I ended up having to on-the-spot pick the final tilt -- not my ideal situation -- 25 degrees is what I selected.

Since then I can see there are two significant factors my quick rule of thumb research didn't take into consideration. The flat roof is of course, not actually flat, and ends up putting the 2nd row effectively 2.0-2.5 inches lower than the 1st row. The second factor is my azimuth offset from due south. I'm at 200 degrees. This extends the effective winter afternoon shadow length by quite a bit (which in winter on E-6 is basically the same TOU, though less beneficial on EV-A)

Interestingly, while I specified 25 degrees, the front row panels vary from 20 degrees (east end) to 23.2 degrees (west), and the rear row varies from 22.5-25.3 degrees. Not too surprisingly really given that the roof slopes in two directions and they probably measured support strut length once.

I've since done calculations for a variety of shadow lengths (incl. height and azimuth adjustment) and jotted down various scenarios (mostly worst case ones) about what time the panels become shadowed. What I'm not sure how to figure is how much annual % impact it really has. I know things like inverter clipping often end up having a much smaller overall impact than they might initially suggest, and I suspect that the annual losses from self-shadowing are likely similarly minimized by the relatively brief period and overall lower insolation when the sun is at very low elevations in winter.

- Does anyone know a good way to figure the annaul losses, or any existing ballpark calculations for theoretical energy harvests based on varying becomes-shaded times?
- Or how many hours of sunshine exposure are good winter goals in term of getting good capture but avoiding too much pursuit of diminishing returns?

As is, I'd guess worst case on Dec 21, I'd be unshaded from about 9am-2:35pm. Because the panels are portrait and 3-diode with each diode group arranged vertically, my understand is I'd lose 100% output of the 2nd row once the first row of cells is completely covered. (Of course, in practice because the shadow is coming at a steep angle, it'll be a bit more gradual).

*Dec 21 until 2:35pm. (
*By Feb 21 it should be good from earlier and until ~4:30pm.
*By March 21, 6:30+pm (clock time benefits from DST change).

So Nov-Jan or Feb end up most affected.

Or looks at it elevation-wise, below these sun elevations:
* 18.5 degrees elevation on winter solstice Dec 21,
* 17.5 on Jan 21,
* 13.5 Feb 21,
* 8.8 Mar 21.

Rest of the year has no issues, first row remains unshaded all year.

ltbighorn said:

I ended up having to on-the-spot pick the final tilt -- not my ideal situation -- 25 degrees is what I selected.

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ltbighorn said:

The second factor is my azimuth offset from due south. I'm at 200 degrees.

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Solmetric tells me that you will produce 98.9% of optimum by pointing at 200 degrees azimuth with 25 degrees of elevation. In other words, your pointing is nearly perfect!

ltbighorn said:

I know things like inverter clipping often end up having a much smaller overall impact than they might initially suggest, and I suspect that the annual losses from self-shadowing are likely similarly minimized by the relatively brief period and overall lower insolation when the sun is at very low elevations in winter.

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Exactly. As you noted, you will not have any self-shadowing on the southernmost row. Also, the shadows will likely never hit every panel in the more-northern rows.

ltbighorn said:

- Does anyone know a good way to figure the annaul losses, or any existing ballpark calculations for theoretical energy harvests based on varying becomes-shaded times?

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I don't know how to make such a calculation. There are many complex variables, including things like what times of day clouds are most likely to occur. What I can do is give you some anecdotal data from my array. I have a form of self-shadowing in the morning since the garage array is to the west and a few feet lower than the house array. This results in year-round daily shadows. Depending on the time of year, the most-shadowed column on the garage roof is not fully out of the shadow until between 9:50 AM and 10:30 AM (latest shadows occur at the equinox for some reason). So how much production do I lose on these three panels? 5.7%. But since I have 54 panels in the entire array, that daily shadowing only reduces overall array production by a measly 0.3%. In your case, you may have shadows on a larger portion of the array, but they will occur MUCH less frequently, so I suspect your impact from self-shadowing will be even lower than mine.

In any case, you will be able to easily calculate the impact after your array has been installed and operational for a year. Simply extrapolate the production from the southernmost row of panels to the entire array to find out approximately what you would have achieved without the shadows.

RegGuheert said:

ltbighorn said:

I know things like inverter clipping often end up having a much smaller overall impact than they might initially suggest, and I suspect that the annual losses from self-shadowing are likely similarly minimized by the relatively brief period and overall lower insolation when the sun is at very low elevations in winter.

Click to expand...

Exactly. As you noted, you will not have any self-shadowing on the southernmost row. Also, the shadows will likely never hit every panel in the more-northern rows.

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Good point. Since it's a row directly in front of another row, I'm guessing 3-4 out of 6 would be hit at any one time during this limited window.

RegGuheert said:

ltbighorn said:

- Does anyone know a good way to figure the annual losses, or any existing ballpark calculations for theoretical energy harvests based on varying becomes-shaded times?

Click to expand...

I don't know how to make such a calculation. There are many complex variables, including things like what times of day clouds are most likely to occur. What I can do is give you some anecdotal data from my array. I have a form of self-shadowing in the morning since the garage array is to the west and a few feet lower than the house array. This results in year-round daily shadows. Depending on the time of year, the most-shadowed column on the garage roof is not fully out of the shadow until between 9:50 AM and 10:30 AM (latest shadows occur at the equinox for some reason). So how much production do I lose on these three panels? 5.7%. But since I have 54 panels in the entire array, that daily shadowing only reduces overall array production by a measly 0.3%. In your case, you may have shadows on a larger portion of the array, but they will occur MUCH less frequently, so I suspect your impact from self-shadowing will be even lower than mine.

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That's helpful, thanks. Given that in the worst case (winter solstice) I'm still good until after 2:30pm, and better than that the rest of the year, it seems like the impact on my shaded panels could be a similar percentage or smaller. Especially since my impact is only in winter, already the lowest light conditions. In a worst case of 5% annual impact, with 4 out of 12 panels impacted, that'd be about 1.66% of overall annual array performance. That's pretty good for a worst case. As you said, after a year (actually, after the shading period of ~Oct-Mar), I should be able to figure out the actual impact.

Thanks!

My system install was completed and PG&E gave PTO in only 2 business days (and a few hours change).

That's 12 M250s and an Envoy-S Metered that have been in service since 7/6/2016.

It took a while to get Enlighten Manager view -- there were some problems initial setup problems that limited me to the basic MyEnlighten view.

Now that I have it it's nice to see the micros benefiting me a little bit in the mornings and evenings. In the summer it's very minor, but if each row had been on a single string, I would have lost ~1.13 kWh of production on a clear July day due to a tiny bit of shading on one panel in the morning, and another panel just before sunset. Though some days I wouldn't -- foggy days don't care about shading! And of course, the winter impact would be bigger when some amount of self-shading comes.

I can see now that the rear row (known shading ignored) generate about 1.9% less over the course of the day than the front row. I can't really say I know why, but if I had guess, maybe it's due to the front row being ~2 degrees more steeply tilted, or the panels receiving slightly less diffuse irradiance due to having the horizon in front of them blocked. However the former doesn't quite hold up, as the difference is present even under heavily fogged conditions.

The only thing left to do now is get the consumption metering fixed. They originally installed Sunpower 100A CTs, thinking they were the same, but the Enphase ones are rated for 200As and clearly calibrated differently, as the consumption readings are way off. They'll be coming back soon to swap them!

Being able to poll the Envoy-S locally is very nice and fulfills one of my main requirements. It's nice to be able to my status terminal scrolling by the current power generation (and soon consumption) in ~3 second intervals. I might graph these temporarily just to get a visual of how rapidly the power levels fluctuate on day vs another. We get some interesting days with wisps of fog blowing by overhead on an otherwise clear day. Long term I think the 5-minute intervals recorded in Enlighten Manager and pvoutput will be more than ample.

ltbighorn said:

My system install was completed and PG&E gave PTO in only 2 business days (and a few hours change).

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Congratulations!

ltbighorn said:

That's 12 M250s and an Envoy-S Metered that have been in service since 7/6/2016.

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Thanks! Please provide a link to your public website and I will add your system to my Enphase Microinverter and Envoy Field MTBF Estimate spreadsheet.