Enphase

newenergy · July 2009

Re: Enphase

Solar Guppy wrote: »

You will be the one, at your expense that gets the calls when an inverter need to be replaced and you have to get into the middle on an array to swap out a panel when its the inverter the failed.

This is why I wouldn't use them except on very small systems. Modules basically never fail, but inverters occassionally do. I don't really want to be responsible for thousands of inaccessible inverters for years to come.

solartek · July 2009

Re: Enphase

BB. wrote: »

A very handy rule of thumb that comes out of engineering and materials physics is the rule of 2 for 10C (18 degrees F).

Basically, anything that increases temperature by 10C will experience a reduction in life by a factor of 2.

Raise the temperature from 35C to 65C--the life will go down by 1/2*1/2*1/2=1/8th of the life at the lower temperature.

Also, applies to the cooling side--you cool something by 10C (18F), the device will last 2x longer.

The other killer for electronics (and most materials) is temperature cycling... In the old days--I found that 2 weeks in a thermal cycling chamber fo disk drives, after cycling ~3 times per day (40F-120F-40F)--anything that lasted over two week was probably going to be a good disk drive.

Operating an inverter under solar panels on a roof, with extreme temperatures and thermal cycling will definitely show how well Enphase has designed/constructed their product.

-Bill

Enphase claims to perform a pretty sophisticated Accelerated Lifetime analysis as described here. Having worked in my previous career for a RF electronics manufacturer that builds both commercial and military hardware, electronics that can survive this type of temperature cycling and high temperature aging tend to be very robust in the field. I'll bet there is not another inverter manufacturer that subjects their equipment to this type of testing environment.

Scott.

ALBANYSOLARGUY · July 2009

Re: Enphase

Sorry group, I work summer events as an electrician for my local Municipality. 4th of July week and all.(I had to work 2 concerts,a street fair, a christian crusade,and a senior citizens festival.PLUS my 40 hr/wk dayjob, AND run my business) I will try to reply to as much as I can since I've been gone. To solarguppy-

You will be the one, at your expense that gets the calls when an inverter need to be replaced and you have to get into the middle on an array to swap out a panel when its the inverter the failed

This may be true. Enphase has a Rapid Replacement Policy(RRP) that will send me another inverter plus $75.00 or $150.00 for replacement depending on whether or not they use the enlighten monitoring system. The customers I have speced systems for using enphase products have been given the choice of a string inverter,or micro-inverters. I am willing to take the chance on enphase. Besides, my customers are the most important thing. I get ALL of my work through word of mouth. I'm not even in the phone book. I'll send 2 guys on a roof to change an inverter for a customer if one fails, and 1 of them will be me. Guaranteed. To Windsun:

A standard inverter can be mounted in the shade, the Enphase cannot.

This is true. Of the PV systems installed in my area that have exterior mounted equipment, I have seen 10 inverters installed by an out of state PV company in direct sunlight. No thought has been given to location, except for material and labor costs. These 2000w inverters are unlocked, as are both the DC and AC disconnects and mounted under an overhang in an area in the northeast that is known for ice. I have been asked to do service calls to troubleshoot some of these units. I don't know if any needed to be replaced, but I found 2 non-functional. To really think about it though, isn't under the panel kind of in the shade? To boB

However, as Guppy says, these units are going to be much more prone to early failure just because they are out in the elements and subjected to HOT & COLD & HOT & COLD &.

These units were designed for changes in temperature and to be mounted outside. I live in NY, it's cold in the winter, hot in the summer. The temp variation here is not too dramatic per day.

Why couldn't you run wires from the module(s) down to the Enphase sitting in the shade ?

The units were designed to be mounted under the panels. As stated in previous posts, the expense of relocating is not cost effective. To cariboocoot

To see them as the one and only solution in all grid-tie applications is foolish.

I give customers a choice, depending on their system. I have only had one taker for a commercial grid tie with enphase. The 3 other prices I have given for commercial systems the customers chose a string inverter. Of the 10 residential systems I have priced,7 have chosen Enphase and signed contracts. The other 3, 1 string inverter and 2 no call back yet. Foolish, by the way, is what everyone said I was when I branched out to PV from my electrical business. To newenergy

This is why I wouldn't use them except on very small systems. Modules basically never fail, but inverters occassionally do. I don't really want to be responsible for thousands of inaccessible inverters for years to come.

Residential might be a hassle, depending on layout. Commercial could be accessible depending on mounting and layout. Again, I'll take a chance on Enphase. Finally, to solartek

Enphase claims to perform a pretty sophisticated Accelerated Lifetime analysis as described here.

If everyone would read the white paper contained in that link, this thread might not last much longer. Look group, as PV gets more mainstream it's going to be upstarts like enphase and helios that are going to work their way onto peoples homes and business'. As stated before my customers get an option. To be able to offer a choice of technologies is the only way to advance my business, and keep up with the competition or pass it. I have spoken with Enphase at great length,I speced the 208 volt 3 phase units for the commercial estimate that called back. I had questions about multiple strings and the means of disconnect as per NEC. Without hesitation there was a recommendation that will comply with the NEC for my AHJ, will be cost effective and will be relatively easy to complete. I expect to see a higher wattage unit in the very near future. This will allow higher wattage panels to be used, cutting down on overall cost. The main reason I used Enphase on my home is because of costs. I can only hope the overall cost per unit remains under $200.00US. I am by no means an expert at PV, but I welcome the challenges you all present. The guy with the Homer head avatar, dwh, schooled me last week in another thread. I look forward to getting schooled again. Good stuff here. So you all know. I am an electrician. First and foremost. 3rd generation electrician in my family. I am IBEW trained and I am REAL picky about how the finished product looks. Nothing is inspected until I do a walk through first. Solar and Electrical. To this point, I've installed for people who pay out of pocket. No incentives requested. I've sent my application to NY State for eligible installer status, to be able to offer the State incentive for future customers. I hope to take the NABCEP test in the spring of 2010. I want to install a megawatt of solar. The right way. I won't be happy until I do.Using Enphase or whatever the customer wants........

boB · July 2009

Re: Enphase

ALBANYSOLARGUY wrote: »

To really think about it though, isn't under the panel kind of in the shade? To boB These units were designed for changes in temperature and to be mounted outside. I live in NY, it's cold in the winter, hot in the summer. The temp variation here is not too dramatic per day. The units were designed to be mounted under the panels.

I was JUST going to say this these ARE kind of in the shade cuz they're behind the module, and then you said it !

On the issues of this unit being "designed" to withstand as many years as they say they will be good for, and installed where they are marketed to be installed, if you were in the manufacturing business, as I am, you'd understand why we have said what we have said here... As well as having seen the insides of these units. But we'll just leave it at that for now, Albany.

But I sure wish you well on your quest to install 1 MegaWatt of solar ! That is a wonderful goal !

boB

niel · July 2009

Re: Enphase

with the inverter mounted just behind the pv the heat given off from the pv will radiate to the inverter quite well preventing any heat generated in the inverter from dissipating as good as most would like. this also may keep pv temps a bit higher. heat dissipation is why we like to advise at least a 6in air gap between the roof and the pv. just because it is an inverter does not excuse it from going against the best interest of the pv and its power generation. heat is the enemy no matter how well they made it to withstand it.

ALBANYSOLARGUY · July 2009

Re: Enphase

boB,

As well as having seen the insides of these units.

I've read every post in this thread and NOW you say you've seen the interior of the unit. So, what did you see....................To niel

heat dissipation is why we like to advise at least a 6in air gap between the roof and the pv.

how do you think they would do on a pole mount?

boB · July 2009

Re: Enphase

ALBANYSOLARGUY wrote: »

boB, I've read every post in this thread and NOW you say you've seen the interior of the unit. So, what did you see....

Lots and Lots and Lots of parts ! (and some electrolytic capacitors too).

Oh, BTW, did I say LOTS of parts ?

boB

mike95490 · July 2009

Re: Enphase

ALBANYSOLARGUY wrote: »

1) how do you think they would do on a pole mount?

2) I want to install a mega-watt of solar

1:
I'd think pole mount would be a fair bit cooler, much more air circulation around the panels.

2:
Is that 1MW at 1 location, or hundreds of installs ?

halfcrazy · July 2009

Re: Enphase

So how do you make a capacitor last 300 years? its got to be magic. I bet they are connected to Solar Magic that's got to be it so we are all set they will last forever.

ALBANYSOLARGUY · July 2009

Re: Enphase

Is that 1MW at 1 location, or hundreds of installs ?

As many as it takes.

TnAndy · July 2009

Re: Enphase

Mega watt installed ?

Already did that.....just took several months to get it.....

ALBANYSOLARGUY · July 2009

Re: Enphase

http://www.enphaseenergy.com/downloads/EnphaseTechBrief_Temperature.pdf Speaking of temperature concerns, just pulled this from an Enphase newsletter I received today.

ALBANYSOLARGUY · July 2009

Re: Enphase

(and some electrolytic capacitors too).

http://www.enphaseenergy.com/downloads/ElectolyticCapacitorLife092908.pdf Hey boB I found this for you.

mike95490 · July 2009

Re: Enphase

ALBANYSOLARGUY wrote: »

http://www.enphaseenergy.com/downloads/EnphaseTechBrief_Temperature.pdf Speaking of temperature concerns, just pulled this from an Enphase newsletter I received today.

<Doubting Thomas Mode ON>

Running Conditions Rooftop test @ Petaluma

I don't know if I would trust that newsletter, till they clarify the conditions a bit.
Looking at weather records,
http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KCAPETAL6&day=15&year=2008&month=7&graphspan=month
July 8 was the hottest day, @ 100.2F That week:
Wind was less than 5mph, gusts less than 10, I think something was left out.

What about pitch of the roof? alignment to the sun?

I recall hearing somewhere, PV panels ran about 40F hotter than ambient ? The "test" PV was only 15F above ambient.
---
Capacitors
50 years for cap life at Palm Springs location. maybe 100y, for a less challenging location. How does that fit into their 300years MTBF est in their other literature ?

Still an un-believer.

niel · July 2009

Re: Enphase

let's see here, 10000hrs best case scenario divided by 5hrs/day of full sun is 2000 days. divide that by 365 days/yr and we find the caps last 5.48 years. how long do they warrant this for again.:roll:

BB. · July 2009

Re: Enphase

They are saying that if the Cap is rated at 10,000 hours @ 105C--if you want to run it for 50 years, then:

Log (50yr life wanted / 5.48yr predicted at spec. temp) / Log 2 = 3.19

105 C - 10C*3.19 = 73.1C ambient (164F)

Or, going backwards (to confirm the math--it has been a long time :roll: ). The difference in spec temp minus the operational temp all divided by the famous 2x life improvement per 10C; then expressed as an exponent of 2, times rated life gives you predicted life at lower temperature:

5.48 years of life (at 105C) * 2^((105C-73.1C)/10C) = 50 year life at 73 ambient for capacitor

However--much of this depends on the actual temperature of the inverter and its internal components, and the environment under the solar panels.

A typical solar panel is rated at 85C, and it should not be unusual to expect a 10C rise in operating temperature of the inverter (SWAG--Scientific Wild Ass Guess)--so worst case expectation of life (at 95C internal cap ambient temperature) would be:

5.48 years * 2^((105C-(85C+10C))/10C) = 10.96 years (not 50 years)

In the end, if the inverter electrolytic caps are running at internal 164F (73C), less a 18F (10C) temperature rise because of case, then this would indicate a maximum of 146F (63C) maximum under solar panel ambient temperature...

Is that realistic--hard to say. I would like to see some worst case "typical" installations (panels on sloped roof, no breeze, hot summer day) and see what the real temperatures are.

In general, for long life equipment running at elevated temperatures (122F / 50C maximum ambient) we tried to ensure there were a few as possible electrolytic capacitors around in our systems... You could not avoid them in power supplies--but that is why I designed in Hot-Swappable Power Supplies to keep the up time high, while allowing for possible (eventual?) failures.

A Xantrex GT series inverter has a temperature specification of

-13°F to +149°F (-25°C to +65°C)

So, the Enphase to get a "50 year" operational life would appear to need about the same maximum continuous temperature specification as the Xantrex Inverter...

However, the Xantex only needs a 10-20 year operational life for everyone to be happy, vs the "50 year" life as suggested by Enphase...

Worst case--50 year life vs 10 year life is a factor of 5 difference between the Central inverter vs the Distributed inverter design requirements (I can play with marketing numbers too

and choose cases that maximize product differences). Assuming the two above max temperature ranges are virtually the same (saves more stupid math by me to account for a 2 degree C difference in max temp):

So, that would indicate that Xantrex could use less expensive parts and still end up with a reliable system (that meets customer expectations of 1 replacement every 10 years) where as Enphase needs to build their inverters with higher spec'ed part with a maximum temperating of a Xantrex Centeral inverter to have the same "happy customers and installers".

I will stop here--the above is probably of zero interest to anyone but me... :roll:

But, I thought it was interesting that when I backed out the numbers using Enphase's, Niel's and my (SWAG) assumptions--that the Enphase needs the same ambient specification to meet their 50yr Marketing Numbers as Xantrex needs to meet their 10 year warranty number.

Real life, however, is never as clean as my mathematical assumptions indicate. There is a whole other side of HALT design and test that needs to account for failure modes other than activation energy (temperature)... The main ones probably being thermal cycling, weatherization, and internal system design (ripple current through caps, etc.).

Without an Enphase inverter and other information (such as temperature and cycling test results)--It would be impossible to do justice "guessing" about what Enphase has done.

I have not looked through Enphase's website for more technical articles... It is just that the one provided by AlbanySolarGuy at least provided some specifications/assumptions that I could hand-wave against and look into their design philosophy a bit (since I had to do a bit of this in my past life).

-Bill

RCinFLA · July 2009

Re: Enphase

All these arguments sound very similar to when the auto industry first started putting integrated regulators in alternators.

A bundle of coils, some electronics, that get subjected to -50 to +220 degrees F, and lots of water. All that this missing is the vibration (well maybe in California)

Cariboocoot · July 2009

Re: Enphase

Actually, there were and still are quite a number of failures of automotive electronics for just those reasons. I know this because I've had to replace a lot of it, from alternators to computers, in many different vehicles over the years. Some stand up better than others, of course, but surely the engineers who designed all of it knew what sort of environment they'd be up against?

Fact is the real world ain't a simulation.

BB. · July 2009

Re: Enphase

RCinFLA wrote: »

All these arguments sound very similar to when the auto industry first started putting integrated regulators in alternators.

A bundle of coils, some electronics, that get subjected to -50 to +220 degrees F, and lots of water. All that this missing is the vibration (well maybe in California)

I don't recall seeing any electrolytic caps in an alternator (it has been decades since I took one apart--

).

But, if you are happy with ~150,000 miles on your alternator... The average conversion for miles to hours of operation is 35 MPH:

150,000 miles / 35 MPH = 4,200 hours

My GT inverter "runs" an average of ~12 hours per day:

4,200 hours / 12 hours per day = 350 days

Myself, I would want my inverter to last a bit longer than a year or two...

-Bill

icarus · July 2009

Re: Enphase

I for one would like to see enphase succeed. My bet is that they will. Will there be failures,, I'm sure,, but for no reason other than wishful thinking I expect the reliability to be acceptable. I certainly am no electronics guy at all, but one would think that they have engineered in some factor(s) for hot application(s).

Just as when the Prius came on the market there was some skepticism and indeed some poison press about reliability and safety. Now almost ten years on the technology has proved itself to be pretty darn reliable with many 100s of 1000s on the road, under pretty trying environments from VERY hot to VERY cold. There are examples of Prius' with over 1/2 million kms on them in Taxi service in both Vancouver and Toronto. Few reported problems with the hybrid or battery systems.

Tony

ALBANYSOLARGUY · July 2009

Re: Enphase

I too would like to see micros succeed. I will let you all know when and if I get a failure. I will contact the other installers I know who use Enphase and ask them to contact me if they have a failure. Try to gather real world data of conditions. Also I may, depending on finances, split my home array in 2 halves and install a string inverter on half to have a basis for analysis. I would like you all to recommend a small<1000 watt inverter that matches the specs as closely as possible to the Enphase units. The most popular by consensus will be chosen. I will install any monitoring for the string inverter I need, and post a link to view both halves. So everyone can make their own opinion. My home array is 8-Suntech STP170S24's..8 Enphase M175-240's. Orientation is due south, angle is 40 degrees. I know it's small, but costs were a big factor. The panels were $475.00 each. I am not yet State recognized the application is pending. I bought this out of pocket, with hopes of expanding when finances were better. Everyone think about it and let me know. ASG

BB. · July 2009

Re: Enphase

And I too hope that Enphase has a long and useful life for their product... It is always good to have options.

I appreciate the hard work that they are doing to design and build a power converter to run efficiently under those conditions. I know that it is not easy.

-Bill

niel · July 2009

Re: Enphase

i'll make it unanimous and say i hope the product succeeds for there is a small place for it.

emo69 · September 2009

Re: Enphase inside

Akeena Solar's - Andalay solar panel

The panel is made by Suntech and it has an enphase micro-inveter built right inside. It looks real inpresive. No rails or wires. I would think people would be talking about it here.

Mike

BB. · September 2009

Re: Enphase

emo69/Mike,

Actually there have been quite a few discussions here about the integrated product offered by Akeena (and others)...

If you type into Google:

Akeena site:wind-sun.com

You will get many hits... Including one with a code question:

Akeena and Enphase

In the end--attaching a 15 year warranty device to the back of a 20-25 year warranty panel seems a strange choice.

-Bill

emo69 · September 2009

Re: Enphase

attaching a 15 year warranty device to the back of a 20-25 year warranty panel?

I never thought about that.
But it really looks slick in the instalation video.

mike95490 · November 2009

Re: Enphase - Solar micro-inverter addresses capacitor reliability issues

From a trade magazine:
http://www.edn.com/blog/1470000147/post/1000050300.html

blah blah blah..... most of the same stuff we've seen here already....

" Other papers (pdf) on the website refer to its micro-inverters being “designed for a service life of 20 years,” but the website lists the warranteed lifetime for its products at 15 years."

Nothing really new, but they list the brand of caps - "Enphase micro-inverters use Nichicon (pdf) capacitors rated from 4000 to 10000h at 105°C. "

So, it's still mostly up in the air for now.

System2 · December 2009

Re: Enphase

I just found this forum and read everything on the Enphase micro inverters. I am seriously looking into setting up a solar system due to a generous feed-in tariff for renewable energy projects in Ontario (80.2 cents/kWh)

I have been interested in solar electricity generation for quite some time and I remember a very similar micro inverter being sold by Trace (now Xantrex). I thought that this would be the future of inverter technology but then it was discontinued. I'd be curious to know what went wrong and hopefully the same thing won't happen to Enphase.

mike95490 · December 2009

Re: Enphase

pmuus wrote: »

I just found this forum and read everything on the Enphase micro inverters. I am seriously looking into setting up a solar system due to a generous feed-in tariff for renewable energy projects in Ontario (80.2 cents/kWh)

It's attractive to folks who'd like to put up a couple of panels..

Then they find out they need permits, inspections, and such. And they never add any more panels because of the paperwork hassles.

When you install a major array on a roof, usually, the single giant inverter prices out a lot better, and still only 1 permit, inspection.

Toner Duckpin · December 2009

Re: Enphase

Have you seen the enphase web site lately. Lowes is teaming up with Akeena for a DIY solar system. Check out the video if you get a chance.

Enphase

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