Micro grid tied inverters on E-bay

Re: Micro grid tied inverters on E-bay

The regulations have changed over the years... My Xantrex GT 3.0 from 3 years ago no longer complies, and, I assume, when it eventually fails, I will have to replace it with the new conforming unit (with the regulations at that time).

People do go "gorilla solar"... What to say. Many probably do it, some may even do it relatively safely. Depending on what is installed, how it is installed, local weather conditions--lightning, windstorms, fire code, etc. all can cause risks/damage/interfere with resale of a home/insurance issues, and such.

Is is cost effective--probably not. Small systems tend to cost more per kWhr generated vs larger systems.

You probably all ready have read the thread regarding the SWEA here.

Somebody on the SolarPowerForum purchased a couple of the SWEA units... One worked for awhile, another was apparently DOA.

There have been other vendors that have done the "one inverter per panel" thing before... Looks like the Enphase Micro-Inverter M175-24-240-S02 may be real (says UL listed on their website).

-Bill

Re: Micro grid tied inverters on E-bay

The Enphase product by changing power to 240 VAC has not fixed very many issues vs DC... My DC system is a higher voltage (~320 VDC) so, in theory, my voltage drop will be less (can be as high as 550 VDC) than at 240 VAC with the same wiring. I have just two strings, so I have no DC breakers/inverters to worry about for my smaller 3kW GT system.

Also, I am not quite sure, but I worry that running 240 VAC wiring on the roof would make damage to my AC appliances a more likely possibility than running DC down a length of cable to a GT inverter mounted a distance from the panels... Typically, long wire runs tend to reduce the conduction of the higher frequency components of impulses such as lighting... I am sure I would probably still have to replace my GT inverter after a near strike--but think that the damage inside the home would be less.

The Enphase systems includes a very nice power line based network--so figuring out a bad unit is probably pretty easy.

I would not expect to be able to determine one inverter failed by monitoring a daily power drop... 6kW would require something like 30 200 watt inverters... That is a 3% drop in output... From watching my system (no computer logging), I would be hard pressed to notice less than a 25% loss of power. The sun+weather is just to variable to see/measure a 3% loss of output.

I see Enphase did address an issue that I saw with another "brick" vendor--As I recall, their modules were sealed on the back of a solar panel--you had to replace both if there was a failure in either. A pretty costly "repair".

Lastly, I am not at all sure about the inverter's lifetime... They talk about 119 years between failures (MTBF). Mounting on a hot roof, power electronics, and trying to hermetically seal the units against moisture (case splits, wire acces, even moisture up the wire strands themselves) is tough in a dramatically thermal cycling environment (below freezing at night, probably above 150F during the day).

Even if they get the sealing done right... For every 10C rise, the life of the electronics typically falls by a 1/2... Just mounting on the roof instead of down below in shade with air flow--life would be impacted by 1/2*1/2=1/4, or a 75% reduction in life if the units run 20C (36F) higher because of their location.

And, if I had the choice of 20 inverters on the roof or one on the ground--I would pick the 1 on the ground because it is easier to replace. And, overall, I believe I will be replacing hand fulls of inverters on the roof in the time I am installing my 3rd inverter on the ground.

One thing to remember about MTBF vs Life... I can have a set of 4 tires on my car and get 50,000 miles out of them before I need to replace them... And, I normally don't expect any flats (from tire Mfg's failures--I drive over a board with nails, my fault), but lets say I get one flat/tire failure in 50,000 miles for the sake of argument.

MTBF = 4x50,000miles for 1 failure = 200,000 miles mean time between failure
Life = 50,000 miles (tread life)

However, I cannot expect more than 50,000 miles out of my tires before the tread is worn down and they need replacement... So every 50,000 miles, I will need to change all four tires even if the MTBF is 200,000 miles or more.

So, while the inverters are less than 10-5 year old:

MTBF=119 years/10years=11.9 years average to first replacement

It is possible by the time I get to 20 years, that, at least 50% of the inverter bricks (making up a sort of plausible number without any data to back it up) will have needed replacement. And if technology has changed in that time (UL/NEC rules, networking hardware/software, brick sizes/function, vendor gone missing, or something else)--I may be left with figuring out the costs to upgrade the rest of the 20, plus the networking and wiring--with most of the work done on a 2nd story roof.

In general--I would prefer to keep the complex stuff near the ground, shielded from sun/rain, and easy to service. Could I be wrong in my assessment--yep... Just my 2 cents worth.

-Bill

Re: Micro grid tied inverters on E-bay

Tony,

The best I can see here would be to start a second thread and copy the Enphase information over to its own thread (and Enphase title)--but even the opening post mixed the two topics pretty well.

Do you (or others) see a lot more to discuss about the Enphase at this time?

Feel free to discuss here--I can always delete the discussion posts (including this one) when we have decided.

-Bill

Re: Micro grid tied inverters on E-bay

I am going to leave this thread as it it... I will create another post with a title about Enphase and a post pointing this this thread...

Even though this thread started about Ebay Inverters, the very next post pretty much hijacked this thread to be about Enphase instead (sorry--that was me).

n3qik wrote: »

...My jeep has 3 computers in the engine compartment. They see 10 to 200+ F, heat, water and vibration. Most of them will last 10+ years. If the, we need a handout, car makers can make durable electronics, the anyone can, if they plan on doing it right and not cut corners.

Actually, while automotive designing and building reliable automotive electronics is not a walk in the park--The actual life is not nearly as long as one would think...

For example, you can use ~35 MPH as the long term average to convert to run time hours (I have over 50,000 miles on a GPS, and the moving average is ~31 MPH for a car that spends much of its time in the SF Peninsula and local freeway driving).

Assume 15,000 miles per year * 10 years = 150,000 miles

150,000 miles / 35 mph = 4,286 hours of operation

4,286 hours / 10 hours per day (rough average "on time" for my GT System) = 429 days

429 days--I would not be too happy if my inverter lasted 1-2 years. I probably would be thrilled if my car's computers/wiring lasted 300,000 miles.

Or another way to look at aging, I see thermal cycles as a major factor for failures... Assume that a car starts/stops ~2 times per day and a solar inverter cycles 1 times per day

That could be, roughly, equivalent to 20 years of GT inverter life vs a 10 year car life--not bad at all.

Which is the correct way to look at GT Inverter vs Car Electronics in terms of lifetime? Not sure, both have valid points.

Nigtomdaw's observation that not many electronics live bolted to the motor, but in the passenger department instead is a good point.

Using that observation, then the GT Roof Top Inverter environment is probably a tougher one that a car (excluding vibration).

-Bill