RegGuheert wrote: AndyH wrote:
Exactly! That's what I tried to show in another thread
. The problem isn't limited to Arizona - the sun is pretty intense 'down here' across the south. Those 170-180°F roof deck temps run through Texas and Florida as well.
But do roof deck temperatures correllate well with microinverter temperatures? It seems there are many factors involved so it would be very hard to know if the climate for the inverter would be hotter, cooler or about the same as the bare roof deck had been. Here are some factors:
- Original color of the roof deck. Of course if the roof is a lite color it will reflect a significant amount of sunlight and will therefore run cooler. A black roof will attain the highest temperatures.
- A producing PV panel (such as one with a microinverter attached) should never attain as high a surface temperature as a black roof would. This is because the PV panel will convert 12 to 18% of the light into electricity rather than heat. OTOH, the PV panel may attain higher surface temperatures than a white roof would.
- The microinverter lives in an environment beneath the PV panel. In cases where the air is mostly trapped around the inverter that environment might resemble a solar cooker, resulting in a large temperature rise in the air around the inverter. In other cases, there will be easy movement of ambient air around around the microinverter perhaps aided by a chimney effect caused by the heating of the panels themselves.
By looking at the peak temperatures in the microinverters on our roof, I can see that there is a fairly wide range of environments found there. Both the hottest and the coldest inverter are found on the garage. The hottest is in the top row, third from the right end while the coolest is in the bottom left corner. The former is at the top of the "chimney" and in and oven, of sorts and the latter is at the bottom of the "chimney" and is very open to ambient air. I will say that the thermal environment would have been significantly better had I run the mounting rails up and down the roof rather than side-to-side. (Of course, the panels would not have fit very well that way!)
In any case, it seems that the M215s should manage to live in an environment for which they are designed in all but the very worst installations/inverter locations. But I'll agree that if the term "Operating temperature range" on the M190 datasheet means the INTERNAL temperature like it does on the M215 datasheet (and I think it does), then those electrolytic capacitors might be spending a few hours during some summer days close to 85C. Is that a problem for the capacitors? I doubt it. According to Nichicon, they should be able to live for 32,000 hours (3.6 years) operating at that temperature. Since they spend the vast majority of their life significantly cooler than that, they should be good for well over a decade. So my conclusion is that none of these capacitors must be worn out yet.
But the high temperatures and daily thermal cycling stress everything, including solder joints. So are we seeing a wide range of random failures with the rate increased by the heat or is there a consistent failure mode in the M190s. While I'm sure Enphase knows the answer since they replace all the failures and pay for return shipping, it's really hard for us to say.
Perhaps someone with microinverters also has a roof sensor. LEAFfan, do you have access to internal temperature data from your inverters? It would be interesting to compare that to your roof sensor.