Cleantech – Update on Microinverters
In a recent blog, I wrote about microinverters and since then, I have received some feedback and new guidance that I believed to be material enough to make an update.
Electrolytic Capacitors: One of the marketing points made by SolarBridge is that their microinverters do not use electrolytic capacitors. This is significant in that these components are often viewed as being one of the weakest links with respect to long-term product reliability. One of the things that decrease electrolytic capacitor life is heat and solar panels on rooftops can get quite hot. Toward that end, in the previous Cleantech blog, I noted that companies like Enphase Energy have taken a similar design approach to eliminate components like electrolytic capacitors. As it turns out, at least some of the Enphase Energy microinverters do have electrolytic capacitors inside them. These are the 4 black tubular components to the left of the photo below.
Note: The picture above is from the J.S. Schaffer report referenced below.
The fact that Enphase Energy product designs did have electrolytic capacitors in them was a big concern for the investors. The concern was so great; they commissioned a detailed study by Dr. J.S. Schaffer to look at product reliability given the components selection. The elevated temperature and corrosion testing performed indicated that a 30-year life expectancy was reasonable. As long as the capacitor manufacturer (Nichicon) does not have any process problems, Enphase should be in good shape reliability wise. If I were Enphase Energy, I would make sure that the supply chain is well controlled to prevent counterfeited/inferior capacitors from being used as their microinverters are manufactured.
Warranty: It has been pointed out that I missed one consumer benefit of an AC Solar Panel because the warranty for the integrated panel and microinverter components would be coming from a single entity, the solar panel manufacturer. Given the competitive nature of the market, companies like Solyndra that went bankrupt and others like First Solar that have recently announce huge layoffs, this might not be a point of comfort in that it is not a solid bet that a given solar panel manufacturer US or otherwise will be around to support a 25-year warranty. To me, this still screams like an opportunity for large, deep pocketed industry participants like ABB, Schneider Electric, Emerson Electric, Siemens and/or General Electric to scoop up a collection of microinverter and panel entities and then provide the industry with a complete, branded, and solidly backed photon to grid product line.
Testing: I am told that integrating a microinverter to a panel in the factory is not generally a problem as it is only a few added steps after the flash testing. In these cases, you would need to add the microinverter and then test again although, in these cases, you would only be checking for correct connections and microinverter function. I still stand by the original blog content with regards to inventory costs.
Safety: The added guidance I received indicated that AC solar panels do, in fact allow them to be installed by less skilled crews which could include homeowners. This still assumes that the homeowners will leave the critical last connection steps to licensed electricians. Even so, I am told that the microinverters do not turn on unless properly connected and have features that make sure they do not create islands of power in the midst of a power outage.
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