When you see an ad like this one can’t help figuring out what the full story is…
There is ground mount solar array in the background. Probably old units from a solar farm.
I’m not sure if I’d spend 30k on something that looks that worn, even if it is half price 
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It’s like the pic of all those geysers at the scrap yard…
Perhaps this inverter solution isn’t working on an industrial scale site?? (They should stick to DC )
That inverter works just fine for industrial purposes. Granted, the newer Tauro is a better option for something that size. It is far easier, for distribution purposes, to AC-couple smaller 30kW or 50kW or 100kW blocks than to have one massive DC setup.
The next step up would be something like the ABB PVS inverters that go up to 5MW.
I know someone that is in charge of all the PV sites for Vodacom. Part of the performance guarantee calls for replacement of all inverters after a certain time. The contractor will then quote for this, or it is included in the maintenance contract. All the PV inverters will be ripped out and replaced with newer models. On some of these contracts you need to guarantee the performance for 10 years and even higher. In the cases I have heard of, replacement happens about 7.5 years after installation. Sure not all of these projects are the same but @Rautenk use to work on these big projects, maybe he knows.
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In most cases, you have 2 guarantees in place:
- EPC performance guarantee
- Operational guarantee
The first one is basically for defect warranties in the first 2 years of operation then the other one is the long-term one where you “decrease” the performance ratio every year.
In neither of those cases would you rip out inverters if they are still working. It would be an unneeded cost unless you had serial failures.
Now in most financial models, there would be a sequenced inverter replacement cost built in, on average (I believe this was a DNV paper) states that your expected lifespan for a string inverter is 12 years (note that it mostly has a normal/bell distribution curve for failures with the majority on 12-year).
So looking at those inverters and noting how close to the 12-year they might be, I would not pay more than R5000 for one.
Then on the replacement part, you will always strive to replace like for like, your balance of the system is designed with specific voltages, currents and losses in mind. Going from 1x30kW to 1x60kW will mean longer DC runs to that 60kW unit (cabling change). Going for more units means that your transformers and cables might not be sized correctly to fit a larger system.
And just for the record, utility-scale projects are being built now with the 200 to 300kW string inverter types. I personally detest central inverters! (And they go up to 8MW now)
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I remember the 12 years as well. Vodacom replaced all the SMA inverters after 12 years on one site. In another instance the guarantee was 5 years, expected life 10 and they cut split the difference in halve stating they wanted it replaced after 7.5. I guess its not the same as the EPC model and was an internal requirement agreed upon between the parties involved.
Why? Is it the higher PV voltages or lack of redundancy or??
Simple: String Combiner Boxes.
A few drawbacks for Central inverters are:
- Limited MPPTs (so losses increase)
- Central points of failure
- More maintennance
- Additional String Combiner Boxes (read fuses)
Some brand of 1500Vdc fuses do not last more than a few months so it puts a lot of onus on your team to replace them. If you don’t have accurate string monitoring (additional cost) then you don’t find this until a maintenance run.
Only thing “going” for central inverters would be the cost component and that is not that big anymore.
Also the central inverters that I had the “luxury” to maintain might not have been the best of the best, so that does skew my view.
But for my last 7 years in maintenance of these plants I can definitly say that time spent on String Inverter plants is way less than on central inverters!
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Geez, and I thought we have issues.