Solar PV with microinverters

thegentleway

charles_b_2 said:

I took a quote from Heatable and it was all remote, noone visits until you accept the quote.  They also changed the battery make when I got the full quote documents. I would say be wary as they use independent contractors for the work ( much like Boxt).
I used a local firm in the end who worked with me (and I had great advice from @Screwdriva ) alongside 2 other quotes, all of which included a free onsite survey  with no obligation (including one from a reputable company that Screwdriva recommended).  There will likely be a world of different solutions and prices, and you need to do some serious research on the right option for you.  I'm going with Solaredge totally (optimisers, inverter, battery, gateway) with anti-islanding in case of power cuts. Micro inverters seem like a good idea, but if they fail you'll have to get back on the roof which adds potentially costs for re-scaffolding.  

Likewise with optimisers but microinverters have a much lower failure rate than optimisers... 

thegentleway

Exiled_Tyke said:

Is this discussion limiting itself to Enpahse?  I did a small extension to my system adding two 300w panels which share a 500w micro inveter.  It does exactly what I need it to and probably is about right for efficiency versus clipping. 

No not at all. Enphase do seem very good but I'm open minded. I'm looking at about 20 panels across 3 parts of the roof, one SE and two SW. One of the SW aspects will get a bit of shade from the gable hence having to consider optimisers/microinverters. 

Screwdriva

thegentleway said:

Likewise with optimisers but microinverters have a much lower failure rate than optimisers... 

I would expect the opposite to be true - a micro inverter is more complex than an optimizer. 

charles_b_2

There is no absolute answer to this question. Brief research suggests that the additional complexity of a micro-inverter increases the likelihood of failure.

Anecdotally: "Converting from Solar DC to grid AC is a 2-stage process. 1st stage is a DC-DC converter that takes array DC and outputs a stable DC voltage for the 2nd stage which is the AC inverter converting the DC to 60hz AC. Micro inverters do both stages up on the roof. Optimizers just do the 1st stage. The second stage runs at the low frequency of 60Hz and as such needs large filter caps usually of the electrolytic type which are especially prone to failure at rooftop conditions. Optimizers ought to be more reliable as a result."

https://www.invertechs.com/What-is-the-failure-rate-of-microinverters.html

https://forum.solar-electric.com/discussion/16964/failure-rate-of-micro-inverters-vs-optimizers

I'm certainly not suggesting they are bad, micro-inverters have a lot of positives and historically they appear to be more reliable than a string inverter, but then a string inverter is easier to replace if it fails as it won't be on the roof.  My roof is more costly to scaffold, so that fed into my own personal determination.  It all boils down to what's best for your situation.

thegentleway

Screwdriva said:

thegentleway said:

Likewise with optimisers but microinverters have a much lower failure rate than optimisers... 

I would expect the opposite to be true - a micro inverter is more complex than an optimizer. 

Well quite. Solar Edge make it difficult as they don't publish their failures rates whereas Enphase do. From online research Solar Edge seem to have poor failures rates, e.g.: https://youtu.be/I4czBPobtg0?si=d6h8FbOxpn0ZRN5I&t=1024

and
 
https://mcelectrical.com.au/solaredge-inverter-optimiser-review/ 

thegentleway

charles_b_2 said:

There is no absolute answer to this question. Brief research suggests that the additional complexity of a micro-inverter increases the likelihood of failure.

Anecdotally: "Converting from Solar DC to grid AC is a 2-stage process. 1st stage is a DC-DC converter that takes array DC and outputs a stable DC voltage for the 2nd stage which is the AC inverter converting the DC to 60hz AC. Micro inverters do both stages up on the roof. Optimizers just do the 1st stage. The second stage runs at the low frequency of 60Hz and as such needs large filter caps usually of the electrolytic type which are especially prone to failure at rooftop conditions. Optimizers ought to be more reliable as a result."

https://www.invertechs.com/What-is-the-failure-rate-of-microinverters.html

https://forum.solar-electric.com/discussion/16964/failure-rate-of-micro-inverters-vs-optimizers

I'm certainly not suggesting they are bad, micro-inverters have a lot of positives and historically they appear to be more reliable than a string inverter, but then a string inverter is easier to replace if it fails as it won't be on the roof.  My roof is more costly to scaffold, so that fed into my own personal determination.  It all boils down to what's best for your situation.

Indeed, but additionally complexity of power optimisers also increase likelihood of failure (and when comparing Solar Edge to Enphase, it increases it a lot more) - it's the worse of both worlds. Still have string inverter failure + optimisers failure.

Agree that replacing a string inverter is usually easier than an microinverter however microinverter failures rates are so low you would be unlucky for it to fail within 25 years. Whereas the string inverter is pretty much guaranteed to need replacement within 25 years.

However, I am leaning towards just a simple string inverter set up. The bypass diodes can deal with the tiny bit of shading I'll get. No need for all the extra complexity/cost. 

charles_b_2

I would agree, simple is better. The reason I went with Solaredge in the end was the DC battery as it will charge if the inverter goes over it's rating. 5Kw inverter.  In peak production over 5Kw it will charge the DC battery, which also means no conversion losses (dc-dc instead of dc-ac-dc). Solaredge means having their optimizers.

Again, my personal preference. Many would opt for an AC coupled battery.

Edit: (Also Solaredge inverter has 25 year warranty)

michaels

We have 2 S facing panels and 14 w facing ones, didn't go with 2 strings as the voltage on the 2 panels was too low so instead have optimizers for each panel.  No failure of anything yet after 9 years.

Telegraph_Sam

For the past 13 years I've been running a Aurora Uno inverter - just left to do its job. A green "power" light comes on when it's working and goes out when it's not at dark. It / the panels seem to react to quite low light levels.
What I have yet to establish is - when the light comes on - if there is some power being downloaded at all, or as I was once led to believe, that there is an excess of power being generated over consumption at any one point. 

I don't have a storage battery but I do have a smart meter whose inner workings are a bit beyond me. I suspect that this might hold the answer.

Heedtheadvice

See manual p33 Operation...https://www.altestore.com/static/datafiles/Others/AuroraPVI3.0-4.2TL_Manual.pdf