Optimisers or not?

crazyhorse

Trying to weigh up whether to go with a larger 7 kWp system on 3 sides of roof which would require 10 optimisers (~€7k) or go with a 5kWp system on 2 sides of roof without optimisers (~€5k). Everything else is equal. Happy with quotes for both systems after plugging into davidhunt calculator. I obviously want to maximise panels but wondering if adding multiple more points of failure (optimisers) is potentially short-sighted and asking for trouble in the long run?

bullit_dodger

Ultimately the money side boils down to an extra 2kwp for €2k, so €1k/1kwp. Fairly good value that.

The question of optimizers is a always decisive here. I'm of the opinion that they're fine. They fail active (as in the panels will still work as if you didn't have an optimizer), and they are generally reliable. That said, they do fail and if you have to replace one, it's a pain in the ass to get someone out on your roof.

If it was me, I'd get the 7Kwp. Others will have different opinions, and they wouldn't be wrong. It's down to your level of risk. I think it's fine.

Did they tell you why you need optimizers. You can parallel two roofs (as long as they are the same panels and numbers of panels) without optimizers. Need to watch the current though.

conor_mc

I’m in same boat, leaning towards optimisers even though I have same doubts as you - more generation versus less to go wrong. I should have checked, but assuming tigo optimisers, I think you’re good, saw something on YouTube that failure rate is minuscule.

crazyhorse

Thanks for reply. I've been told optimisers required as there will be shading on panels from neighbour's chimney. My understanding is that with the larger system two roofs will be parallel with same panels and no. of panels, as you mentioned.

crazyhorse

Think Tigo optimisers here also

curioustony

I thought, possibly incorrectly, that for hard shadows like poles and chimneys the inbuilt bypass diodes did the job. It was really only for diffuse shadows (e.g. distant trees) that optimisers came into their own.

Earlier panels did not have bypass diodes, and optimisers were always needed.

Am I way of the mark here?

conor_mc

you’re correct @curioustony, I assumed though that the optimisers were needed to accommodate two aspects on the one string - that’s the problem that my installer proposed optimisers for. Tbh, I don’t understand why bypass diodes don’t work for that level of hard shading, unless at least one aspect would be too small to hit startup voltage?

AndyBoBandy

I have panels on 3 aspects, so needed 11 optimisers on the 11 panels split over 2 of the aspects…

Best decision I ever made….

My aspects are (String 1) SE (4 panels), SW (7 panels). String 2 NW (6 panels)

conor_mc

which two aspects are optimised @AndyBoBandy? Any particular reason(s) why those two were chosen?

Why do you feel it was a great decision, are they adding considerably to your generation?

AndyBoBandy

it’s the SE & SW strings that are optimised.

It didn’t really matter which strings were chosen as it would have meant either 10 or 11 optimisers, so they went with the 2 aspects closest to each other..

For me it’s great as my roof space was fairly limited (with some installers quoting from “it’s not worth it at all” to “maybe 4-5 panels if your lucky…”

Adding the 3rd NW aspect was the bonus for me which is what the optimisers allowed, as it’s 2.04kWp on that aspect, and at times I’ve seen it generating 1.5kW… (when the 1st SE & SW string has reduced to maybe only 300W of output…), so it extends out my meaningful generation period by a few hours…

My system was installed in October 2021z

conor_mc

thanks for sharing that @AndyBoBandy, I’m in same boat as you were, my clearest and larger roof aspect is just about NNE with space for 3.4 kWp. With chimney on S roof and maybe only 3 panels on W roof, seems they’d be best to optimise. Unless optimisers would help considerably with generation from the diffuse light on a North-facing array?

cormacl

I have a 2nd string with 4E, 4W & 5N, optimisers on the lot. Works very well for something several installers told me would not work at all or generate much. Seems to be more and more installers now open to this kind of setup to work with the limited space some customers have.

Shot here is from the Tigo CCA that monitors the modules. Values are in Wh (DC). In real AC kWh I generated 27.6kWh today in what was a light overcast day. 11.2kWh from 8 south-facing panels and 16.3 from the 2nd multi-aspect string. The optimisers are a must for the multi-aspect and full panel shading scenarios. A1 & A8 below are out of direct sun for most of the day as they are on a single story extension right behind a south-facing house.