PV Power optimiser  - Page 1
Forum section: electronics / general

author: tszaboo
author_rank: Super Contributor
timestamp: March 11, 2020, 03:59:41 pm
content: Hi. I'm installing PV on my roof (I finally have a roof, yay!) and I've been asking several companies for a quote.All of them seem to send me a system with power optimizers, and the inverter is from Solaredge. Or they offer you another system, after asking for it, with chinese inverter and low quality panels. Im confused. The panels seem to cost 120 EUR each, and the optimizers around 50 EUR. I've seen a study in the past about microinverters, and the ROI on them was terrible. Basically the conclusion of the study was, if you get shading on your roof, get an inverter with two strings, not one. Because all you do with the microinverters is increase the ROI of the whole system. This is how my qoutes look like:9x panel = 1000 EURInverter = 700 EURoptimizers = 450 EURInstallation material = 300 EURWork, cabling etc = 800 EURTotal without tax = 3200 EUR, tax reclaim possibleWhen I ask for SMA, Fronious, ABB or other brand inverters, they dont have itI have the feeling that they are trying to upsell me, and sell me magic boxes, with minimum amount of work, instead of placing panels, which would make more power.

author: Ice-Tea
author_rank: Super Contributor
timestamp: March 11, 2020, 04:20:37 pm
content: Do you have a lot of shade or polution on your roof? No? Then optimizers are a waste. Actually, theywastea few %. Simple as that. Not to mention you doouble the amount of connections and components that can go bust.Also: pretty easy to do it yourself. I did a few months ago. Nothing much to it.

author: tszaboo
author_rank: Super Contributor
timestamp: March 11, 2020, 04:43:57 pm
content: Quote from: Ice-Tea on March 11, 2020, 04:20:37 pmThere is a tree in the garden, that could provide partial shading in the morning. But the entire mathematics of the systm seems to be off. The optimises cost the same as 3 panels, that is 33% extra peak power, and they claim 5-25% improvement***. Maybe I can consider cutting down the tree (and plant one elsewhere).I'm doing a google search, and I'm only finding the sales pitch. There is no independent tests done, or it is not published, or SEO is bad for it.*** on a heavily shaded roof in ideally bad conditions

author: Ice-Tea
author_rank: Super Contributor
timestamp: March 11, 2020, 04:52:30 pm
content: Not sure if you need much more research. You seem to have the math downThat said: there's a potential issue with adding panels. You'd probably exceed the max voltage on a single string and dividing it's probably suboptimal for 2 strings..

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 12, 2020, 01:53:29 am
content: Try pricing out a DIY solution. A lot of DIYers have found that it is indeed possible to do it cheaper even after factoring in the cost of time.I have also seen an optimizer that only needs to be installed on the panels with actual shading problems, not all of them. Maybe we need open hardware PV optimizers to open the way to making them cheaper?

author: Styno
author_rank: Regular Contributor
timestamp: March 12, 2020, 08:19:57 am
content: Aside from shading, there is another reason for choosing optimizers: different panel orientations. If your roof faces multiple directions or has different angles then it might be crucial to use optimizers (or a multi-string inverter or multiple smaller inverters).

author: Siwastaja
author_rank: Super Contributor
timestamp: March 12, 2020, 08:38:01 pm
content: Obviously, as you have shown, adding finer-grained MPPT control to squeeze a possible few percent of power does not work out if it's spread on several physical stand-alone modules. 50 EUR for a few-hundred Watt MPPT converter is bullshit, it should come for practically free. There might be nothing wrong in engineering of such module itself, but clearly no one has been looking at the big picture.Most of the cost is in,1) product design NRE,2) casing BOM,3) wiring BOM,4) marketing,5) sales margin,etc.,So if you need to addanybox to the system, it can't go much below $50. The solution: don't add boxes.The key to make efficient, low-cost, and reliable systems is integration, i.e., cutting down the number of "boxes" or modules, for exactly this reason. You see this pattern everywhere: as long as some field is novel, they make a huge market ecosystem out of complicated modules, parts, and services of building complete systems out of such modules, for the early adopters.And once someone really thinks it through and integrates everything in an efficient single unit (or minimizing parts; also minimizing marketing bullshit), then the mass market will get the best state-of-the-art without paying premium. Sadly, we are still not there when it comes to solar power.The problem can't be micro-optimized; you need to think about the whole picture of minimizing cost, maximizing efficiency and reliability. All of thatcanbe done in one go, but it can't be properly done when playing with the currently available modules.

author: boB
author_rank: Frequent Contributor
timestamp: March 12, 2020, 09:32:46 pm
content: The best way to mitigate partial shading is by using a chain-sawAnother thing you might be able to do is to wire the PV array such that the shaded modules cause smaller loss. You should be able to see where and when that shading occurs during the day and throughout the year too.If the module is completely shaded, then an optimizer won't help at all. The bypass diode(s) in the module itself take care of bypassing the module and then that particular string of PV voltage drops by that one module voltage. They CAN help IF they are only partially shaded but as was said earlier, they can actually reduce your energy production if not needed.In the Solar Edge system, there is no choice in not using their optimizers. They help with keeping the voltages in check (< 425V ??) for some of the S. E. systems, if not all of them.Micro-inverters have their place of course for installations with shading issues.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 13, 2020, 11:58:44 pm
content: Quote from: Siwastaja on March 12, 2020, 08:38:01 pmWhat about have the optimizers each handle 4 panels? Also, the cost of the parts in one of those optimizers is likely well below $50, hence why an open hardware optimizer could really keep costs down.

author: SolarMan
author_rank: Contributor
timestamp: March 30, 2020, 04:55:49 pm
content: Quote from: NANDBlog on March 11, 2020, 04:43:57 pm