Solar for Beginners [ask your questions here]

StormForce13 · 27-05-2024 05:29PM

Unabashed solar dummy here. Very happy with my new solar PV system, but rather confused by the following:-

Last Monday, warm and humid, wall to wall sunshine without a cloud in the sky. Lovely curve on my PV output graph, but as you can see below, the max kW reached was about 3.7

Last Thursday, cool, cloudy, showers with decent periods of sunshine in the afternoon.

This output graph is a lot less curvy, but a peak of 4.4 kW was reached on a couple of separate occasions. (That's my theoretical max.)

So how come the peak output achieved was significantly lower (by about 17%) on what seemed to be a perfect PV day? 🤔

Thanks.

Eleusis · 27-05-2024 05:34PM

Temperature will throttle the max output of the panels. So cooler days will have higher peaks during sun

StormForce13 · 27-05-2024 05:37PM

https://www.boards.ie/discussion/comment/122190573#Comment_122190573

That's very interesting thanks. I wasn't aware of that.

Presumably it also means that a cool summer could be up to 17% better (from a PV generation perspective) than a warm summer!

Eleusis · 27-05-2024 05:39PM

I think thats why May is so good in ireland for solar production vs july and aug.

17% does seem alot though, so that may not be the entire reason.

DC999 · 27-05-2024 07:46PM

https://www.boards.ie/discussion/comment/122190593#Comment_122190593

Yeah, in the heatwaves in May+June last year I was getting perfect curves but a lower overall peak on the curve than on cooler sunnier days. Down to panel temp.

Can also be the inverter temp. If it gets too hot, some inverters throttle the output. If it's in the attic which is already baking and the inverter is going full tilt on a bluesky day…keep an eye on inverter temps getting 50C+. Some here put fans under them in the summer. The manual will list an optimal operating temp.

lawrencesummers · 27-05-2024 08:24PM

There was a link somewhere here that i cant find now to evaluate a solar quote, anyone know the website?

con747 · 27-05-2024 08:28PM

https://www.boards.ie/discussion/comment/122191177#Comment_122191177

This one? http://davidhunt.ie/solar/

kaisersose77 · 28-05-2024 10:05PM

I'm just using my eddi as expensive timer! to heat hot water each night in cheaper rate. I noticed recently water wasn't as hot in the mornings and so checked the myenergi app and saw this. April was consistently over 2.0kW like the start of May. Any suggestions what could be causing the generation to start decreasing like this? Time period hasn't changed.

Thanks

kaisersose77 · 28-05-2024 10:13PM

Ignore me! Figured out I had a home assistant automation turning eddi off at sunrise.

10-10-20 · 28-05-2024 11:30PM

https://www.boards.ie/discussion/comment/122195810#Comment_122195810

I was going to say that it looked like a curve alright.

bullit_dodger · 29-05-2024 01:00PM

SOC = state of charge. It's basically the same as the battery level on your phone. Phone battery = 54% is the same as battery SOC = 54%. A fancy way of saying the same thing on how full your battery is.

Related to that is "Depth of discharge" and for house batteries typically they go from 100% → 10%. Depends a little on the manufacturer. What this means is say you buy a battery that is 10Kwhr in capacity. Well, your "usable" amount is only 9kwhr as the battery likes to go from 100%→10%. Without getting into the tech, just take it that the batteries don't like to be depleted down to 0% regularly. You can do it, but repeating 100%→0% will shorten the useful life of the battery, so the recommended is 100%→20%, although most can do down to 10% with no ill effects.

On the charging side, you can set the times and levels that you want to go to. I've automation with sets my charge level - but for most people, they set the times (say 2am → 5am) and set it to 100%, and then whatever level the battery is at…..let's say it was at 23% full, it will charge from the grid until it gets to 100%, or whatever limit you have set, and once it's charged it will stop importing power from the grid. Then outside the "charge time" you have set…..it will satisfy the house by slowly depleating the stored energy it's got to meet house demands.

So in you example,

So if the grid charge window is 2-6am and SOC was 10% does this mean that the battery will only charge from the grid during those hours and outside of this window once depleted to 10%

It means that at 2am your battery was 10% full, and it will charge it from 10% up to 100% from the grid, that probably won't take 4 hrs to 6am, so at some stage during the 4 hrs, it will stop charging.
Once 6am comes along, then your battery will start discharging and meeing house demands.

As for amps etc - I wouldn't bother too much about that. for 95% of people baring techs like myself and a few others here, let the defaults on the inverter work for you, no need to change anything and you'll get years out of a battery.

MicktheMan · 29-05-2024 07:49PM

I would appreciate some advice on the following please.

What are the regulations which need to be heeded regarding charging a small (say 2kWh) battery from a 430w solar panel on the roof of an isolated shed and then using the stored power to power some stuff (lights, power tools, chargers etc) in the shed using a micro inverter? There is no grid connection to the shed in this instance. Thanks

mjatkey · 29-05-2024 08:08PM

https://www.boards.ie/discussion/comment/122197671#Comment_122197671

Perfect, thanks makes sense. Thanks

10-10-20 · 29-05-2024 08:52PM

https://www.boards.ie/discussion/comment/122199392#Comment_122199392

Hi. An isolated shed (ie one with no grid connection) is just that and isn't subject to any regs, per-say. You could run wild ferrets through the place if you so wished. The only thing is that you'd need an off-grid inverter as a micro-inverter won't suffice as it requires mains input voltage to synchronise from. An off-grid inverter will create it's own AC sine-wave and supply the attached load independently of any mains system. Best bet would be to look at some of the wiring/architecture methods provided by Victron as they specialise in off-grid systems and you'll find the recommended safety systems documented there also.

AndrewJRenko · 31-05-2024 04:00PM

Can I ask a 'dummies' question about the impact of nearby trees on effectiveness of solar panels?

We have a mini forest over our back wall, so maybe 6-7m from the south edge of roof, with trees going 3-5 above the height of the house. This means we don't get much sun in the back garden in afternoons and evenings, but it's great for privacy.

Does foliage like this have a significant impact on the effectiveness of solar panels? The foliage isn't over the house, but would restrict direct sunlight for certain periods.

Eleusis · 31-05-2024 05:17PM

I think forestry 6-7m from a south roof will be very bad.

Also not legal or safe to have forestry that close to a house. Forestry trees fall pretty easy.

10-10-20 · 31-05-2024 05:21PM

https://www.boards.ie/discussion/comment/122207276#Comment_122207276

Yes, a significant impact. The production from a shaded panel can drop to ~20% of the max if the shade covers one or more of the individual cells. 'Half-cut' panels won't help significantly and neither will optimisers unless the shading is isolated to a minimal number of panels.

slave1 · 31-05-2024 06:13PM

In short, yes, when shaded the production will be severely impacted and this is assumedly when the sun is low so early morning/late evening/Nov/Dec/Jan/Feb

Eleusis · 31-05-2024 09:47PM

https://www.boards.ie/discussion/comment/122207758#Comment_122207758

At 6-7 away and 4-5 meters above roof level, that would block all direct sun in winter I would have thought

AndrewJRenko · 03-06-2024 12:34PM

https://www.boards.ie/discussion/comment/122207559#Comment_122207559

https://www.boards.ie/discussion/comment/122207584#Comment_122207584

Thanks for the feedback, disappointing and all that it is. Is there any way to quantify the problem with a light meter or similar, or remote survey based on maps and photos to assess if there's any reasonable chance that panels will work here?

10-10-20 · 03-06-2024 12:43PM

https://www.boards.ie/discussion/comment/122215304#Comment_122215304

Yes, you can, but you'd need specialist software to model the seasonal sun paths and obstructions. Somebody posted such in one of the threads on here last week,

https://www.boards.ie/discussion/comment/122206904#Comment_122206904

Let us know how it goes!

micks_address · 03-06-2024 01:25PM

Hi folks,

Looks like I may have an immersion issue. I'm getting max temp reached on the eddi when I know the water is cold. I popped off the immersion cover this morning and to reset it looks like you turn the temp dial all the way to left and it clicks, then I turned up the temp setting again and put cover on. Turned on immersion RCD again and tried the eddi with same result. Immersion only about a year old, as is the tank.. I don't see a button to reset the immersion which others have mentioned before?

Cheers,

Mick

bunderoon · 03-06-2024 01:58PM

https://www.boards.ie/discussion/comment/120568457#Comment_120568457

Have you have any issues with vibrations or wobbles in high wind? Looking at how far apart the horizontal supports are on the panel and how exposed you are.

I've got 550w panels (7.5ft high!) and will put a run in the middle. I'm in an exposed area and am even considering a 4th to help sleep better.