Solar PV Peak Output?

grahamc2003

wensleydale wrote: »

Interesting thread as I have 11 panels split 5 SE and 6 SW- all 250W.

I'm not getting the output I expected but am not sure if there's a good way of checking all are working.

The peak output I've ever seen is c1.6KW and when the sun is on the panels facing SE the output is v v low- c250w or so which I believe could actually be coming from the other 6 panels.

Is there any way of actually checking all is well?

Today generated c7kw and was a really sunny day.

Thanks

Rich

I have 7 250w panels facing SW, and my experience is very similr to yours (i.e. about 250w as soon as the sun hits them in the morning, and a peak of 1.6kw spotted so far, with the highest daily generation of almost 7kWh. (I've had mine just over a month).

So from that it cretainly looks like your se panels don't seem to contribute much, if anything. Maybe they're not connected correctly.

I take it that you have two strings and an mppt for each. My sunnyboy has twin strings, but a single mppt, which is useless except when each string has identical orientation (and shading if any).

jamesingram

GaryMo wrote: »

Many argue that DNC = TIC so 5kWp of panels on a 3.68kW inverter would be in the band of up to and including 4kW. Doing this could help installations with split roofs and those subjected to shading issues.

Yep , that how I'd see it .
your max output will only ever be 3.68kW =DNC
so no need to inform of any changes other than that.

hobbo ,
have a play with the powerone inverter design tool,
no need to download
http://stringtool.power-one.com/
main concern with addtional panels on the east facing string
would be going over the Dc input voltage limit of the string and inverter.

make sure you adjust ambient temp. range to give cell temp. between
-10 deg C to 70 deg C

Pennylane

Today was gorgeous and we managed 11.55 KWh according to our display. Just when I think I'm beginning to understand SP's I get all confused again.:o

Martyn1981

wensleydale wrote: »

It's a sunny boy and I have the software on the laptop- can you advise what I need to look for.
Shading wise- there's a chimney stack but only covers part of one panel for a short time.

Any chance you can post the exact model of inverter you have. Better still if you can look at the ID sticker on the side and give it's full model. E.g I have a SB2500HF, but there is also a simpler SB2500, and a better SB2500TL.

I'm wondering if you don't have dual MPPT, or if you do, if the strings haven't been wired correctly. I'm only guessing, but if both strings are going into one port, then your inverter may be ignoring the lower voltage string completely.

Anyways, post back and we can have a good thunk!

Mart.

wensleydale

Its a SB 2500 HF 30.
Thanks all.

Martyn1981

wensleydale wrote: »

Its a SB 2500 HF 30.
Thanks all.

Hello Wensleydale. First let me caveat this with you need to speak to an expert / your installer, but I'm 99% certain that that model is a single MPPT. It can take 2 strings, but they would need to be identical in all aspects size, orientation and roof angle.

You really need an inverter with dual MPPT which effectively treats both roofs as separate entities. I suspect with your 5 + 6 set up, the inverter is ignoring the lower voltage string (the 5 panel string). Even if both roofs had 5 or 6 panels each, the different orientations wouldn't do too well either.

I think you need to have a chat with your installer.

Anybody else? Do you think I've got that right?

Mart.

Martyn1981

Found a tech page

look at 'technical data' and 'input DC' it states 1/2 meaning 1 MPPT and 2 strings.

http://www.sma.de/en/products/solar-inverters/sunny-boy/sunny-boy-2000hf-2500hf-3000hf.html

What panels have you got? I'm wondering what the voltage of each is, as the min voltage states 175, which is 35V per panel on a 5 string, or 29V on a 6 string.

Mart.

Hobbo2006

jamesingram wrote: »

Yep , that how I'd see it .
your max output will only ever be 3.68kW =DNC
so no need to inform of any changes other than that.

hobbo ,
have a play with the powerone inverter design tool,
no need to download
http://stringtool.power-one.com/
main concern with addtional panels on the east facing string
would be going over the Dc input voltage limit of the string and inverter.

make sure you adjust ambient temp. range to give cell temp. between
-10 deg C to 70 deg C

I'll have a look thanks.

The west string already has 11 panels so I presume that matching this on the east string would be ok? I think that there would Only be enough roof space for 10 on the east side.

Hobbo2006

Lemoncurd wrote: »

Ours is local to you Hobbo, 2.96kWp system facing due south with minimal shading. At the moment my remote monitor is showing peaks of around 2.4kW each day (haven't looked yet today). I've just had a look through data at 5min intervals downloaded last May and the are several data points of 2.964 but nothing higher.

Most I've seen so far is 2.5kW. I'll have to check the inverter as that keeps a record. Today was nice 13.06kWh. The generation graph was like an equilateral triangle, slightly squashed at the top. Slight shading for an hour whilst the sun goes behind a tree. Guess that would be worse when the leaves come out.

Just wondering who would notice if I put another 5 on the east side.

jamesingram

Martyn1981 wrote: »

Hello Wensleydale. First let me caveat this with you need to speak to an expert / your installer, but I'm 99% certain that that model is a single MPPT. It can take 2 strings, but they would need to be identical in all aspects size, orientation and roof angle.

You really need an inverter with dual MPPT which effectively treats both roofs as separate entities. I suspect with your 5 + 6 set up, the inverter is ignoring the lower voltage string (the 5 panel string). Even if both roofs had 5 or 6 panels each, the different orientations wouldn't do too well either.

I think you need to have a chat with your installer.

Anybody else? Do you think I've got that right?

Mart.

Yep , that sounds about right Mart.