Current PV panel prices

HeyRevolver

Hi, I'm checking for momentary peaks usually with the bluetooth Sunnybeam, but also directly at the invertor screen.

Great responses here by the way.

zeupater

HeyRevolver wrote: »

I have a 3.5kWp array (14 x 250W).

The invertor is an SMA Sunny Boy 3000HF which I've just checked with google.. not very good with this technical stuff but... it says Max. Input DC power 3150W and Rated Output AC power
3000W. Also Max. efficiency of 96.3%.

So I guess the invertor is capping it at 3kW ?

I'm told if one of the panels wasn't working the whole array wouldn't be working....

Hi

So .. "So I guess the invertor is capping it at 3kW ?" .. is the issue. You'll not see instantaneous readings which match the potential for the panels, however, when the panels are running warm there will be little difference between your inverter and one which is sized to match the panel potential ....

HTH
Z

HeyRevolver

zeupater wrote: »

Hi

So .. "So I guess the invertor is capping it at 3kW ?" .. is the issue. You'll not see instantaneous readings which match the potential for the panels, however, when the panels are running warm there will be little difference between your inverter and one which is sized to match the panel potential ....

HTH
Z

Thanks Z. I guess I'm only missing out on a little peak performance in that case. It's at least good to think that all 14 panels will be performing well the majority of the time (with our countries weather). May still question it with the installers. Seems a mismatch to me.

Martyn1981

EricMears wrote: »

Certainly does ! I reported a momentary peak of 4.07 at 11:39 ; the 5m average for then was only 3.5 (which is indeed around 85% of Kwp)

Exactly the same here (well, not today, but over the weekend), noticed that sustained peak is running at about 3.1 86% (3.6kWp system), 2 weeks ago when the air temp was lower, the system was holding at around 3.3 91%. But longer and lower seems to give bigger daily totals.

Mart.

HeyRevolver

Does anyone else have this issue where their invertor caps the potential output from their PV system ? It seems quite common on other quotes I received also.

Martyn1981

HeyRevolver wrote: »

Does anyone else have this issue where their invertor caps the potential output from their PV system ? It seems quite common on other quotes I received also.

Hiya HR, you'll probably find quite a few on these threads if you read the system specs. There are also a few different forms of capping.

Some systems have undersized inverters, like yours, which work on the basis that they loose a bit off the top some days, but are a little more efficient at other times, plus they might switch on a bit earlier, and off later.

Then there are also the G83/1 capped inverters, which should limit output to 16A or 3,680W at a nominal 230V. Been reading a few discussions, and there is now another factor, some of these inverters are now being programmed to limit output to a 'true' 3,680W, as the 16A limits could put out a lot more if the voltage coming into the house is much higher, eg if voltage 250V, then a G83/1 16A limited inverter could still put out 4,000W.

Sorry for the long answer, but there are now a few various caps, and if DNO permission hasn't been sought to exceed 16A then more and more 4kWp installs will probably be installed with sub 4000 inverters eg 3600, 3800, 3900 models etc.

Mart.

WestonDave

It was suggested to us on the basis that we're having a split system (9 panels SE facing, 7 SW facing - going on the roof as I type!) and so the chances of us ever hitting 4Kwp were low, and also on the basis that as the panels will degrade giving lower performance over time the capping effect would be shortlived, it was worth saving a bit and having a lower power inverter. That makes a lot of sense when costs are tight because what you will lose is the odd hour when ambient temperatures are low enough but the sun strong enough to get absolutely peak performance from the panels in the first few years. In the end I declined to change because I preferred the SMA inverter to the Aurora which was the lower power option (it was a 3.6kwp one so not as far down as you've gone).

That was one reason we chose the installers we did - they gave us options on panels and inverters, gave us the pros and cons from their perspective, and then left us space to do our own research and come to a decision for ourselves, whereas others were more of a "take it or leave it " package.

(Edited to add - because we have two aspects we needed a dual string inverter which tends to push you towards the higher rated ones anyway, which would be a valid reason for not recommending going below the 3.6kwp Aurora)

HeyRevolver

Martyn1981 wrote: »

Hiya HR, you'll probably find quite a few on these threads if you read the system specs. There are also a few different forms of capping.

Some systems have undersized inverters, like yours, which work on the basis that they loose a bit off the top some days, but are a little more efficient at other times, plus they might switch on a bit earlier, and off later.

Mart.

Thanks will take a look see.

I actually downloaded the SMA Sunny Design software and for my 3.5 kW panel system I compared the SB3000 invertor I have that caps output at 3kW to the SB3600 which wouldn't cap any higher end potential.

Funnily enough the software said both invertors would perform roughly the same over the year. Although I could quite understand why!

The SB300 I have did have a slightly better efficiency but only about 0.6%!

HeyRevolver

sorry that was meant to be:

"Although I couldn't quite understand why!

The SB3000 I have did have a slightly better efficiency but only about 0.6%!

Martyn1981

HeyRevolver wrote: »

Thanks will take a look see.

I actually downloaded the SMA Sunny Design software and for my 3.5 kW panel system I compared the SB3000 invertor I have that caps output at 3kW to the SB3600 which wouldn't cap any higher end potential.

Funnily enough the software said both invertors would perform roughly the same over the year. Although I couldn't quite understand why!

The SB300 I have did have a slightly better efficiency but only about 0.6%!

Hiya HR, I've had a good play with the Sunny Design programme too, just for fun, but quite enlightening as to the wide(ish) range of inverters to panel array size that they consider suitable. I've also had an e-mail conversation with SMA directly about this issue, and they refer to Sunny Design as indicating what is correct and suitable. This is important as the package will indicate if net panel voltage is too high or too low for any selected inverter.

The reason that they 'may' perform roughly the same (how will you ever know?) is that the smaller inverter should be a little more efficient, and therefore scrape out a few more watts, but of course lose some when generation is very high - good sun, and cold panels.

I posted a much more detailed and comprehensive response some time ago, that I lifted of another forum (after checking first) that far better explains the sizing of inverters than I ever could, hopefully this link will work:-

Martyn1981 wrote: »

Holy Exploding Undersized Inverters Batman!

Any help?

Mart.