Solar PV Peak Output?

Hobbo2006

Firstly, Happy Cloudless Day Everyone! (if you live near me that is). I'm sure today is going to be the best so far.

I'll admit that before my solar panel installation I knew nothing about them whatsoever. I had no preconceptions at all. I was just concerned with whether the panels would return roughly what the SAP calculations said they would, and therefore the FIT payouts would be as quoted.

After installation I'm starting to find out more and ask questions. One of which is about the peak output of the system. I see that although we have a 4kW system the peak output is rarely above 2kW. Presumably the close we get to Jun 21st the better that will get. Just wondering what peak output's other installations get?

Would anyone be able to work out what the peak output would be of the following system?

11 x 250w panels facing West, 5 x 250w panels facing East, Aurora Power One 3.6 outdoor inverter

Is there anyone with the perfect installation? Due South, 4kW, optimum angle, no shading that could post their peak output figures?

I know that the invertor can take up to 4.25kW, according to Aurora's own manual so is there room for 5/6 more panels to go on the East side of the roof? (there is physical room for this).

My guess is that it's not as simple as this but maybe, just maybe it is! :cheesy:

EricMears

Hobbo2006 wrote: »

Firstly, Happy Cloudless Day Everyone! (if you live near me that is). I'm sure today is going to be the best so far.

I'll admit that before my solar panel installation I knew nothing about them whatsoever. I had no preconceptions at all. I was just concerned with whether the panels would return roughly what the SAP calculations said they would, and therefore the FIT payouts would be as quoted.

After installation I'm starting to find out more and ask questions. One of which is about the peak output of the system. I see that although we have a 4kW system the peak output is rarely above 2kW. Presumably the close we get to Jun 21st the better that will get. Just wondering what peak output's other installations get?

Would anyone be able to work out what the peak output would be of the following system?

11 x 250w panels facing West, 5 x 250w panels facing East, Aurora Power One 3.6 outdoor inverter

Is there anyone with the perfect installation? Due South, 4kW, optimum angle, no shading that could post their peak output figures?

I know that the invertor can take up to 4.25kW, according to Aurora's own manual so is there room for 5/6 more panels to go on the East side of the roof? (there is physical room for this).

My guess is that it's not as simple as this but maybe, just maybe it is! :cheesy:

It would indeed be simple to add a few more panels. However, that would drop you into the next FIT band and indeed it would probably 'expel' you from the old scheme altogether.

My installation is far from 'perfect' - it's been put a high as possible to avoid shading from nearby trees so is on top of a very shallow dormer roof. Even on Summer Solstice day I won't quite get to optimum angle but I am fairly confident of getting to 4kw. I peaked at well over 3.5kw in late August so should get to same sort of peak next month and hopefully better still during good days in May, June & July (if we have any !:mad:).

A near neighbour has a similar set of panels but on tracking frames. Even his isn't 'ideal' as there is some tree shading early and late in day.

Hobbo2006

seagull09 wrote: »

Understand that completely - a very valid concern, and one which I have found with my setup (wrong inverter, mainly) that I will not get to SAP and possibly not even to PVGIS estimate which for where I live is actually lower than SAP. Bit of a pain, that is.
As you have the proper inverter though for a split array setup you have a good chance of making the target.




As you have an east west split I would doubt you'd ever see a peak of much more than 3kW - that would be on a day when you were making the maximum 2750W from your West panels, and a couple of hundred from your East panels. Because although cloudy conditions will give you more consistency between east and west, it has to be sunny to get maximum, and on a clear day the side facing away from sun won't be doing very much. You might get an occasional fluke where clear sun from west reflects off white clouds in east to give you over 3kW.

But the thing with solar is that every single system seems to perform differently, so who knows. I don't think you'll get bad figures anyway.

ah so an elaborate system of mirrors instead then?

EricMears

Hobbo2006 wrote: »

ah so an elaborate system of mirrors instead then?

I've (briefly) considered that too ! Suspect it would need planning permission as mirrors would need to be fitted well away from the permitted developmnt zone but more importantly they'd be subject to enormous wind stress.

Martyn1981

Hobbo2006 wrote: »

Would anyone be able to work out what the peak output would be of the following system?

11 x 250w panels facing West, 5 x 250w panels facing East, Aurora Power One 3.6 outdoor inverter

Is there anyone with the perfect installation? Due South, 4kW, optimum angle, no shading that could post their peak output figures?

I know that the invertor can take up to 4.25kW, according to Aurora's own manual so is there room for 5/6 more panels to go on the East side of the roof? (there is physical room for this).

My guess is that it's not as simple as this but maybe, just maybe it is! :cheesy:

Hello Hobbo, I think Eric and Seagull are spot on. At a quick guess I'd say your peak would be short (5 mins max?) all West plus a few hundred from the East, so maybe 3kW. Sustained, probably 90% West + 2 or 3 hundred East, so 2.8kW maybe?

A perfect due South 4kWp would probably sustain around 3.6kW, but see short peaks of perhaps 4 or 4.2kW.

Assuming you're not exceeding any voltage maximum input (not kW limit, but actual sum of panels voltage) then you're probably right that you could put some more on the East.

There used to be a rule that any change within 12 months would mean re-assessing the new total system. However, I believe that changed last year, and now any addition will be treated as a separate install, however subject to the total kWp rate appropriate at that time. So say you were able to add 4 more panels, the new 1kWp system would get the tariff appropriate at the time of installation but for a 4-10kWp system based on the total installed capacity of 5kWp. But your existing 4kWp system would be left unaffected. Does that make any sense?

As you'd be using the same inverter and TGM, the quarterly readings would be proportionalised (probably 4:1) unless I'm missing something obvious, or they're not true East and West and have a slight +/- performance.

Mart.

PS E / W split is a great set up, giving you a nice wide, long generation, and in your case, lots of power later in the day when you are more likely to use it. M.

GaryMo_2

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.

wensleydale

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

EricMears

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

Possibly.

If you've got a SunnyBoy inverter and can run the SunnyExplorer software, you can look at the DC current & voltage of the two strings separately. That may also be possible with other inverters but afraid I don't know which. If you tell us what inverter you've got, somebody with same one may be able to advise.

Or of course you might have a shading problem but that's usually easy to spot from a neighbour's upstairs window. If you can see a shadow on the roof you have a problem.

wensleydale

EricMears wrote: »

Possibly.

If you've got a SunnyBoy inverter and can run the SunnyExplorer software, you can look at the DC current & voltage of the two strings separately. That may also be possible with other inverters but afraid I don't know which. If you tell us what inverter you've got, somebody with same one may be able to advise.

Or of course you might have a shading problem but that's usually easy to spot from a neighbour's upstairs window. If you can see a shadow on the roof you have a problem.

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.

Lemoncurd

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.

EricMears

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.

From the basic display window, click on the 'spot values' tab then expand the paragraph marked DC measurements.

I'm assuming the SE facing panels on one string & SW facing ones on the other. In which case before noon you'd expect to see a lot of generation on one string but much less on the other and positions should be reversed after noon (not an instant switch of course - for an hour either side of noon they'll probably be pretty similar).

Highly unlikely, but if installer has coupled up panels in his sleep and put some SE & some SW on one string and a similar mix on the other then you'll always be generating at whatever the lowest individual panel in a string is producing.

Doesn't sound like a major shading problem - but of course you need to wait until Sunny Explorer confirms something odd is happening then rush out & look.