Quotes and install questions

Martyn1981

Zarch wrote: »

Can't believe i've not asked this before, but what generation can you expect from panels in full shade?

These East-ish facing 300w panels i'm hoping to put in will be in full shade from 2pm onwards. So it could still be a bright summers day everywhere else.

What performance do you get in full shade during the day? Good, bad of indifferent?

East and 2pm takes the pressure off. They will lose some gen especially in the summer, but will be losing power anyway from 2pm onwards.

On a perfectly clear blue sky (very, very rare) my west panels generate almost nothing in the morning, and my east panels next to nothing in the evening, whereas with a little bit of white, the light still gets reflected back down, which shade won't affect.

No escaping the fact you will lose some gen especially from 2pm to 4pm, but not too big a worry. If they were west facing panels, then it would be a disaster.

JKenH

Martyn1981 wrote: »

On a perfectly clear blue sky (very, very rare) my west panels generate almost nothing in the morning, and my east panels next to nothing in the evening, whereas with a little bit of white, the light still gets reflected back down, which shade won't affect.

Ah, that probably explains why a couple of days ago with my East and West facing roofs I had disappointing overall power from a crystal clear sky. Peak PV was just over 4 kw compared to over 5kw today with some cloud about.

Zarch

Almost ready to hit 'buy' from CTS. Almost certainly going to go with 17 x 300w (5.1kWh) rather than 17 x 320w (5.44kWh). Cannot justify the extra £700 as discussed previously.

They've said the DNO application/approval will be zero cost which is nice. Although we've still not heard back from the DNO application and that has been with them a month now...... they turn the applications round in 'up-to' 45 days, so they've jut 2 weeks left.

If DNO approval comes through we are sticking with the 5000kWh inverter. Nothing much to be gained from dropping to 3680 CTS say and they'd recommend the 5000 model. Obviously, DNO rejection could change this.

I noticed there is a £45 wi-fi module required for the Solar Edge inverter if you can't run ethernet to where your inverter is. Luckily i've got a spare powerline adapter and i'll just run that into there and save the £50.

So what is the delay you ask? Well my roofer can't come until October to repair/relay the roof on the dormer. And i'm not putting panels on there without it being in tip top shape and currently its showing its age.

Running over into October means the FIT rates drop ever so slightly into the final quarter of the year, but its less than tenth of a penny, so would only be losing about £35 over 10 years.

So the quote for the whole shanbang is £6400. I'm hoping this might reduce if we go into October and components drop in price.

Maybe the 320w come down to viable price? Not holding my breath.

I just want to get it all installed so I can start looking at daily graphs!! :rotfl:

pinnks

Good job! Hope the install goes well. I am sure you'll report back in due course...:beer:

JKenH

I have a 7.8kwp system with 4.2 kwp on the west facing (80* west of south) roof with a 39* pitch. The panels on that roof feed into a Sofar Solar 3680TLM inverter (3.68kw). I live in not so sunny north west Lincolnshire. Given our latitude, and the orientation and pitch of the roof is the inverter ever going to limit output from those panels? (I see that Pinnks has a 4000TL for his 3.5kwp array with a similar orientation and pitch.).

I am suspecting not but would welcome the views of you technical guys on here.

The 3.6kwp of panels on the east side of the roof (100*east of S), same pitch, have their own inverter.

Out of interest can anyone speculate as to the peak kw I might see from my installation in ideal conditions. Best I have seen is 5.95kw.

Thanks in anticipation.

Coastalwatch

JKenH wrote: »

I have a 7.8kwp system with 4.2 kwp on the west facing (80* west of south) roof with a 39* pitch. The panels on that roof feed into a Sofar Solar 3680TLM inverter (3.68kw). I live in not so sunny north west Lincolnshire. Given our latitude, and the orientation and pitch of the roof is the inverter ever going to limit output from those panels? (I see that Pinnks has a 4000TL for his 3.5kwp array with a similar orientation and pitch.).

I am suspecting not but would welcome the views of you technical guys on here.

The 3.6kwp of panels on the east side of the roof (100*east of S), same pitch, have their own inverter.

Out of interest can anyone speculate as to the peak kw I might see from my installation in ideal conditions. Best I have seen is 5.95kw.

Thanks in anticipation.

Hi Ken, I'm no expert but popping onto the pvgis website and plugging your figures in it suggests that the total losses in the PV array to be 23%. Thus removing this from your peak output of 4.2 kW leaves a figure of 3.2 kW. From this it would seem that your inverter is unlikely to limit output of your system.
Applying these simple figures to the entire system then 7.8 kWp minus 23% returns 6.005 kWp.


There may of course be other issues not shown here to take into account but from my simple view your max figure seems to confirm that all is in order. One other clue to all this would be the curve on your output graph. If you have a gentle curve all the way up and back down then peak would appear to be reached. If on the other hand the curve has a flat at peak output then your output could be limited by the Inverter.
Happy to be proved otherwise!

JKenH

Coastalwatch wrote: »

Hi Ken, I'm no expert but popping onto the pvgis website and plugging your figures in it suggests that the total losses in the PV array to be 23%. Thus removing this from your peak output of 4.2 kW leaves a figure of 3.2 kW. From this it would seem that your inverter is unlikely to limit output of your system.
Applying these simple figures to the entire system then 7.8 kWp minus 23% returns 6.005 kWp.


There may of course be other issues not shown here to take into account but from my simple view your max figure seems to confirm that all is in order. One other clue to all this would be the curve on your output graph. If you have a gentle curve all the way up and back down then peak would appear to be reached. If on the other hand the curve has a flat at peak output then your output could be limited by the Inverter.
Happy to be proved otherwise!

Thanks for that. Sounds as though everything is hunky dory then. Is that 23% down on peak PV or would that be the shortfall over the year? I was only expecting to be about 10per cent down in the summer but more in the winter.

Martyn1981

Ken, gut feeling for me, is that you are fine, very fine!

There will be times, perhaps April & October when the sky is clear and temps are low that the 4.2kWp will max out, possibly even go 100%+, but these will be short times before the panels get hot. 90% is more likely the peak, so 3.78kW, but again not for significant periods, and the smaller inverter will be more efficient at lower generation times, so overall may be a better package than one closer to 4.2kW.

You don't hear it so often now, but there used to be a rough guide that for the UK a 10%-20% undersized inverter would give you the most annual generation. It would depend on location and orientation, so south facing on the Cornish coast you might go with closer to 100%, but for off south orientations it's worth considering 'poor' weather generation for the UK, whereas you wouldn't bother for sunnier climes.

Extrapolating from my system (5.58kWp), I see brief peaks of 5kW (when there are clouds or sun showers) and sustained gen of 4.2kW, these are summer figures when the sun can 'see' all the panels, so around 11am - 3pm. For you that would work out around 7kW and 5.87kW, which seem to fit with your experience and Coastalwatch's calcs.

Looking good.

JKenH

Thanks Martyn, that is really interesting. I remember looking at the graphs for my best day so far, my one and only Hawaii which was in late July and saw peak PV was only about 4kw. It was a stinking hot day. Just recently when the sun has deigned to show its face I have seen peak figures regularly above 5kw.

Hopefully on a cool day like today we should see something good. My day did not get off to a great start though as my system tripped out again, just as it had yesterday at 6.45 am. Foolishly after getting up at 6 I had gone back to bed and dozed off so hadn’t picked up on that until 7.45. When the panels got up to speed I saw 2.83 kw then it slipped back and is now climbing again. The sky is quite consistently clear so I was a bit puzzled by that peak - could it have been because the system had just woken up again? Optimum orientation for the panels on my east roof would probably be about 6am BST but of course the sun would be lower in the sky then. I am thinking that the sun will be at 90* to my panels at about 12.30. BST so my East facing panels should peak somewhere between those times.

My west facing panels will pick up as the sun gets in the sky and mess my calculations up of course so I will just have to go in the loft and keep an eye on the inverters. Presumably as the day warms up performance will fall off as well.

Do you fancy writing a programme, Martyn, so we can get our predicted PV by just entering our latitude, pitch, date, time of day air temp, and any other variables you can think of? Only joking but it would be fun and I suspect you are the man who could rise to such a challenge.:):)

Zarch

Even though this conversation is taking my install thread off topic!!

I can't help but get involved.

How about this site?
https://pvwatts.nrel.gov/index.php

You can put a location in (not as exact as PVGIS as it seems primarily North America focused). But find somewhere reasonably local and you can then download a full year of hourly generation estimates in .csv format.

Might be worth you guys who have some actual generation data to compare these estimates against.

Have fun. :rotfl: