Solar Panel Guide Discussion

Martyn1981

oldskoo1 wrote: »

Hi all been researching solar panel installs for the past few days.

My roof is south facing, literally 183 degrees, its of normal angle with no shading, no trees but the house nearby might block the summer sun around 30mins to 1hr before sunset (on roof). We tend to get sun on patio and garden until 7:40pm.

Does high efficiency of the 330w Benq really make much difference or is it just a space consideration (i.e. i need less panels to generate 4kWh?).

Hiya. Glad you wrote the bit about efficiency/space consideration. That saves me from having to write a huge explanation. Basically, efficiency in similar kWp sized installs is irrelevant. A 4kWp system is a 4kWp system, and other than some sales claims, will generate roughly the same, regardless of the efficiency ratings of the panels.

However, higher efficiency panels will do this whilst taking up less space, but unfortunately whilst also taking up more cash. If roof space is plenty, then no need to look further than regular panels, typically 250Wp and ~1m by 1.6m.


Don't blame you for researching panels and (soon?) inverters, but may be a waste of time. You need to get some installers round and get some quotes. They will suggest the panels and inverters that they typically source (depending on their supplier, and what prices are current at that time - this may simply mean what container load recently arrived from China).

Once you have quotes (and panels and inverters) you can do some research to check that these are (if nothing else) reasonably well known, and others on here have same/similar.

Regarding your not wanting "anything premium or clever". If you have a good southerly roof, with minimal shading, then any claims that a premium/clever product will boost your generation are probably BS. So stick to your guns.

If you need some general PV advice, and haven't already read them, try sections 1 & 2 of the FAQs.

Best of luck, and keep chatting.

Mart.

oldskoo1

Thanks Mart really informative!

Regarding efficiency and space, I read it's also mostly bs, however I did read that the sun power panels for example can capture more energy at higher temperatures.

This suggested to me that on the same day, same roof there would be a difference in kWh generated so this lead me on a search for the best panels and inverter for the £.

I'm also confused about wether I need micro inverters. I have no shading and they are premium but apparently easier to diagnose problems easier to monitor panel output. Then to add complexity I found the solar edge optimiser solution. Getting their inverter and optimiser module for each panel is probably going to be around £1,300 for a 16 panel array. The only test I found suggested it produced more kWh when tested alongside other inverters on the same roof even with no shade. I'm referring to this test : http://www.solarstarpower.co.uk/inverters.html

So it kind of made me think the solar edge inverter and optimiser solution was worth gettin, hooked up to a Chinese panel like the ja solar or benq 250, both of which are cheap around £130-150 each.

Seemed to me ja panels and solar edge kit would be £3,700 cost, but then I have no idea how much thr fixings and mountings are, I will need a lot of cable, brackets, monitor etc. I assumed another 1k for additional materials and 1k for install including scaffolding somewhere in that extra 2k.

I've only submitted 1 quote so far to Evo energy. Will be looking at the Phoenix works too.


Will be reading the FAQs now too

Thanks

Martyn1981

oldskoo1 wrote: »

This suggested to me that on the same day, same roof there would be a difference in kWh generated so this lead me on a search for the best panels and inverter for the £.

I'm also confused about wether I need micro inverters. I have no shading and they are premium but apparently easier to diagnose problems easier to monitor panel output. Then to add complexity I found the solar edge optimiser solution.

Hiya. Gonna contradict myself now, but whilst I think it's usually a good idea in life to find and invest in the most efficient kit, with PV you do have to consider the cost, and the resultant return on investmnet (ROI). No point spending 10% more capital to get 5% more return.

So, there may be some small gains from the very best panels (I'm really not sure) but the extra cost may result in a lower ROI.

Micro's or PO's - I've got a SolarEdge system on my heavily shaded WNW roof. I can't praise it enough, it's brilliant. But if you don't have shading, then it's main benefit isn't needed. There are additional gains, for instance most panels have a 5% performance tolerance, usually ranging from 0 to +5% these days. You could conclude from that, that the average panel is +2.5% but an ordinary inverter will run the whole string at the lowest common denominator, whereas a SE system could get the best from each panel. There are other small pluses like this, see this video (and the next 2 parts) for all the info:

SolarEdge

but the non-shading factors are quite small, and a SE setup will probably cost about £500 more than a regular system. That could be about 10% more cost, so you'd need 10% more generation, and there is still the issue of access if one of those extra 16 bits of kit on your roof goes wrong.

From your original description of your roof, and the minimal early evening shading I don't think you need to think outside of the box. Try to get a regular system with average panels, and an average inverter hopefully for a price as near to £5k as possible, then sit back and enjoy.

Or more probably, stress for a month about spending so much dosh on this new magic thingy, before realising that it pretty much does exactly what you expected ..... then sit back and enjoy.

Mart.

oldskoo1

Thanks again Mart

Do you have any recommendations on which high efficiency reasonable cost inverter to look out for in the quotes I receive.

This is a pic of the roof from around 11am

Martyn1981

oldskoo1 wrote: »

Thanks again Mart

Do you have any recommendations on which high efficiency reasonable cost inverter to look out for in the quotes I receive.

This is a pic of the roof from around 11am

It's weird how the world looks different as you get new interests and hobbies - but have to say that pic is PV roof !!!!!!!

There could be dozens of inverter makes (and even more models) quoted, so have a Google at the specs when the quotes come in, but for starters here's an interesting price range for well respected and popular models:

The German high reputation company SMA with their SunnyBoy range. Excellent shade management software (if you have shade), a good reputation and high(ish) cost:

SMA 4000TL

Cheap Chinese Samil range, that's quickly built up a good reputation with some of the respected installers that I've pestered for information over the years on the Navitron forum. Shade management isn't as good, but they are cheaper, are fractionally more efficient, and have a longer standard warranty:

Solar River 4000TL

Don't drive yourself insane over this, do some research and ask for a little reassurance on here regarding the kit suggested as and when quotes come in.

Are you feeling a little more confident/happy about things yet? Or steadily more confused as the knowledge base builds and you temporarily start to drown?

Mart.

oldskoo1

Mart i'm much more confident with whats on offer and what to look for but its like going further down the rabbit hole.

For example, i feel i have a range of panels and inverters i know enough about / are good enough quality / even highly efficient for the pricing thanks to the knowledge you and others have shared. But the rabbit hole is enticing as now i'm reading about healthy voltages on the panels, how to interpret the stats and i'd like to know how the array is configured. I just find it all very interesting.

Maybe naive still but i'm still thinking the Benq 280w panels and now this samil inverter after reading some posts on navitron.

As i'm paying attention to the roof now (yes i do agree it would be rude not to install solar on there), i realised at around 7pm tonight when i came home that the bottom left edge is partially shaded, i'd say the bottom left 1/4 was shaded and looking now at 7:40pm only the top 1/4 of the roof is in sun.

Sunset is in 20 mins. So i'm wondering with the samil string inverter does the entire array drop down its power or can it be configured so the top row keep going strong until sun down.

//Edit here is the situation i'm talking about. Nearby house and horizon is very elevated with hills.


Wondering if the panels can be configured to keep going strong along the top or right maybe. I suppose its less than 1 hour to sunset when this was taken so i probably don't need to worry.

Again gaps in knowledge here but i'm enjoying learning.

p.s. i won't get too hung up on the hardware, i will see what quotes come in.

I'm contacting
EvoEnergy
Phoenix works
GreenDay
CTS Renewables
TP Solar

Evo is the only one i found myself but i suppose thats because they have a bigger marketing budget than the others and are easily found on google.

zeupater

oldskoo1 wrote: »

.... i realised at around 7pm tonight when i came home that the bottom left edge is partially shaded, i'd say the bottom left 1/4 was shaded and looking now at 7:40pm only the top 1/4 of the roof is in sun.

Sunset is in 20 mins. So i'm wondering with the samil string inverter does the entire array drop down its power or can it be configured so the top row keep going strong until sun down ....

... Wondering if the panels can be configured to keep going strong along the top or right maybe. I suppose its less than 1 hour to sunset when this was taken so i probably don't need to worry ....

Hi

From the length of the shadows (chimney & alarm box) it looks like it's almost time to lose direct sun off the front face anyway. As daylight hours increase you'll find that the shadow will progressively move down the roof due to the sun being at a higher angle at the time the photo was taken, but as sunset becomes later it starts to move towards NW and with that roof aspect you'll be generating comparatively little after 19:40/20:00 anyway so it's probably not worth worrying about it ...

Regarding the configuration of the strings, if you're looking at a 4kWp system you'll probably be going for something like a SB4000TL which has two MPPTs and shade management, so as long as the installer configures the strings an the different MPPTs and enables the SM that's probably as good as you'd get .... We get some mid-winter shade from trees ~40metres away in our front garden and our panels are configured into 10+6 arrays on separate MPPTs to mitigate ... a decent installer should note & make allowance for this.

Today looks to have been a pretty decent day for generation over much of the country, so there should be loads of systems on PVOutput (http://pvoutput.org/) with pretty smooth bell-curve generation, so have a look at some nearby south-facing systems to see what generation levels they achieved at this time in the evening today .... also look at their late evening mid-summer (last year) generation levels to confirm the significance of the potential for evening losses ....

HTH
Z

oldskoo1

Thanks Z I will register with pv output and see what I can find nearby.

I thought it's probably not worth thinking about so late in the day. I'm still reading up on now they are configured.

One thing sprung up, looking into the samil inverters, the 4000 model only has an AC output of 3.68kW.

Compared to the SMA at 4kW. So is the samil going to limit the ful potential of the panels?

I know they do a 4500 model but that outputs 4.2kW which is over the standard regulated upper limit of 4kW.

oldskoo1

Wait a min, I'm connecting some dots here.

My electric car charge point had a long 35m run of 6mm SWA and reported 222-225v 32amp with distance drop. So assuming my house voltage is around the average 230v 16amp that's 3.68kW same as samil.

So is the 4kW panels linked somehow to the grid limit. Bit hazy after the calc. Could have sworn I saw a post somewhere showing someone's panels producing 255v 16amp

Should I be concerned about samils lower limit.

Martyn1981

oldskoo1 wrote: »

Mart i'm much more confident with whats on offer and what to look for but its like going further down the rabbit hole.

Sunset is in 20 mins. So i'm wondering with the samil string inverter does the entire array drop down its power or can it be configured so the top row keep going strong until sun down.

Wondering if the panels can be configured to keep going strong along the top or right maybe. I suppose its less than 1 hour to sunset when this was taken so i probably don't need to worry.

Again gaps in knowledge here but i'm enjoying learning.

Congrats, your brain is doing great, and your knowledge is just one step behind.

For large roofs with lots of panels, the total voltage will usually exceed the max the inverter can cope with, so two (or more) strings are needed. Therefore, the sensible thing is to separate the panels according to shading. This would usually mean a top and bottom string, or a left and right string, but simply based on how the shading will impact, so that it's contained on one string at a time.

So, yes you're absolutely correct, it should be configured sensibly. But as Zeup says, your shading is minimal, since the time of day (given your roof orientation) will mean generation has dropped significantly already. Doesn't mean it won't be noticeable, but you have to consider the value of the lost generation against spending to mitigate, and other than sensibly designed strings, probably not prudent to do much more.

Also, both inverter examples I posted have dual MPPT's, meaning that the separate strings will actually run independently. See the bottom half of this post for a full(er) explanation

Martyn1981 wrote: »

Most inverters can handle multiple strings.

Must admit to being a little out of my depth now, but I think that with your minimal shading, a single MPPT inverter (but 2 strings) might be better, as I think a dual MPPT inverter works out fractionally less efficient than a single. (Might have read that on Navitron) but in the examples given, in that other thread, the efficiencies are identical!

oldskoo1 wrote: »

One thing sprung up, looking into the samil inverters, the 4000 model only has an AC output of 3.68kW.

Compared to the SMA at 4kW. So is the samil going to limit the ful potential of the panels?

&

oldskoo1 wrote: »

Wait a min, I'm connecting some dots here.

My electric car charge point had a long 35m run of 6mm SWA and reported 222-225v 32amp with distance drop. So assuming my house voltage is around the average 230v 16amp that's 3.68kW same as samil.

So is the 4kW panels linked somehow to the grid limit. Bit hazy after the calc. Could have sworn I saw a post somewhere showing someone's panels producing 255v 16amp

Should I be concerned about samils lower limit.

Don't be concerned. 4 things:

First, I cheated, I wanted to post near identical examples, but the site didn't have a 3.68kW capped SMA model to pick, so I compromised knowing that the installer will almost certainly cap it (when installing) to 3.68kW, then registering it as such. Why, because,

Secondly, in the UK you can install a system capable of exporting 3.68kW, then inform the DNO (district network operator) who will then register it. The DNO needs to know about each and every SSEG (small scale electricity generator) on it's system, to ensure each part can cope.

But, if you want to install a system that can potentially exceed 3.68kW (even if only theoretical) then you have to ask the DNO for prior permission.

Thirdly, it's irrelevant. Once the panels get hot, their generation will drop off 10% fast, a few seconds, perhaps 1 min. So a 4kWp system will rarely exceed 3.6kW for long. You may see short spikes during cloudy weather of 100% even 105%, but sustained generation will be lower. So an inverter that caps the very top, will not noticeably effect generation. Highest generation spikes are often seen in April/Oct when the sky is clear, but temps are low. However total generation will probably be less than in the summer when temps drag down performance, but the longer day generates more in total.

Fourthly, undersizing an inverter a small amount might be beneficial in the UK. You lose a little bit to capping, but it will hopefully be slightly more efficient at the lower end (start, finish, poor weather) and may outperform a full size (or oversized) inverter.

Mart.