Improving output from existing MCS 4kW array

[Solarexploits]

I have a 4kW (17 x 230W panels so actually 3910W) MCS array, installed back in 2011, so long ago paid for itself with the FIT payments, the inverter is a Sunny Boy, never had any problems or faults with the system since installation. The array is almost due W facing, very slightly SW/W & is shaded by trees for part of the day, part of the array, particularly early to mid morning & late afternoon/early evening, depending on time of year, substantially worse in Winter than Summer. It produces, typically, around 2,900kWh a year, consistent for last 3 years, since some trees were removed which reduced shading, can't remove any further trees/shading due to TPO's on the tress

 

I'd like to improve the output if possible; obviously this was installed back when no one was installing micro inverters or any form of individual control, the company that installed is long gone into liquidation, they told me it was installed as 2 parts, presumably in parallel to reduce the effect of the shading, though I've never actually checked this by confirming how panels are connected

 

I have zero knowledge of the more modern methods which I believe have more control over individual panels which I understand improves output

 

Can someone please enlighten me on any possible improvements (I already use a Solic immersion controller which is giving me free hot water around 7 or 8 months & reducing gas usage for some of the other 4 or 5). I assume by recognising  a single shaded panel & "removing" it from the array improves the performance of any series connected string?

 

What systems are out there, at what sort of cost & how much grief & aggravation to install?

 

Any info most welcome, thanks in advance

[SteamyTea]

12 minutes ago, Solarexploits said:

aggravation to install

Will almost certainly involve scaffolding, removing the modules, fitting the micro inverters or 'smart controllers, then rewiring back to a new in inverter.

SMA has a good, dual string MPPT built in, though, as you say, does depend on how the modules were originally wired.

Getting 3 MWh per years, depending on your location, sounds pretty good.

Have you run the numbers though PVGIS to see what it predicts?

 

If your car does 40 MPG and you drive 8000 miles a year, improving it to 45 MPG saves about 1 MWh of energy.

Edited May 17, 2022 by SteamyTea

[Solarexploits]

Just had a look at PVGIS - not sure I'm doing it right, location is Thundersley, Essex, I have kWh at 3.91 & azimuth at -60 (I believe correct for 10 degrees off due West, that's a slight guess), roof slope at 35 degrees, again, a bit of a guess it suggest an output of over 3,600kWh, that would be an increase of over 20%, if I could even get a 10% improvement then that would be worth around £150 a year in FIT payments to say nothing of further reduced leccy bills & also a reduction in gas usage as it improve output to the immersion

 

However, £150 a tear doesn't sound worth stripping panels off the roof & replacing the inverter!

 

I'd hoped the smart controllers could be connected direct from the panels & mounted underneath them, without removal, also hadn't considered it would require replacement of the inverter. Why does inverter need to be replaced? I'd assumed it would simply "see" a slightly increased input coming to it, I take it that's not the case?

 

Re cars & mileage, I already have a fully electric Kona - great piece of kit, 300 mile range in Summer, more like 220 or so in Winter. averages around 4kW per mile, more round town, less on motorways

[SteamyTea]

3 minutes ago, Solarexploits said:

it suggest an output of over 3,600kWh

But you have some tree shading, and you cannot get rid of that.

Your modules may have lost a few percent of their performance in the last decade as well. Have a look back at your old data to see what it was producing.

Your current inverter may be a bit oversized, but probably not worth changing.

 

Used to go through Thundersley, every day, on way to school in Westcliff on Sea. Life was in black and white in those days.

[SteamyTea]

9 minutes ago, Solarexploits said:

averages around 4kW per mile

I hope it don't. More usual to measure it in Wh/mile.

My old oil burning Ford (take the boy out of Essex, but not Essex out the boy) uses about 1.5 kWh/mile.

[Solarexploits]

Ok, next daft question, could I add solar optimisers to each panel (DIY?)?

 

Are these "panel specific" or can I buy, say, a 300w optimiser to use with a 235W panel (I think my original figure of 230W was in fact incorrect!)

 

Does this then mean I can keep the Sunny Boy inverter, or do the optimisers need to "talk" to an "intelligent" inverter to work correctly

 

Bear in mind, I'm not looking for absolute max efficiency here, just something that might be economically viable

[SteamyTea]

I have seen optimisers added to each module (still need to remove modules) and then wired as normal into a SMS SB (4000 TL).

Don't remember any advantage, but it was an unshaded install anyway, just a customer being ripped off.

Edited May 17, 2022 by SteamyTea

[Solarexploits]

Ha Ha! I meant 4 miles per kW!

[Solarexploits]

So from the sound of things there's nothing I can do (reasonably cheaply) with the existing array that's going to improve output, other than if the shading could be removed/improved?

 

I'm actually getting more out of the system now than it ever put out in the early years, but I know we were able to reduce the shading 4 years back with some tree lopping

[SteamyTea]

More lopping.

Copper nails can help to attach things to trees.

 

[Dillsue]

Within the FIT scheme youre only supposed to change things on a like for like basis ie replace a 235w module/panel with a 235w(ish) new panel. Adding optimisers is a system design change and would likely need approval from your FIT payer. We have a FIT system with optimisers so they are a permitted bit of kit but a retro fit probably needs approval and fitting by an MCS accredited installer. 

 

Sums probably wont add up so maybe best to keep the panels clean and the trees pruned as best you can.

[joth]

8 hours ago, Solarexploits said:

can't remove any further trees/shading due to TPO's on the tress

You can still make changes to the trees (esp lopping that maybe needed for safety), you just need to file an application

https://www.gov.uk/apply-work-on-protected-tree

We've done several

 

[Solarexploits]

On 17/05/2022 at 18:41, joth said:

You can still make changes to the trees (esp lopping that maybe needed for safety), you just need to file an application

https://www.gov.uk/apply-work-on-protected-tree

We've done several

 

Yeah, just done exactly that, we were able to make a substantial difference with some removal/lopping a few years back, the more recent work has little effect in Summer, but will improve things slightly in Winter, unfortunately given the price of tree surgery that's going to be a Loooong payback period!