Changing system capacity - FIT

Martyn1981

tunnel wrote: »

Think this may answer my own question,

Still think its open to challenge,if a FIT provider doesn't change their contract T&C's in line with goverment policy they're leaving themselves wide open. Just my thoughts.

Martyn,On your extensions,have you had an export meter put in? Do you think its possible to "use" the leccy off the 1st install but export more from the extensions to make use of the 4.5p export tariff?

Damn, that's a good question! I assume (please note entirely my assumption) that with an export meter export will be aggregated in line with the relative generations of both systems. So if one system generates 4 and the other 2, but export was measured and was 3, then it would be paid on the same ratio of 2:1. Does that make sense.

I've thought of getting an export meter, but EDF don't do them for free or reasonable, so might just wait for a smart meter circa 2099?

Just thought, I should have something on extensions in my 'extensions' e-mail folder (yes I really am that sad) back in a bit.

Mart.

Martyn1981

tunnel wrote: »

I'm pretty similar to yourself mate, existing is ESE(1.96kwp),extension will be SSW(2kwp) and considering a WNW(2-2.5kwp)(my missus at home all day with 2 small kids and uses the leccy for fun:mad:)

Tunnel

Stop distracting me!!! I was going to do some e-mail tidying.

If you add SSW to the ESE then ignoring any shading, the new system should outperform the old one slightly. With me so far?

So, replacing your existing inverter (what is it?) with a hopefully more efficient one, will help, also save long term costs as only one not two to replace in 15 years or so, and as they'll then be sharing a TGM, when generation is allocated on a kWp to kWp basis, some of your new units will clock up as old ones. Sound interesting? You can of course add a new inverter and still run both through the same TGM, like my original system which has one TGM and two inverters.

Back to e-mail sorting.

Mart.

Martyn1981

Right, found this document, but it's a PDF. I'm sure you'll be able to find it somewhere on the OFGEM site:

Feed-in Tariffs: Guidance for renewable installations (Version 3)

Page 22

Extensions to FIT accredited installations

2.50. Where a FIT installation is extended using the same technology type, the extension is assessed as a separate eligible installation. If successfully accredited, the extension will be assigned a separate eligibility period and separate tariff code based on the aggregate TIC of both the extension and existing FIT installation. Both installations will, however, share the same FIT ID on the Central FIT Register (CFR) - the register on which all installation details are stored.

I'm like a squirrel, never throw anything away!

Mart.

tunnel

So, replacing your existing inverter (what is it?) with a hopefully more efficient one, will help, also save long term costs as only one not two to replace in 15 years or so, and as they'll then be sharing a TGM, when generation is allocated on a kWp to kWp basis, some of your new units will clock up as old ones. Sound interesting? You can of course add a new inverter and still run both through the same TGM, like my original system which has one TGM and two inverters

Very interesting indeed! My inverter is a sunnyboy 2000(i think) so would need changing to a 4000 for the 2nd string. I didn't realise you could do what your suggesting,looking at the pvgis for both, one out performs the other by 100-120kwp,would my FIT provider just split the TGM reading in half (for arguments sake) thus giving me an extra 50-60 kwp at 45p?

Tunnel

Martyn1981

tunnel wrote: »

Very interesting indeed! My inverter is a sunnyboy 2000(i think) so would need changing to a 4000 for the 2nd string. I didn't realise you could do what your suggesting,looking at the pvgis for both, one out performs the other by 100-120kwp,would my FIT provider just split the TGM reading in half (for arguments sake) thus giving me an extra 50-60 kwp at 45p?

Tunnel

Yes. They'd divide the TGM by 3.96, then allocate it on the ratio 1.96:2. You can probably see why I didn't want my old ESE TGM shared with the new WNW panels, since generation is roughly 800kWh/kWp and 670kWh/kWp respectively.

Check what inverter you have as the efficiencies of the SB2000, SB2000HF and SB2000TL vary. Using Euro efficiency ratings, my SB1200 is approx 91%, my SB2500HF about 94%, and my SE2200 (SolarEdge) is about 97.5%.

Whilst a SB4000TL (capped to 3.68kW) or a SB36000TL may cost around 3 to 400 pounds more than a SB2000, they should have efficiencies around 96%, and would share the start up (and shut down) voltages, so might switch on earlier and off later.

Some thoughts.

Add the SSW system with a 3.68kW compliant inverter once the new tariff brings down prices. Get the upto 4 rate then consider the WNW, which will get the 4 to 10 rate (DNO permission needed).

Or (DNO permitting) add the SSW & WNW at the same time to get a better price, sharing an inverter and TGM, and leaving the existing TGM alone. The FIT rates are similar 14.4p v's 16p.

Or (bit naughty this one) if you think you'll get DNO permission, add the SSW to the ESE, and also install the WNW as a separate system at the same time (to get a better price), but don't register the WNW till the SSW has been. Though for 1.6p, that's a lot of hassle.

Or strip out the SB2000, do both new systems, running all 3 of them through a SolarEdge inverter, with the SSW making up for some of the TGM losses from the WNW. Again DNO approval needed as a 3.68kW capped inverter will waste too much on a system of that size, especially when the sun is in the SW.

I'm having fun, have you noticed?

Send me a PM if you want more info on DNO approval, or I'm happy to 'thread it' if anyone else is interested.

Mart.

tunnel

Add the SSW system with a 3.68kW compliant inverter once the new tariff brings down prices. Get the upto 4 rate then consider the WNW, which will get the 4 to 10 rate (DNO permission needed).

This probably looks best at the minute,one question is,why are the inverters capped at 3.68,I'm a big believer in going over size,my current system can generate 2.05kwh(not for long periods admittedly) so i'd ideally like something thats at least capable of 4kwh.

Here's a dumb question,who's DNO?

Tunnel

Martyn1981

tunnel wrote: »

This probably looks best at the minute,one question is,why are the inverters capped at 3.68,I'm a big believer in going over size,my current system can generate 2.05kwh(not for long periods admittedly) so i'd ideally like something thats at least capable of 4kwh.

Here's a dumb question,who's DNO?

Tunnel

Who is DNO? DNO is God!

District network operator, for me, Western Power Distribution. They are the guys that maintain the network, fix faults etc.

There is a 16A max rule for self commissioning. This is usually converted to 3,680W at an assumed voltage of 230V. This is usually referred to as G83 stage 1 compliance.

Here's my guys rules:-

http://www.westernpower.co.uk/New-Connections/Generation-Enquiries-tariff-arrangements/Generation-Enquiries/Small-Scale-Embedded-Generation/What-size-solar-PV-system-can-I-connect-to-qualify

"The rating of the single phase PV system is the lower of:

The rating of the inverter (based on 230V) and
The sum of the ratings of the PV panels x the maximum efficiency of the inverter.
For a 100% efficient inverter rated over 3.68kW, only 3.68kW of PV panels would qualify.

4kW PV panels would qualify, for inverters up to 92% efficient or if the inverter was only rated 3.68kV.

4kW PV panels would not qualify if the inverter is rated over 3.68kW and is more than 92% efficient."

TBF most 4kWp systems won't hold over 90% for very long, so a 'free' 4kW inverter, or a 3.68kW capped inverter, or a 3.6kW inverter will probably run very much the same, with annual generation totals very similar. The 3.6kW may even b slightly better as it'll be running more efficiently for more of the time.

Download 'Sunny Design' for a play if you're bored, it's free and you can experiment with varying panel and inverter combos. It'll give you a score for suitability. The above 3 examples would all score 100%.

To get permission, I had to submit an application form, plus old and new system schematics, plus PDF attachments of the G83/1 compliance certificates for the 3 inverters I was planning to use. That way I now have permission to export upto 5.9kW (being the sum of my 3 inverters).

I did a G83 stage 2 application (for multiple SSEG's (small scale embedded generator)), but since I already had 2 and was adding 1 more, I really should have done a G59, but this is far more paperwork, and has a small fee (£40 with WPD). Might be worth ringing your DNO for a chat, I found them to be incredibly friendly and helpful.

Worth pointing out, going over 3.68kW is not easy, and will depend on the type of connection you have. I got lucky, the whole road was re-cabled in March, and each house is now separately supplied (no loops), otherwise I'd have got a no. Also will depend on just how many other SSEG's are in your area.

Have I put you off yet?

Mart.

tunnel

I guess i'll put the ssw panel extension on first before i start with the gods(DNO...:rotfl:)

I've spoken to my FITS provider,SSE and i'll only get the lower rate but can do a split generation as you suggested through the TGM..1.96:2.00,at least this way i can have some at the higher rate. They said they're getting masses of complaints about it but are getting overuled by OFGEM.

Seems the contract i have isn't worth the paper its printed on. If the goverment can change that then god help all us pv'ers if they decide to change the tariff rates we're being paid, 25 year contracts that they can change to suit themselves.:eek:

Tunnel

Martyn1981

Hiya tunnel. I know the idea of an extension is still in its infancy with you, but please note the issues I raised on the 'Feed-in tariffs delay' thread from 15/8/12 onwards.

https://forums.moneysavingexpert.com/discussion/3512647

For any extension, you'll need an EPC of D or better before the extension is commissioned, rather than before the FITs application.

Not a particularly difficult problem to avoid, but crucial that you're aware of it. I've updated the extension section of the FAQ thread.

Fingers crossed OFGEM will tidy this up a little, adding more carrot and less stick would encourage further household energy investment, as it does with the initial installation rules.

Mart.

Ferdy147

What's the highest reading a 3.92kw system should produce?

Looking at my inverter (SMA 4000TL) then the reading is sometimes (although not for too long) at about 4100 - should that be possible?