4 KW or Under

[irishjohn]

No you have lost me.

The FIT rate is decided by the TIC. You need to understand the statutory definition. It is not the sum of the installed panels.

The MCS form asks for the DNC. The advice they then give in the help document is:
"For the declared net capacity field, enter the kW peak (kWp) capacity of the system once it has been installed. E.g. a PV array which has ten 200W will be a 2kW system, therefore enter in 2.00 you will not need to enter the units, only enter the figures."
.....which is NOT the DNC

Say you have a panel capacity of 4.2kW on a 4kW inverter. The TIC and DNC according to the statutory definitions is 4kW and the owner should get the less than or equal to 4kW FIT rate. If you were to put 4.2kW on the MCS form, representing the installed panel capacity, I am willing to bet the owner would struggle to get the 4kW rate. So I would put the DNC which is what they ask for and assume their advice is wrong.

Regards
Bruce

I would never assume the advice from the people that make the rules or pay the money is wrong, that is just unprofessional. What would be wise is if you asked the Electric companies, MCS, Ofgem and NICEIC.

Having made these enquiries to all of the above including NAPIT, they all confirm TIC not DNC. Also as I mentioned, over 4kw TIC or DNC is G59 which every way you look at it.

4.5kw is 4.5kw whichever way you look at it. If you dress this up as 4kw you will at some point be found out and may have to pay back all the additional benefit you have received and the person certifying may lose their MCS accreditation.

Check before you act. DYOR.

 

[Worcester]

Remember neither TIC or DNC are they number of panels x their stated output.

Both TIC and DNC have legal definitions.

For solar PV TIC is the number of panels x their stated output x the inverter efficiency
DNC = TIC - the consumption of the generating system (in our case the inverter)

This might sound strange, however think of a massive power station where all the control systems will use a lot of power, so the DNC and TIC could be quite different.

In an SSEG Solar PV system, that consumption is negligible, hence for our purposes TIC=DNC

THE MCS Certificate and FiT payments should declare the TIC - that's what is defined in the legislation, as per my posts elsewhere, hence you could install 4.6 kWp on a range of roofs, and with an inverter limited to 3.68kWp you are both compliant with G83 AND will also be in the <=4kWp FiT band.

No argument, the above is all covered in legislation irrespective of what a range of 'professional bodies' may say.

 

[PvNewbie]

No argument, the above is all covered in legislation irrespective of what a range of 'professional bodies' may say.

Worcester...do you have references to the legal defs?

Newb

 

[Worcester]

Yep, check out "Schedule A to Standard Licence Condition 33" which you'll find in the 'ENERGY, FEED-IN TARIFFS, Feed in tariffs: modifications to the standard conditions of electricity supply licences" document.

Simple really

Oh, here's the link http://www.decc.gov.uk/assets/decc/what we do/uk energy supply/energy mix/renewable energy/policy/fits/1_20100331172153_e_@@_fitlicencemodification.pdf

Which you'll find halfway down this page: Publications Library: Category Specific Publications : Department of Energy and Climate Change

The number and size of the panels are simply the "Eligible Low Carbon Energy Source"

 

[Antscran]

If you oversize a system say 4.5kW on a smaller inverter that has a nominal output of 3.6kW say, you will be clipping power anyway and only in winter will you see the benefit in increased output. Combined with the fact that the government has made a large U turn already and will probably look at this in the very near future, I heard there are questions being asked in Glasgow by the DNO regarding this and basing the output on the nominal output of the inverter.

If you apply a good efficient design in the first place and match the panel strings voltages with the chosen inverter efficiency graph, you will get a far better system in the long run!

 

[irishjohn]

Yep, check out "Schedule A to Standard Licence Condition 33" which you'll find in the 'ENERGY, FEED-IN TARIFFS, Feed in tariffs: modifications to the standard conditions of electricity supply licences" document.

Simple really

Oh, here's the link http://www.decc.gov.uk/assets/decc/...0100331172153_e_@@_fitlicencemodification.pdf

Which you'll find halfway down this page: Publications Library: Category Specific Publications : Department of Energy and Climate Change

The number and size of the panels are simply the "Eligible Low Carbon Energy Source"

So where exactly does it say or imply 4.5kw = 4kw or output is Inverter output???

"Eligible Installation" means, on a Site, any Plant Owned by a FIT Generator
capable of producing Small-scale Low-carbon Generation
from the same type of Eligible Low-carbon Energy
Source, the Total Installed Capacity of which does not
exceed the Specified Maximum Capacity;

 

[DomB]

I do wonder if the TIC / DNC definitions are a bit of a moot point here..

The MCS certificate's instructions specifically ask us to enter "the kW peak (kWp) capacity of the system once it has been installed. E.g. a PV array which has ten 200W [panels] will be a 2kW system". It's just that some plonker has used the words "Declared Net Capacity" on the certificate.

kWp seems to be the only consistent thing across all the parties involved; even the definition of 16A is up for grabs with UK Power Networks using 240V and SSE using 230. So in my mind it would be right for the MCS cert to be wanting us to enter kWp.

I wonder what the people who aren't following those instructions would do when the inverter on one of their systems dies in 10 years time and the efficiencies of the replacement models are higher - will they re-submit the MCS cert to be over 4kWp and mess up the customer's FiTs?

 

[DomB]

p.s. liquidity, y'asked earlier for that list of inverters SSE allow :

View attachment G83 Compliant Inverter ratings - JLM.pdf

It's a pdf, hope that works..

Cheers

 

[Worcester]

@DomB

If you read the latest legislation you see that the FiT bands are based on TIC NOT kWp

You can find it all for yourself on the DECC Website, - it was clarified with the latest review document when the Tariff bands were changed for >50kWp

We therefore remain convinced of the need to make changes as a matter of urgency and will implement the proposed changes by amending the Standard Conditions of Electricity Supply Licences. This means that the following changes will be made to generation tariff levels for solar PV installations at the following scales for all installations with an eligibility date3
on or after 1 August 2011.
Band (kW Total Installed Capacity - TIC) Tariff (p/ kWh)
>50 kW – ≤ 150 kW TIC 19.0p/ kWh
>150 kW – ≤ 250 kW TIC 15.0p/ kWh
>250 kW – 5 MW TIC and stand-alone installations 8.5p/ kWh

That's pretty unambiguous.

kWp is a term specific to Solar PV, TIC and DNC apply to all the generation methods.

To be absolutely correct TIC and DNC should be actual measurments and calcutions as part of the commissioning process as the would be for any 'traditional' generating plant.

If you want still more information read the Satutory Instrument 2011 No 1181 and you see how they've moved from DNC to TIC, also read the explantrory notes where it says:

"Ensuring consistency by changing the measure of capacity used in setting the specified maximum capacity of eligible installations under the FITs scheme from declared net capacity to total installed capacity;"

So it doesn't really matter what the MCS website says, LAW takes precedence. You should therfore be using TIC and DNC as appropriate. I can point to lots of places where the MCS website has stuff wrong on it, so it is actually those that are specifying kWp that are under valuing the opportunity for their clients.

p.s. I have access to a VERY strong legal team and they have been through this with a toothcomb, so I will still confidently carry on using TIC and DNC for my registrations.


@Antscran
If you have an East / West roof at 45 degrees with 2.36 kWp installed on each (4.72kWp Total), because of the angles of irradiance, you will find that a Power-One PVI-3.6 which is limited to G83 /1 (3.68kW), will yield one of the best outputs possible, now that IS a "good efficient design" that maximises the revenue opportunity for the client.

 

[PvNewbie]

Do angles of irradiance come into the equation then when working out TIC? I note Worcester in an earlier post, you say....

For solar PV TIC is the number of panels x their stated output x the inverter efficiency

and say in the previous post...

If you have an East / West roof at 45 degrees with 2.36 kWp installed on each (4.72kWp Total), because of the angles of irradiance, you will find that a Power-One PVI-3.6 which is limited to G83 /1 (3.68kW), will yield one of the best outputs possible, now that IS a "good efficient design" that maximises the revenue opportunity for the client.

A 4.72kWp Total system x a 90% inverter efficiency(say) still gives a TIC of 4.25kWp, which is over the 4kWp band. I know that angle of incidence of light will have an effect, but that doesn't seem to be part of the equation. How would we allow for this?

 

[DomB]

Thanks & fair dues Worcester - I have come over to the dark side - looks like the FiTs are based on TIC so the definition is important..

Without meaning to harp on about it - if the definition of TIC is "the maximum capacity at which an EligibleInstallation could be operated for a sustained period without causing damage to it" have you found somewhere it defines exactly how we should calculate TIC; it sounds like you're taking into account angles of incidence etc as well as the inverter efficiencies?

EDIT: Sorry - I guess I was typing the same question at the same time as yourself there PVNewbie

 

[PvNewbie]

Great minds think alike. I guess 'angle of incidence' is the final piece of the jigsaw. I Worcester can enlighten us...then great!

 

[solarfred]

Great minds think alike. I guess 'angle of incidence' is the final piece of the jigsaw. I Worcester can enlighten us...then great!

The key word in the definition may be "could" making the angle of incidence irrelevant.

 

[Colibriman]

My head is hurting reading and trying to absorb all of this thread, but its invaluable stuff.

Keep the good discussions coming and hopefully at the end of it it will become clearer where we actually stand.

One more thing...if angle of incidence counts when working out DNC, does direction ?

 

[BruceB]

I'll pick up the baton and have a go.

There is no single answer to getting to a TIC figure, but sticking with simple PV and giving some examples:

- If you have an inverter which has an output capacity greater than the output of the panels attached to it and all those panels are facing in the same direction of roughly south, then a good estimate would be:
TIC = kWp of panels * inverter efficiency

- Conversely if you have an inverter which has an output capacity less than the output of the panels attached to it and all those panels are facing in the same direction of roughly south, then a good estimate would be:
TIC = output capacity of the inverter

- Where it gets more complicated is where you have in the example Worcester gave say 2.3kWp of panels facing East and 2.3 kWp panels facing West. The two arrays are never operating at full capacity at the same time and you can knock up a spreadsheet that takes account of angle of the roof, its latitude and hence declination of the sun depending on day of the year and see how the array outputs vary at different times of day. The true TIC might be either the inverter output or less than that. But it can never be more than the inverter output. So that is a safe figure to quote provided you can do the 3 dimensional trigonometry to show that the inverter would not be overloaded by the East/West arrays.

Regards
Bruce