What's your opinion on + 4kW peak?

[SolarCity]

Interesting discussion. However, if the TIC is taken as the system (inverter output) what happens in the scenario where you have installed 4kw of modules on a G83 inverter, and then want to add more modules, keeping the G83 inverter? What info do you give to your FIT provider? Would you even bother notifying them? They will see the system output increase over the year so they will notice something has changed, and as they only see Kwh figures from your TGM (not peak outputs) from their point of view the capacity of your install has gone up...

Edit: the MCS cert contains an estimated annual generation figure which will not longer be true...

I'm not sure I know what you mean. If you install more panels then you will still need to inform both the DNO and the supplier.

The discussion here is regarding the 4kW threshold and where it actually lies.

 

[TedM]

The confusion arises from disparate views from both the legal and the technical (electrical engineering) viewpoints. There is a small area where the two can coincide and, to me, that is where TIC is the inverter AC output.

Whether that was the original intention of the definitions is not easy to say. But I would submit that if DECC/OFGEM want PV panels alone to define the capacity of TIC then the definitions will need to be re-written.

 

[Gavin A]

Whether that was the original intention of the definitions is not easy to say. But I would submit that if DECC/OFGEM want PV panels alone to define the capacity of TIC then the definitions will need to be re-written.

this is the crux of it. The law is what is written on paper, not what someone at DECC now might wish had been written. They are of course free to go back to parliament and change it if they want to, but up to that point everyone should operate on the basis of what is written into the legislation.

tbh it's also the only basis for determining it that makes any logical sense, and determining it in the other way could easily be open to legal challenge for unfairly discriminating against people with east / west roofs who'd be getting paid a lower rate for a system that was only capable of generating the same amount of electricity over the year as a 4kWp south facing system, that also cost more to install than the south facing system. Not 100% sure on that, but I'd think there would be grounds for that somewhere in the law.

 

[SolarCity]

But I would submit that if DECC/OFGEM want PV panels alone to define the capacity of TIC then the definitions will need to be re-written.

Totally agree. And therefore I think Gavin is in a very strong position.

 

[BruceB]

Interesting discussion. However, if the TIC is taken as the system (inverter output) what happens in the scenario where you have installed 4kw of modules on a G83 inverter, and then want to add more modules, keeping the G83 inverter? What info do you give to your FIT provider? Would you even bother notifying them? They will see the system output increase over the year so they will notice something has changed, and as they only see Kwh figures from your TGM (not peak outputs) from their point of view the capacity of your install has gone up...

Edit: the MCS cert contains an estimated annual generation figure which will not longer be true...

The answer must be:

a. you go by the legislation, ie has the system been expanded (has TIC changed), in determining whether MCS needs to know; and

b. you go by your FIT contract in determining whether you have made a change of which your FIT supplier requires notification.

 

[SolarCity]

Another side to this is that we are supposed to be advising our customers as experts on the subject. By designing to current legislation then we are maximising the potential benefit to the customer and should be advising them accordingly.

Incidentally, I have never installed more than 4kWp of panels but I actually believe I have badly advised some of those whose potential could have been more - particularly with regards to east/west split.

 

[moggy1968]

yes, think I'm in the same boat. I have thought about increasing panel numbers like this but shied away from it due to the lack of clarity on the matter.

 

[babba]

If we stuck all the past and future threads about this subject together, they could reach the moon and back before this is sorted out

 

[it'llneverwork]

Very interesting thread!

I've been asked the question by a client that has 50kW TIC, and is asking whether he can add to it to generate more on days with low insolation, given that the CL48 installed can be capped to 50kW AC.

Also our sparks are asking about TIC and DNC, and what to advise customers to put on FIT forms - whether to go with the G83 3.68kW or the DC/panel rating at 4kW.

No definitive answer it would appear.... much like everything in our industry at the moment!

 

[wstevew]

If you have 4kwp east and 4kwp west and they switched half way through the day what is the capacity?

Equivalent to a moveable array.

 

[Ian-LS]

That would have to have an above 4 kW inverter so therefore wouldnt be eligible for <4 kW PV FIT rate. The capacity should be whatever the inverter is rated at, but as been discussed there is no clear guidance and what the TIC should refer to. Logially it should be the lesser of the panels and the inverter.

 

[wstevew]

Why would it require an inverter greater than 4kW if it only has 4kWp of panels connected at any one time.

 

[Ian-LS]

ok just run this through sunny design and with a 3600 TL it predicts you will lose 7% of your output through the inverter limiting it to 3.68 kW. I would suggest that 8 kW with 4 kW on each roof would be over the top if trying to claim it is a < 4 kW PV System. I suppose yuou could argue you are gaining more than 7% in increased generation by using 8 kW of panels

I suppose in theory it could work but I doubt any installer would quote on this basis

 

[wstevew]

The point I was making was if 8kwp of panels is not allowed to be connected to a 3600TL for the <4kWp FIT. What if you had a device to physicaly disconnect one array and connect the other at the optimum time on an east west split.

That way only 4kwp of panels would be connected at one time. Its an expensive tracker.

 

[SolarCity]

You wouldn't need to. As long as you got your voltages and current within the accepted range of the inverter then you could stick 8kWp of panels on a 3600TL inverter.