5kw panels, G83 Inveter, 3.68 TIC. Anyone actually done this?

[Gary K]

Keeps her trim :53:

Bonus - 2 FITS for the price of one

 

[FB.]

And on the power one data sheet I have, you can go to 2kW on each mppt on the 3.0kW inverter and 3kW per mppt on the 3.6 and 4.2kW inverters

Maybe the outdoor version, but not the indoor version? At least not the version I have.

 

[FB.]

Is this possible? Surely there is no excess energy - just potential energy that isn't realised? Nothing will get sent back through the panels, will it?

Are you sure that Power One Inverters only have a warranty for strings of 2kWp each?

If the electricity hasn't got anywhere to go, it will generate heat (resistance) and the panels/cables will get hotter than they normally would.

The indoor PVI 3.6 is limited to 3.75kW for a single string, or 2kW for each MPPT - according to the manual which came with mine.

Unless mine's an early version with different spec to the current models?

 

[SolarCity]

If the electricity hasn't got anywhere to go, it will generate heat (resistance) and the panels/cables will get hotter than they normally would.

Surely if it has nowhere to go, it goes nowhere? I could be wrong, but I've not seen it the way that you do.

 

[moggy1968]

without a flow of current it just sits there, as potential energy. Otherwise the whole grid would get hot if not enough electricity was being used.

 

[SolarCity]

Regarding power limits on inverters, I would have thought that voltage is the issue rather than power. I seem to remember an SMA rep claiming that only over-voltage could damage their inverters.

 

[solarfred]

Customer has insisted on 4.5kw as there are 2 strings on pitched roof and 1 string on flat roof using SMA4000TL. He is surrounded by trees which will affect the output at certain times hence the increase in panel numbers. Inverter limited to 3.68kw and supplier is EDF which have a form asking for TIC and DNC (Others just have "Installed Capacity")
What should he enter as the two figures now? The system cannot operate at 100% .

 

[FB.]

Surely if it has nowhere to go, it goes nowhere? I could be wrong, but I've not seen it the way that you do.

Energy of photons in sunlight are absorbed by the electrons in the solar cell.
Once the energy is in the electrons, they will move around the circuit and generate a flow of electricity.
If the energy in the electrons can't be vented-off as movement of the electrons through the system, then the energy must be ofloaded in some other form - heat, light, radiation, movement etc.
So if the solar panel can't move all the "energised" electrons, then those electrons will give up their absorbed energy to the solar panel as heat. This might not be noticed on an oversize array since the panels will be over-producing anyway, so there will still be "full power" flowing - but the panels will be working at a higher temperature and probably have a shortened lifespan due to more temperature fluctuation.

 

[FB.]

without a flow of current it just sits there, as potential energy. Otherwise the whole grid would get hot if not enough electricity was being used.

That would imply a solar panel acts like a battery; able to "store" energy.
It can't be stored; the energy absorbed from the photons in sunlight must be released almost instantly - as a flow of electricity or as heat.

 

[Gavin A]

sorry FB, but you're wrong on this.

The potential is there, but the excess is never converted to electricity in the first place, because the inverter draws the power from the panels at a less efficient voltage for the conversion process.

What excess energy there is will presumably either remain as light, or be converted directly to heat on the surface of the panel, but it won't be converted from light to electricity to heat.

 

[SolarCity]

FB, what about a panel which isn't connected? The photons will still hit the panel but no power is generated - the potential is there, but the power isn't.

 

[FB.]

FB, what about a panel which isn't connected? The photons will still hit the panel but no power is generated - the potential is there, but the power isn't.

It'll simply get hotter.

 

[FB.]

What excess energy there is will presumably either remain as light, or be converted directly to heat on the surface of the panel, but it won't be converted from light to electricity to heat.

The highlighted bit implies the panel will get hotter.
Which is what I was trying to say; if the sun's energy gathered by the panel can't be converted to electricity, it will become heat and the panel will get hotter than if it could send a flow of electrons around a circuit.

 

[PvNewbie]

To help answer SolarFred's question (as best I can). If you look at previous threads, TIC = DNC (effectively for PV). However, I've just filled in a Southern Electric FIT form and notice that their definition of TIC is number of panels * panel power (which to me is a redefinition) and DNC is 'what was entered on the MCS notification for DNC'. Which to me, would be 3.68kW. Why Southern Electric can't just ask for 'kWp of panels' instead of re-defining of TIC I don't know. There's underhand changes going on to the legal definitions and we need to keep a beady eye on the rules!

MCS help doc defines DNC as 'The declared net capacity should be entered in kilowatts (kW) and is the capacity of the system onceinstalled, taking into account any losses. It should be entered up to two decimal places only, withoutthe units for example 1.95. '

Is there not a help document with the form? On mine I had to answer TIC as the help document described it (panel power x number of panels) but felt like putting 'THIS IS INCORRECT AS THE LEGAL DEFINITION OF TIC.'

If you phone up and ask for help I bet you'll get a 'panel power x panels' answer. If not, perhaps you should go to the customer explain it to him and ask what he would like to put??

 

[solarfred]

Everyone has wasted a lot of time arguing around this pathetic situation. I know what I am going to suggest to the customer and it will be totally within the "current" definitions. What happens after that is none of my business. A system that is compromised by physical restrictions on available sunlight should not be further penalised by definitions of TIC just to suit various suppliers who are keen to restrict agreed payments via the FIT scheme.