Any Solar PV gadgets out there?

ChiefGrasscutter

This is done to prevent the solar panels inverter back feeding into the local network. In the event of a local fault (tree down across line etc) It would be exceptionally dangerous for those trying to repair the fault.
They could isolate the incoming supply at the local substation so one end of the broken cable would be safe, but they would have no way of stopping the various local solar installations feeding voltage into the other end of the broken cable.
Hence the requirement that in the event of incoming mains failure the inverter must switch off.

debitcardmayhem

Thanks espresso and CGc

Kernel_Sanders

ChiefGrasscutter wrote: »

This is done to prevent the solar panels inverter back feeding into the local network. In the event of a local fault (tree down across line etc) It would be exceptionally dangerous for those trying to repair the fault.
They could isolate the incoming supply at the local substation so one end of the broken cable would be safe, but they would have no way of stopping the various local solar installations feeding voltage into the other end of the broken cable.
Hence the requirement that in the event of incoming mains failure the inverter must switch off.

I can confirm that the whole system does shut down, although it starts up again 4-5 minutes after power is restored without you having to 'reboot' anything. However, this does mean you are without solar power at the time you need it most. Surely some simple electronics could be devised which requires power from the National Grid keeps the export cable open.

fwor

Kernel_Sanders wrote: »

Surely some simple electronics could be devised which requires power from the National Grid keeps the export cable open.

It would indeed be relatively simple - but would you get permission to connect it to the grid?

The cynic in me suspects that the main energy generation companies would not tolerate the approval of a PV controller that permitted the user to export power but not consume theirs - even if it were designed to "fail safe" externally.

ChiefGrasscutter

Rather than a system that senses mains failure and a cut off switch, you need a system that senses mains failure and activates a changeover switch so now the house is operating in what is called "island mode". It is a self contained generating and consuming entity and is floating free from the grid and indeed will loose synchronism with the grid as the frequency can now move up/down as it has no longer any 'tie' into the grid which holds it in step and ensures that electric clocks keep perfect time.

Of course this would come at more expense and complexity for both the changeover switch and the need to arrange a synchroniser electronics to re-synchronise the house back with the grid (ie making sure it is operating 'in step' with the grid in layman's language) prior to switching back and re-connecting it to the grid.

All quite common in industrial environment. Every generator from small wind turbines to nuclear stations has to have this kit to synchronise the output waveforms to the grid waveforms prior to re-connecting.

.........and to make it all fail safe.

Savatherm

SMA (the inverter manufacturer) does market a stand-alone back up system - but at a vast cost. Basically you have a battery to spin a DC motor which creates the equivalent of a generated AC waveform to fool the inverter into thinking it has mains power - but it also shuts down the export option for safety reasons.
It only works for as log as you have battery power - so how big a battery do you want to buy?

Savatherm

To get back to the original thread - there is now a control box on the market which will switch Immersion Heaters on when the sun shines by monitoring the PV output to the consumer unit. Nothing fancy but relatively cheap.

leboof

Ah, yes, I see one on ebay and other places. This is perfect.

Basically, I can set up a system to switch on a 1kw(ish) immersion heater element only when the panels are generating enough wattage. I could then topup the heat with gas at the end of the day if necessary. Brilliant.

Cheers all...