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Old 10-30-20, 07:19 PM   #5
Lurking Renovator
Join Date: Oct 2020
Location: Cambridge, UK
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I can see a few issues:
If you get a feed in tariff (as it's the UK), they won't like you messing with the DC from panel to inverter. You could inject DC here, and "make" money!
Normally a 2kW string of 8 panels would be at a higher voltage - I'd expect more like 70V per panel, so around 500V.
4kW at 12V is a lot of current - normally people would try and avoid such heavy currents, due to the losses in the copper wiring.

A much simpler option, avoiding the possible legal issues & dangerous side with the high voltage DC, would be to charge up batteries from AC, and then use them for certain loads. You could set a timer to charge the batts at mid-day, so they always get charged, and usually it's free. 12V lighting is a very suitable load, maybe power for a laptop. It won't charge up from PV when there's a power cut, but it's a lot simpler.
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