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Originally Posted by wodahs
with this does the excess power made by the solar system feed back in to the grid ? or just waste ?
also why if you have a stand alone off grid system would you still want to be grid connected ?
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Hi, answer to second question first. I do not know, except that the capacity of the off grid system might not be able to provide power to the premises in the longer term when weather conditions do not allow sufficient charging across a number of days. In that circumstance you might want to be able to access grid power, eg restaurants do not want foodstuffs, either fresh or pre-prepared to spoil.
First question, which I think, is that you want to know if the capacity of a system that can be connected to the grid, or stand alone, wastes that part of its capability that is not being used to power the premises when it is off grid? Well, you could argue that it gets wasted, but better to understand that the generator simply adjusts its output to match the load that is being supplied. In the case of a PV array feeding an inverter the dc input current falls to match what the inverter sees on its output side. If the generator is an ICE driving an alternator it simply uses less fuel and can last for more hours.
Zilo's changeover switch concept can be automated and is for places like Hospitals and airports, where loss of grid power could be life challenging. (You don't want operating theatres or lead in to runway and runway lights suddenly being without power - bit disconcerting for surgeons and pilots.)
I own an ICE powered alternator, but connecting it up to the house so that all I have to do is start the thing up is a challenge because the alternator location is remote from the distribution board and I do not have a dedicated feed circuit for it. Also I'm not sure if the output frequency is stable enough to get the PV system inverter working. Still working on a solution for this.
Hope I've helped.
Cheers