Sure, but now we're talking about some freak situation where you have multiple sources with a combined allowed load of more than 32amps with 3 or more connected devices drawing at their max rating or above, but only when on battery power when you have no grid connection. Like, it could happen but we're entering the "fun to think about" territory.
Why not when grid connected? The problem arises when you are grid connected.
You draw 31 amps from the grid, you draw 6-7 per battery or solar installation behind the circuit breaker. The circuit never trips because the amount crossing the breaker is 31 amps, but the wires could be dealing with 37+. With battery and solar that could be 43+. Some idiot puts two or three of these in their house or puts them on an extension cord, wires are going to get warm.
This is not daisy chained (HN markup hates diagrams) but hanging off wall circuits and power boards. With a situation like this (in 240v) the batteries will sink 2x10A and the PV will supply 16A through point P1. The CB will not trip, nor will appliance fuses.
Since you can just buy 800W modules from Aldi for €300 people will definitely do this by accident. However, it will likely go away because Aldi et Al are also selling their Balkonkraftwerk with batteries included (2000Wh at 1700W) for €1000.
If the comms-over-powerline standards were working then devices could talk to their CB and reserve/advertise capacity. But sadly the power companies have just been fighting to ban home automation and smart grid technology.
I mean sure but right now in the UK you can only add one 800W source without planning permissions.
I'm just not sure what we're trying to say here - can someone create a dangerous situation for themselves by ignoring the rules? Yeah of course.
My example above was for a 32+ amp source(or a collection of sources) which can operate with the grid off, like most battery systems in the UK can - they just have a relay that disconnects the grid when the grid is offline. So it's not illegal, but it's also something that would require a planning permission to have. Can someone just go any buy themselves 10x800W modules, plug them all into one ring and burn their house down? Yes,but that was never a legal setup in the first place.
Traditionally we have been quite prescriptive about what people can do electrically on their side of the meter, in the name of protecting people from themselves. (Even with a grid isolation switch.) Allowing generation that isn't wired in by a licensed electrician is a big change in regulation, so people are jittery and vested interests are using that.
So it isn't no risk and it isn't a huge risk. Some people will do stupid things. I think we could do more to protect people using plug-in generation, and simultaneously improve grid regulation and reduce costs. As engineers I think we are duty bound to achieve these objectives, but accountants run energy companies now and donate to politicians, and politicians run policy. What we have left is technical innovation that creates economic impetus.
So I'm in favour of technology that makes low cost PV+storage safe and available, economically and with just enough regulation.
With the US banning Chinese inverters, it will be interesting to see if that spawns new tech, or if they just licence build/assemble Chinese junk. Prices will be higher initially but competition should be strong. Unfortunately US standards for software/interoperability seem absent. IEEE 2030.5 is not nationally mandated in the US AFAIK, and it is weak on cyber assurance.
IEEE 2030.5 is also designed for grid to consumer and doesn't anticipate having multiple PV devices that need to talk, let alone batteries. The Germans just exempted everything below 960W, so people routinely have several panels plugged in.
