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‘If 1.5m Germans have them there must be something in it’: how balcony solar is taking off
(www.theguardian.com)
this post was submitted on 22 Dec 2024
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No, that’s not how it works in the general case. There are ways to setup a house to back power but it’s more complicated than just plugging it in.
Without proper safeties in place back flowing power to the grid becomes extremely dangerous for line technicians
On loss of power these inverters cut off within 20 ms or so. These are grid-tied, not insular (though with hacked firmware some of the models can be made insular-capable).
20ms are exactly 1/50th of a second i.e. our grid frequency I think there's some more leeway. A whole oscillation being gone surely is suspicious and you want to shut off but that might take another millisecond or two.
It's not a hard realtime cutoff spec, more a relais native actuation time. And from the behaviour I've seen they are ramping up slowly over minutes when the mains power is back, which seems a sensible thing to do.
Maybe just look at how these inverters work before babbling about. These kits all come with standard off the shelf micro inverters, or rarely bigger string inverters, and will feed back up to 0,8wk into the grid if the energy is not used in the household. If the connection to the grid is lost they turn off within less than 50ms, making them completely safe for line technicians
Even more precisely: If the energy isn't used on the exact phase the inverter is connected to. You might be simultaneously backfeeding 800W on one phase and draw 3000W from the grid for your kettle on another, pretty much every single installation (at least in Germany) is three-phase at the main breaker panel, then distributing (and three-phase for the stove). Good ole Ferraris meters only record the total sum (the wheel would turn at the speed of 2200W) but you're still using grid infrastructure which is one of the reasons why the installations have to be small: Because your utility can't bill you for grid usage.
Yes that’s the setup I was talking about. Not every grid in every country is setup for this though
So what you're saying is that the general case is that it feeds back into the grid unless there are additional measures taken? But at the same time, it's not the general case? Huh?
Which is why, where I live, you have to register your devices with the utility company.
I was saying the general case is that they aren’t tied to the grid, but that they could be setup to do so. I’m almost definitely wrong about how often these are tied to the grid though.
Yup! I’d be shocked if a country didn’t make you inform your utility.