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Comment by CodeWriter23 | Hacker News Reader

There was a carport fire in my building back in the 90's. The firefighters got all set up to turn their hoses on it but did not actually start using water to fight the fire until the utility guy from the city arrived to de-energize the supply from a nearby vault.

How does that safety protocol work when the electrical connections and supplies are distributed around the house and may be inaccessible due to fire?

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In Germany, where this kind of plug-in solar panels is very common (1.5 GW installed power) it is mandatory that the inverter powers itself down as soon as the grid is offline/disconnected. It has to be so fast that you can savely touch the plug after unplugging it. I guess it's standard everywhere.

Actually the rule is that your solar system must stop feeding power to the utility if the utility is down. You are allowed to run in isolated mode if your system supports that. Yes, even in Germany.

Every way I can think it through, isolated mode means your house is disconnected from the utility when you lose power, which requires more equipment than can be contained in a plug in solar panel.

Yeah the only code compliant way this is possible is if an additional sub panel is installed and maybe/probably a transfer switch that needs to be manually pulled in order to disconnect the sub panel from the main panel. Possibly OP is confused about running in zero export mode? Would love to hear how we could be wrong…

Thanks for the answer instead of a downvote.

The ones I’ve seen tested cut off in half a cycle, even with multiple ones on the same circuit.

I even upvoted, no idea why you're downvoted here. It _is_ a potential issue that you pointed out.

I imagine the solar panel will detect when the circuit it is plugged in to is de-energised and stop supplying supplemental power to it.

This is exactly how our rooftop solar works. The inverter only supplies ac power if it can sync to the grid frequency meaning that the system disconnects without a live grid connection. Even if I had a battery, this would still be a requirement under local regulations.

companies that sell plug-in systems argue that safety risks are minimal or nonexistent. Mr. Scherer of Craftstrom said his company’s systems would not shock electrical workers because they shut off automatically within one second of a power disruption or grid outage.

Mr. Boyce of UL Solutions said his company would certify panels only if they did not pose a risk to consumers or utility workers.

Maybe the fact that these panels are legal around the world and soon will be legal in a number of US states should be a sign to you that this is not a relevant concern.

The device looks for an existing signal from the grid, and if it doesn't find it, it stops feeding power. It even waits for 3-5 minutes before trying again plus some random jitter to avoid thundering herd. It's been a standard in Europe for a while and now finally in the US. This of course depends on the utility and state as not all of them have adopted it but it's quickly becoming the standard everywhere.

IEEE 1547 (interconnection behavior), UL 1741 (inverter product safety), UL 3700 (plug-in solar). (also there are newer revisions you need of some standards like UL 1741)

Also, utility line workers always treat everything as live until they isolate it and confirm it’s not live (or do the work live in some cases).

I once chatted with some line workers working nearby, and I asked them what they did about residential solar. They said they didn’t particularly care about anti-islanding: if they needed to, they would deliberately short all the customer wires to ground, and if anything hadn’t turned off, then breakers would trip.

They even do that to large transmission lines. First shutdown/isolate, then connect to ground or short circuit. If anyone then accidentally turns something back on it will fail immediately.

A few years ago a transmission line in the Netherlands was energized while it shouldn't be, during maintenance work, which resulted in the whole line starting to smoke, sag and spark: https://youtu.be/nyjCrP38ICc

https://en.wikipedia.org/wiki/Balcony_solar_power

  In the United States, Underwriters Laboratories developed the UL 3700 standard specifically for plug-in solar devices, establishing safety specifications for microinverters and connection systems used in these applications.[2] UL-certified plug-in inverters are designed to automatically shut down during grid outages, preventing backfeed that could endanger electrical workers.[7]

So that is the standard failure mode, but do customers understand how it works?

If I had a balcony solar panel, I'd definitely expect it to be providing backup power when we need it the most. I'd expect it to charge a storage battery, not backfeed into the grid.

Surface area means a lot for solar panels. An EV with a solar panel on top is laughable. I own a solar backpack that couldn't charge its power bank within 3 weeks of daily full sun. A "balcony solar panel" may not keep your smartphone charged.

Consumers in Germany generally understand that this is a cost-savings device, not a backup supply of electricity. You tell your neighbors and friends to get it because of the energy bill savings.

They are not as weak as the toy panels you are describing, but they are regulated to 800W max anyways.

The stated purpose for balcony solar is to reduce your power bill. Nowhere does it state it's for backup power. And whether it helps at all depends entirely on your own situation. If it turns out that you can generate, say, 420w for 8 hours, that's 3.3kW, which is a decent amount of power, probably 1/4 to 1/8 the total draw of many homes. That means 1/4 to 1/8 off your energy bill once it pays for the solar panel.

If you want to convert a solar panel into backup energy, there are many ways to do that, but no solar panel+microinverter are safe to just plug into your home. Whether it's a transfer switch, a "solar generator", or a grid-forming microinverter system, they all require you to be physically disconnected from the grid to continue generating power, or to have things plugged into an explicit "backup load" circuit which doesn't come from the grid.

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