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Comment by kccqzy | Hacker News Reader

In Europe it's somewhat common to have a small solar panel just on your balcony (i.e. not permanent attached to the building) and simply plugs into a nearby wall receptacle. https://www.theverge.com/24150901/ecoflow-powerstream-review...

For those wondering, the article did discuss the safety matter of using a power outlet as an inlet. And the article also points out that while this is allowed in several countries in Europe it's not allowed in the U.S., but I suppose you could always plug appliances directly into the battery instead.

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We are starting to have this in the US, in fact I have a company coming by to do an install of a system like this on Monday. Technically you should be able to mostly diy it, but it uses a smart panel that gets attached to the main to prevent backflow, which needs an electrician, and for now they are running its own circuit.

Wild. I wonder how they deal with the back feeding issue. Is there something about the home wiring in those countries that prevents it? (or do they just not care and line workers know to check if a line is truly dead?)

The device detects that and prevents back feeding. So in case of a power outage it completely shuts itself down.

So when the power goes out it no longer powers your fridge or whatever else you need powered. But it's easy enough to unplug the fridge from the wall and directly into the battery.

I feel the real danger of back feeding is not that american line workers can't be bothered to check if the line is truly dead before starting to work. It's that the line could be reenergized at any time.

Lineworkers will ground/earth the line with a very good connection (e.g. metal rod into the ground) before working on it, as far as I know.

(At least, this is what electricians working with 33kV in industry in Europe do, e.g. if doing maintenance on a cable to a datacentre.)

I haven't seen them doing that on power outage post storm line repairs near me, usually during those they're working as fast as possible because they have dozens of other spots they need to repair.

Hopefully they're bonding the line to their bucket at least.

Probably I've just not seen them ever drive in a ground rod while doing basic line repair work.

Also just the frequency with which work happens on the distribution grid. Most of Europe has almost all distribution lines underground (only running high-voltage transmission lines above ground), and unless somebody digs in the wrong spot they tend to just stay there. In the US meanwhile they are mostly above ground where they are susceptible to storms, falling trees, aluminum ladders and all kinds of other stuff that would cause a line worker to be called out

Automatic transfer switches are a thing, but generally you want the supplies sync’ed.

A manual break-before-make transfer switch will do the job. Not much help if you’re not home and the mains goes out and your food spoils, though fridges will stay cold for hours if left shut, and longer if there’s a lot of thermal mass in them - try to keep most of the empty space in your fridge and freezer filled with water bottles.

The microinverter just turns itself off if it doesn’t detect line voltage in the outlet. In the U.S. evidently it’s required to also have some sort of backflow preventer in the panel as well.

Fair, I always forget that most inverters require an existing line voltage to follow instead of being able to generate their own ex nihilo. I was also picturing one of the battery banks that do have the ability to create their own signal too.

if there is no power, the inverter shuts down and doesn't feed power in.

it is actually simpler. The inverter stops power flow if it does not detect a grid voltage.

The actual power coming from a balcony setup is tiny, a thousand watts ballpark. The typical house will consume the vast majority of that capacity.

Even if some flows back to the grid, it will likely be consumed by losses in the transformer and wires.

You’d be surprised how few watts a fridge and a TV draw, 500 watts combined, and that’s only while the compressor in the fridge is running. Don’t open the fridge very often, or keep a lot of thermal mass in the form of filled water bottles in there, and the compressor in a fridge will spend most its time not running.

Now I'm curious... Is your last suggestion correct? Wouldn't the time to cool down between pause intervals be proportionally longer due to the higher thermal mass and cancel out any savings gained by the long pause? Maybe the overall energy draw is even higher because the heat losses are higher when you spend a longer time with a high dT.

The water bottles don't warm up as quick as the air they replace that flows out of the fridge when you open it; so they have two effects first they take up space that new hot indoor air can't move into and second they then help chill that air slightly through their own thermal mass.

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