I was just researching this and the new Enphase IQ8 microinverters will run without grid power. You are correct though it is common for microinverters to require grid power to operate, which seems pretty surprising!
It's usually a safety feature. If there is a downed power line and you lose grid connection, energizing your (otherwise dead) side of the downed lines could easily kill the lineman who comes to fix it.
Oh certainly it is important to have some kind of cut-off to prevent back-feeding the power lines, but I thought that would just be part of the system design.
It is! The easiest design is to require existing grid stable power and supplement it. :)
Anything else is difficult to do reliably, and would generally require some kind of smart monitoring system, electrically actuated mains rated switch (not easy, cheap or durable it turns out), additional sensors, etc.
The design we're talking about just doesn't output power unless there is an existing sine wave to follow. Pretty foolproof, since anything that provided it would also be the one responsible for electrocuting the worker.
I’m typing this from a computer I’m holding in my hand that’s more powerful than the ones used to put men on the moon. A box with three connections - grid, solar, and house (four if you have a battery) with sensors and disconnects and the smarts to not backfeed and electrocute linemen just doesn’t seem impossibly complex. Especially when we’re talking about home solar installs, which cost several thousand dollars to begin with. There’s got to be some other force at play here preventing this device, which is the most obvious way of implementing a supplementary power system connection, from being widespread.
Add in all the other stuff and an extra couple thousand to the cost of the solar installation is why it isn’t as common. Because most people don’t care enough to pay the extra amount. Some do.
If you wanted it enough to pay the extra, most electricians wouldn’t mind adding it in I’m sure.
That makes sense! I guess being new to this it is just counter intuitive to think that you could install a big solar panel system and still suffer power outages. But I see what you mean.
To the breaker on your solar (or genset) the resistance of the neighborhood is gonna look indistinguishable from a short circuit so you'll need to at least disconnect from the grid if you want to power your house. From there your next problem is that solar panels don't handle being overloaded very well so you either need a ton of them ore batteries.
Often, but not always. There are a number of ways lines can and do fail that produce high impedance, including a tree downing a service connection, breaker tripping, etc.
2. Your appliances don't like brownouts and voltage dips whenever a cloud passes overhead. Try to run a house without a power buffer and you'll burn up power controllers all over your house.
Unfortunately the battery market is extremely tight due to so many car manufacturers trying to switch to BEVs ASAP and stressing the raw materials markets. That and COVID shortages. Prices are very high and availability is usually "8-12 month waitlist".
I wonder if it’s possible to retrofit a Tesla to work as a bootleg Powerwall in tandem with residential solar - should brownouts become a common thing.
My Google-fu isn’t strong enough to find anything on the topic that isn’t on the level of “tremendously sketchy YouTube video” and I’m not about to risk my car and house experimenting off the back of that sort of thing.
I don’t know about Tesla specifically but this is a thing that some EVs can do. The new Ford F-150 lightning can do it. This is generally called vehicle to grid, vehicle to load, or bidirectional charging. A quick search shows maybe Tesla hasn’t added it yet. But here’s some details on the Ford lightning setup:
