Balcony Solar is coming

[Fuddyduddy1952]

If you're that cheap, you wouldn't buy solar panels.

I don't have solar panels.
This thread as usual goes off the rails into the world of the insane, and I'm a retired electronic technician/engineer and we're into the world of grid backfeeding from an 800W (max) solar balcony panel! I don't know whether to laugh, cry, get mad or better yet don't reply!
Years ago quite a few deaths occurred from CRT high voltage, and I've experienced 40kV (unregulated runaway) anode across my chest...but actually more deaths occurred from falls, heavy CRT TVs falling on someone.
As Moss pointed out those panels are designed to shut down, can't backfeed even IF they fed 120 into a step-down transformer you could zap a fly...that's about it.
Carry on though...lots of good laughs here!

 

[ponytug]

In Europe, they glossed over the household circuit line overloading by claims of being within the wiring design safety factors, though I have my doubts (otherwise why wouldn't the circuit have a higher amperage rating to begin with?). I suspect that it helps to embed wires in conduits and masonary to reduce one's view of the inherent risk. I find the global variation in wiring standards interesting as different areas have focused on different items as being locally important. (E.g. the UK and plug fuses)

Personally, I could see certain wiring layouts with maximum loads might be problematic overloads after adding balcony solar, but it isn't as if there aren't already house fires from improper or poor wiring today, so I'm not sure how much actual additional risk an extra 800W on a 15A branch circuit really is in the grand scheme of things. I guess that we will find out.

All the best,

Peter

 

[MossRoad]

No lineman deaths due to backfeed doesn't mean there is no hazard from backfeed. It means the backfeed protections that are required on generators and inverters are working...

Never said there wasn't a hazard. There is.

But it doesn't mean backfeed protections are working at all. At best, it means lineman are trained to assume all lines are hot and ground out everything as a practice.

 

[Phil Timmons]

Never said there wasn't a hazard. There is.

But it doesn't mean backfeed protections are working at all. At best, it means lineman are trained to assume all lines are hot and ground out everything as a practice.

UL 1741 Equipment is VERY [re]liable (in auto disconnecting). Sort of funny throw-back -- most local sites have been required to also have a local manual disconnect (lockable, observable knife blade is the typical spec) for the Utility to do LOTO (lock-out-tag-out). We just plan and install those routinely as part of design, and that way it is there.

As this (local Solar PV, and other Grid Tie) builds out across the US, it might be interesting for Grid Operators to run periodic (and planned, scheduled) tests. Flick the power off from time-to-time on circuits and make sure things really go to zero. Just musing. Have not heard any discussion on that.

The present look-ahead is to allow some Inverters or sites on the Grid to have some "ride-through" capacity. Where the Inverter can take some minor frequency shifts, or some limited "high" or "low" voltage and stay connected -- those are events that trigger the auto-disconnect. Called UL 1741 SB. That way all the Solar can work together to help stabilize the Grid when things are wonky.

Out further are "Grid-Forming Inverters." Those are sites that can come up and from a "Black Start" (completely dead local Grid). At that point things could run with no "spinning" generators.

 

[coldsteelva]

Good info Phil. I never really paid much attention to the procedures and technology that make the grid stable. Even after the northeast blackout in 2003, when I was living up there, it never really made sense to me how important AC frequency was or that systems would be programmed to scram/shunt/shutdown if the system became too unstable, thus leading to blackout and requiring a black start. I learned quite a lot after the 2021 Texas ice storm made that information mainstream public knowledge as ERCOT/Texas was just a few minutes away from a total collapse where it would have been life threatening due to the cold.

 

[Phil Timmons]

Good info Phil. I never really paid much attention to the procedures and technology that make the grid stable. Even after the northeast blackout in 2003, when I was living up there, it never really made sense to me how important AC frequency was or that systems would be programmed to scram/shunt/shutdown if the system became too unstable, thus leading to blackout and requiring a black start. I learned quite a lot after the 2021 Texas ice storm made that information mainstream public knowledge as ERCOT/Texas was just a few minutes away from a total collapse where it would have been life threatening due to the cold.

2003 was a "Cascade Failure." Where losing one section made the next unstable and drop off. We have improved that with "ride through" settings on the Control Relays at the Transmission (the BIG Towers) level. Allows for reliability over equipment protection.

2021, Texas Winter Storm URI, was mostly a Natural Gas Generation fail. Cold beyond the design specs. (dohhh! Engineering) along with fuel allocation issues. Coal and Nukes also had a high Fail Rate. Cannot send power that you do not have.

In the case of Texas -- we have MASSIVELY expanded Solar PV in the last 5 years. Most days Texas is now operating on more Solar PV than Gas. Total Texas daily Solar PV production has now typically exceeds California.

Attached is yesterday for Texas.

 

[ponytug]

For comparison, California;

 

[sd455dan]

No balcony solar but now that summer is coming on, almost 3 days of sun in a row, with minimal grid support EV charged up off solar as well.

Wife got me a new shirt, made me smile. 7KW of panels still to be installed once they're up, Sunny days should be making over 100 KWH a day.

I look at solar with more of a preppers attitude. All grid tied equipment is UL1741 as well.

If there is one thing I have learned about solar in general it is the difference in clouds/shading massive affect on output. Not uncommon to see a 92% loss in generation even at Noon if weather is not clear. Same for tree or building shading panels.

Like working in a coal mine... might find a diamond on that special day but a whole lot of lump of coal days (at least the coal can be burned to keep warm).
Rainy today may see a whole 8 KWH of production

 

[shooterdon]

No balcony solar but now that summer is coming on, almost 3 days of sun in a row, with minimal grid support EV charged up off solar as well.

Wife got me a new shirt, made me smile. 7KW of panels still to be installed once they're up, Sunny days should be making over 100 KWH a day.

I look at solar with more of a preppers attitude. All grid tied equipment is UL1741 as well.

If there is one thing I have learned about solar in general it is the difference in clouds/shading massive affect on output. Not uncommon to see a 92% loss in generation even at Noon if weather is not clear. Same for tree or building shading panels.

Like working in a coal mine... might find a diamond on that special day but a whole lot of lump of coal days (at least the coal can be burned to keep warm).
Rainy today may see a whole 8 KWH of production

Very surprised the output drops that much on a cloudy day. Makes the investment even less attractive.

 

[sd455dan]

Very surprised the output drops that much on a cloudy day. Makes the investment even less attractive.

Yeah we are pretty far North and get more than 1/2 cloudy days a year, need a lot of panels and storage batteries to even things out on grid use. By fall last year we were more than 1/2 power produced by solar, after a mild winter with more rain and clouds than snow then sun we are not caught up to 1/2 on the grid supply yet. It is sunk cost but a bucket list item for me, that is close to being fully implemented.

 

[ericm979]

Very surprised the output drops that much on a cloudy day. Makes the investment even less attractive.

I've been surprised how much my panels generate on cloudy spring days. Maybe I had low expectations.

Today for example it's been foggy, overcast, and raining at times. So far 15kw of panels have generated 20kwh of power, which is a little ahead of the house's usage.

In December they would not have been close. The sun's too low and the panels are not aligned for maximum winter production. But we have 1:1 net metering, so we don't need that. Summer over production can make up for winter shortfalls.

Part of the bid process was to get estimates from the solar companies of how much power we'd generate. I also did my own estimates using the NREL PVWatts tool. Both of those take cloud cover into account using local historical weather data.

What I didn't know is how much power the house would use. It's essentially a brand new house- all we kept from the old house was the basement. So I won't know if we have enough solar until a year has elapsed since it was connected to the grid. If we don't, that's ok. If we make more, Oregon lets me assign solar credits to other meters. The shop on its own meter can use any excess.