Topic: Solar panels/power glitch duirng switch overs?

[DaleReid]

Just thinking as I was reading an article about more solar panels being encouraged.

I've had solar panels that provide hot air during sunny (and not sunny) periods and also pre-heat water for the hot water heater. 

If I were to replace those with photoelectric panels, I could potentially use the panels for something more far reaching than just hot air.

I know that the chatter is that when the sun shines and you are producing more power than needed, some districts will allow  you to run the excess power back into the local supply and get paid for it.

If you don't install massive and very expensive batteries to hold the excess power, you either have to sell it back, or dump it.

Here's my question.  Fortunately our local power supplier has been incredibly stable, with only occasional glithces during thunderstorms or some drunk hits a power pole.

I have some UPSs around the house for computers and some other stuff like weather stations to keep them running if there is an outage.

What happens when you don't have a battery backup system, have solar producing power and on good days selling it back to the utility, and it clouds up/sun goes down/ or the solar array stops making enough power for the house.  This would occur at least once a day (night time).

How does the system switch from panels back to grid?  Does the power for the whole house go off for a few seconds and the switch occur?  Are there smart entrances that keep locally produced power in synch with the electric company and seamlessly change over on one of the 60 cycle fluctuations?  I can't see putting the whole house on a UPS, which is essentially what the big batteries seem to do with the proper inverter, but there will still be times that the flow will have to revert to no-sun conditions.

Has anyone put solar in and know the answer, or has read somewhere how this works?
Thx.  Dale
 

[CW2274]

Just thinking as I was reading an article about more solar panels being encouraged.

I know that the chatter is that when the sun shines and you are producing more power than needed, some districts will allow  you to run the excess power back into the local supply and get paid for it.

That's the way it is here in Tucson. You can hardly find a building or once open space that doesn't have a million solar panels on it.

It's sounding more and more, just like with EV's and windmill farms, that there's nothing "green" about them, either. Of course, that's all about who you ask...

[WeatherHost]

"How does the system switch from panels back to grid?  Does the power for the whole house go off for a few seconds and the switch occur?  Are there smart entrances that keep locally produced power in synch with the electric company and seamlessly change over on one of the 60 cycle fluctuations?"



Without batteries, there will be some switchover, but should only be a second or less in most cases.  It's just a contactor switching from source A to source B and back.

With batteries, the change would be seamless since you're running off the batteries and the source change is what's charging them.  That may vary based on system design, but what I've seen is the batteries act as a filter/UPS to work against fluctuations.

Solar is useless at night and very ineffective on cloudy days, so without batteries, it won't help you much.

A full system is a combination of utility, solar, wind and batteries.  Maybe a generator too.



With my 16Kw generator, there is an automatic transfer switch (ATS) that monitors utility power.  When that fails, the ATS senses the loss, sends a command to the generator to start and waits a few seconds for it to come up to speed and stabilize, then switches.  Power loss to the house is generally about 10-15 seconds.  UPSs on various devices can easily carry that.

When utility power is restored, the opposite happens.  Switchover is first, then the command is sent for the generator to shut down.

[DaleReid]

OK, thanks for the info. I don't know anyone locally who has a setup (yet).  With my hot air it makes no difference to the power to the house, so in over 30 years it of course has never interfered with my power.