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I don't get it! how does it work?

Posted by scryn (My Page) on
Thu, Nov 3, 05 at 12:15

I was looking here trying to figure out how net metering works.

http://www.etmsolar.com/gridtie.htm

(hopefully that link will not be deleted)

I just don't understand how you send the electricity that you make from your solar panels through your electrical box backwards. How does that work? is this just a simplified drawing and that is not how it really happens??

thanks!
-renee


Follow-Up Postings:

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RE: I don't get it! how does it work?

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It's "F M" . . . . 'Friggin Magic . . .

I've got a system designed and installed by ETM; been here a bit over a year now. And yes; your meter can indeed run backwards. I've supplied a VERY healthy percent of my annual electricity usage for my residence during the past year.

Electric meters ( well, the "old fashioned" mechanical ones with the moving dial ) are really just a specialized motor . . . and when power goes OUT to the grid; it will run backwards. Net metering basically means that if you use a kilowatt hour ( kWh ) and then later on replace it with one of your own; you owe nothing for electricity. Also know that there is other interconnect stuff required; so as to prevent the possibility of hurting someone working on the lines during an outage trying to restore things . .

It's quite involved technically as far as the equipment goes and how it works . . . but as an "end user" such as myself; it is pretty darn close to just let the equipment run and do it's thing.

You are correct in wondering how it's done; the DC from the panels goes through an inverter . . . which has the ability to produce power JUST like the power company; and to "synch" up with it as needed. Such equipment must meet utility requirements and others as well. In my particular case; I also chose to have battery back-up; when the grid does go down; the switchover is so fast that you can barely detect it. It also reconnects when things are back to normal; automatically. I'm an electronics guy myself; and while the basic principles are fairly straght forward; actually doing it at the power levels involved, to everyone's satisfaction; is indeed a daunting engineering task.

I've got 2800 w of PV panels, a 4 kW inverter; and about 1000 lbs of batteries that comprise my system. I've got a write-up I did if anyone is interested; email me with a REAL email address and I can send it along. I welcome questions too . . and rather enjoy showing it to anyone who has some interest in it . . . and right now, NY has some GOOD incentives for such systems . . when you toss in the tax credits as well; they all ended up covering ~ half the cost of my system . . . . I'm about 25 miles north of Syracuse if that matters . . . .

Bob


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RE: I don't get it! how does it work?

Obviously you have a special electrical installation, but really it is that simple. The electric just goes backwards in to the power grid. Like any cable, electric can go in either direction. Obviously it only goes one way at one time. You're either using grid power, using grid power with some electric from the solar pannels, or sending power in to the grid. The direction changes depending on the output from the pannels and the amount of electric being used in the house.

The power grid itself can have extra electrical capacity installed anywhere on it, just as consumers can be hooked up at any point. So, it's quite easy for excess power from your solar pannels to go in to the grid and be consumed by your neighbours.


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RE: I don't get it! how does it work?

Thanks. we are looking into a system and I think i talked to you before, Bob. We have a perfect southern facing roof, however I am not sure if it is large enough.
We are filling out our Info for ETM right now! I don't think we can get anything done till after winter, but I guess that will give us time to save!
-renee


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