Net Metering - How does it work?

Status
Not open for further replies.
J

jimb

Member
Location
Kentucky
Hello to all,

I've been seeing more and more articles in trade mags concerning electrical cogeneration and net metering practices but I'm looking for some help in understanding how the consumer's power system integrates with the POCO's grid. While I can see how two power sources can be paralleled, I don't see how it can be done 'safely' (I'm probably stuck in a rut because of thinking about how stand-by systems are installed). This is probably old-hat to some of you guys but none of this stuff has filtered down to my remote neck of the woods yet.

Thanks for any help,

Jim
 
Re: Net Metering - How does it work?

One method is to use an "induction generator".

A standard induction motor driven above synchronous speed by a suitable prime mover, will act as an alternating-current generator, also called an asynchronous generator.

Below synchronous speed the machine draws electrical energy and acts as an induction motor. As the speed is increased, (driven for this purpose by a wind or hydro turbine, or other prime mover) at synchronism the power component of current (the in-phase current) becomes zero and changes polarity, so that above synchronous speed the machine gives out electrical energy as a generator, feeding into the grid and running the meter backwards.

With regard to safety, the machine depends on the grid for excitation, so that if the grid goes down, it just stops generating.

Ed

[ March 03, 2004, 10:09 AM: Message edited by: Ed MacLaren ]
 
Re: Net Metering - How does it work?

The entire electrical grid is comprised of paralled sources. Smaller cogen source are protected by reverse power relays, directional overcurrent relays, voltage phase sequence relay, etc. These devices quickly separate the sources when failures, internal and external, occur.

The local utilities will generally have specifications for the type of protection they require when paralleling to the grid.
 
Re: Net Metering - How does it work?

Thanks for the replies!

Ed, I see what you mean by using an induction generator but that I was thinking that these systems would allow the customer to have power even if the grid is down. I suppose that's where the relays etc. that wanderer mentioned come into play.

The cogeneration I have read about sounds like a great deal for industrial and commercial environments but it seems like it would be awfully expensive for residential. Does anyone have any experience with residential installations that augmented utility power with renewable energy sources? I know I'm behind the curve on this but I think it's a great thing and would like to learn more about it (or course, Kentucky might not be the best place to try it).

I've done some searching on the internet and while I have found several sites about solar power etc. I haven't been able to find a comprehensive site that would explain what was needed and very importantly, how much it costs. If anyone has some links to some sites it would be very much appreciated. While Kentucky has enacted Net Metering, the folks at the POCO where I live aren't very knowledgeable about it. For the time being, this is just to satisfy my curiosity, but it might come in handy in the future.

Thanks again,

Jim
 
Status
Not open for further replies.
Top