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  #1  
Old 12-28-2005, 10:52 AM
bup bup is offline
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Feeding back into the electric grid

If I create an electric generator, how complicated is it to feed that electricity into the community grid? Do I need a permit? A business license? Will the power company pay me?
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  #2  
Old 12-28-2005, 11:04 AM
Shagnasty Shagnasty is offline
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I read the Mother Earth News which tends to cover such things regularly. Remember that the electric grid covers much of North America and maybe more. Power generation companies just feed into the entire thing and get metered for what they put in. There is no way to control where electricity ends up like you would oil, water, or gas. There are some programs that let private homeowners feed electricity into the grid and get credit for it. It would be rare for a private homeowner to generate enough electricity to cover all their power needs. They just put in and then take out as needed. That ensures a steady supply like everyone else has. They get credits for what they put in versus what they use in total. I have no idea what equipment it takes to feed into the grid. It may be subsidized in some areas.
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Old 12-28-2005, 11:30 AM
Napier Napier is offline
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I think I read that power companies are obligated to let you do this, but am not too sure on this point.

As a practical matter, you have to feed AC into the grid, and it has to be synchronized with the grid, which sounds pretty complicated. However, if you run an induction motor (for example pretty much any motor that says it runs at 1750 rpm) connected to the grid, and try to turn the motor faster than it's already going (for example use a windmill or a turbine or a gas engine), then you'll be pushing power back into the grid. If you generate more power than you're consuming elsewhere your electric meter should run backwards. Even if you don't, you will still be reducing your bill.
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  #4  
Old 12-28-2005, 11:32 AM
gotpasswords gotpasswords is online now
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Check with your local utility. It's far more complicated than just wiring up your generator to the house wiring. At a bare minimum, you'll need a permit from the local building inspector and written permission from the utility. The interconnect equipment is probably pretty well standardized now, but it's not entirely simple - for one thing, it needs to be able to rapidly disconnect itself from the grid in case grid power goes down.

My utility has an FAQ page for residential/small commercial (under 10 KW) producers, and one of the questions is "Why do I have to fill out so much paperwork?"

If you generate enough power to result in a net draw of no power from the utility, you won't be charged by them for electricity. Keep in mind that there's a host of non-electricity charges on the typical bill, and you'll still be paying those.
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  #5  
Old 12-28-2005, 11:33 AM
GorillaMan GorillaMan is offline
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Here's one example of a British company that does operate such systems: http://www.greenenergyuk.com/site/se...rgy/index.aspx
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  #6  
Old 12-28-2005, 12:20 PM
Nanoda Nanoda is offline
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A friend of a friend (both University professors) has a super-high efficiency home, and uses solar panels to generate electricity. IIRC, he said not every power company has the ability to take power back in to the grid, and since you'd be feeding your electricity to your neighbours, the power companies will insist the quality be very high (thus the paperwork and expensive electronics).

Once that's set up, the biggest problem is bureaucratic. Some months he makes enough electricity to have a net surplus, meaning the power company owes him money. Every now and again he gets a new power company employee calling him, all confused 'cause they have this strange situation where he gets $$$.
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Old 12-28-2005, 12:40 PM
David Simmons David Simmons is offline
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Check with your local utility. They will make the connection for you and show you how to operate and maintain your system. They have a vested interest in not having novices messing around all by themselves with the meter and power lines.
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  #8  
Old 12-28-2005, 12:48 PM
flurb flurb is offline
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Quote:
Originally Posted by Nanoda
. . . and since you'd be feeding your electricity to your neighbours, the power companies will insist the quality be very high
I'm not sure I understand: how can the electricity come in different levels of quality? It's just moving electrons, right?
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Old 12-28-2005, 12:58 PM
Troy McClure SF Troy McClure SF is offline
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Quote:
Originally Posted by Nanoda
Some months he makes enough electricity to have a net surplus, meaning the power company owes him money. Every now and again he gets a new power company employee calling him, all confused 'cause they have this strange situation where he gets $$$.
Couldn't find a cite, but I remember a report on (I think) KTVU in which a guy in the rural North Bay had either a generator or solar panels, and he got a few bucks back from PG&E every month.
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Old 12-28-2005, 01:28 PM
Crotalus Crotalus is offline
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Quote:
Originally Posted by flurb
I'm not sure I understand: how can the electricity come in different levels of quality? It's just moving electrons, right?
One of the ways of measuring the quality of electricity is the amount of non-standard frequencies in it. Many low-end home generators produce 60 cycle current with lots of other frequencies in it. This so-called "dirty" power will not operate some solid-state devices, like modren heating controls.
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  #11  
Old 12-28-2005, 01:52 PM
ethelbert ethelbert is offline
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One issue you need to address is how to avoid feeding power back into the grid when there is a power outage. This is a very serious safety issue for workers dealing with downed lines. The power company can cut the power to these lines, but since you are feeding power back into the grid, they are potentially (and lethally) live.
I know people with solar generation capabilities who do exactly what you are proposing to do (in Northern NJ), so it is not uncommon. Just have a licensed electrician do it (or inspect it before it goes live).
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Old 12-28-2005, 03:05 PM
spingears spingears is offline
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Quote:
Originally Posted by bup
If I create an electric generator, how complicated is it to feed that electricity into the community grid? Do I need a permit? A business license? Will the power company pay me?
A transfer switch and connection monitoring may be required.
Why not call Commonwealth Edison or whatever electric company bills your electric service?
If they don't know no one will!
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Old 12-28-2005, 05:59 PM
engineer_comp_geek engineer_comp_geek is online now
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This is not something that a DIY person should be attempting. Get someone qualified to do this sort of work. There are some very specific safety and metering issues that need to be addressed. If you make something unsafe, the electric company will probably disconnect your service until you fix it right.

I used to work for Ohio Edison many years ago. It was actually not all that uncommon for large farms and certain types of businesses to generate their own power. Most of them hooked into the power company's system, so that they had a backup in case their own system went down. The power company was required by law to buy any excess electricity that the individuals supplied. However, they weren't required to pay anywhere near the same rate that they charged their customers. If you think you are going to get rich off of the power company, think again.

It's easy to make a generator system. It's much more difficult to make a generator system that is safe and reliable. Make sure you know what you are getting yourself into.
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  #14  
Old 12-28-2005, 08:51 PM
drbuzz0 drbuzz0 is offline
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Actually this is something I've always wondered about: How do you keep electricity in phase with the mains grid. If it's even off by a little, you could have some major problems.

I know that when the utilities combine power from multiple generating stations onto the grid that they*used to* use a complicated system that sometimes even involved mechanical synchronous convertors. (akin to what used to be used to power subways and such) But I'm pretty sure that current technology has progresssed well beyond that. I don't know though.


As far as power quality, the power comapny is going to basically want to make sure that you're not sending any unwanted frequencies into their system, that you're not adding any kind of an underlying DC componant to the grid and that there are no rapid spikes or drops generated by the generating equipment, as these could damage nearby equipment.

I'm very lucky where I live. My power is absolutely gorgeous. If you look at it on an oscilloscope it always looks like a perfect sin wave, even when the dryer is running or something. A frequency counter always gets the same reading: 59.99 Hz. The fact that it's not dead-on 60 may be because the counter needs to be calibrated a bit better. The voltage is always stable and right on the money and it never seems to drop by much, even when something big starts up.

If somebody nextdoor started dirtying up my power with their old Coleman generator, I wouldn't be very happy about it.

-Steve
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Old 12-28-2005, 09:18 PM
David Simmons David Simmons is offline
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Quote:
Originally Posted by drbuzz0
Actually this is something I've always wondered about: How do you keep electricity in phase with the mains grid. If it's even off by a little, you could have some major problems.

I know that when the utilities combine power from multiple generating stations onto the grid that they*used to* use a complicated system that sometimes even involved mechanical synchronous convertors. (akin to what used to be used to power subways and such) But I'm pretty sure that current technology has progresssed well beyond that. I don't know though.


As far as power quality, the power comapny is going to basically want to make sure that you're not sending any unwanted frequencies into their system, that you're not adding any kind of an underlying DC componant to the grid and that there are no rapid spikes or drops generated by the generating equipment, as these could damage nearby equipment.

I'm very lucky where I live. My power is absolutely gorgeous. If you look at it on an oscilloscope it always looks like a perfect sin wave, even when the dryer is running or something. A frequency counter always gets the same reading: 59.99 Hz. The fact that it's not dead-on 60 may be because the counter needs to be calibrated a bit better. The voltage is always stable and right on the money and it never seems to drop by much, even when something big starts up.

If somebody nextdoor started dirtying up my power with their old Coleman generator, I wouldn't be very happy about it.

-Steve
The power company will show you how to get your system in phase with the power line in order to make the connection. Once the connection is made your generator will stay in phase if it is a rotating machine. If it tries to go faster, i.e. produce a higher frequency than the line, it will be retarded to line frequency by a strong magnetic force in which case it will be putting power into the line. If it is going too slow it will be speeded up to line frequency by a strong magnetic force in which case it will be taking power from the line.

Getting the rotating machine in phase is the problem. You have to start with your generator at the same voltage as the line or maybe a trifle higher. One simple method is to connect the neutral of the generator to the neutral of the line. Then connect a light bulb from the hot line of the generator to the hot line of the lamp. When the line and generator frequencies are relatively far apart the bulb will light. As you speed up or slow down your generator, depending upon what your generator frequency meter reads, and the frequencies get close to each other the lamp will begin to pulsate at the difference frequency. When the frequency of pulsation is slow, say one light-on light-off cycle every couple of seconds, you can make the connection whenver the light is out because at that time the line and your generator are in phase and at the same voltage. From then on they will stay in phase as described above and you can vary the amount of power you are putting into the line by increasing the input to your generator.

Power generating stations have sophisticated control systems for bringing generators on and off line.

If you start with direct current, as from solar cells, then your voltage can be converted to the line frequency by using the line output to chop your dc and thus you and the line will autmatically be in the correct phase and frequency.

Again, the power company will show you how to do all of this. In fact I'm pretty sure that they will insist on showing you how and in making sure that your equipment is adequate and proper for their use.

As engineer_comp_geek said, the power company will not tolerate a mickey mouse collection of junk.
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