I thought a transfer switch was used to disconnect you from the grid so that you would use solely your own power. This would prevent you from “spinning the meter backwards” as mentioned in Una Persson’s link.
Just as guns are always loaded, electrical lines are always energized.
I believe that you contact the utility. In some places the law requires the untility to buy your excess powere.
For solar + grid systems there is a cut out switch, line voltage is required for the solar panels to feed the grid, if it drops off the circuit opens up and doesn’t accept power from the panels till line voltage is restored. I would assume such a setup is required for wind power, or other home grown electricity that touches the grid.
In the solar power systems I’ve seen, the system disconnects itself from the grid if there is a blackout. I imagine the wind systems use the same kind of thing. You can only pump power into the grid while it’s functioning.
ETA: What kanicbird said.
Una’s link ballpark’s the cost between 7 and 10K with a weasel word payback “in as little as 5 years”. Was your experience much different?
I guess that one of the problems with any of these alternative power sources is that there is significant overhead in getting the generator - whether solar, wind or whatever - connected to the rest of the house’s power grid. Otherwise we’d all be taking advantage of the ubiquitous attic turbines to supply whatever minuscule KWs they are capable of.
I seem to recall a $20,000 installation cost estimate for a modest home for tower, blade, turbine and minimal electrical hookup (no batteries). Since my electric bill is only about $90/month now, and the turbine would only provide part of my needs, the payback would be much too long. Unfortunately, I did not write the exact amount down, and it was not a formal survey of my needs, anyway. Also, a wind generator could be sized small or large; small would only supplement the grid, large could produce excess. Municipal codes might prohibit the larger installations, and in my particular case, the county passed a strict ordinance a few years ago that effectively makes larger ones impossible to erect.
I was also worried about vibration, which is more of a problem in smaller ones (larger ones spin more slowly). My property isn’t large enough to site the turbine very far from the house; it would probably be attached, making vibration a concern. Solar photovoltaic would be a better choice, but that, too, is still too expensive.
At 7K it could supply all my electrical needs for 5 years and still not pay me back.
A guy in the Grant Park neighborhood in Atlanta just got approval for a 45-foot wind turbine much to the chagrin of his neighbors, who are worried that it will be an eyesore.
I think what** KRM** means is that suppose the utility disconnects the line from the grid in order to do maintainance? Your wind charger is still connected and happily spinning away putting power into the line. How is the safety of the workers insured?
Well, the utility knows that you have a wind powered generator so the contact you by having one of the linement come to the door. He disconnects your generator and puts a seal or a flag on the switch to insure that no one reconnects it until the linemen are finished. The linemen also make sure the line is not energized before they start to work.
In some cases the maintainance is done with the line energized but that’s another story.
Don’t forget that in many states (such as California), the power company is required to buy any excess electricity you generate, so you could actually show a profit on your investment some months.
Which exposes the problem for the utility (and your neighbors). Imagine 10 or 15 neighbors with generators and the lineman forced to visit each (maybe they aren’t home) and insure that each is locked out before he even gets to the problem that caused the outage.
Yes they do but their biggest concern is that the line doesn’t accidentally re-energize while they are making repairs. Throw in the possibility of homeowner windmills malfunctioning or the possibility that some homeowner mistakenly throws the switch back over and its a disaster waiting to happen.
Hooking a windmill up to the power grid is a bad idea. Having a windmill perform dedicated energy tasks fir you home isn’t too bad of an idea after all. Let the windmill heat water, charge DC devices etc but keep it off the grid and away from the utilities rules.
Why? My reasons
1 - The utility has the right to mandate that the proper equipment is there to protect their lineman (this relay equipment can be expensive).
2- They also have the right to require periodic inspection and testing of your equipment (Also expensive)
3 - The utility gets to charge you 7 cents to 15 cents per kWh for the power you use but in most jurisdictions they only have to pay you the wholesale price for the power you deliver to them (usually less than 5 cents per kWh). Remember, they are the ones who built the power grid out to your house and the ones who will deliver your surplus energy to your neighbors for you.
4 - Your neighbors may not be thrilled with you for adding another 30 min to a 4 hour outage because the utility lineman had to visit your house before he could fix the problems at their houses.
Like my neighbors think about me when the power goes out. Rightly or wrongly, they will blame the power company
All grid-tie systems automatically disconnect when the grid goes down, they synchronize their inverters to the grid, so the grid power needs to be present.
Your local utility isn’t going to accept that as a given. They will still require proof (periodic certified testing) that the equipment works as required. Whether or not the probability of backfeed is 0, if the utility doesn’t control the equipment they will demand that it is proven and inspected, usually at annual intervals.
That’s why all inverters designed for grid-tie are utility-approved.
What’s so hard? It’s like I said above – an automatic transfer switch. They know when there’s incoming power or not. They’re routine, and used with home generators all the time. I don’t mean a manual transfer switch for using your little portable generator, but the things used for fixed, natural gas backup generators. Completely automatic, completely safe to the power works and neighbors. The only difference for the windmill is adding switch blades to back feed to the commercial power only when commercial power is available, and there’s no reason to switch power to/from your house.
The lineman coming to the door was partly figurative. In this day an age of telemetered meter reading it’s not far-fetched to think the utility can remotely disconnect and lock out home generating equipment whenever they want to. The interface between the power line and the home generator is entirely under the control of the utility since they control what is connected to their lines.
Getting the home generator back only line after outages is another question and one I can’t answer.
The question was how is the safety of linemen assured. The economics and feasibility of wind powered generators connected to the grid is a separate question.
Can you explain this a little better. There are numerous manufacturers and thousands of load serving entities (utilities) in the USA alone. I’m unaware of any universal approval system.
David Simmons
I’m not disagreeing that the technology exists to accomplish distributed generation supplied by home windmills. In fact, I believe that the application of home energy sources will grow.
My arguments are to address the ops question. That is, the technology isn’t commonplace because the cost is unattractive. There are a lot of things that need to be done to make it attractive —like the following
- Drop in equipment prices
- Improved communications and control methods from the customer to the utility (most customers are connected on a “dumb” system which has no communication capability in the connection. In fact the utility relies on customers phoning in to assess the operating status of their distribution systems)
- Incentives to the utility. They have no reason to embrace customer owned generation unless there is something in it for them.
Balthisar
If I’m right the backup generators you are talking about aren’t the ones sized for home use. Again, I don’t disagree that the technology exists. I’m challenging the feasibility based on the cost of that technology.
Guys, in my past life I worked for a utility for over 25 years and worked in power planning for over 15. There’s a lot of new technology out there that catches a lot of buzz. Solar, wind, fuel cells, distributed generation - they all hold some promise but the main reason they aren’t popping up in every back yard is the cost. Some will eventually but in answer to the ops question, the payoff isn’t big enough, yet.
There probably isn’t any Universal approval system, and any Utility that wants to prevent competition can make up any rules they want to prevent grid-tie. That said, all current major grid-tie inverters are FCC/UL/CSA approved and are designed with the safety of both the user and the Utility in mind. Remember, the alternative-energy companies are always in a battle with the Utilities, and they want to be sure that there are no obvious reasons for disqualification.