Electrical Flow

[tljones]

But I have to ask it.

I have been lookinf at something like the breezy 5.5 which is a sychronized induction generator. My question is this.

In this application the generator only puts out power if there is first power in the grid, so there would not nescessarily be any batteries. My utility says that because we do not have net metering, we would need to put in another meter to measure power delivered out to the grid. So my question is this.

Does a mental model of water flow in the system make sense here. What I mean is, I have two streams of ppwer (water) coming in, Grid and Wind. When my wind low, there will be a net negative in the pool (demanded power from the home) which because the wind is not blowing would be supplied from the grid. In normal wind conditions my supply from wind might nearly equal my  load so the pool would be steady, and most flow could come from wind. When the wind is blowing well, or in times of low demand, the power from the genny flows into the pool and because it cant go into the demand, flows out into the grid.

There would not need to be any controllers on this system? Or is this complex to control?

My thought process being that if that is true, then it dramatically lowers some of the non genny and tower related costs of setting up the system.

How is my visualiztion wrong??

Thanks

[Flux]

I don't follow all your problems.

You can't synchronise an induction generator, you can use it to feed power into the grid, using the grid as its source of magnetising current.

You will need some form of control. You will need to sense when it is turning above synchronous speed so that you can switch it in. You also need a reverse power sensor to knock it off when there is not enough wind, otherwise it will motor and run as a fan.

If the power it produces is less than your needs it will just act as an energy saver and you don't need to worry about the extra metering. If it produces more than you are using then you will need metering to find out how much excess you are feeding to the grid.

Control is fairly simple as long as the alternator is powerful enough to hold the blades down. If you pull out it will run away and it will also run away if the grid supply fails. Your most complex control will be in preventing these abnormal conditions.

A fixed speed induction generator will not make best use of available winds but it is simple and if you can prevent over speed on loss of load or pull out then it will be reliable. You can make better use of the wind with 2 alternators with different pole numbers but not likely to be worth the effort for a small machine.

Flux

[tljones]

That is a good point, I was not seeing that in my mind, of course you will need to stop current from flowing from the grid to the motor in low wind periods.

Thanks.

It seems to me that they have a fairly good model of controlling runaways, or at least as good as you can without building a furling tail into the equation. Generally I look to overbuild something so you can brute force the stop instead of being elegant. We get strong winds here, but generally not gale force unless in an isolated thunderstorm. I think in  that condition you just lock it down. These guys system is running in an environment very similiar to my own.

I am a visual type of person, and I want to imagine the power supply of my home as a rain barrel sitting just on my side of the power meters with a series of inflows and outflows.

I guess part of my thought process problem revolves around the idea of power conditioning (not sure if that is an accurate term or not) in relation to blending into the grid. If I want to take power from an axial flow, I first need to rectify to DC, then through a controller to charge the batteries or directly into an inverter which then converts the power back from DC into a useable and (blendable???) (homogonous???) enough product to be put out onto the grid (into the barrel in this analogy). If you dont go through all of these steps then you cant get an A/C grid useable commodity to use in your home. You could use DC appliances, or isolate circuits into a cheaper inverter with manual switching or something, but you cant just plug it into the system. It appears to me that this system gets around all of that. When the system reaches operating conditions it switches on and begins to put its power into the power supply barrel.

So, if you isolate the generator with a flow stoppage device to keep current from going to the generator during low output periods, do you need any other form of controller to manage where the power flow goes?

For instance, if my neighbor is using 2kw hrs on the grid, and I am using 2 kwhrs on the grid, while I am only producing 1kwh then I only want to be bringing in one kwh off the grid to supplement my use. Because I cannot be net metering in SD, I need to know that my 1KWh is not going out onto the grid and feeding him at 2.6cents while I pay 8.5 bringing 2kw into my house. Now I know that does not make any sense, but that illustrates the question. If the pool of power sits in a barrel with inflows and outflows, and I control the outflow back to the genny, do I need and other form of treatment or control (other than the utilities electric meters) to manage where the outflows from the barrel go? There would have to be two meters which only flow one way each. One only measuring inflow from the grid and one only measuring outflow to the grid. Everything on my side of the meter would be in the barrel.

I know the analogy may sound silly, but I trying to visualize this in my head. And flowing water is easier for me to think about than electrons.

Tom

[Flux]

Your flow analogy is ok. If you are consuming 2kW and the turbine is producing 1kW then you pay for 1kW. If the turbine produces 3kw then you pay for nothing. If you had net metering your meter would run backwards and give you credit for another day.

If you are not allowed net metering the utility will supply you with one meter that runs when you use power. If you are generating excess then it will stay still so you pay them nothing. If they are kind they will let you run another meter showing the energy you supply to them and they will pay a reduced rate.

If you do it on a small scale and rarely produce more than you use it may not be worth the trouble of trying to extract money from them, but it will cost you nothing when you are generating all your needs.

You don't need any power conditioning equipment unless they insist on power factor correction to correct the lagging power factor your alternator takes from the grid.

In a small installation I doubt that they will worry about power factor correction. You will have to satisfy them that if the grid fails you will not generate power back into the line. With an induction generator without power factor correction this is virtually impossible but you still have to convince them, it is conceivably possible that line capacitance could cause self excitation but it is only a theoretical issue. Any power factor correction would allow the possibility of self excitation.

The concept of an induction generator is simple, the politics is well beyond me, that you would need to sort with the utility. It is probably simpler to connect an approved inverter than an induction generator that is perfectly safe but with no approval.

Flux