How can one grid tie a generator

[NZer]

Hydro elaborated

Hi Rick
Sorry I didnt put a bit more info with my message, I wasnt sure if you would reply.
So here is a full explanation:
Gross head is 13 meters and by my calculations net would be 11. The pipe through the dam wall is 100m and 300mm is diameter. The size of the turbine intake would allow 160l/s, 2.26m/s water velocity through the 300mm pipe which i used to get friction losses.
The turbine was built by Otago University here in NZ and ive been told that shaft RPM at 10m of head will be 880 at its most efficient speed. It is currently set up to run v belts.
All of the Power generated will need to go directly onto the grid but I have many meters on my bill so I have talked to the power company and the power created will cancel at 1-1 some of the other power I use.

Im still confused as to the possibility of over revving an induction motor that is of a larger rating than our maximum theoretical power available.
The motor I have is 22 Kilowatt, 400 volt, 1400 rpm induction motor. If maximum power is generated at 1442 RPM and I was to rev it up over this under no load then turn it on- would the torque created by the power generation not slow down the motor to below 1442 to an equilibrium point (still above synchronous speed) where the force created by the turbine would equal that by the generation of power by the motor (less losses due to belts, friction etc) eg 10kw.

I had looked into ram pumps but it would not be feasible.

Thank you very much for your time
Kind Regards
Tim

[ashtweth]

What an overwhelming amount of info, the caliber of which makes me feel like i am in a master class

A GEET hybrid, well, if you really wanted to go that far dont forget you could make the GEET into cooking also
YouTube - CAAF - The Gemini Reactor

There might be a bit involved for getting the pulley to regulate the electric motor to 60 hertz ? i think it would be more economical to get an already made genset with the generator attached and GEET that?

Ash

[rickoff]

Hi Rick
Im still confused as to the possibility of over revving an induction motor that is of a larger rating than our maximum theoretical power available.
The motor I have is 22 Kilowatt, 400 volt, 1400 rpm induction motor. If maximum power is generated at 1442 RPM and I was to rev it up over this under no load then turn it on- would the torque created by the power generation not slow down the motor to below 1442 to an equilibrium point (still above synchronous speed) where the force created by the turbine would equal that by the generation of power by the motor (less losses due to belts, friction etc) eg 10kw.

If you could keep it running at 1442 RPM then you would develop the full power as rated. It will definitely slow down if you start tapping the power at that speed, so the output will definitely fall initially and require further regulating on your part. How much it falls will depend upon the actual overall efficiency rate of your installation. Remember that, in the calculation example I gave, I factored in a 50% efficiency rate, which I consider to be on the conservative side. Your actual efficiency rate may be more or less than that, though. A 22kw IM would be rated at 29.5 horsepower (HP = 1.34102209×kW), which is a hefty motor, and certainly will require more of your turbine's available output to spin at a certain rpm than a motor half that horsepower, which would be closer to matching your turbine's output. I understand that you chose the 22kw motor so that there would be little chance of overheating it, and that's fine. That's a good idea, but if your turbine output is more closely matched to a 10kw IM then a 12 kw IM would offer overheating protection while requiring less drive torque from the turbine than your 22 kw motor. Therefore, you may find the 22kw IM to be overkill for your application, and may want to test a smaller motor to compare outputs and overall efficiency differences. The larger the IM that you couple to the turbine, the lower your overall efficiency rate will become, of course, up to the point where your turbine is incapable of overdriving the IM to generate power.

I had looked into ram pumps but it would not be feasible.

Why is that? You certainly have an adequate outflow from the lake to accomplish this, and could even set up a separate outflow just for the ram. Is it because constructing a holding tank above the lake level would be too difficult? You say there is already a dam, so couldn't the holding tank be elevated say 5 meters above the dam to give you additional head and a better regulated flow rate?

[tecknomancer]

Self-Excited Induction Generators

Here is a useful study from 1999 from the National Renewable Energy Laboratory NREL is a U.S. Department of Energy Laboratory

Investigation of Self-Excited Induction Generators for Wind Turbine Applications

This may help when the grid is down

[rickoff]

Here is a useful study from 1999 from the National Renewable Energy Laboratory NREL is a U.S. Department of Energy Laboratory

Investigation of Self-Excited Induction Generators for Wind Turbine Applications

This may help when the grid is down

Yes, this is an absolute necessity if operating off grid. As I mentioned in post #7 of this thread, a standard IM will not act as a generator unless it receives an outside frequency signal. Plugged in to a household electrical receptacle, the IM receives its outside frequency signal from the 60 hz Grid power sine wave. When the grid goes down, IM power generation stops. That's why a self-excited IM which produces its own sine wave, or an external sine wave input, is needed for producing off grid power generation. That's a bit off topic for this "How can one grid tie a generator" thread, but is still useful and related information. In a wind turbine application, you would want to take every advantage of the wind that is available, and if using an IM for generation could not do that if depending on a sine wave from the grid.

[ashtweth]

Guys that's unbelievable info it should all be in a PDF with your credits.Thanks a lot Rick/tecknomancer /ALL.

Ash

[pmanske]

Thread resurection

Hi - I'm res-erecting this thread. My utility lets me sell power if its made with biomass and WVO qualifies. They let you sell up to 10 megawatts at $.155 per kilowatt hour.

I appreciate the info here. I'm stuck on grid tie. I need help with synchronization. I thought about using wind/solar inverters but these are too pricey. Why does wind electricity need to be inverted? Its already AC.
I thought about taking out the circuit but its not worth it.

Any ideas?

Thanks.

Phillip

[kcarring]

Hi - I'm res-erecting this thread. My utility lets me sell power if its made with biomass and WVO qualifies. They let you sell up to 10 megawatts at $.155 per kilowatt hour.

I appreciate the info here. I'm stuck on grid tie. I need help with synchronization. I thought about using wind/solar inverters but these are too pricey. Why does wind electricity need to be inverted? Its already AC.
I thought about taking out the circuit but its not worth it.

Any ideas?

Thanks.

Phillip

Phillip,

If you have substantial output, it may be that your tie in need be certified by an electrician before any payout program will be implemented anyway, you should look into it further from a legalities / red tape point of view. Your wind electricity is likely 3 or 6 phase AC, not single phase. Sorry can't help a whole lot more without knowing your area/setup.

[ewizard]

One of the big problems if it hasn't already been mentioned is getting your power that you are generating synchronized exactly with the grid power. Think of a nice 60 cycle sine wave. The power you generate has to be aligned exactly with the 60 cycle sine wave from the grid or you'll be doing damage in a lot of ways. And of course the voltage has to be regulated closely. The only way I know to do that is with a good grid tie inverter and those are not cheap but if you shop around you can find some big discounts on them. I think designing such a circuit to handle higher power and sync it to the grid is probably beyond most peoples ability and then it would need to be certified or you could be liable for damage to the grid or your neighbors electrical devices.

I know from seeing grid tie inverters that it can take a minute or so for them to sync up to the grid before they will tie in. I just don't see that as a do it yourself type of project except maybe a couple people here. But in the end I'll bet you'd spend more in time and money than you would to just buy one. And having just now taken a quick look on fleabay I see they have really come down in price for some of the cheaper grid tie inverters. I'm seeing some lower power ones for only a $100 so it would seem to be seem there is little reason to not get one. I'm not sure how reliable the cheap ones will be but I do know Xantrex is one of the best quality and one of those can be had for around $1500 for a 3000 watt unit.

[sucahyo]

One of the big problems if it hasn't already been mentioned is getting your power that you are generating synchronized exactly with the grid power. Think of a nice 60 cycle sine wave. The power you generate has to be aligned exactly with the 60 cycle sine wave from the grid or you'll be doing damage in a lot of ways. And of course the voltage has to be regulated closely. The only way I know to do that is with a good grid tie inverter and those are not cheap but if you shop around you can find some big discounts on them. I think designing such a circuit to handle higher power and sync it to the grid is probably beyond most peoples ability and then it would need to be certified or you could be liable for damage to the grid or your neighbors electrical devices.

That remind me of George wiseman solution of speeding up an electric fan to make it as generator. The wave would follow the grid but since it is accelerated it charge the grid instead.

[ewizard]

sucahyo, can you elaborate on that a bit or point me to info on George Wiseman's ideas?

[sucahyo]

sucahyo, can you elaborate on that a bit or point me to info on George Wiseman's ideas?

I lost the link unfortunately, I may refer to wrong man. I remember to read it in this forum.

From what I remember, if we speed up electric fan motor by 15%, we charging the grid instead of using it.

Maybe this:
Induction generator - Wikipedia, the free encyclopedia
Asynchronous Generator, Use a Induction Motor As A Generator

The precaution is it only generate proper voltage and frequency if the grid is on.

[rickoff]

Re: George Wiseman

can you ..... point me to info on George Wiseman's ideas?

The info you are looking for was described and linked in my post #3 in this thread. Here's a link to the book that I mentioned in that post. I have had one for quite some time, and it is excellent - tells you everything you will need to know about the subject of grid tying, and all the protective and switching circuits are included. Reverse Your Electric Meter, Legally! [4901.99.00.503] - $14.00 : Eagle-Research Store George Wiseman operates Eagle Research, and has several interesting paper books and e-books available. I would also suggest you go back and read my posts #3 and #7 on the subject.

Rick

[rickoff]

One of the big problems if it hasn't already been mentioned is getting your power that you are generating synchronized exactly with the grid power. Think of a nice 60 cycle sine wave. The power you generate has to be aligned exactly with the 60 cycle sine wave from the grid or you'll be doing damage in a lot of ways.

This is no problem if you are generating using an induction motor (IM) that is not self-excited (does not produce its own sine wave). A non-self-excited IM plugged into a household receptacle will get its synchronizing sine signal directly from the grid, so will always be in perfect synchronization with the grid. You can read more about this in paragraph 2 of my post #7 of this thread. Also see post #20.

Rick

[rickoff]

My utility lets me sell power..... they let you sell up to 10 megawatts at $.155 per kilowatt hour.

Phillip

Your figure of 15.5 cents per kilowatt hour sounds quite a bit overstated. The amount is more likely $0.0155 per kwhr. For example, I live in Maine and my electricity (after the first 100 kwhr's) is billed at about $0.06, or 6 cents per kwhr. It is quite unlikely that any power utility would pay more for electricity supplied to them than they would charge to supply it to their customers, and typically they will pay only a fraction of what they charge to customers for the same amount of power. For that reason, one is better off to sell any excess power directly to a neighbor rather than to the utility company. Your best strategy is to use the grid tied IM to produce just enough power each month to prevent your electric meter from advancing more than 100 kwh, and then to divert any excess generation to your neighbor through a meter. Your neighbor would most likely be happy to pay you 3 or 4 cents per kwhr for any power you would supply him with. The reason I say that you might as well leave 100 kwh on your meter each month is because you will have to pay for it anyway as the basic charge for connection service, and it will keep the utility from raising the questions that would arise if your meter was reading backwards each month. Note that any power produced by the IM (which is plugged into a household receptacle) will cause your electric meter to run backwards unless all of that power, or more, is being currently consumed in your household.

Rick