Beam me to Planet Gore !
Posted on 03/07/2012 9:50:56 PM PST by Hunton Peck
These wind systems have inverters that convert whatever power is coming out of the generator into 60Hz synchronized power for the grid. The rotor blades can be feathered or furled to reduce the power generated.
Thank you for the link to the PDF of generator specs, that’s ideal. As I thought, all the generators described there are asynchronous variable speed with power frequency conversion to match the line 60hz.
Fascinating reading... I’m an electrical engineer (among other things) so I’ve got lots to enjoy in that document. Thanks again!
Actually I do the 80 ft vertical ascent and descent totally free. But I turned 60 this year and probably will have to start using safety aids. No point dying over it, even if it is fun.
The problem as you say with the wind zealots is they do see it as a savior, and there ain’t no such thing. It’s great for small local power, but stupid for large scale wind farms, no economic sense to it.
Yep, that’s pretty much what I thought, too, and confirmed in the PDF linked above.
That is exactly the problem of scale.
For a small system like mine, AC/DC input to DC storage to AC load is easy and reliable. I have 3-5 full days of ride in the battery bank, a week if I trim my electrical usage. It’s essentially a big UPS. :)
But at large scale that becomes technically challenging, maintenance becomes a nightmare, and the economics don’t work well.
When I designed the system in 1989, I considered not only batteries, but also stored water and flywheels. Batteries won for me, but I know you can buy flywheel systems that are pretty slick these days.
Liberal Government Wonk Solution:
Tear down more dams...
There’s an untold story here....
Washington state is systematically tearing down hydroelectric dams so natural habitat can be restored.
It is only a question of time before we will be begging other states for electricity on windless days.
We're destroying jobs (those that cannot be sustained with energy prices through the roof), and forcing them off-shore. We create a few millionaires with tax dollars (a large percentage kicked-back to the DNC), and we reduce the income taxes from the laid-off workers who lose their jobs due to high energy prices.
The Tax Burden is being forced upon the few who actually have income, while more than 50% of America now pays no income tax (and it's getting worse every day). Buggered-up un-employment numbers don't create any revenue to pay for all the payoffs and corruption payments.
““Feathering” is limited in some cases as this technology has not been fully spread to all wind generation. Bottom line is wind and solar are poor forms of power relative to hydro and nat gas. Once a grid has too much wind and/or solar reliability goes. It is very much a case of diminishing returns as wind is added to a grid.”
Don’t forget ‘smart’ meters. They’ll simply shut off crap in your house when the wind stops blowing, or the sun stops shining - or they’ll just black you out if they need to. We will be living a new lifestyle with those monsters.
No - the 60Hz has nothing to do with the speed at which the blades spin. I was making the point that the power produced must equal the power consumed. When there is too much generation then the AC power Frequency deviates by going over 60 Hz. When not enough the AC power in the grid goes slightly under 60Hz. But too much deviation and then there are cascading failures.
Wind leads to these deviations being greater than in a grid with no wind generation.
Ah, ok, I misunderstood your point. Sure, no argument there.
But I still don't think I agree with this:
> When there is too much generation then the AC power Frequency deviates by going over 60 Hz. When not enough the AC power in the grid goes slightly under 60Hz
Line frequency is controlled on the basis of long-term time accuracy -- that is, the power companies have gear that makes sure that while the 60Hz freq does vary plus or minus a hair, the long-term average is very precisely 60.0000...
Why? Because if were anything else, every clock that reads line freq to keep time would drift fast or slow. And in fact the clocks don't drift. Line-freq clocks are extremely stable over long periods in most of the US and have been for decades.
> Wind leads to these [frequency] deviations being greater than in a grid with no wind generation.
I'm very interested by that comment and would like to learn more (from a technical, power transmission point of view). Got a reference/cite/link on that?
Certainly, the available power varies more with wind generators on the grid -- wind is nowhere as reliable or constant as other sources. But I don't understand why that would affect frequency. Thanks in advance for the link....
And when i was in the air force I was a power production specialist, that is a diesel mechanic and an electrician. Power plant operator.
This article somewhat addresses what I am saying about wind posing a problem with frequency control. My knowledge, however, doesn’t come from articles. It comes from me being an expert.
Very cool. My professional work has not (yet anyway) included large power generation or transmission, so I appreciate the opportunity to learn more about it. FWIW, about 30 years ago I got to design and send into production 3-phase inverters for up to 400 HP AC induction motors (for variable speed operation in large office and apartment building HVAC installations, production line conveyors, and such). But I've never gotten a chance to work the grid -- that's the SERIOUS power. :) Maybe someday, though I'm now 60 and may not get the chance.
Thank you for sharing your knowledge. Much appreciated.
Very interesting post, that. And I do see what you've been driving at better now.
I will guess -- and please correct me if this is inaccurate -- that ERCOT's situation is that their generators (or most of them) are synchronous, that is, their generating rotors (hydro, steam, etc.) are locked to the 60Hz power they produce, and therefore varying load causes them to speed up or slow down, because their speed is regulated dynamically and affected by their load. The same effect that causes a fixed-throttle automobile to slow down going uphill and speed up downhill.
Obviously, there are integral/differential control systems in place to regulate the speed of the generators in the face of changing loads. But a bunch of wind machines, with varying power output based on changing wind speed, are going to play hell with the regulation controls so carefully put in place over the past decades. They add a noise factor into the control system equations.
I'm trying to understand, so please help me here. Does that sound about right?
> My knowledge, however, doesn’t come from articles. It comes from me being an expert.
That's why I'm asking. I have enough background and experience in electrical engineering to know that I'm NOT an expert in power production and transmission, but I'm always eager to learn. Thank you for your time to comment.
It all sounds right what you say except the synchronous part. I think all generation on the grid is synchronous, or synced, to the grid. But we may be just having terminology issues.
The problem is that nat gas, coal, and hydro, and many peaker turbines (essentially jet engines) have automatic generation control (AGC). Plants with AGC will ramp down quickly when the frequency is high and ramp up when it is low. It is a feedback loop that is required to keep the grid stable. Nuclear, wind, and some hydro and some peakers do not have AGC. If the grid does not have a sufficient number of Megawatts of up/down range on AGC then there will be a much greater chance of the grid losing stability after a first contingency (i.e. fancy talk for a large generator or trans line quickly and unexpectedly going out of service).
So then the economics comes into play - not all MWs generated are created equal. Due to wind not only not having AGC, but actually going in the OPPOSITE direction when there is a contingency (plant trip), it is the worst type of generation. It is fine in small amounts but there are diminishing returns.
Read about Germany’s grid if you want to know what happens when their is too much wind and solar.
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