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Post by pidgey on Dec 15, 2008 3:39:23 GMT
Used to be that I was the only peak oiler here, welcome! Personally, I think that so goes RCO, so goes our economy. Most business models just don't deal well with energy costs skyrocketing. And if they can't even correctly identify the problem then they're going to be doubly hard-pressed to deal with it. The current riots in Greece are but a foretaste of what's coming everywhere all too soon.
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Post by ron on Dec 15, 2008 10:11:22 GMT
Nice first post Frank, look forward to lots of interesting discussion with 'Ron' who wants to put solar heat collectors over the entire state of Arizona ;D Well it would be about 10% of New Mexico but you're on the right track! Or was it Nevada? Or maybe Arizona... Or 3% of each. Or something like that. Didn't I lay this all out in a post a while back?
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Post by ron on Dec 15, 2008 10:24:56 GMT
Yup, I did! I'm talking solar thermal, and it's either 10,000 square miles or 30,000 square miles to theoretically provide 100% of the US's electricity needs, depending upon to whom you are talking. 10,000 square miles is an area just 100 miles square; 30,000 is a little under 175 miles square. Arizona is 114,000 square miles; New Mexico is 121,000 square miles, Nevada is 110,000 square miles. So we'd need somewhere between 3 to 10% of the land area of those three states. The Federal Government owns and the BLM operates something crazy like 90% of the land. I went and looked it up: 26 million acres is about 41,000 square miles. Another 19,000 square miles, give or take. I can't find the exact numbers without a fight, so I'm going to guesstimate that BLM Nevada administers about 70,000 square miles give or take 20,000. See this map: www.blm.gov/pgdata/etc/medialib/blm/national.Par.93357.Image.-1.-1.gif
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Post by nautonnier on Dec 15, 2008 10:29:34 GMT
Nice first post Frank, look forward to lots of interesting discussion with 'Ron' who wants to put solar heat collectors over the entire state of Arizona ;D Well it would be about 10% of New Mexico but you're on the right track! Or was it Nevada? Or maybe Arizona... Or 3% of each. Or something like that. Didn't I lay this all out in a post a while back? Several times Ron - several times I wonder how solar and wind would do on east coast with the ice and such. Maybe a small problem. How about solar and wind in North Dakota and Montana? This is more interesting - were there any wind turbines in the New England ice storm areas? If so did they continue operating? In theory only a small amount of ice on the back of a blade could significantly reduce its efficiency. That is assuming a large slow moving turbine could continue to run in ice storm conditions
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Post by pidgey on Dec 15, 2008 17:17:43 GMT
No matter--if the grid goes down you don't have the excitation for the stator of an asynchronous inductive generator.
This means you're dead in the (frozen) water.
As a doornail.
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Post by ron on Dec 15, 2008 20:18:01 GMT
Isn't it cool that we have intelligent people who can think of these eventualities and that we'd have backup power supplies?
Of course they's have to be at least as smart as the folks who can, did and will guarantee that nuclear plants are/were/will be fail safe.
I don't know if they'd operate well in a frozen state. One would hope they'd expend a bit of their own energy and warm themselves and their blades when necessary.
I don't understand this inductive generator problem to which you keep referring. Would you be able to explain it in terms a non ee could understand? How does the problem differ from having other sources on the grid?
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Post by pidgey on Dec 15, 2008 20:51:29 GMT
An old generator had permanent magnets in it that pulled the electrons through the windings when the rotor was spun. This kind doesn't--you basically have an electromagnet that is powered by the actual grid. If the grid goes down, you won't generate any usable electricity whatsoever no matter how fast or hard you spin the rotor.
While that particular explanation is given to describe behavior in a major power outage, it doesn't directly tell you the problems that can occur when you've got too many of the damn things coupled to the grid and wind velocities are varying too much. That's the problem that I'm usually alluding to. In such a case, transient spikes can destabilize the grid to the point of causing cascade tripping of the other generation plants to the tune of a major blackout. Think in terms of several states at a time.
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Post by ron on Dec 15, 2008 21:32:19 GMT
Spikes in voltage or current?
(Why the use of electromagnets, lack of gigantic magnets?)
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Post by gettingchilly on Dec 15, 2008 21:53:48 GMT
Larger generators always have electromagnetic excitation as you can't get the flux density from permanent magnets. Small wind generators usually use permanent magnets but don't generate a lot of power (got one on my boat). Usually the big gennies self excite from the residual magnetism and this generates +ve feedback then away you go, but a bit more effectively than co2 of course. Seems odd that these huge wind generators don't self excite, any (big) wind engineers out there.
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Post by ron on Dec 15, 2008 22:36:23 GMT
Thanks.
You'd think that even a small "self-exciting circuit" would be provided within a multi-million dollar system, or at least it would be highly possible if this induction thing was a major stumbling block. No?
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Post by solartrack on Dec 15, 2008 23:16:28 GMT
Larger generators always have electromagnetic excitation as you can't get the flux density from permanent magnets. Small wind generators usually use permanent magnets but don't generate a lot of power (got one on my boat). Usually the big gennies self excite from the residual magnetism and this generates +ve feedback then away you go, but a bit more effectively than co2 of course. Seems odd that these huge wind generators don't self excite, any (big) wind engineers out there. GE and others use a doubly-fed asynchronous generator with electronic frequency and voltage conversion. They use an asynchronous generator rather than a synchronous generator which is the type directly connected to the electrical grid. They recover well from a grid failure or at least advertised as such. This is, if you consider a 1-5 MW a large wind plant. This link has a nice EE for none EEs type explanation: www.control-design.de/home_eng/Applications/Windenergy/body_windenergy.html
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Post by pidgey on Dec 15, 2008 23:18:47 GMT
Well, remember: you're talking about an AC grid. Since wind generators can't control their speed (effectively enough), you have to use the asynchronous induction generators. In order for the power generated to be synchronized to the grid--excitation must come FROM the grid.
That's why.
The grid doesn't itself store power--it's always a balance between the collective load and the collective generation. Therefore, the collective generation must always be trimmed to the load. Having a significant component of generation that's essentially unpredictable can spell real trouble for the balancing of supply and demand, especially if said component can produce deltas that the supplemental generation can't match.
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Post by ron on Dec 15, 2008 23:24:21 GMT
How does a home A/C inverter synchronize itself with the grid when it feeds power back to the grid? Do all of these asynchronous PV panels/inverters cause a similar problem that must be dealt with?
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Post by solartrack on Dec 16, 2008 3:39:20 GMT
How does a home A/C inverter synchronize itself with the grid when it feeds power back to the grid? Do all of these asynchronous PV panels/inverters cause a similar problem that must be dealt with? Not sure what Pidgey meant but the async generators aren't trying to sync as their frequency goes up and down with wind speed. They just convert it to DC and chop it with a fancy circuit that balances output load with load on the motor. Devaning the blades allows them to store extra speed as power in the blades...think flywheel. Same for home generation. There's enough 'slop' (phase lag) in the load...(peak of the current vs peak of the voltage) of the load for modern switcher circuits to detect and follow. Ever wonder why TVs got so light. Its all high freq switchers. Take the AC and convert to DC with coils and diodes and a cap, chop it at 10-200khz thru a small transformer and then do what you want with the other side by choking the tranformer. Same thing but a larger scale of current. But the weather dependency is a killer here, To power gas turbines which like to run all the time just for peak costs more than the power the mills produce so you have to use solar and wind to provide peak use or pump water for storage or such. Which again loses efficiency. Hey, I built my first electric car in 1974 during the first gas crunch. The same problems have not yet been solved some 35 years later. Fusion was only 50 years off so all we had to do was last to 2025. Well, have far have we gotten? So I have to ask: Without new generation capacity how do these brainiacs plan to convert the transportation sectors to electrics? California ia already having rolling blackouts? No new coal plants. No nukes. I have horses but they produce more CO2 than the car since they're on 24 hrs a day. So who has the magic beans?
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Post by pidgey on Dec 16, 2008 4:31:41 GMT
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