Slashdot Mirror
Power Electronics Help to Control Electrical Grids
An anonymous reader writes: "IEEE Spectrum magazine has a timely article about how power electronics are proving necessary for the widespread connection of wind turbines to the electric power grid. It explains many issues that currently make it difficult to utilize wind power. Older articles discuss other issues affecting the nation's power grid."
Maybe what we need is more control over the power, we need better systems and routines to warn us before something goes wrong. Not after.
----- Friends, l33tists, l4m3z0rs! Lend me thy keyboards.
We either need more power plants, to curb demand, or a fairly efficient way of storing excess power capacity in the winter to be used in the summer.
Everything else might buy you time, but it is only delaying the inevitable.
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
The critical point here is that to have "exotic" devices, you have to be able to manage them to make the power grid meaningful stability. Often, the hip environmental crowd (okay, so I am often one of them), complains that there isn't enough use of alternative energy in the mainstream grid. However, if we dedicated a meaningful amount of the grid to energy extracted from yak dung, what happens if there are problems? The grid elsewhere has to make up the slack (often at a higher price and inefficient) or we have problems like last week. The more technology develops, the more we are likely to be able to use alternative energy...goo goo gah joob.
About two years ago I went to the Electrical Manufacturing and Coil Winding Association's Expo in Cincinnatti, OH. There, they had a number of seminars on fuel cell technology. There was much talk about the (at the time) brand new hybrid cars from Toyota and Honda, using fuel cell technology to power personal electronics, the challenges left to face in making fuel cell technology practical, etc. One possible future that was presented (15-20 years down the road, so they said) was having a large fuel cell power your entire home. I mean, it's your house, you could theoretically put it anywhere you want (even underground) so that it's out of the way, right? Residential electrical service might consist of a truck coming by to refill your home fuel cell every month or two. Anyway, if such a future were to come about, rolling blackouts like what we saw (or didn't see, come to think of it) in New England and eastern Canada could very well become a thing of the past.
Food for thought. But there's no guarantees that it's not half-baked. =)
Take the most common electrical generator most of us own, the alternator in your car. This item is driven by the engine's crankshaft, and it's speed goes uo as the crankshaft's revolutions speed up. Of course too fast, and the power the alternator makes will cook the battery (which it feeds). Hence the built in voltage regulator that all alternators have. Is the answer so obvious that they have missed it?
Is that some rich 'environmentalists' don't want wind power where they can see it.
h tm l
http://www.startribune.com/stories/484/4041637.
I guess that wind power is OK as long as it is in someone elses backyard...
Here's a question that I haven't seen asked yet... everyone's comparing this whole thing to the blackout of 1965, but what about the backups that were supposedly put in place to deal with the much-feared and hyped Y2K bug?
Wired 7.04 published an issues entitled 'Lights Out' that detailed many problems, including the problem of a single failure spreading across the entire continent.
Billions were spent in the USA and Canada on solving this... so where did that money go?
I know at least in mocroprocessors, wires that contain DC current that is always in one direction have a tendency to break...
Rather than having massive acapcitor banks to balance the load, what's to stop us letting the windfarm run free, using all the energy to liquefy salts (by simple heating elements with low inductance, so phase-lag isn't an issue), then feeding the heat energy into the grid via turbines?
Either that, or have a big capacitance and an invertor on each windmill.
oh brave new world, that has such people in it!
DC still isn't perfect. When you get voltages high enough you can no longer make a circuit breaker for instance, because the sparc never stops. (There are solutions, most involving blowing something in the breaker so the plasma of the arc doesn't complete the circuit)
DC is also more dangerious. AC crosses 0 volts 120 (100 in europe) times a second, so if you touch a line and it doesn't fry you instantly you can let go, sort of. DC forces your muscles to contract, which can cause you to grab the conductor harder. (depending on how it effects you, it can also throw you violently away from the conducter). AC will relaxs those muscles several times a second giving you a chance to let go. And don't forget the arc in the previous paragraph if you do manage to let go of a DC line.
Of course in the voltages involved with cross country power transmission it is all theroitcial nonsense, you die either way. In lower voltages it can make a difference. Eventially voltages get low enough that it doesn't matter. Unfortunatly without knowing exactly where and how the power travels though you nobody can tell what will happen in any particular case, which is why we tell people to stay away.
As a last point though: induction moters cannot work without AC. This isn't going to be a point for much longer though. Already some manufactures are finding that it is better to use electronics to make their own AC to their specs. (Some maytag washers for instance use 3 phase moters, and the controller not only generates AC in the required 3 phases from the one phase that comes in, it sets the exact speed they want the moter to turn at eliminating complex gear boxes)
Has anyone from Slashdot researched a home version of these wind turbines? Anything that would decrease monthly power bills involving a clean energy source is alright in my books.
I love the smell of Karma in the morning
Surplus electricity that cannot be consumed by nearby grid users can be used for an electrolysis process to produce hydrogen. The hydrogen can then be stored and distributed for fuel cells.
www.virtualeli.com
Elijah Chancey www.elijahsadventure.com nomadic IT consultant, bicycling across america "all that you touch / and all
That's one way. I remember when superconduction came on the scene. One of the ideas was an underground superconduction coil. Basically an induction coil, on a much bigger scale.
Energy density that can be stored in an inductor is much lower than the energy density of chemical fuels. This is especially true given that high-temperature superconductors break down at on the order of a 1 T magnetic field, but even without a superconducting breakdown field limit, tensile stress goes up enough to produce a limit that falls far short of chemical energy densities.
That's why fuel cells are so nice, even with something as annoying to store in bulk as hydrogen.
If hydrogen storage became a serious problem they could use methane as a fuel (with reforming cells), and burn the high-carbon reform byproducts with the hydrogen produced from electrolysis to get methane again, but that would arguably be more annoying than just storing the hydrogen.
Basically, wind turbines may introduce other environmental problems, just as most other energy plants do. They're not entirely "clean" as many would like to believe at first glance.
The main problem, which has been quietly stepped aside by all wind power advocates I talk to, is the environmental effects of removing such vastly huge amounts of kinetic energy from wind flows, in order to harness the power. Think globally.
Wind is an important environmental factor, it equilibriates (sp) places around the globe. You can feel the 'north wind' around the changing of the seasons (up here in North America at least) when cold air rushes north or south, depending on whether Canada is heating up or cooling down. Trade winds flow across the oceans, the Jet Stream equilibriates around the globe over land and sea. Vast arrays of wind turbines will extract large amounts of kinetic energy from these streams, and can (note, I don't say 'will', but nobody has ever accurately affirmed or denied this) severely disrupt global equilibrium cycles.
The effect could be colder Canadian winters and warmer Mexican summers, and parallel for Europe/Asia and southern hemisphere. I'm sure many of the Europeans reading this right now are thinking of the heat wave currently encompassing Europe. From what I understand, this is a slow-moving pocket of hot air that is taking awhile to disperse. Imagine more effects like this, where there is reduced ability for thermal air equilibrium over large-scale continental distances. Canadians might not like to have more severely-cold winters, nor Mexicans with hotter summers either. But these are possible outcomes of massive installations of wind farms, yet few people want to think about them.
That said, if some modelled this sufficiently, perhaps the effects could be minimal. Perhaps they could even be beneficial, such as preventing hurricanes and tornadoes. But to deny any side effects of long-range wind extraction is foolish.
Someone here on slashdot tried making the argument that the area needed for windfarms exceeds the rate of deforestation, but (s)he just pulled stock quotes and numbers from wind websites, and didn't account for the fact that the turbines need to be spaced out, they can't be stacked one right on the other. Also, someone (same or different, I can't remember) tried implying that the amount of kinetic energy harnessed from the turbines is dwarfed by lost kinetic energy of forests swaying in the wind. If someone wants to make that argument again, please provide numerical rates of energy loss for these forest wind shears. Thanks.
Anyway, this is the primary concern of mine against large-scale deployment of windfarms. Hopefully these problems won't be an issue, but let's be careful about the potential problems before praising them as the end-all-be-all of our power problems.
make world, not war
My Step-fathers brother, a college professor at a major university, has created a software routine that will compute the transient stability of the entire North American power grid in a few seconds on a cray super-computer. With this software a loss of one line would keep the lose on that one line instead of cascading the problem throughout the grid. It would also have the benefit of maximizing the power that flows throughout the system. It has also been run on PG&Es old Apollo computers. They were doing a study with PG&E and it basically proved their engineers wrong. Which is what killed the project, since the engineers were making the decisions about the project. I have been trying to convince them to take up the project again and this time taking it to the federal government....I hope they do!
" do not remember the figures, but this is the reason why AC was chosen for power distribution, even though there were various factions hyping the danger of using AC (electrocution and such)."
I'd say it had more to do with the difficulty in steping up and steping down voltages for long distance transmission before the advent of power electronics. Compare this to a common transformer which was well within the technology of the late 1800's. Actually, besides the transmformer problem, DC systems are actually quite a bit less complicated then AC. Also, for longer runs they're also cheaper.
You should read about the Edison & Westinghouse battle for a practical power distribution system. It's pretty interesting.
-Chris
--an unbreakable toy is useful for breaking other toys--
In fact, DC is much more efficient to transmit long distances that AC, as there are less line losses.
It's used in Sweden and New Zealand that I know of. I've worked on the New Zealand link. It carries DC from the Benmore Dam (Largest earth dam in the Southern Hemisphere) several hundred km's to Wellington, including several km's of undersea transmission.
The DC is converted to/from AC using 2 poles, the original a mercury arc valve system, the new method is a gi-normous Thyristor.
The link runs at 270 kV, and there's talk of moving to 300kV
At peak capacity, it can run at over 1200 MWs, and it routinely uses the ground as a return path.
All in all, it's pretty cool tech !
-- You can't give it, you can't even buy it, and you just don't get it!
About a half-hour prior to the blackout, I was reading an article online--I forgot the URL completely--which discussed the use of superconductors to augment the circuit breaking elements of the power transmission system.
Now, IANA Electrical Engineer, however, I found it interesting, in hind sight especially, that these superconductive elements would be used to soften the blow on circuit breakers, which sometimes cannot react to an overwhelming surge, which will blow right through them.
I won't go into the details, especially as I don't have the article before me for cut-n-paste cheating. However, it was intriguing that superconductors, in this case, were proposed for use not as conductors, but instead to react by becoming less-conductive with the increase in flow, etc, in a much faster manner than the mechanical breakers.
Now, if we could only get some wind farms up and running here in Michigan, and in substantial numbers... (I've seen the one in Southeast Wyoming, and it was truly awe-inspiring!)
Mmmmmm... Bold, yet refreshing!
As copyright owner of this comment, I authorize everyone to defeat any technological measure which limits access to it.
American Superconductor purchased a little company called Integrated Electronics in 2000. Integrated Electronics developed/designed the majority of the power electronics that go into that DVAR system they are mentioning. The owner of the company was/is a power electronics genius. His name is Jeff Reichard. He now owns a new company called Tier Electronics which has a small home page at www.tierelectronics.com.