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.
A little ironic that this article on a world wide power grid was published in the September issue of Wired.
:)
IEEE Spectrum magazine has a timely article
It's kind of funny how articles about the power grid appear in magazines across the world every month of every year, but the ones that just happened to appear this month are "eerily prophetic".
Steady As She Blows
;-)
Looks like they're hard-up for readers.
The coolest voice ever.
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.
Impressive as the gains have been, it isn't quite clear yet that the wind can blow a fat cock up the ass of the developed world's fossil-fuel dependence.
What sort of tools would you use to determine that?..
http://use.perl.org
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?
The problem with power distribution is the medium: electric power lines. It makes more sense to generate power cleanly and locally, with fuel cells at the core of the distributed power generaters. For fuel you use hydrogen reformed from fossil fuels or hydrogen rich biomass, or hydrogen created from excess wind, solar, or any other source. Then transmission lines don't matter so much, pollution is reduced, and the world is a happier place.
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?
For those unaware of what's going on, here is a quick excerpt of President Bush denying money for a secure grid... (Source)
On top of this it was announced that grids would be targeted by terrorists.
(source)Here is a link to a mirrored doc of the Electronic Power Risk Assessment, there is going to be a huge amount of finger pointing, and political partisan bs behind this entire incident, but read it for yourself in plain english how your (P)Resident will not fund plan for a more secure system.
Off topic? I think not
MoFscker
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)
You obviously have no concept of AC and DC electricity. Its not just a matter of stepping voltages, its also a matter of line losses and safety. High DC voltages are much more dangerous than similar AC voltages. On top of this, the line losses would make long-range transmission of DC power impractical.
IIRC, power electronics deals with the regulation thereof. A good example is the creation of a power supply which turns AC into a smooth DC. Look here.
Towards the middle the article explains how the europeans deal with the problem ... they just use improved turbine designs. After you see the following paragraph:
... isnt that how it was supposed to work. Shouldn't variable speed turbines be much more developed in the us because they were patented here?
"The idea has been slower to catch on in the United States, where GE Wind Energy, in Tehachapi, Calif., has deftly defended patents on variable-speed turbines that will be on the books through 2011. "
Nice to see the patent system working again. I guess the Europeans were lucky because GE Wind energy decided not to file their patents in europe (or they were not granted).
But then again, shouldnt patents help innovations
Frankly i dont know why GE systems does not promote variable speed wind turbines now that they have the protection, and if they cant, why they dont sell affordable licences to companies that can. It could be due to the usual burocratic inefficiency, or it could be something sinister.
Yet this is not the first time i see an owner of a patent sit on the technology and not develop it while other people are perfectly able to do so. We all remember how a company that does not take the trouble to make portable email devices, tried to stop a company that does make them.
While it's true that most wind turbines use induction generators, they do so for several reasons, including:
All the turbines I have worked with have either had modest capacitor banks to correct for reactive power, or used insanely cool AC/AC back-to-back inverters to produce line quality AC.
I'm also concerned about the article's allegations of power intermittence. Wind turbine rotors have a fair amount of rotational inertia, so they're not capable of passing every flutter of the wind to the generator. It seems that this part of the article is a sales pitch for a new product that the vast majority of installations won't need.
I was also amused at the requirement of wind turbines to "ride through" grid frequency variations. This is basically a nice way of spinning the fact that wind turbine controllers are often far more picky about the frequency they'll accept or put out, than the rather poor regulation that applies to our power grids.
An finally, that picture. Where on earth did they get it? Apart from the fact that it's a contravention of every safety code to climb the tower of a running turbine, the climber must be a human sloth. To get that kind of motion blur on wind turbine blades, you'd have to have several minutes' exposure. Thus our perfectly sharp climber (and their horse) must be moving incredibly slowly ...
I hate how people use flaws on both sides of the political parties to somehow make their own party's flaws 'justified'. Everybody sucks, everybody makes mistakes, the whole two wrongs kinda deal. The fact is Davis sucks not just because he's a democrat but because he sucks. Also Bush sucks because he is a crappy president not just because he's a republican.
WikiAfterDark.com It's a sex wiki, go now!
Unfortunately DC power distribution is highly inefficient. When transmitting power down a long lenght of wire DC creates a much higher voltage drop (power loss) across the line than AC.
I 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).
Also this is why AC is transmitted at such high voltages for the large runs... for the same amount of power, a higher voltage means less current, less current means less voltage drop across the line, therefore less loss of power...
GE manufactures a turbine rated for 3.6MW output. Ge is currently an industry leader in these types of turbines though, they are desiged primarily for offshore use. Smaller MW ratings between 1.5 and 2.8 are more common. Unfortunately, even with wind turbines producing @ 3MW it would require approximately 1.26 Million of them to meet the U.S.'s current power demands. Currently Coal plants are responsible for the majority of our power capacity in the U.S.
While the *idea* of wind power is certainly a nice one, and the notion of helping the environmement is well intentioned, the reality is that wind is insufficient as a power source and as a result - it's ability to displace the most polluting source, coal, will be ineffective. Other solutions will be required to truly solve the pollution/capacity problem that we face.
A potentially viable start to "solving" some fo these problems would be to distribute residential power generation, especially in dense urban areas. Technologies such as fuel cells, and compact turbines could be used for this. An added benefit of this strategy would be zero emissions and heat reclemation in the case of fuel cells, and better regulatory control over the emissions of compact gas fired turbines.
My two cents.
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
http://www.cnn.com/2003/US/08/16/blackout.chron.ap /index.html
The timely coincidence between MSBLAST and power blackout is certainly _there_.
http://www.securityfocus.com/archive/1/333505/2003 -08-13/2003-08-19/0 3 -08-13/2003-08-19/0 . php
http://www.securityfocus.com/archive/1/333513/200
http://www.automationtechies.com/sitepages/pid641
http://www.pbs.org/wgbh/pages/frontline/shows/cybe rwar/view/
aspecially watch video #4. Just after 911 a cyber terroristic attack againts the powergrid was warned for by Gen. Clark from the Pentagon and other cyber security officials.
Robert
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!
This is one area that electric cars may be able to provide a valuable service in what's known as vehicle to grid. A small company in california has been doing a lot of research on the topic and it looks promising. Theoretically, if you get enough electric cars that are plugged into the grid whenever they're not in use, they can provide near-realtime load balancing by remote dispatching from the power company. Say the power surge that took out the grid happened, but this time with a few hundred thousand electric cars plugged into it. The company could send a broadcast to the cars to absorb the extra load within a few seconds, and stop the cascading failure. Conversely, if there's a sudden demand spike, the cars could be ordered to temporarily supply it until the spike subsided. Obviously there's many technical hurdles but the general idea is very cool.
Forget the crappy low-flow toilet that makes dimwits feel oh-so-good but takes 6 flushes to get rid of the Dark Matter. Use a regular toilet which takes 1 flush.
Why not have dual-flush toilets with a #1 handle and a #2 handle. Surely we can muster the technology. Most people don't actually want to waste water.
I have such a thing in my appartment. And you know what? I never use the low-flush button. Why? Because if I do, the toilet fouls up so fast that you have to clean it twice a week. Ugh. Another factor being that I don't pay a separate water bill, and where I live the water supply is abundant. The water company even has to run water through the mains pipes sometimes to avoid impuritities sticking to the walls of the pipes.
Anyway, as the previous poster said, a more useful system than these low-flush toilets would be to utilize gray water.
" 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 the UK we have at least one pump storage station for evening out loads - but not for months at time. Its basically two large lakes one above the other, excess power pumps water up, then when there is a surge in demand it goes back down through a generator.
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.
First the number of nuclear plants in the United States is somewhat over one hundered not one thousand.
The nuclear industry in this country is in terrible financial shape, because even with generous government subsidies it is hugely uneconomical. Nuclear power happens to be a very expensive way to boil water. You may be aware that nuclear power creates something called "nuclear waste". The government has provided the largest subsidy to the nuclear industry by promising to dispose of this waste at government (read taxpayer) expense. Fifty years into the history we still do not have a open repository for high - level civilian nuclear waste. (I believe that a military repository in Carlsbad, New Mexico is open or will open soon.) This nuclear waste has some unfortunate properties, such as extreme toxicity and long-term persistance (thousands of years). Releases radiation (the kind from breaches of reactor containment and waste storage systems, not the venting of mildly radioactive gas that are a part of normal plant operation) can cause widespread health effects. The problem here is that continued use of nuclear power creates additional waste, piling up for thousands of years - all to boil some water. (Another subsidy is the services that the government provides to the nuclear industry in the forms of security and regulation.) Nuclear power currently provides 14% of the electric power in the United States.
As far as your comments about wind, solar and water go, I'll address them one at a time.
* Water - Hydroelectric power is currently providing about 12% of the electric power in the US, though there is little room for growth, due to opposition to new dams.
* Wind - Did you read the article? There are hopes that wind will provide up to 20% of US power. This may be a bit optimistic, but the interesting part is that wind power went from being from an eco-hippie dream in the 1970's to a serious business in the present - without government subsidy. (Note to bird-lovers the newest wind turbines are large enough that the blades spin slowly and harm very few birds.)
* Solar - Applications of solar power are booming as cost and efficiency of photovoltaic cells improve. In many cases it is cheaper to use solar than to connect to the grid, such as temporary highway signs and homes more than 0.25 mile (0.4 km) from the electric grid. It is, however unlikely to ever be a significant percentage of electric power in the US.
The gigantic oil reserves that the poster refers to may the the Alaska National Wildlife Refuge, which has enough capacity to supply the US for 180 days. The percentage of domestically produced oil here is around 50% and has been falling for years and is porjected to continue to do so regardless of what the government chooses to do.
There was one source that is important that was not mentioned in the article or your post - conservation. This does not mean self-deprivation. It does mean higher standards in efficiency for all sorts of devives like the computer monitor you are currently staring at. It turns out that there's lots of savings to be had here and the additional cost to the consumer are greatly exceeded by the savings over the appliance life. The important point here is that we may not need to increase the amount of power generated to imporve standard of living (in the developed nations - developing world is a differnt case) even with moderate population growth.
Coal's technology has improved 300% from the 1970's with great advances in efficiency and emmission controls (scrubbers). Coal's tragic flaw it its C02 emissions. Unless someone figures how to capture and store the CO2(sequestration) then it will continue to be a problem if you are concerned about the greenhouse effect.
I have to agree with the poster's comments on the hydrogen economy. I just don't understand where the power is supposed to come from.
-Jon