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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.
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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".
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. =)
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?
"or a fairly efficient way of storing excess power capacity in the winter to be used in the summer. "
Storing a season's worth of extra power for a season's worth of time is unworkable. However, storing excess power during the low-demand part of the day to ease spikes in demand later that same day...that is being worked on already. It was in either Discover magazine or the MIT Technology Review, but they're working on what is basically a huge fuel cell battery. Right now it's just at a military base, but the idea is to put one of these big batteries in every major city to act as a buffer. It'd ease both the peak demand on the power plants AND some of the stress on the transmission lines.
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)
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 ...
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.
All you need is a means of storing off-peak supply for on-peak demand. I hear that in British Columbia, they pump water back up into hydro-electric reservoirs during the night. Maybe regular power plants can have big flywheels.
We can blame the environmental movement for there not being enough power plants.
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...
Sorry, I just don't see how terrorists would be motivated to try to cause blackouts.
Sure, they cause inconvenience and economic losses: but these are people who want to mess with our heads. The lights go out, people walk home, a little miffed, life goes on. A major building blows up and people are quite a bit more afraid of the world.
They managed to get the grid up mostly over the weekend. I'd say for something as complex as the power grid over 5 states that's pretty damn good. It'd cost billions upon billions to retrofit our power grid to something modern using some accelerated schedule, and I don't see how you expect our president to be jumping to spend any more money just because we had a so far isolated incident.
There's already plans in place to upgrade our systems over time, you can easily read about them in these articles. Bush may be a bad president but I don't see how any president should be so swaded policy wise by every incident that happens to a very large and complex country.
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.
Bullshit, we can blame ourselves for overconsumption and the NIMBY's (Not In My BackYard) more than the environmentalists.
f er Nuclear in much higher mix than we do today. We also need more cradle to cradle industries that take waste products and turn them into fuel for the next industry - reducing power consumption and limiting the need to dig more out of or cut more off of the earth.
I hate that knee-jerk response to everything - "It's the environmentalists fault".
Even with all the technology that we've created to make lower power devices we just find a way to get more devices. I saw how they were working on LED's as a better, more efficient lightsource that can do task lighting for about 1 watt of power. I mention this at work and some jackass comes up behind me and says how cool it would be to be able to have a wall full of them and be able to change the color of his walls with his mood - POWER SAVINGS - what power savings?
It's a balancing act. First we have a grid that's just too old and extremely expensive to update. There's a mix of powerplants that are aging, there's poor planning, no incentive to change energy usage habbits, poor city design that promotes heat which in turn increases energy consumption due to airconditioners, extra showers, fans, and refridgerators. Then you have people who don't want a soot belching powerplant in their backyard, or off their favorite camping spot, nor do they want to pay extra for a more expensive cleaner burning plant, or pay extra tax dollars to have research into alternative plans like more efficient solar/wind/water/et al. Somewhere in there you have the environmentalists trying to conserve as much of nature as humanly possible before we end up having to chop down all the trees just to put up oxygen factories because we cut down too many of the fucking trees.
Noone wants to compromise their lifestyle to get to plan X, Y or Z.
My feeling is that we need a decentralized system where power is created in much smaller "nodes" and distributed from those points. Nodes could be created in house basements or in larger buildings and be connected to more evenly distribute power over shorter distances reducing the waste that happens when power has to be transmitted over miles and miles of cable to a destination. Additional efficiencies could be found as nodes throttle based on time of day and demand for their area. Grid failures would be reduced because nodes could throttle based on the failure of other nodes. We need more expensive but higher efficiency (and somewhat safer (no oil fires)) superconductor main lines. We need more incentive and more instructions on how we can save power and reduce use and what power saving products are good and can in turn save us money. We need much more diverse power sources Wind/Sun/Hydro/GeoThermal/FuelCell/Gas/Cleaner-Sa
I want giant catapillar like machines like TBM's that crawl through landfills chewing up trash and spitting out useful products. Sorting all the garbage into recycled materials and fermenting the rest as fuel to continue on in it's job or produce energy for nearby cities.
I want to see someone come up with a plan that doesn't attempt to single out ONE group of people as THE PROBLEM.
"Do not be swept up in the momentum of mediocrity." - anon
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.
It's safer and simpler to pump water uphill into reservoirs to be extracted hydroelectrically later. That's what they do currently. earth-fill gravity dams are much cheaper and more reliable than massive electrolysis plants.
If a job's not worth doing, it's not worth doing right.
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.