Power Electronics Help to Control Electrical Grids 292
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."
Control is the key... (Score:5, Interesting)
Simple Tweakage (Score:3, Interesting)
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.
Management *is* key... (Score:5, Interesting)
fuel cell (Score:5, Interesting)
Food for thought. But there's no guarantees that it's not half-baked. =)
Hello, a VOLTAGE REGULATOR, perhaps?!?!? (Score:2, Interesting)
One of the issues that stops wind power. (Score:5, Interesting)
http://www.startribune.com/stories/484/4041637.
I guess that wind power is OK as long as it is in someone elses backyard...
The Y2K bug... A flashback (Score:5, Interesting)
Wired 7.04 published an issues entitled 'Lights Out' [wired.com] 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?
Re:Switch to DC (Score:3, Interesting)
Re:Simple Tweakage (Score:5, Interesting)
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.
Why not (Score:2, Interesting)
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.
Re:Simple Tweakage (Score:2, Interesting)
Re:Switch to DC (Score:5, Interesting)
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)
Re:fuel cell (Score:4, Interesting)
Re:Simple Tweakage (Score:5, Interesting)
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.
home use?? (Score:4, Interesting)
use surplus electricity for electrolysis (Score:2, Interesting)
www.virtualeli.com
Re:Simple Tweakage (Score:5, Interesting)
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.
Re:Simple Tweakage-As the coil turns. (Score:3, Interesting)
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.
Wind power MAY introduce problems (Score:3, Interesting)
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.
Transient stability is the answer. (Score:2, Interesting)
Re:Control is the key... (Score:2, Interesting)
the power companies(at least the ones that are responsible) monitor their grid constantly and if the currents go over the limit for some part they re-route some power from reserves so that the overloaded lines get back within their limits. even the losing of one major power plant shouldn't be noticiable here, let alone bring the whole nation down, you can't take much chances with that when you buy big amounts of power from russia. the grid that went down in usa was supposedly designed in this fashion too (it's not exactly new concept anyways), only that it was constantly overloaded which doesn't leave much space to use the reserves (at least that's the picture you get from media). such spikes on large enough grids don't come 'instantly', a million people doesnt suddenly get home and press the light switch on the same second..
and i must say that brownouts shouldn't be happening in developed countries, they are avoidable! they just don't happen (because it IS more favorable to cut the power rather than letting it happen, and also theres no reason for it to happen if the lines are not broken and if the lines are broken then it's obviously time to cut it). if they're overloaded all the time then the system is already fscked.
Re:Switch to DC (Score:3, Interesting)
" 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
Re:Management *is* key... (Score:2, Interesting)
The second issue is that nuclear plants aren't generally cold startable; that is they need the grid to be up for startup because they require a great deal of power for pumps, control, etc. Gas-turbine and hydro plants are generally cold startable.
Taking all this into account, a reliable grid needs a mix of plant types for reliability. It would be impractical to have a completely nuclear power system; doing so would require power storage of one type or another to cope with demand changes, much as you would in system a large proportion of renewable sources. And before you rebut by saying 75% of France's generation capacity is nuclear, take into account that they trade a great deal of power with Germany, who use mostly thermal sources. It's the boundaries of the electrical grid that matter, not the political ones.
Long-Distance DC Power Transmission (Score:2, Interesting)
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 !
Coincidentally... (Score:3, Interesting)
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!)
Duh (Score:2, Interesting)
DVAR Power (American Superconductor) (Score:1, Interesting)