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Batteries To Store Wind Energy
Posted by
Soulskill
on Sun Dec 28, 2008 01:58 PM
from the charging-at-wind-mills dept.
from the charging-at-wind-mills dept.
Roland Piquepaille writes "Scientific American reports that Xcel Energy, a Minneapolis-based utility company, has started to test a new technology to store wind energy in batteries. The company is currently trying it in a 1,100 megawatt facility of wind turbines in Southern Minnesota. The company started this effort because 'the wind doesn't always blow and, even worse, it often blows strongest when people aren't using much electricity, like late at night.' It has received a $1 million grant from Minnesota's Renewable Development Fund and the energy plant should be operational (PDF) in the first quarter of 2009. If this project is successful, the utility expects to deploy many more energy plants before 2020 to avoid more polluting energy sources."
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What sort of Batteries? (Score:3, Funny)
I hope it's not 9 volt. Those are hard to find.
Seems silly to use this. (Score:3, Insightful)
Why are more utilitys not using something like what beacon power is doing.
Storing energy in flywheels. Spin it up when the wind blows. Draw it off when you need it. They last for a very long time when compared to batterys.
Batterys are kind of high priced for a low lifetime. Require all kinds of nasty chemicals to make and need to be disposed of someday. And take HUGE banks to store what a large flywheel would store.
Seems silly...
Re:Seems silly to use this. (Score:4, Interesting)
I heard a story of a datacenter in California doing this for backup power. The center was powered off of the mains, and also had a large (20ft or so) flywheel kept running. If the power cut, the flywheel powered the necessary systems for the minute or so it took the generators to start up.
Seemed ingenious to me.
Parent
Re: (Score:3, Informative)
Caterpillar offers such a system: http://www.cat.com/cda/layout?m=37516&x=7 [cat.com]. Their flywheel UPS keeps the electronics up and running allowing the diesel/gas turbine generators to start. The idea is you don't need a big battery bank that holds minutes or hours of power. You just need enough power to allow the generators to kick in and transfer switch to resume power. It is much more efficient, cost effective and low maintenance than batteries.
Another idea for high density power storage is the molten salt [wikipedia.org]
Re: (Score:3, Interesting)
Re:Seems silly to use this. (Score:4, Informative)
Flywheels are attractive for short-term peak power delivery. They have low failure rates and easy fault detection (if the wheel is intact and spinning at the required speed, you know how much energy is available).
For long term loads (hours) flywheels aren't competitive with lead-acid batteries, let alone more exotic types such as the NaS battery the article describes. For example, the Active Power CSDC-500 [activepower.com] flywheel storage system supplies 50kW for 138 seconds = 1.92kWhr. The cabinet is 78" x 54" x 34" and it weighs just over 3 tons. Four long-term loads, a system with two 12V 100Ahr VRLA batteries [cdpowercom.com] would be 14" x 14" x 10" and weigh 140 lb.
A flywheel based system has nowhere near the energy density of a battery storage system. Peak power density is the flywheel's forte.
Parent
Re: (Score:3, Funny)
Why are more utilitys not using something like what beacon power is doing.
I read that as "bacon power" and I just imagined the greasiest power plant ever.
Re:Seems silly to use this. (Score:5, Interesting)
I remember that flywheels were considered for electric cars as well.
Some of the issues I remember off hand were:
1. Specialized materials needed to build flywheels that are small, yet heavy enough to keep spinning for a long enough time after being "charged"
2. Getting the energy IN the flywheels in the first place - it takes more energy to get them spinning than what you draw from them.
3. Given the high velocities - what will happen when they fly apart? Also, the gyroscopic effects they generate while spinning.
4. The heavy mounts needed to safely position them negated any advantages through increased weight.
I don't know if any of these apply to stationary flywheels built into power plants though...
Parent
Re:Seems silly to use this. (Score:4, Insightful)
I remember that flywheels were considered for electric cars as well.
Some of the issues I remember off hand were:
1. Specialized materials needed to build flywheels that are small, yet heavy enough to keep spinning for a long enough time after being "charged"
2. Getting the energy IN the flywheels in the first place - it takes more energy to get them spinning than what you draw from them.
3. Given the high velocities - what will happen when they fly apart? Also, the gyroscopic effects they generate while spinning.
4. The heavy mounts needed to safely position them negated any advantages through increased weight.
I don't know if any of these apply to stationary flywheels built into power plants though...
They don't apply for a power plant:
Parent
Re: (Score:3, Interesting)
Other advantages of being stationary are that you can afford the space/weight to add additional infrastructure which you would never fit in a vehicle.
For instance:
- you could try building it in a near-vaccuum or at least low-pressure chamber to make air resistance negligible
- the heavy and complex equipment needed for extremely low friction bearings (or even something frictionless) could be much more easily constructed on land
For some reason I love flywheels. They're just so much more elegant than chemical
Re:Seems silly to use this. (Score:5, Interesting)
Parent
Re: (Score:3, Informative)
Re:Seems silly to use this. (Score:4, Insightful)
In a stationary mount, you don't have to worry about gyroscopic affect
Not completely accurate [ion.org]. The rotation of the Earth will cause a stationary gyro to put some torque on its bearings, depending on your latitude, just as a Foucault pendulum veers over time. It's not a big effect, but there are no "small effects" when we're talking about gigawatts of kinetic energy :)
Parent
Re:Seems silly to use this. (Score:4, Informative)
3. Given the high velocities - what will happen when they fly apart? Also, the gyroscopic effects they generate while spinning.
For a stationary plant, have it spin horizontally, and build it underground.
If it does suffer a catastrophic failure, loss of life and damage to surrounding infrastructure should be minimal
Parent
Re:Seems silly to use this. (Score:4, Funny)
Parent
Re:Seems silly to use this. (Score:4, Informative)
The weight of a flywheel is far less important than the weight. Energy of motion is a product of mass times velocity squared, so doubling the rate of rotation quadruples the amount of energy stored. The ideal for many applications is to find a material that is very light, but won't fly apart at high speeds. I remember reading about somebody trying something with carbon nanofibers, but that was a long while back.
The weight doesn't matter much for energy seepage either. A good flywheel will be suspended by magnets, so regardless of the weight, the friction due to weight is effectively zero. There is still air friction and electrical losses to deal with.
Getting energy into them isn't a huge obstacle either. I've scoured the web, and it looks like the people actually selling flywheels-as-UPS solutions are claiming 90% efficiency.
Something may be missing in my understanding here. The article claims that the battery backup for the wind farm costs about three million dollars per MWH, whereas the flywheel backup system I'm looking at right now [vyconenergy.com] claims that it can give you about 200kWH capacity for about $50,000. That's $250k per MWH installed, and very low maintenance costs.
Their claims could be overblown, or I could have my math wrong, or there is something I'm missing that makes the flywheels unsuitable for this application. There might also be a huge economic opportunity, but somehow I doubt it.
Parent
Re: (Score:3, Informative)
That first sentence was supposed to be "The weight of a flywheel is far less important than the rotation speed."
Re: (Score:3, Interesting)
A good flywheel will be suspended by magnets, so regardless of the weight, the friction due to weight is effectively zero. There is still air friction and electrical losses to deal with.
Put the flywheel in a permanently-sealed vacuum chamber. Accelerate and decelerate it with magnetic fields as well. Effectively it's a large electric motor that accelerates the flywheel when you feed power into it and a generator that decelerates the flywheel when you put a load on it.
Re:Seems silly to use this. (Score:4, Informative)
Put the flywheel in a permanently-sealed vacuum chamber.
no such thing. Not that it's a big deal. Commercial vac dewars and such have ports for pulling out excess atmosphere that seeps in anyway. you would use the same thing here. Wrap the outside of the chamber with LN2 pipes to cool the air inside so that is is less energetic and "falls" to the bottom of the chamber, then with the help of a turbo pump suck the chamber of all air present that is reasonable to get out.
-nB
Parent
Re: (Score:3, Interesting)
Actually, a few Formula 1 teams are adopting a flywheel solution to implement KERS (Kinetic Energery Recovery System) for the upcoming 2009 season.
http://www.greencarcongress.com/2007/11/second-major-f1.html [greencarcongress.com]
From memory, BMW and Ferrari have opted for different technology though.
a dam sounds like a pretty good battery to me (Score:5, Insightful)
Re:a dam sounds like a pretty good battery to me (Score:5, Interesting)
The best places for wind turbines (open plains) are usually far away from the best places for dams (canyons). The increased cost of building transmission lines and increased losses on those lines makes your solution impractical for most locations. A few exceptions may exist, but most "wind alley" locations like TX, OK, and IA don't have the elevation changes needed for hydropower.
Parent
Re:a dam sounds like a pretty good battery to me (Score:4, Informative)
Oklahoma already has two hydo plants and one pumped storage plant. You don't need huge elevation changes, a few hundred feet will do.
Parent
Re: (Score:3, Insightful)
"A few hundred feet" is almost impossible to come by in the most ideal wind-power locations such as the I-states (Indiana, Iowa, Illinois) and west Texas. You can see the curvature of the earth in central Indiana over the corn. But as I said, there are some exceptions.
There is, I believe, one small hydro plant in Illinois, for example. One. But there are something like 40,000+ square miles of good windpower territory in Illinois. Unless you use the existing grid somehow (don't know if you can), building tra
Wind/Water Reservoirs (Score:3, Interesting)
In the wind alley, they do a lot of farming, right? Why not create two level reservoirs, one a hundred and fifty feet higher than the other, and then when there is excess production, you pump the lower reservoir into the higher one. Even better, find some underground features that would make it easy to create underground reservoirs with different elevations. And if you hit a hot spot of granite, even better - redirect the steam so it spins some turbines.
Drought presents problems to open air reservoirs. It m
Re:a dam sounds like a pretty good battery to me (Score:5, Funny)
Parent
I'd want to store it in a hydro tank... (Score:3, Interesting)
I'd pump water UP to store the energy and let it flow DOWN to release the energy.
Granted it might not be as efficient as battery storage but it would be cheap, deploy-able right now, and it can be made as large as needed, plus it can be used to extinguish fires "downhill' and slake thirst.
It doesn't even have to be in the same place as the wind farm. Just in front of it, like in the mountains like the ones that cause the chinooks winds in Alberta.
I can see setting up a mountain top reservoir, filling it with water pumped by excess energy and emptying it when needed.
Re:I'd want to store it in a hydro tank... (Score:5, Informative)
Parent
Re: (Score:3, Interesting)
They do this off the Grand Coulee Dam. But they are hardly ever used, as they are only really needed when there is need for flood control, AND lack of Power Need.
There already exist these giant "batteries" and couldn't the power be utilized for things like this, rather than something new?
There seem to be a ton of places where one could use excess energy at night, that you wouldn't need a new "Battery" source.
Re:I'd want to store it in a hydro tank... (Score:5, Interesting)
Selling a few million plug-in hybrids should help quite a bit.
It would be even better if those cars were on the Internet so they could talk to the power company. For instance if I tell my car to be charged by 8am the next day, it could negotiate with the power company to draw power whenever it is cheapest.
Parent
Re: (Score:3, Interesting)
I know there's been some consideration to storing energy in freezers. It's not technically storing, it's more like shifting power draw from peak to off peak times allowing for the capacity to be more efficiently used.
Basically with refrigerated warehouses being set a few degrees colder off peak and being allowed to warm subtly during peak. It's always below the necessary temperature, but the cooling system is off during large chunks of the peak consumption hours.
Re: (Score:3, Informative)
they do that here in Ireland [wikipedia.org]
ive been at the facility few years back, quite impressive engineering stuff (for a small country)
Vanadium redox (Score:3, Informative)
sounds like a cool potential battery technology too. The battery element determines the power, and the amount of energy storage is only limited by the size of the tanks.
http://discovermagazine.com/2008/oct/29-the-element-that-could-change-the-world/ [discovermagazine.com]
Store the energy in a massive weight (Score:5, Interesting)
Re:Store the energy in a massive weight (Score:4, Informative)
Assuming concrete is reasonably environmentally friendly this would be a pretty clean solution.
Concrete has a massive carbon footprint. The calcination of lime releases a lot of CO2, on top of the fossil fuels used in manufacture and transport.
Parent
Re: (Score:3, Insightful)
Who's objecting? There's a difference between naysaying and simply pointing out the downsides, as well as the upsides, of some potential solutions.
Ignorance is what got us into this predicament in the first place, sheesh.
Re:Store the energy in a massive weight (Score:5, Insightful)
How did I know that environmentalists already had an objection? It's like I didn't even have to read the response... The usual thing to do in these circumstances is pump water uphill, but I'm sure there's an immediate objection to that, too.
Hills have an enormous carbon footprint :)
Seriously, right now you're having a problem with reality, not "environmentalists". For some reason many otherwise rational Americans have developed a persecution complex--- if something doesn't make sense (scientifically, or engineering-wise) they get pissy and blame the evil environmentalists. But in reality it's just life getting in the way, and life does that. We engineer around it.
In other words, if concrete has a huge CO2 cost (more than is acceptable for the application described by the parent poster) then that's just bad luck. If the application itself doesn't make sense, then that's even worse luck. But move on and try something else, don't shoot the messenger.
Parent
Re:Store the energy in a massive weight (Score:4, Informative)
I did some calculations (yay!), and came up with the following: Raising the Empire State Building (365,000 tons of material) to the height of one meter would store a little shy of a megawatt hour of energy.
I'm imagining this weird future city where the buildings slowly rose and fell as energy was stored and withdrawn. It's a cool thought, but it seems that the engineering difficulties would be considerable, and the payoff not so much.
A system where water was stored at the top of a skyscraper might be more feasible (putting the weight a hundred times higher means you only need 1% of the material. You might be able to do something with water, or a block on a chain. But the storage payoff seems relatively small.
It might make more sense to deal with material that's already being lifted up and dropped down. Like integrating some sort of storage and release system for the water already being pumped to the top of skyscrapers. Given separate reservoirs for potable water and sewage, and some leeway about when to pump water in and release waste out, something might be arranged.
The calculation: 365000 tons * 907 kg/ton * 10 joules/kg * 1kWH / 3,600,000 joules. The 365000 tons figure is from this kid's site [esbnyc.com].
Parent
Re: (Score:3, Insightful)
Why concrete? Cement is ridiculously energy intensive to produce. Why not stick with water, or if you really want something more complicated to handle but heavier, go with good ol' rock. We'll need to conserver all the cement and steel that we can in the coming years.
1,100 Megawatts? (Score:3, Funny)
Aargh, units confusion again. (Score:5, Informative)
I am so sick of science writers who mess up the story because they don't understand the units of energy and power.
The article says the batteries store 7 megawatt hours. Fine.
Then it goes on to say "meaning the 20 batteries are capable of delivering roughly one megawatt of electricity almost instantaneously" WTF does that mean? Power, measured in megawatts is by definition an instantaneous unit. What's with "almost instantaneous". Also, the rate of discharge of a battery MW is unrelated to its storage capacity MWh, so the entire meaning of the sentence makes no sense.
Then the article says, "Over 100 megawatts of this technology [is] deployed throughout the world," Huh? Battery capacity is measured in megawatt-hours, not megawatts.
Then the article says, "costing roughly $3 million per megawatt" same thing. Battery cost must be proportional to megawatt-hours, not megawatts.
I suspect that their idea is to make a battery with 24 megawatt-hours of capacity able to deliver 1 megawatt of power uniformly for 24 hours, then say so.
Shame on Sciam writers and double shame on Sciam editors for not mastering such basic units in an article about energy.
How about a little economics. The article mentions two understandable numbers, an 11 MW wind plant, and 7 MWh of battery capacity. The combination of the two, allowing for wind variations during the day believably deliver 1 MW continuously to the grid. That's 24 MWh per day.
Now the batteries cost $3 million, and the wind generators cost $22 million. Total $25 million to deliver 1 MW of base load. That's $25 billion per GW.
The peak generating capacity of North America is about 750 GW. Let's say 250 GW when levelized to base load. Therefore, to supply 100% of that with wind and batteries would cost roughly $6.2 trillion dollars. Now Al Gore says, "No problem. We can do that in just 10 years." WTF is he thinking?
Even if we did spend $6.2 T, there will still be periods where not much wind blows for large regions for many weeks at a time. I live where it's cold, and I know that when it hits -30F, the wind is almost always still and the sky dark, and that it can stay like that for a couple of weeks. We therefore, need to double or triple the $6.2T plus more for transmission, to provide backup power sources, plus the means of delivering the energy over large distances.
Wind and solar are wonderful for up to 15-1-20% of the total grid generation and the cost of construction and operations dominate. More than that, and reliability and deliverability of the electric supply become dominant in the economic equation.
Re:Aargh, units confusion again. (Score:4, Informative)
Then it goes on to say "meaning the 20 batteries are capable of delivering roughly one megawatt of electricity almost instantaneously" WTF does that mean?
It seems pretty obvious to me... it means that the output of those batteries is available at a moment's notice, i.e. as soon as the operator presses the "gimme battery power" button. Compare that with, say, a natural gas turbine that might need 20 minutes to spin up to full power.
Parent
Re: (Score:3, Informative)
When they refer to "megawatts" in a power plant or storage, they're generally referring to the peak output capability. For example, the 20 Megawatts almost instantaneously would mean the batteries can supply a peak power of 20 Megawatts. The "almost instantaneously" means there is no significant time delay between the request for more power and actually getting the power out (which you might have with a coal fired plant for example).
The "megawatt hours" defines
Re: (Score:3, Funny)
Some sort of cylindrical container for holding liquids one intends to imbibe?
You'd better patent that before someone else does.
Re: (Score:3, Informative)
Capacitors, at least the few I have seen, generally want to release their stored energy all at once. How is this addressed when supercapacitors are used? For example, let's say you have a supercapacitor that can power a light bulb for eight hours. How do you make it actually provide a lower current over those eight hours instead of providing all of that energy in a single instant and frying the bulb?
By understanding I=V/R [wikipedia.org].
A capacitor has a certain voltage (whatever you charged it to) and an internal resistance. The load (light bulb) you attach also has a certain resistance. The discharge rate is determined by those two resistances (added together) and the voltage. The "all at once" just means that the internal resistance is almost zero, so if you connect a load that also has zero resistance the capacitor will discharge very quickly. If your load doesn't have near-zero resistance, there won't be any rea
Re:as a sailor (Score:4, Funny)
Parent
Re: (Score:3, Funny)
Yeah, but the comments here don't make me want to kill people.
Re:How about Hydrogen (Score:5, Insightful)
Hydrogen is a PAIN.
Hydrogen embrittlement makes storage and transportation a problem as does it's low density.
If you are going to make hydrogen you might as well take the next step and convert it to NH4 and use it for fertilizer or CH4 and use it for fuel. NH4 will also work as a fuel if you want. Both would work in a fuel cell or a gas turbine.
Of course Nuclear doesn't have these problems and if they would allow fuel reprocessing the storage problem would go away as well. As to safty modern western reactors have a great record. And any one that brings up the C word is just spreading FUD since it that disaster would never have been allowed to have been built in the US.
Parent
Re:How about Hydrogen (Score:4, Informative)
So if a reactor is built in the US to today's abbreviated containment standards, yes, that reactor would include a failure mode similar to what occurred at Chernobyl.
The failure mode at Chernobyl was very specific to the design of the RBMK-1000 and to it being near the end of the core life. The problems at Chernobyl were that it had a positive coolant void coefficient, the reactor was burning Plutonium (delayed neutron fraction of 0.2% versus 0.65% for 235U), the graphite moderator was not thermally coupled to the fuel or coolant, and last but not least, the scram rods increased reactivity at their initial portion of travel - the Chernobyl accident was triggered by an operator scram'ing the reactor.
American light water reactors were design explicitly to have a negative coolant void and temperature coefficient.
FWIW, I do have a degree in nuclear engineering.
Parent
Re: (Score:3, Interesting)
The sodium-sulfur [wikipedia.org] batteries they are using are apparently 89-92% efficient (efficiency should increase with scale - these batteries must be kept at a temperature of about 300C and because of the square-cube law [wikipedia.org] it's much easier to keep very big things hot). Large (>100kW) fully-inverting UPSs are often 94% [mgeups.com] efficient - the rectification/inversion needed for this could be similarly efficient.