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The Future of Wind Power May Be Underground
Hugh Pickens writes "When the wind is blowing, it is usually the cheapest peaking power available. However utilities need consistent always-on power from large, cheap coal and nuclear power plants that are the backbone of the electric grid. Wired reports that operators are looking at Compressed Air Energy Storage (CAES) using abandoned mines and sandstones of the Midwest to store compressed-air. This converts the intermittent motions of the air into a steady power source by using it to run air compressors to pump air into an underground cave where it's stored under pressure. The first CAES plant in the United States actually went online in McIntosh, Alabama in 1991 where engineers created a geological pocket 900 feet long and up to 238 feet wide in a dome by pumping water into it to dissolve the rock salt. When the (briny) water was pumped back out, the salt resealed itself and they had an air-tight container."
actually went online in McIntosh
...Apple had something to do with this!
Instead, build long tunnels between major cities, evacuate them down to between 0 and 3 psi, and run high speed trains through them. The trains would need very little energy to run thru the extremely thin atmosphere, and the pressure diffential can be used to generate electricity when needed. 2 birds, 1 stone.
Another solution for the large scale storage of electricity is the inflation of airtight bags deep under water. Since water is so heavy, it exerts a lot of pressure against the air, leading to a cheap method of energy storage. The problem with all compressed-air systems is that have losses due to the non-isothermal nature of the process. That means some energy is lost as heat during compression, and you don't gain it all back thanks to Carnot. The energy density by volume is quite low, unfortunately, but in this application, that's basically irrelevant.
For the curious, the energy density of compressed gas, is 100*P*ln(P/A) kJ/m^3, where P is the maximum pressure and A is the ambient pressure. That m^3 term is in the volume when compressed.
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So this is more efficient than just storing the electricity? That must say something about the sad state of current battery technology.
cheaper to use salt caves, oilwells, etc etc
The problem with these energy storage techniques for renewables is every single one of them would be more economical if they were used as load leveling systems (suck extra energy during down times, release in peak hours) rather than supply leveling systems (suck extra energy in high production hours, release it in low production hours).
The reason for this is day-to-day and monthly power consumption is a very easy thing to predict, so we know very well how much storage we need and if it will or will not be enough. Using these systems we can level the load and allow the greenest power sources (nuclear, followed by hydro) to produce the vast majority of power we need (because they can run at near 100% 24/7).
The wind is a very much harder thing to predict. So how much storage is needed? Who knows. What we DO know is that every single wind power station is going to need gas turbine backups for when a) the wind doesn't blow, b) demand is high and c) storage is depleted.
Using energy storage to allow nuclear and hydro to run most economically is a far better choice than using it to level the output of wind power.
The first question I thought of was, "Why not just use pumped hydro power?" Then, oddly enough, I read TFA and found the answer in it:
And, as noted in the summary, compressed air energy storage (CAES) been tried and it works:
steveha
lf(1): it's like ls(1) but sorts filenames by extension, tersely
Pumping stuff into the ground that isn't normally there tends to give me the willies anymore. "Stick it where the sun don't shine!" isn't such a great solution, IMO.
Besides which, why not just build Vanadium batteries or invest in carbon nanotube ultra-capacitors (which could have direct benefit to mobile energy storage)?
I'm curious... I wonder how high the psi could get before something broke. I mean, the weak link would definitely be the seal (one would think). I suppose you could get some pretty dense air underground... very interesting idea.
If you can read this... 01110101 01110010 00100000 01100001 00100000 01100111 01100101 01100101 01101011
This is the Slashdot-misunderstood version of the Wired dumbed-down version. Here's some of the more serious stuff.
Wind Operations Dispatching Training: This is the grid system operator's view of wind power.
There's a lot going on. Since electricity deregulation, the power distribution companies don't own much generation capacity. They buy power from generating companies. So there's a market system and contracts in place. The contracts are now more long-term; the "auction every half hour" scheme California had for a few years is out of favor. Now, the planning horizon is about one day.
There's a whole series of PJM online courses, and if you go through some of the basic ones, you'll be able to talk about electric power intelligently.
So, the idea is to get more power by letting the air out, than consume it to pump the air in?
I assume we should reverse those first numbers: we spend 1,000 watt-hours to gain 870 watt-hours later. Cool to see that it beats pumped hydro.
http://www.nytimes.com/1991/09/29/business/technology-using-compressed-air-to-store-up-electricity.html
And it's cheaper than pumped hydro!
Interesting. Of course, if you use this with a wind farm, you don't get this benefit; the plant discussed here is a coal plant, with plenty of waste heat.
The above article is from 1991. Despite all these advantages, the idea never took off before now. It saved money, but not a huge amount. But since the wind blows when it blows, not when you want it to blow, I can see this being a useful thing for a wind farm.
steveha
lf(1): it's like ls(1) but sorts filenames by extension, tersely
I mean, the weak link would definitely be the seal (one would think).
I, for one, think that the weak link would be the compressors. Most gas pumps just aren't especially efficient. If only someone would invent a pump that's better than current designs, the world's energy problems could be quickly solved.
Here's what the N.Y. Times article said:
The chamber in Alabama could hold 5,500 psi, but the pump is only capable of 1,100 psi. Design a better pump, and the cavern could store significantly more air.
Learn the rules so you know how to break them properly.
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Wind -> Electricity ->compressed air ->electricity. That should give some serious losses. On top of that, windmills have gearboxes, brakes and all kinds of complicated crap to make them run perfectly in sync with the phase of the power grid. So question is, would it not be cheaper to mount a basic compressor in the nacelle and have it run directly on the axle, then pump the air through a set of pipes. Yes pipes have losses too, but remember the main cost of the windmill is its purchase, so a cheaper design might pay off?
10 ?"Hello World" life was simple then
The problem is that trains need people on board who in general want to breath, spoiled brats they are.
So, the train would need an oxygen supply on board, added weight and explosion risk and a LOT of oxygen because people do a lot of breathing. It would also need to scrub the CO2 out, because it is after all a closed system.
Then the train needs to enter a normal area to let people in and out without explosive decompression.
It can be done, but is just not worth the hassle, especially when aerodynamics don't matter all that much for a train. The nose after all is only a small part of a LOOOOOOOOOOOONG train. The carriages don't add much to wind resistance, you can in a way decrease air-resistance per carried passenger by just carrying more passengers.
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You may solo them, I prefer them in a group.
Hole in the ground vs 200 tonnes of battery.
Deleted
Sadly, tunnels large enough to carry trains, as modern subways will prove, are prohibitivley expensive.
however, compressed air is a good energy storage medium.
Assuming a 900 foot by 300 foot by 300 foot cavern was filled with compressed air with a pressure of 300 bars, would have a potential energy of roughly 50 gigawatt hours. (source: http://www.tinaja.com/glib/energfun.pdf) Or enough to run the entire united states for about an hour. This is a massive pool of energy, and significantly more cost effective than a battery.
HOWEVER, there lies a rub. When you compress air, you generate a massive amount of heat as the thermal energy stored in the air is highly compressed. This heat energy, unless properly reclaimed and stored (I.E. In a molten salt bath) just leaks away, stealing a huge chunk of the potential energy with it. When the air is uncompressed, there is significantly less heat energy stored in the air, and thus the expanded gas is very cold. This limits how far it can expand again, and creates a formidable problem in the form of condensation.
What you need to do to get EFFICENT compressed air storage, is either store the heat in an efficent manner, and add it back to the compressed air. OR you can gradually warm it back up to room temperature through a heat exchanger as it expands.
All in all, the challenges to attaining decent efficency are considerable.
What might be an easier way to achieve the same energy storage using similar principles, is to turn that same cavern they created into a giant hydro dam. Basically, create an enclosure of equal size below it. When energy needs to be stored, pump the water up to the higher cavern. When energy needs to be released, release it through hydro turbines into the lower cavern.
People have been storing electrical energy using water for a long time (over a century). The basic idea is the same, but in the case of water and hydroelectric dams, the solution is easier (you just run the turbines as pumps, putting water into the resevoir instead of letting it drain out). According to the wikipedia article on Pumped-storage hydroelectricity :
In 2009 the United States had 21.5 GW of pumped storage generating capacity, accounting for 2.5% of baseload generating capacity. PHS generated (net) -6288 GWh of energy in 2008
In 2007 the EU had 38.3 GW net capacity of pumped storage out of a total of 140 GW of hydropower and representing 5% of total net electrical capacity in the EU.
And, yes, people have considered using pumped-storage hydroelectric to even out the variation in wind power.
I myself doubt that compressed air storage would ever amount to more than a fraction of pumped hydro-electric storage, but it might be useful in very dry or very flat regions.
But will it smell as good?
A brick or stone built house of app. 100m^2 placed on a flat pressurized air-bag can store 3 days of average energy consumption of a household by pumping it up by 3 inches ( 8 cm )
Additional benefit: cushioning against earthquakes.
This idea claims to be prior art for any patent claim coming thereafter!
Even better (but not for generating energy): Make the trains levitate on magnets in the vacuum tube, and make the tube slope down away from the station. You get speed by going down the slope, lose little energy on the way, and at the destination the slope goes up, storing the energy for the next ride.
Bert
PS Don't do this in Chile
Nobody thinks "Only Solar". It's used as a strawman for saying why we can't use solar. Nobody thinks it must be "only solar". However, many people do seem to think that the only answer is nuclear.
Go figure.
But what renewables have in spades are two features nuclear/coal don't have:
1) low startup times. you can use a 1% complete windfarm, you can't use a 1% complete nuclear power station
2) resilience. you lose a turbine, you lose a lot of generation capacity from a traditional power station. Not so much from a 500-turbine wind farm
Instead of one huge tank, maybe hundreds of smaller tanks at fueling stations for compressed air cars. It could be our transportation needs are widely different in the future, some vehicles needing liquid fuel, some using batteries, some using onboard storage of compressed air, etc. So the gas stations would need a variety of "fuel" to sell.
Getting the straight poop from "Wired" is like expecting it from Fox News.
Air--pumped storage is dead from the get-go. You compress air and a goodly percentage of the energy ends up as heat, which has to be removed from the compressor cylinder heads and is lost. Then the hot compressed air loses heat to the walls of the cavern. Then when you let the air expand, it cools off and you lose pressure from that effect too.
A rough guess-- you lose 50% of the wind energy coming and going.
You can do better by pumping water uphill, where you don't have the compressive losses.
I like it, but switch it from direct compressed air to pumping water uphill instead, for the pumped hydro storage. The hydro storage is the only place that generates electricity. I guess you'd have to run tests, which wears out faster, pumping air or water. The water at low pressure though would likely be safer. Certainly simpler to make, too.
TFA says: "They had a unique problem, Nakhamkin said, in that their daytime load far exceeded their nighttime load, the opposite of the regular pattern." This is NOT a unique problem. It is NOT the opposite of the regular pattern. The normal pattern is heavy usage durring day excess capacity at night. Existing hydo systems pump at night and generate during the day. I suppose that is is possible for some system to have heavier demand at night, but I cannot imagine where that would be. Air condidioning is higher during the day (its hotter), industrial users use more during the day (not all industrial users are 24/7 and even those that are generally are busier during the day), transit systems run more during daytime hours, and on and on. Animal intelligence ranking -> Mice, dolphins, humans, chimps, ........., cockroaches, journalists, sports journalists.
The dems have picked Wind and Solar PV as being the 2 big winners, yet neither is really all that good. Solar PV will remain the highest costs for at least 1-2 decades to come. Neither are baseload power.
Right now, Ethanol receives more than 50% of all the money that flows into AE. Its subsidy is actually bigger than the R&D, tax breaks, AND subsidies for all the rest of the AE power. And Ethanol still has a lot of money going into its R&D.
In addition, ALL OF AE (including ethanol) receives less than Coal, Oil, Natural gas OR Nuclear subsidies. IOW, it is the sucking hind tit. That needs to change.
The easy answer is increase R&D to AE, esp. items not currently being done. That esp. includes geo-thermal and Solar Thermal. These two are way behind. Probably the most important one is to change the subsidies. They are way out of line. They need to be simplified to allow and encourage new techs. Here is what I have been pushing with 2 congressmen:
We also need this to be LIMITED TIME, as in 10-20 years, NO LONGER. The idea is to get us off of Fossil fuel dependencies, diversify our energy matrix, drop our pollution, remove our dependencies on imports (America imports natural gas, coal, fossil fuel).
The above would obviously remove the subsidies that we have in place for fossil fuel (and we have a LOT which skews the market badly; Coal is actually the most heavily subsidized). And it would encourage NEW techs to come in. This approach would encourage the coal and natural gas production to add Solar Thermal in most places in America (it makes ZERO sense in the northwest, and possibly northeast).
The storage would encourage not just this one, but thermal systems. To be honest, the stored air is actually EXPENSIVE. A better one is stored heat. Easier to make smaller, on the order of MW, and can be done everywhere.
One last place that America (hopefully the west) really needs to consider is building HVAC. They really should subsidize or better yet, tax breaks for moving away from Fossil Fuel heat/General AC over to geo-thermal heat pumps, Solar, etc. combined with better insulated homes. One useful idea is to have if configured so that businesses have incentives to offer these as services to homes. For example, business offers insulation and geo-thermal heat pump to house and then gets the monthly savings. When house is sold, the system is paid off. IOW, it should be treated as primary loan separate from the house loan. That way if building forecloses, then these companies will not be screwed. One last idea for a tax break
I prefer the "u" in honour as it seems to be missing these days.
rough guess-- you lose 50% of the wind energy coming and going.
Rough answer, you are wrong, RTFA and RTF Thread, particularly (#31435384) http://hardware.slashdot.org/comments.pl?sid=1578760&cid=31435384
You can do better by pumping water uphill, where you don't have the compressive losses.
no, you can't, again, RTFA
here it is 2010, and I'm still using cutesy acronyms from the early 1990s, seriously though RTFA has never been a more appropriate response
What about cooling air to a liquid state and storing that?
Democrats or Republicans. They are both taking us to the same place and they are not afraid of us anymore.
Most power-generating windmills favor high tip speed to high torque. Pumping windmills are considered undesirable for power generation due to this and the added fact that large the gearboxes needed to convert that torque into power increase the weight of the turbine itself. However, transporting a working fluid does favor high torque, and high torque windmills with lots of blades function better in low wind. (This is evidenced by their historic use in well pumps.) Using a more typical (and cheaper) farm-style turbine to lift or compress a working fluid and then allow it to move through a second power-generating turbine or piston at ground level may favor intermittent, weaker winds while providing a direct source of compressed gas or liquid. For instance, such a windmill coupled to a compressor and radiator could plausibly serve as a refrigeration system for a cold cellar or cold sink without any electricity at all.
Not that it matters too awfully much. The future of wind power, and indeed the only rational direction it can possibly be taken in, is in high-altitude glider based systems, not in turbines restricted to the first couple hundred meters above ground level or so.
http://www.youtube.com/watch?v=AEZjzsnPhnw
I'm convinced that the air compressor was invented by some guy who was having sex doggy style and noticed that as he rapidly pulled in an out air started compressing in his partners vagina. Next time your having sex with your partner and really going at it notice how your penis works just like an air compressor forcing air into the vagina. I'm convinced that many scientific insights occur in the bedroom.
. Using these systems we can level the load and allow the greenest power sources (nuclear, followed by hydro) to produce the vast majority of power we need (because they can run at near 100% 24/7).
I was going to moderate you down, but decided to respond instead.
Nuclear power requires relatively constant output levels- it's a pain in the ass to change power levels.
Hydro has no such issues. They can't take out more water than is being put in over the long run, but that's about it. In fact, if they can take out less, that means they can use more later. They should come up with a name for that! Maybe...supply leveling!
Please help metamoderate.
make it a well-hung unicorn, then.
I know it takes a lot of energy, but it can be done anywhere you have the windmills and a source of water. You don't need abandoned mines, the right geology, to drill into the earth and bore out storage underground (how is that considered environmental, anyway?). And what happens when the ground ruptures and you have an atomic bomb's worth of pressurized air?
The hydrogen can be used as a fuel source for more than just electric generation, it is portable and can be moved around (perhaps concentrating the small amounts generated everywhere to make a useful larger amount), and we gain the expertise in handling, converting and creating it. It's environmentally friendly and we already know how to burn it. You can even create it in locations where you can't realistically transmit the power you can generate (I wonder if Iceland couldn't get out of their financial jam by using geothermal to create hydrogen from sea water and then sell it as a fuel...although there's probably more money in siting aluminum smelters.)
I wonder if someone had just decided that hydrogen creation was a good idea and started doing in 10 years ago when large scale wind farms had been developed how much hydrogen could have been generated up this point.
While I was in my hometown of Waxahachie, TX over Christmas I found out that one of the companies using this technology was looking into buying the old tunnels used for the Super-Collider that was being built there. Some of them had been filled in, but there was a considerable amount of space available for it. However, Unlike the tech mentioned here, instead of using wind power to pump the air out, they would actually buy power strait from the grid during the night, when power is cheap, and then selling the stored power during peak hours. Eventually they would suppliment the grid power with solar to increase the profit margin. It has noting to do with clean energy though, and everything to do with making money. I never heard if the deal ever went through or not.
Another way to store the energy is to spin up giant flywheels. Then when you want to recover the energy, just allow the flywheel to spin down while turning a generator. Alternatively, if there is no wind, just allow other more steady sources of green power to pick up the slack.
Lets hope that Engineers don't try this at a Phosphorous Mine.
This is real http://www.oceanenergy.org/
This is running.
This is possibly the future.
use wind power to make power, and to convert sea water to fresh water and make fuel from water, to make amonia.
Liberty freedom are no1, not dicks in suits.
The 1991 NY Times article states that they achieve an 87% efficiency with compressed air, substantially better than hydro pumped storage's 70-75% efficiency.
Windmils ain't free; they need maintenance, and do break in unexpected ways. The right kinda land ain't free, either; gotta survey, find sealable underground where there's wind, which is not a common combination. And, the compression/decompression process loses about 80% of the original power. However, this is needed; the federal Bonneville Power Administration revealed the surges in wind power nearly fried the NW portion of the Western Grid in 2008 by overload, in a report announced on KGW news last night. And, since http://www.transmission.bpa.gov/business/operations/Wind/ shows wind is reliable 4% of the time, we have to store it somehow. But, it won't be cheap.
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I tend to think the only problem with this plan is...if for some reason a fissure or earthquake ends up happening...
what happens to that cave/mine....will there be any environmental issues or even maybe dangerous circumstances
to compressing air within this manner.....and also, if there is a leak, it will be hard to know about until
we go to use it and notice no compression of air happening.....unless they were to also add some sort of sealed barrier from the
inside and maybe even add a sort of implicit device that pings back compression info and sensors for being able to find broken
seals.