From Stanford University
Stanford scientists calculate the carbon footprint of grid-scale battery technologies
Americans take electrical power for granted whenever they flip on a light switch. But the growing use of solar and wind power in the United States makes the on-demand delivery of electricity more challenging.
A key problem is that the U.S. electrical grid has virtually no storage capacity, so grid operators can’t stockpile surplus clean energy and deliver it at night, or when the wind isn’t blowing.
To provide more flexibility in managing the grid, researchers have begun developing new batteries and other large-scale storage devices. But the fossil fuel required to build these technologies could negate some of the environmental benefits of installing new solar and wind farms, according to Stanford University scientists.
“We calculated how much energy it will cost society to build storage on future power grids that are heavily supplied by renewable resources,” said Charles Barnhart, a postdoctoral fellow at Stanford’s Global Climate and Energy Project (GCEP) and lead author of the study. “It turns out that that grid storage is energetically expensive, and some technologies, like lead-acid batteries, will require more energy to build and maintain than others.”
The results are published in a recent online edition of the journal Energy & Environmental Science.
Most of the electricity produced in the United States comes from coal- and natural gas-fired power plants. Only about 3 percent is generated from wind, solar, hydroelectric and other renewable sources. The Stanford study considers a future U.S. grid where up to 80 percent of the electricity comes from renewables.
“Wind and solar power show great potential as low-carbon sources of electricity, but they depend on the weather,” said co-author Sally Benson, a research professor of energy resource engineering at Stanford and the director of GCEP.
“As the percentage of electricity from these sources increases, grid operators will need energy storage to help balance supply with demand. To our knowledge, this study is the first to actually quantify the energetic costs of grid-scale storage over time.”
Pumped hydro
The total storage capacity of the U.S. grid is less than 1 percent, according to Barnhart. What little capacity there is comes from pumped hydroelectric storage, a clean, renewable technology. Here’s how it works: When demand is low, surplus electricity is used to pump water to a reservoir behind a dam. When demand is high, the water is released through turbines that generate electricity.
For the Stanford study, Barnhart and Benson compared the amount of energy required to build a pumped hydro facility with the energetic cost of producing five promising battery technologies: lead-acid, lithium-ion, sodium-sulfur, vanadium-redox and zinc-bromine.
“Our first step was to calculate the cradle-to-gate embodied energy,” Barnhart said. “That’s the total amount of energy required to build and deliver the technology – from the extraction of raw materials, such as lithium and lead, to the manufacture and installation of the finished device.”
To determine the amount of energy required to build each of the five battery technologies, Barnhart relied on data collected by Argonne National Laboratory and other sources. The data revealed that all five batteries have high embodied-energy costs compared with pumped hydroelectric storage.
“This is somewhat intuitive, because battery technologies are made out of metals, sometimes rare metals, which take a lot of energy to acquire and purify,” Barnhart said. “Whereas a pumped hydro facility is made of air, water and dirt. It’s basically a hole in the ground with a reinforced concrete dam.”
After determining the embodied energy required to build each storage technology, Barnhart’s next step was to calculate the energetic cost of maintaining the technology over a 30-year timescale. “Ideally, an energy storage technology should last several decades,” he said. “Otherwise, you’ll have to acquire more materials, rebuild the technology and transport it. All of those things cost energy. So the longer it lasts, the less energy it will consume over time as a cost to society.”
To quantify the long-term energetic costs, Barnhart and Benson came up with a new mathematical formula they dubbed ESOI, or energy stored on investment. “ESOI is the amount of energy that can be stored by a technology, divided by the amount of energy required to build that technology,” Barnhart said. “The higher the ESOI value, the better the storage technology is energetically.”
When Barnhart crunched the numbers, the results were clear. “We determined that a pumped hydro facility has an ESOI value of 210,” he said. “That means it can store 210 times more energy over its lifetime than the amount of energy that was required to build it.”
The five battery technologies fared much worse. Lithium-ion batteries were the best performers, with an ESOI value of 10. Lead-acid batteries had an ESOI value of 2, the lowest in the study. “That means a conventional lead-acid battery can only store twice as much energy as was needed to build it,” Barnhart said. “So using the kind of lead-acid batteries available today to provide storage for the worldwide power grid is impractical.”
Improved cycle life
The best way to reduce a battery’s long-term energetic costs, he said, would be to improve its cycle life – that is, increase the number of times the battery can charge and discharge energy over its lifetime. “Pumped hydro storage can achieve more than 25,000 cycles,” Barnhart said. “That means it can deliver clean energy on demand for 30 years or more. It would be fantastic if batteries could achieve the same cycle life.”
None of the conventional battery technologies featured in the study has reached that level. Lithium-ion is the best at 6,000 cycles, while lead-acid technology is at the bottom, achieving a mere 700 cycles.
“The most effective way a storage technology can become less energy-intensive over time is to increase its cycle life,” Benson said. “Most battery research today focuses on improving the storage or power capacity. These qualities are very important for electric vehicles and portable electronics, but not for storing energy on the grid. Based on our ESOI calculations, grid-scale battery research should focus on extending cycle life by a factor of 3 to 10.”
In addition to energetic costs, Barnhart and Benson also calculated the material costs of building these grid-scale storage technologies.
“In general, we found that the material constraints aren’t as limiting as the energetic constraints,” Barnhart said. “It appears that there are plenty of materials in the Earth to build energy storage. There are exceptions, such as cobalt, which is used in some lithium-ion technologies, and vanadium, the key component of vanadium-redox flow batteries.”
Pumped hydro storage faces another set of challenges. “Pumped hydro is energetically quite cheap, but the number of geologic locations conducive to pumped hydro is dwindling, and those that remain have environmental sensitivities,” Barnhart said.
The study also assessed a promising technology called CAES, or compressed air energy storage. CAES works by pumping air at very high pressure into a massive cavern or aquifer, then releasing the compressed air through a turbine to generate electricity on demand. The Stanford team discovered that CAES has the fewest material constraints of all the technologies studied, as well as the highest ESOI value: 240. Two CAES facilities are operating today in Alabama and Germany.
Global warming impact
A primary goal of the study was to encourage the development of practical technologies that lower greenhouse emissions and curb global warming, Barnhart said. Coal- and natural gas-fired power plants are responsible for at least a third of those emissions, and replacing them with emissions-free technologies could have a dramatic impact, he added.
“There are a lot of benefits of electrical energy storage on the power grid,” he said. “It allows consumers to use power when they want to use it. It increases the amount of energy that we can use from wind and solar, which are good low-carbon sources.”
In November 2012, the U.S. Department of Energy launched the $120 million Joint Center for Energy Storage Research, a nationwide effort to develop efficient and reliable storage systems for the grid. The center is led by Argonne National Laboratory in partnership with the SLAC National Accelerator Laboratory at Stanford and a dozen other institutions and corporations. Part of the center’s mission is to develop new battery architectures that improve performance and increase cycle life – a direction that Barnhart and Benson strongly support.
“I would like our study to be a call to arms for increasing the cycle life of electrical energy storage,” Barnhart said. “It’s really a basic conservative principal: The longer something lasts, the less energy you’re going to use. You can buy a really well-made pair of boots that will last five years, or a shoddy pair that will last only one.”
Besides the embodied issue with renewables you should also look at efficiencies. Coal plants are 60% efficient but solar cells are at best 35%.
“Atlernative”, not “alternate”? It matters to pedants like me & many.
Ouch, I mean “alternative” (slaps self with wet dishcloth)
..now figure out re-wiring the entire country
Energy storage question: (and I know there are environmental controversies but I’m just asking for info/ideas) …. in areas such as West Virginia where there is a lot of potential for massive surface mining, has anyone examined the economics of setting up pumped hydro locations as, say, an elevated area is surface mined…?? Since a lot of money is already spend removing coal and reclaiming the land, could it be economical to set up reservoir basins for pumped hydro??
Probably couldn’t make enough of a difference for any national scale of electricity but might be of use for local/regional projects.
I know the enviro issues for such surface mining (mountaintop removal) and also for use of coal remain, but I’m wondering about the economics of it if energy storage such as pumped hydro were a priority….
I seem to recall some of this discussion before. Many times. Years ago. By sceptics. We were right.
This is a very useful study. 700 cycles seems a bit pessimistic for lead acid batteries, but then a more typical figure of 900-1000 realized with 6 volt golf cart batteries seems the limit based on my experience isn’t that much more.
Many of the technical dreams of the innocent (many of whom are politicians) do not survive a thorough cost analysis that considers ALL of the costs which can be anticipated.
Energy storage as a crutch to prop up renewable power generation. No thanks.
“Only about 3 percent is generated from wind, solar, hydroelectric and other renewable sources. ”
Isn’t Stanford in California and don’t they know that ‘hydroelectric’ is not considered “renewable”.
“while lead-acid technology is at the bottom, achieving a mere 700 cycles.”
Does this mean I have to get a new car battery after 700 starts?
Hey Charley, what about th 2nd Law of Thermo. How much of the power you put into each system can you get back out. Did not see any of that in your ESOI.
I wonder if they considered the cost of the AC to DC and DC to AC convertors needed for a battery storage system. Those things don’t come cheap.
My favourite energy storage technology is supercapacitors (or ultracapacitors) – e.g. http://www.greenbiz.com/blog/2012/06/10/ultracapacitors-next-big-thing-energy-storage
But lets do a little math.
Say you wanted to provide energy storage backup for a 1Gw alternative energy generator for 1 day – so 1Gw provided for 1 day when the wind doesn’t blow.
To do this, your ultracapacitor storage facility would have to store
1Gw x 1 day
= 1 billion joules / seconds x 86400 seconds / day
= 8.6 x 10^13 joules / day of energy
By an interesting coincidence, this is similar to the energy released by Little Boy, the nuclear bomb which destroy Hiroshima (6.3 x 10^13 joules – http://en.wikipedia.org/wiki/Little_Boy ).
So if your ultracapacitor storage facility ever suffered sudden catastrophic dielectric failure, as highly stressed capacitors sometimes do, the resulting abrupt release of energy would be indistinguishable from a 10 kiloton nuclear explosion.
http://silentadmin.gsans.com/my-toolbox/electronics/why-do-electrolytic-capacitors-fail/ ,
A Brisbane company has already developed zinc/bromine batteries that can charge and discharge 100% versus the lead acid much lower capacity. Here is the link. NZ has some taking the place of extra wiring needed to upgrade the capacity of end of line places that are remote. In Qld the batteries are located at small towns to off-set peak load and recharge in low use times.
http://redflow.com/redflow_Home
‘Renewable energy’ only makes any sense in remote locations, or if someone can invent a sensible means of storing electricity in a way hugely more cost efficient and effective than a giant battery.
In effect, this is the elusive Holy Grail of ‘renewable energy’ and is not going to be found anytime soon.
I don’t think they will have much luck with the battery push. Increasing the cycles would be great… except the fact that for most battery usage, cycles are meaningless because for most they get thrown away long before the charge cycles are used up.
Sorry link is http://redflow.com/
The irrational fear of carbon dioxide brings out the crazy, even in some smart people.
Alternative energy is very similar to alternative health.
It’s all a bit of harmless fun until you trully need either. No reiki master, acupuncturist or homeopath is going to cure you of cancer or replace your hip. When push comes to shove only fossil fuel or medicine is good enough for humanity. Everything else are just talking points.
David. coal plants being 60% efficient is bull biscuits; that’s beyond.the carnot cycle ideal.
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Here’s a story about a Scottish islander who brews whiskey. A storm brought down the electric so he used his Nissan Leaf to supply a week of elektrickery for his home until the supply came back on.
Once again sensible people realize that there is no such thing as a free lunch!
Lets not forget, When the adverts start, everyone jumps into the kitchen and puts the kettle on. The power stations have to ramp up the power for this hours before. It costs them, (and you) money.
The act of LOAD BALANCING is going to be a big money spinner. Britain has it’s “Electric Mountain”, its scale is truly amazing. It’s nothing to do with being “green”; just perfect common sense.
I’d say we’ll dealing with some ignorance here about grids, pumped storage and so on.
For example, the “turnaround loss” for most pumped storage facilities is 20% or more, if
it includes transmission losses. Whether these storage penalties were factored in is unknown from the description. A possible penalty of close to 30% might occur, depending upon how far away the facility is located. And pumped storage ain’t cheap – the figure I saw for one of California’s several planned facilities showed that a facility that has the output capacity of an equivalent nuclear power plant was not a whole lot cheaper than building a nuclear plant. Pumped storage facilities can only hold about 10 to 15 hours’ worth of maximum output. They therefore mostly can shift unreliable solar or wind power pretty much for a different portion of the same day. The same can be said for batteries or any storage medium – if the wind or sun disappears for more than a day or so, conventional backup is required. In other words, I don’t see how you can shutter any conventional plants, and these conventional backup facilities cost money to operate even if they produce no power whatsoever. Also, tell these “experts” that “renewable” does NOT mean unreliable. Geothermal is reliable and so is hydro (in the near and medium term). They also avoid the issue of solar panel carbon costs, ditto for wind. I’ve seen some very high carbon figures for producing solar. panels.
The pumped storage that was built in the past had a far different purpose : to allow cheap power from nuclear or coal plants to be produced above the current demand level, and send that to storage for later in the day when demand exceeded the base load plant capacities and therefore help avoid what was then very expensive gas peak load generation. They actually saved money, which California’s facilities will not do – they simply add to to cost of their solar and wind.
All rather theoretical since renewables (wind/solar) are never ever going to supply 80% of US energy consumption, surely (?). Cover the entire area with properly separated wind mills and one gets what – those brighter than me have probably computed this, but i have a notion I read it wasn’t enough.
“You can buy a really well-made pair of boots that will last five years, or a shoddy pair that will last only one.”
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It is not necessarily the boot, but what the wearer subjects it to.
I mean, this is about a work boot, right ?
Or a modeled boot?
Speaking of Carbon footprints; you irrational CAGW science deniers criticize Al Gore unfairly.
Who knows or cares if he owns a private jet or just rides in them occasionally? Who cares how much he flies first class? What does it matter if his mansions consume more power than an African village?
Listen carefully to the man. He has carbon offsets and carbon credits. He helped invent the system and one of his companies is a “carbon credit” bank. That means it is clearly OK for him to leave a huge carbon footprint. His carbon credits pay for them! His companies are carbon credit zillionaires.
Al Gore could light an oil well head and use the 300 foot candle of flames to spit roast whole Brahman bulls 24/7 for the rest of his life without harming the environment in any way.
Just ask him.
In the matter of cycle life of a lead-acid cell; its definition must be carefully considered to account for devolution of the technology. Traditional lead-acid cells were disassembled and restored. There used to be cells in submarine service after many lifetimes.
About lithium cells, consumer grade cells are still rated 300 – 500 cycles and 3 – 5 years corrosion limits IIRC. http://batteryuniversity.com/
The most effective storage technologies for energy already exist and are in use: they are called Uranium, coal, natural gas, and petroleum.
Too bad Stanford did not evaluate these energy storage technologies.
“Does this mean I have to get a new car battery after 700 starts?”
No because you are only using a small portion of the battery’s charge to start the car. Maybe a few percent at most for easily started car. But if you start the car 100 times and turn it off to use up , then drive and recharge completely, and do that 700 times, that would be a miracle because the car battery is not made to be deep cycled and would probably stop recharging after 70 full discharges.
This press release doesn’t mention that the researchers calculated the disposal cost for these storage technologies, which could be substantial in the case of batteries. And what becomes of a dam after it dies?
Batteries ?
Boeing might lose billions of dollars, because they installed an (apparently) faulty battery in their newest airliner.
Battery technology is a field waiting for a breakthrough.
I love it. Alternative energy, ‘ruinables’, are already grossly inefficient; so then you devise ways of making them even more inefficient by charging up batteries or using pumped storage.
These people just make me laugh – to what lengths will they go for their ‘renewable’ dream. OK, I will answer my own question – as far as grant money provided by gullible politicians will take them.
This calls to mind my upbringing in a mainstream monotheistic religion. We were taught that masturbation was a heinous sin.
Ok, now I’m going to have to jump in very quickly with both feet to answer the inevitable question that’s coming at me: “Why, on earth does a discussion of masturbation have any relevancy to a climate change science website?”
Forgive me, but I believe it has complete relevancy. You see, to tell a newly adolescent male not to masturbate is, not to put too fine a point on it, to tell him not to do something that is, well, absolutely, thoroughly, completely, and utterly impossible not to do. And, since it is a demand that breaks every single law of physics, biology – in fact, everything – therefore rendering compliance, um, impossible, why bother to torture somebody by demanding that they not do something that they simply cannot not do? There is a reason, of course, but the real reason cannot be stated so a whole bunch of fictitious in-the-future maladies such as blindness, impotence, madness, hands turning into bat wings, and such, are attributed to a wholly normal activity in an ultimately failed attempt to get the poor soul to comply with the impossible and when he fails – which he will – to at least feel guilty and worried.
Now, is the authoritarian, quasi-religious, state-sponsored campaign, to combat global climate change beginning to have a wee resemblance to the foregoing? I mean, the only thing that predated fire in human development was, well, sex. After that, fire’s the next best thing. It preceded the wheel, the written word, civilization itself. Our Stone Age ancestors new how to use it. And now, we are being told to do the absolutely, thoroughly, completely, and utterly impossible thing to do, which is give it up. And, since in the scheme of human affairs the real reason, just as in the masturbation example, cannot be stated, a whole slew of fictitious in-the-future maladies are being conjured up so as to make us poor souls attempt to comply with the impossible, fail, and feel guilty. We need fire for chrissake!
I suspect, and this is a question for you, Lewandowsky, that there is an innate class of human beings who believe that by demanding the impossible from people provides themselves with the ultimate in a juicy feeling of control and power.
And this is why, all those hi-tech solutions to climate change yada yada, in the end, are probably no more useful than cold showers and salt peter.
I strongly disagree with this statement. Wind and solar power DO NOT show great potential as anything “low-carbon”. Just the manufacturing, installation, maintenance and disposal are highly carbon-intensive, let alone the other changes we are discussing here. The word for this is “delusional”. Sorry, Sally, but you’re living in a dreamland of unicorns and leprechauns if you truly believe this statement.
If a grid-scale battery was required, it would be ridiculous to expect banks of small lead-acid batteries. This kind of scale would probably require gigantic tanks filled with replaceable plates and circulated acid, which would reduce maintenance costs and be a lot more efficient. Of course, it would also increase the risk of such a facility, Imagine a few thousand gallons of extremely corrosive acid leaking, or the potential for an attack of some kind.
There is a reason the grid was never provided with storage capability: it’s too expensive given the current state of technology. That was true 50 years ago and is true today. Instead, utilities concentrated on providing reliable, clean generating facilities. Now we have people trying to dismantle what has taken a century to build, without the intelligence of having something to replace what they are planning to dismantle.
Virtually every plan I’ve ever heard of for utility-scale energy storage has a major downside, and the inevitable waste is unconscionable. Pumped storage is only a few percent efficient. Flywheels have the danger of spinning apart, and require the raw spinning material. Heat storage, etc. etc. all have very, very low efficiency and more potential for catastrophe than simply continuing the natural evolution of power production (which includes NUCLEAR as a major factor).
It’s not “clean” energy. It’s development causes environmental disruption during recovery and processing. Just because it happens in someone’s else’s backyard (e.g. China) doesn’t make it clean or green.
It’s not “clean” energy. Since current technology produces energy in low density, it requires large scale displacement of people, animals, and vegetation. Just because its proponents don’t talk about it, doesn’t make it any more efficient or less disruptive.
It’s not “clean” energy. Both in development and actual use, there are animals and plants destroyed. With windmills in particular, there are thousands of birds and bats killed annually on the blades.
It’s not “clean” energy. It cannot be reasonably isolated from the environment and requires extensive buffering to compensate for driver (i.e. solar radiation, atmospheric currents) variations. The buffers themselves are neither “clean” nor “green” before and after their useful lifetimes.
It serves no useful purpose — other than to distort the conversation — to continue using euphemisms and obfuscation to promote the merits of technology which is not capable of serving as primary energy producers. Not to mention the environmental and human disruption they cause during pre-manufacturing and actual use.
Are we paying a premium solely with the sole purpose of living in ignorance?
The use of solar energy and atmospheric circulations as drivers to produce energy can serve in niche markets. They can be used reasonably in geographical locations where the sun shines or wind blows predominantly. They can be used economically in geographical locations where energy consumption occurs in isolation. They can be used efficiently for application which do require extensive buffering, for example: desalination to recover potable water. They are not suitable for general purpose, large scale deployment. And since the drivers are by their nature circumstantial or unreliable, they will never serve that purpose with their current design.
Effective energy storage is a crucial component even though it can’t effectively make renewables effective. However, the ability to load level throughout the day will always pay off regardless of your power source. An excellent power storage medium is hydrogen/fuel cell tech. Like anything it’s not perfect but it’s another technology which can help effectively improve power grid efficiency.
arthur4563 says:
March 8, 2013 at 3:19 pm
I’d say we’ll dealing with some ignorance here about grids, […]
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Absolutely. The whole premise of storing energy to feed to the grid later assumes that you will have plenty of time where production far exceeds demand, so there is actually available power to feed into the storage!
From the time you burn a lump of coal to the time electrons reach your wall socket, about half of that energy is lost. Converting the majority of grid capacity into a massive storage system, with assumed huge, centralized banks instead of distributed nodes, would just further reduce that efficiency.
Curious as to why they have apparently not considered inertial (flywheel) storage. I’d be interested in seeing how that would compare with these other approaches.
It has been noted above there will never be enough renewable generation capacity to make much of a dent in our power needs. However, storage is very helpful to avoid the terrible consequences of directly connecting unreliable power sources to the grid. Sudden changes in generation can damage the grid. These fluctuations may be caused by changes in wind speed or clouds for PV.
To avoid damaging the grid, autoresponse is required to change demand. That means the utility must monitor all electronic devices in your home and be able to turn them off, during a “power emergency”. In practice, these emergencies will occur regularly. The smartgrid network is bidirectional, and all data are allowed to be mined. What is the limit? Apparently none. There are plans afoot to replace the internet we know with a “more secure” powerline broadband.
The only excuse for this intrusive smartgrid is the inability to store power. Even if renewables are later acknowledged to be impractical, they will already have the smartgrid infrastructure in place, which is all they really want.
And why can’t we just store power as H2 made from H2O? Liquefied, it is more compact, about 4 gal H2 for the same energy contained in a gallon of gasoline. Compressed gaseous H2 is very dangerous due to the high pressures required to contain a useful amount of energy in a practical volume.
DD More says:
> “while lead-acid technology is at the bottom, achieving a mere 700 cycles.”
Does this mean I have to get a new car battery after 700 starts?
By “cycles” they mean deep discharge-recharge cycles. Your car battery almost never goes through the full cycle and its lifetime is more likely to be limited by the decay of the active material in the plates at full charge — typically 4-5 years. That is a much longer time than the time it lasts when fully discharged, which is measured in days or even hours. If you totally drain your car battery and let it sit discharged for just a few days, it’s gone. One common way to kill a car battery is taking regular short trips day after day. On a well-tuned car, it takes 15-20 minutes to restore the charge lost while starting the engine, so if your trips are shorter than that, the battery keeps drifting away from the safe charge level and soon decays into a useless pile of dust. Few people use their cars like that, but those who do end up with a dead battery very quickly.
The number of starts is a meaningless metric.
In the context of energy storage for the grid, they are really talking about deep cycles.
A utility-scale flow battery has been constructed at Little Barford by Regenesys and is claimed to be able to jump-start the UK grid in case of a total blackout.
Renewable energy is second class anyway. I favor superrenewable energy, the old renewable energy locked in the Earth as “fossil fuel.” When finally released from its long slumber, it becomes wood or biofuel or vegetation, which becomes these things again every time it is burned. We all understand (I think–can’t be sure with the modern “Public Fool System”) that wood is renewable because it turns back into carbon dioxide and water vapor, absorbed by another tree, where it captures the energy from sunlight in a formerly well-known process called photosynthesis. Wood is renewable, so coal, releasing energy to become wood, is superrenewable.
Only fossil fuels are superrenewable because only fossil fuels generate an increase in the living matter of the biosphere. Dams and other storage media are essential for human welfare, but more life comes only from the source of life–carbon dioxide. Every living thing derives all its tissues from the biochemical reduction of carbon dioxide.
When you consider the cost of grid-level storage in order to mitigate the unreliable nature of wind and solar energy, it should be clear it is much more sensible to simply build more capacity, especially nuclear if you stay up nights worrying about CO2.
There isn’t much of point to using battery storage for large scale systems because you have to make your system that much larger just to charge them and still maintain your output to the grid. Charging them from fossil defeats the purpose of the renewables. As a specific boutique use or just to make yourself feel good, maybe. But don’t charge me for them.
During the winter a few years ago Bonneville Power Administration had a stretch of about 12 days where their wind system never exceeded 50 MW output from their 1700 MW capacity. If that portion of their system was essential just imagine how many batteries would have been required. And how many extra turbines would be required to keep them charged. The same thing can happen with solar.
Any essential power must always be covered by sufficient fossil, nuclear, or hydro. Talk about 80% renewables in the future is fantasy.
Instead of worrying about storing excess capacity, would it be practical to have electric heaters in the basements of homes in northern parts where the heaters can go all the time for 8 months a year or more without making a house too hot? Of course I am not suggesting relying on this to completely heat a house, but to use any excess to reduce the times the furnace comes on.
This and the like studies are so full of holes that they can hardly be considered any more than first order approximations. But at least such trivia does not cost millions.
@Eric Worrall: 2:33 pm
Good observation. That is a problem with all energy storage methodologies. Look at the problem Boeing is having with Lithium Ion banks.
I have a fondness for magnetic-bearing vacuum enclosed variable density flywheels. The composite materials are readily available and they can take large power rates for charge and discharge. But if they fail…. You have a ten-ton loose cannon looking to expend it’s kinetic energy into anything in its way! Neighboring flywheels are probably what you want nearby.
So for any storage methodology we have to ask: How can it fail? How much warning can you have? How big will be the boom?
Dams can break. Oil storage tanks can blow up. A coal unit train could crash and catch fire. Natural Gas pipelines can rupture and explode. These are traditional “chemical” means of storing energy for electric availability on demand. We know how to build these and can usually give warning of pending failure.
Distributed storage will almost have to be an element of a solution. We can’t have one failure cascade into another storage unit. But then those units need to be as foolproof as a gasoline station. When you think about it, that’s a tall bar to hurdle.
Storage. The third rail of alternative energy. Graduated to Achilles’s heel status?
The energy efficiency seems really terrible. Of course, if you think wind and solar costs nothing, then you can make it look attractive.
AndyJ — Carnot efficiency for combined cycles… > 50%
http://mit.edu/16.unified/www/FALL/thermodynamics/notes/node67.html
http://www.axionpower.com
Replaces the Lead negative electrode with one of activated carbon. Eliminates sulfation. Great power and charge characteristics. Increases cycle life at least 4x … been tested to 2500 cycles at 100% depth of discharge. Probably good for much more. Low cost, recyclable. Norfolk Southern is putting them into hybrid locomotives and all-electric switchers. Grid-storage apps in development now…
Bob says:
March 8, 2013 at 5:43 pm
Spot on Bob, as you point out wind and solar certainly aren’t free, far from it they’re very expensive compared with conventional non-subsidised modes of generation. If high cost storage is added, then the cost multiples become even more “unsustainable”.
Candlewood Lake near Danbury CT is a hydro storage facility built in the ’20s and still in operation http://en.wikipedia.org/wiki/Candlewood_Lake . The wikipedia article does not have any info about generating capacity.
If they are successful at stockpiling all energy reserves at night then the cost of energy at night will go up. And because there will be all that excess stored energy available during the day it will drive down the price of daytime energy.
Tell me again what problem they’re trying to solve.
A pumped storage system requires a dam and lake destroying the natural ecology locally. The lake depth varies greatly producing mud flats and swamps when low. The papers I read in the 1970s stated a hydroelectric dam during the first twenty years of its existence releases as much GHG (carbon dioxide and methane from rotting vegetation) as a coal fired power plant of similar output. Does anyone have good recent data on this?
Storage of any kind requires a large excess of capacity to account for the worst case (say 1% chance per year) of non-production from wind and solar, as well as downed power lines, etc.
Thanks, Anthony.
There are many interesting findings in this paper, some propaganda too, but that is just to be expected.
I can’t find the reference/link just now, but I seem to remember there was a paper reviewed here on WUWT a few years ago from a Brtitsh academic pointing out that the concrete needed to make the hundreds of pump-storage facilities which the UK would need to get sensible amounts of power from wind made the whole thing a non-starter for CO2 emissions reduction.
Can anyone else find this? I may have it wrong.
While it sounds impressive to invent a new metric (ESOI – energy stored on investment), the metric that is missing is how much the energy we would be buying under such a regime would actually cost. In particular,how much would it cost as opposed to just using conventional energy and the existing grid system.
That’s the ‘metric’ that always seems to be missing from puff-pieces about so-called renewable energy. As for the massive battery infrastructure that would be required for a typical city – I wouldn’t want to live within 100 miles of it. The tiny lithium-ion batteries in mobile phones can burst into flames – the slightly larger versions burn cars to the ground.
None of the technologies they mention pass the tests of safety or efficiency for even small scale generation for communities larger than a few thousand people.
No thanks.
Where will they put the batteries? How many acres? Covered? How strong the floors. How big are the AC to DC and DC to AC converters? Let’s see the wiring diagram. How will they find the failing batteries? How will they replace them? What happens to the dead batteries?
Lead-Acid batteries are the equivalent of banging rocks together to make sparks. Any analysis of the future that looks to 19th century technology for guidance is not that impressive in terms of it’s predictive value. LiFePO would have been a better measure. Even still the energy equivalent of the Cubic Mile of Oil the globe uses is silly to even major in battery storage. In most places we only need a a few hours of storage. And I know the whole purpose of this blog is to find and attack straw-men arguments, but for the more open-minded readers might want to consider electrosis of water as green energy storage method.
http://www.nrel.gov/hydrogen/renew_electrolysis.html
RE: David Larsen says:
March 8, 2013 at 2:11 pm
Besides the embodied issue with renewables you should also look at efficiencies. Coal plants are 60% efficient but solar cells are at best 35%.
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Sorry David, but you’re measuring the wrong thing. Efficiency for coal makes sense because you have to bring in the material, but for solar, none of us pays for sunlight. The real measurement / comparison is, how much per kWh do solar cost and how much per kWh does coal cost? I don’t recall the exact numbers, but in general, coal is still cheaper per kWh than solar.
If energy storage were so easy then it would have already been implemented. The UK runs twice the number of fossil power stations it needs because demand fluctuates. The grid must be designed to handle peak load of 70GW, although average load is around 40GW. The fluctuations in demnd must be met real time, mainly through gas. An all renewable grid is completely impossible in a country like the UK without truly massive hydro resources. A decarbonized future in the UK without a large nuclear base load is nonsense. In the short term only fossil fuels can dispatch sufficient power to handle the random intermitancy of wind power. Gas is the only resource which can be held in reserve to quickly meet peak demand. Wind is randomly intermittant and if it were to reach more than ~10% peak capacity would threaten the grid with complete collapse as its output fluctuates so wildly.
Lead-acid storage systems achieve about 700 cycles. Err, that is a battery replacement every 2 years or so. Is there anyone out there that thinks, in their heart of hearts, that any of this is truly feasible?
As to pumped storage. Great idea, but all of the UKs locations are in protected wildlife areas. Our last one, Dinorwig, had to be placed INSIDE a mountain to keep the Greens happy. You could put St Paul’s cathedral in the cavern they excavated. You can imagine the cost.
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@Andyj
“David. coal plants being 60% efficient is bull biscuits; that’s beyond.the carnot cycle ideal.”
Well, a combined cycle coal gasification plant does not consist of only one cycle so it gets far more energy from the fuel than a steam boiler.
Get the coal hot. Spray water on it to crack the water (absorbs heat) to make coal gas. Feed the gas into a turbine and burn it getting shaft power turning a generator. Funnel the waste heat into a steam boiler, run turbines on the steam. Put a condenser on the back of the steam cycle literally pulling the steam through the turbine by sucking on it. The system efficiency is far higher than the best coal plant making steam only. The electricity produced is more expensive because the system is complicated.
In places where the the waste heat is needed for space buildings (combined heat and power plants are all over North Asia) the efficiency is very high because the return pipes are about 50-60 C. Peak Coal will be in about 2070 so we have about 100 years to develop a compact U235+Thorium CANDU-like nuclear power plant design that can burn its own waste products into heavy metals.
Solar power is about an order of magnitude more expensive than coal power per kWh.
Could a suggestion be made to the relevant authority that Stanford University — or any other — should be required to publish the value of the grant which is given from government when they publish the result of their labour in constructing a report such as this. I think bloggers call it the “give us a grant please” type of report. Anyone with some engineering sense would see the resultant objections right away.
Re the cost of inverters: A company in Cambridge Ontario (next to Waterloo) makes thyristors for power control that will handle 8 MW (using a single junction). Inverters are a small portion of the cost of an online UPS. It is the batteries which are the problem.
I also favour the capacitor solution, super or ultra or whatever it will be called by then. Hypercaps?
Long distance transmission lines can be reduced in size if they run continuously. This reduces reticulation infrastructure costs, especially if the storage is ‘per home’. If they can be made safe, a 50 kWh unit would probably serve most houses.
Well, what a surprising finding: the life time costs of a battery in a deep cyciling application are predominantly determent by its cycle life, which is currently too short for use in large scale energy storage. Who pays these chaps?
As for pumped storage, given suitable topography it can be viable for peak lopping, but to consider its use to balance unpredictable generating capacity is a stupidity only exceeded by the proposition that a large slice of the energy needs of an advanced indusrial economy can be met by tens of thousands of wind turbines. The latter is akin to powering a bus with tens of thousands of AAA cells: Its just about technically feasible, but no one in their right mind should contemplate doing so.
Lithium ion batteries, 6000 cycles if related to a Nissan Leaf being charged once per day that equates to 16.48 years, not a snowballs chance in hell. Lithium ion batteries are substantially different to other forms of battery inasmuch as they begin to decline immediately after the point of manufacture whether used or not and Nissan have already admitted that their Lithium ion batteries for the Leaf will be next to useless after 5 years and seriously in decline between 3 and 4 years. These guys must be been charging and discharging many times each day in order to get to 6000, which is not the same as being used in a stop start environment, load and no load. In the case of lead acid, this product is used extensively in fork lift trucks in distribution warehouses, they are used daily 364 days a year with at least 2 sets of batteries for each truck and they last 5 years+.
80% from renewables? and I thought Colorado was the State that legalized dope.
I will repeat my “unexpected effects” prediction – when renewables have either driven electric costs too high or made the grid unreliable most households will buy whole house generators. Of course these generators are less efficient than power plant turbines and not as well maintained. This will result in more CO2 production than if we had just built coal/gas powerplants to start with.
And the folks in SCE’s service territory will be the first to have energy storage required-
CPUC Requiring 50 MW Of Energy Storage In ‘Landmark Decision’
http://solarindustrymag.com/e107_plugins/content/content.php?content.12106
“The California Public Utilities Commission (CPUC) has unanimously approved a long-term procurement decision ordering Southern California Edison (SCE) to procure between 1,400 MW and 1,800 MW of energy resource capacity in the Los Angeles basin to meet long-term local capacity requirements by 2021.
Of this amount, at least 50 MW is required by the CPUC to be procured by SCE from energy storage resources, as well as up to an additional total of 600 MW of capacity required to be procured from preferred resources – including energy storage resources.”……………………..
I wonder how the costs of the assets are going to show up (if at all) on your utility bill?
Posted January 2012, current cost zinc air $1,000 per kw or $1billion per Gw But don’t we already store energy coal, oil, gas, uranium?D. J. Hawkins says:
January 17, 2012 at 3:57 pm
George E. Smith; says:
January 16, 2012 at 11:27 pm
So how big would one of these zinc-air batteries be for a small one megaWatt storage plant with say 10 days of full output capacity…
Based only on the information provided on their web site, a standard 40-foot container can store 6 Megawatt hours deliverable at a rate of 1 Megawatt. For 10 days storage for a 1 Megawatt power plant you would need 24X10/6 or 40 containers. The archetype “40 footer” is 8 feet high by 8 feet wide. Assuming a 16 foot separation for moving things around, which is probably WAY more than you need, the containers would occupy a 152 foot by 320 foot area (based on a 6 by 6 grid, with 4 left over in a seventh row), or 48,640 square feet which is just over an acre. Obviously this isn’t counting the interconnecting infrastructure. Looked at another way, this would support a 10 Megawatt plant for a day. Modern base-load plants tend to be in the 1,000 Megawatt range. To support such a plant for one day would require 100 acres of storage. Even going up to your original 10 days with a 1,000 Megawatt plant, you’re looking at a smidge over 1.5 square miles of storage.
Problem is, there hasn’t been a major pumped-storage facility (admittedy, they do take alot of land) built in many decades ’cause envirowacks won’t permit it.
““Pumped hydro storage can achieve more than 25,000 cycles,” Barnhart said. “That means it can deliver clean energy on demand for 30 years or more.”
Certainly more than 30 years – lots, lotsmore. This little gem:
http://www.fhc.co.uk/ffestiniog.htm
has been going since 1962, is still going strong, and is not only delivering simple load shifting to the UK grid, but also supplying vital services such as reserve and response. Oh, and it’s still using the same mechanical and electrical plant; only the controls have changed appreciably.
I’ve come to see “The Grid” as becoming anachronistic, when the technological feasibility of on-site generation is increasingly cost-enabled by the Overhead/”Delivery” costs (not to mention subsidy add-ons) of centralized generation. Office parks, High-Rises, Apartment/Townhouse complexes and other high density situations are easily heated, cooled and electrified with multi-fuel, low-maintenance, highly efficient gas turbines. Look up Capstone Turbine, for example.
j ferguson says:
March 8, 2013 at 2:23 pm
This is a very useful study. 700 cycles seems a bit pessimistic for lead acid batteries, but then a more typical figure of 900-1000 realized with 6 volt golf cart batteries seems the limit based on my experience isn’t that much more.
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Depends on the depth of discharge. In the battery biz a cycle means a full charge and a full charge.
They could have just dusted off one of hundreds of such studies from the 1970s and saved their time.
Storage was the defect then and remains the defect now.
Curiously, if we were inventing electricity today, we would not be able to get regulatory approval to allow public use of it.
Your opinion of your government will never be higher than it is today.
Granted, “alternative” power sources can’t replace fossil and nuclear power in the near future. However, as pointed out above, it can help to reduce the need for overcapacity production, as in the uk, if adequate storage were provided.
When considering the high cost of alternative power, most of the critics ignore the high cost of any sort of insurance generally. When considering insurance costs, one has to gauge the cost of catastrophic uninsured failure. If the cost of failure is unacceptable (ie. unaffordable), then ANY affordable cost of effective insurance is cost-effective. If that insurance also reduces the production cost of the service insured (ie. by reducing the need for overcapacity), then so much the better.
Aside from the inherent shortcomings of currently available electrical storage technology, there is a lack of integration among various alternative power generation technologies, and between off-grid and grid-connected local power generation systems. Integrating these systems would do much to make them both more attractive and affordable.
For example, combining geothermal, solar and wind energy with pumped storage and user selectable grid integration would make a much more attractive package for end users. Using potable water which could be tapped for emergency consumption would make it even more marketable.
Currently, at least in my area of Western Canada, it’s impossible to buy even the simplest off-the-shelf home solar and/or wind power system that can provide both grid integration and local power backup capacity in the case of a grid failure. Geothermal heating is offered at a cost of tens of thousands of dollars for residential use, but no one offers an integrated backup system that would keep your precious geothermal heat flowing when grid power is down.
With a very few (happy) exceptions, the posts on this thread have been decisively unconstructive. Seeing things rigidly in black and white doesn’t advance science or technology. Let’s figure out how to make the best of what we’ve got instead of rushing to throw ideas and technologies onto the trash heap without a second glance.
Surely any cost benefit calculation for both financial costs and energy costs should be cradle to grave. The paper only looked at one half of the issue, I suspect that battery disposal / recycling costs both financial and energetic would be significant.
They also ignored other technologies, one commentator mentioned compressed air, another ignored technology would be conversion of excess energy into hydrogen.
That’s not the way you do, you use Sodium Sulfur batteries. Presidio Texas has a $25 million BOB, Big ol Battery, that stores four megawatts of power for up to eight hours. That works out to $0.78/Watt Hr. which seems a bit expensive, but then it’s real-world technology, not the usual greenie pie-in-the-sky stuff.
Hoser said:
H2 is also the smallest gas molecule which makes it most difficult to contain, and it also makes steel brittle.
Oh, and I almost forgot, it is also a “Severe fire hazard. Severe explosion hazard. Vapor/air mixtures are explosive. Pressurized containers may rupture or explode if exposed to sufficient heat. Electrostatic discharges may be generated by flow or agitation resulting in ignition or explosion”. http://www.nfpa.org/assets/files/PDF/CodesStandards/HCGHydrogenMSDS.pdf
Re: @Eric Worrall: 2:33 pm
Eric, you and I blundered.
1 GW/day might be equivalent to 10 kilotons, and if there is a failure it would indeed be a 10 kiloton near instantaneous release…….
But that was just the energy STORED!
Let us suppose our capacitor or battery bank is storing a GW-day and it shorts out
You release 10 kilotons of electrical energy PLUS you will vaporize a million tons of METAL by the flash and immediate COMBUSTION cascade. We might be in the Mega-ton range of a disaster.
If you have a GW-day oil storage tank, or coal mountain, the inferno will be spectacular. How much mass other than the oil or coal is being burned?
Now imagine a Lithium-ion battery. The same amount of electrical energy will have to be released. But how much of the mass of the battery will burn in the atmosphere if it get’s hot enough? I recon a good deal of it is combustable. Ever see aluminum burn?
A ClaytonPower 400Ah Lithium-ion battery will store 617 kJ/kg
= 617 KW-sec/kg
= 0.171 KWH / kg of battery.
or 7.1 KW-Day per TON of battery.
Use your 8.6 x 10^13 joules = 1 GW-day
We need 140,000,000 kg of 400Ah Lithium Batteries just to store 1 GW-day.
1 GW-day is about one 100-car coal unit train
Coal energy = 6.70 KWH / kg coal
coal with 40% energy conversion = 2.68 KWH / kg coal
coal unit train = one hundred 100-ton hopper cars = 10,000,000 kg coal.
coal unit train 100 cars = 1.12 GW-Day elec gen
So imagine a 1 GW-day battery bank the size and mass of TEN 100 car coal unit trains.
Then imagine it shorting out and catching fire.
http://www.iafss.org/publications/fss/8/375/ (2005)
The thermal runaway of a ton of coal or oil is a LOT higher than 75 deg C.
A couple more numbers:
A kg of coal burned for electricity at 40% efficiency yields 2.68 KWH / kg.
Or you need 0.373 kg coal for 1 KWH.
A ClaytonPower 400Ah Li-Battery gives 617 KW-sec / kg or 0.171 KWH / kg.
or you need 5.83 kg battery for 1 KWH.
Therefore, you need 15.6 kg of battery to store the energy from burning 1 kg of coal at 40% efficiency.
This is my first post here though I have been following this blog for over a year. I find it very educational and I am starting to understand some of the complexities of so called global warming. I have spent most of my working life in construction mostly as a carpenter but I tend to actively learn as much about other trades as possible. One of those trades was well drilling and another was process piping for clean rooms. One of the storage types mentioned in the article was compressed air. I thought about that for a bit and realized that building a storage system using cargo containers would need a lot of area and a lot of reinforcing and rebuilding of the containers. We already drill wells and line them with steel pipe for water and petroleum. Some wells have quite large diameters and go quite deep. Process piping involves welding a smooth bead that doesn’t impinge on the diameter of the pipe sometimes from the inside and sometimes from the outside. This process would enable the casing to be seamless and airtight and could be done with currently available technology. Once the well is in place it would have a movable plug installed that would be heavy enough to keep the air under pressure at whatever pressure the system required to operate. It would be filled by any mechanically or electrically driven compressor pumps which could be powered by wind, solar, hydro, geothermal, tidal, natural gas, electrical, or whatever. The advantages of a system like this are low impact, small footprint, and they can be put nearly anywhere with little environmental impact. They also don’t have to be vertical allowing them to be placed horizontally into the sides of mountains to take advantage of the wind power available along ridge lines. Since I came up with this over the last hour and it therefore is quite rough I look forward to your input.
After doing some more figuring I realized that the horizontal idea won’t work with the weighted plug idea so please disregard that idea. Thanks.
Article in WSJ, Mar. 11, 2013, Opinion: Bjorn Lomborg:
Green Cars Have a Dirty Little Secret
It is chocked full of statistics. Read and file it. Much of the dirty little secret comes from the electric car’s lineage from a lithium mine and smelter.
If an electric car is recharged by a fossil fuel power source, it emis 6 oz / mile of CO2. Gasoline car: 12 oz / mile. But considering the 30,000 pounds it started with, the electric vehicle will have to travel 160,000 miles before it’s carbon footprint is better than a gas car. (Gas as an 80,000 mile head start, and only looses 6 oz per mile to the electric).
Assuming you don’t have to replace the batteries. You will. So, it will never catch up.
If Electric car is recharged totally by solar, then if a Leaf is driven 90,000 miles, it will total 76% CO2 lifetime of a gas car — 8.7 tons of CO2. Carbon credits amount to $48.
143 comments in just four hours on a Sunday night.
@Walter Royal at 5:40 pm
Vertical storage of compressed gas is technically feasible, but it will boil down to cost.
The real problem, however, is that you might be limited to 18 5/8 in casing to a depth of 1000 m.
That is only 175 m^3 of volume. If you put CO2 in the casing at 50 atm, you might get 500 kg/m2 or a total of 88 tons in storage.
While the surrounding earth might serve as some protection in the high pressure state, the earth’s temperature and heat flow will never allow CO2 to liquefy. It would be ideal for a room temp gas to liquify under pressure, like propane or butane, in vertical storage. CO2’s critical point is 73 atm and 31 deg C which makes it an atmospheric gas and potential source for high pressure storage, but it is not going to liquefy under these circumstances.
Two other design problems. We must design for maximum pressure at the top, Say 50 atm = 750 psi in an 18 5/8 casing. But we must also design for atmospheric pressure at the bottom of the tank and guard against crushing the casing from outside lithostatic pressure, maybe 1500 psi.
What would it cost? $0.5 million? Maybe $0.20 million if assembly lined? Uncertainty a factor of 4 either way.
http://www1.eere.energy.gov/geothermal/pdfs/egs_chapter_6.pdf (pg. 10). And what is the carbon footprint of all that drilling, steel and cement per 175 m^3 storage tank?
An interesting question, all in all.
A cool PPT on well design and completion: (3 MB)
http://gekengineering.com/Downloads/Free_Downloads/A_Guide_to_Well_Construction.pdf
One energy storage mechanism that is rather old hat is the freezing of large tanks of water when energy is cheap and plentiful, and then using the ice to assist air conditioning systems during peak power use. It counts as a means of storing electrical energy in a form you will use later.
I am of course totally disinterested in their carbon counting adventure as I see no evidence that CO2 is harmful in any way; but I like that somebody finally recognizes that making batteries costs energy. Well done, academics!
Personally I have invented a method for estimation of energy use during production of a product. As energy has a price, even in politically price fixed markets, it is possible to estimate the energy used in the making of the product by looking at the comparative price/performance ratio.
As the price/performance ratio of electric cars is far inferior to any gas car, I have concluded that transportation using an electric car is a very wasteful activity; in terms of money, and via dividing the amount of money by the price of energy, also in terms of energy used.
Simple rule: When something is cheaper it costs less energy. Energy is the Master Resource and becomes primary determinant of the price the more we move forward in automation of production.
@Stephen Rasey on March 10, 2013 at 9:16 pm
Thank you for that feedback. The costs were something I had no idea about on the scale involved. I wonder if dead wells could be sealed at the bottom and used for storage of compressed air. Why did you use CO2 in your example? Is there something inherent in its properties that make it conducive to compression more than normal air? I hadn’t expected to compress the air to a liquid just to store it at high pressure to use it to run turbines to take up slack in electricity production for peak usage. Once again I thank you.
@Walter:
I was using CO2 initially to see if I could get it liquify at high pressure. Alas the critical temperature prevents it from being stored as a liquid or solid. At best, it will be a supercritical fluid.
And that might be good enough.
http://www.peacesoftware.de/einigewerte/calc_co2.php5
I found this CO2 properties website where you can plug in pressure and temp and get back density plus a dozen other parameters.
At 40 deg C With pressures of 60, 70, 80, 90, 100, 110, 120 bar
gives densities in kg/m^3 of: 149, 198, 278, 485, 629, 659, 689.
so there is a point around 90 atm where you can stuff CO2 down the pipe without a great increase in pressure. You can more than double the amount of gas down hole between 80 and 100 atm. This might make it a very good gas for energy storage. Most of the energy will come back out at 80+ atmospheres without much decay for the first 80% of the energy input. That sounds promising to me….. technically speaking. the economics are still dubious.
Compressed Air at 120 bar, 40 deg C gives 132 kg/m^3 and 60 bar is 67 km/m^3, so it is very linear in the feasible range, at lot less energy storage available than CO2. 200 bar is 214 kg/m3. 300 atm is 300 kg/m3. 400atm is 370 kg/m3.
You could use CO2 from a coal fired powerplant but use solar or wind to compress the gas downhole whenever you have too much solar or wind power to use…. (HA! What a concept!)
As for using depleted wells instead of drilling new ones…. hadn’t thought of that.
120 atm would be 1800 psi…. I’ve seen 18 5/8 casing listed at 198 bar for burst pressure. (Modern Well Design p137 in Google books) Air would be the only gas available at a soon to be abandoned well and Air looks much worse than CO2 economically. You can get higher pressures at smaller diameters, but then you are storing less gas.
I see your point about air not being as good and I guessed that it might have something to do with its density so I looked up another atmospheric gas, argon, which has a higher density than co2. The site you sent me to had a calc for co2 and for nitrogen (which fared little better than air but no calc for argon. So I hand this back to you because you have the knowledge of which I have a severe lack. Both argon and co2 are easily made or extracted so a small mobile plant could be set up on site to produce either using solar and/or wind to run it and put it in the hole then to power the recycling of the spent gas back into the hole.There are hundreds of thousands of oil wells in the US so it wouldn’t be hard to find one to test this on.
Walter, getting argon out of the air would be very expensive in energy use. I was using CO2 only as a semi-sequestration from a CO2 rich source, such as a coal plant. The only working fluid practical for existing wells that dot the country would be plain old air.
I meant “semi-sequestration” as in a temporary storage of CO2 under pressure from flue-gas and then release it to the atmosphere when power demand needed it. But it is just a exercise in physics. Economically it is a dead end. It is far better to crank up the coal plants to meet demand. Using the well doesn’t reduce the amount of CO2 released, only when it is released.
Ok, I see what you were thinking. I was looking at it more as a battery to store solar and wind power without having to actually build batteries. The wind power to load the tubes wouldn’t have to generate electricity as it could pump the air straight into the hole and a network of piping and automatic switching would connect a group of wells together creating a large battery bank. I’m less enthused with solar unless they were hot line collectors generating steam to run a mechanical pump. At any rate the inconsistent power production of wind and solar would be somewhat mitigated by combining both systems at a site and by the volume of high pressure air available to run the generators.