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.”
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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”.