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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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.