Utility-Scale Energy Storage and Zinc-Air Batteries

Apparently, this company (EOS) has overcome the recharge limitation that exists in conventional zinc-air batteries, and supposedly has several patents on the technology. If true, this technology would be a big boost for all sorts of battery powered technology, not just grid storage. The big question: what is the conversion efficiency? – Anthony

Guest post by Mathias Aarre Mæhlum


Illustration of Eos Aurora, the first zinc-air utility scale battery by Eos Energy Storage. It delivers in a 40 foot standard shipping container.

In the next few years, an increasing amount of wind turbines and solar panels is expected to be built all around the world, reducing the stress that coal, fossil fuels and other polluting methods of harnessing energy does on our environment.

There are several challenges related to the electrical grid we face when solar, wind and other renewable energy sources reaches 10, 15 and 20% of the total useful energy generated. This article focuses solely on energy storage. Why is energy storage important?

Wind and solar energy (other renewable energy sources as well) are highly fluctuating. We are having a hard time predicting the flow of the energy resulting in two main problems:

How can we assure that we have enough energy to satisfy the rate of consumption? Imagine days where the amount of energy harnessed does not reach the demand.  Or if we flip the coin, days where we generate too much electricity and want to store the surplus for times when energy is scarce.

A stable flow of energy is also important. If we are to exchange our current base load energy systems with renewable energy sources, we need some kind of device between the electricity generation and consumer, ensuring a stable and controllable flow.

Batteries have previously not been applicable for utility-scale energy storage. There are several reasons for this, but most important is the price tag. In the last ten years, technological advancements have been made in a battery that utilizes zinc and air as reactants. The key here is that the air comes from the outside rather than acting as a reactant within the battery.

This result in one very interesting thing: Since there is only one reactant in the battery itself, we can expect an increased energy density. In theory, this can be up to ten times the density of ion-lithium batteries. In addition to this, zinc-air batteries are expected to have a lifetime of 30 years. This things all help with lowering the costs, allowing us to use the technology on larger scale.

It looks like zinc-air batteries on utility-scale could be a valuable addition to our renewable energy systems and help us transition towards the smart grid. The first utility-scale zinc-air batteries are promised to be on the market within 2013:


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Sorry, but you lost me when you implied that solar panels and windmills were not “polluting” but that coal and fossil fuels are. Certainly, a gas-powered generating station is hardly a source of pollution, unless you want to count CO2 as “pollution”. On the other hand, windmills are intrinsically visually polluting and otherwise throw off a lot of pollution when built and decommissioned.


Excellent, new patented battery technology. Now an oil company can buy it and sit on it for the next 20 years.

Billy Boumout

Hmmm, another “break-through” in the field of energy tech promising to deliver us unto salvation … yawn.


Zonc-air batteries? 😉
REPLY: typo – fixed -A

If photovoltaic cells were free, their installation costs would still make them cost uncompetitive. Thermal solar is even more expensive. Wind is by far the most variable, and will still need back up generation for the many extended periods when wind generation is not sufficient to bridge the gap between product and demand. Of course, the batteries will not be free, and will add substantial expense to the whole process. One natural gas, next generation coal, or nuclear plant – such as the Liquid Fluoride Thorium Reactor (LFTR) that China, India, and the United States are committing enormous resource to develop – would provide inexpensive power without expensive battery and other generating backup.
Hydro, pressurized gas, and battery storage are not needed, and never will be. Even if the world continues on its Quixotic quest to eliminate CO2, nuclear will always be by far the best option.

John F. Hultquist

Zinc is found underground, usually with other metals such as lead.
Wikipedia claims: “ At the current rate of consumption, these reserves are estimated to be depleted sometime between 2027 and 2055.”
So, along with all the other problems of solar and wind there will be additional mining and a price increase as use ramps up. Somehow this all sounds like a solution for special situations and not one for “utility-scale” deployment. Color me skeptical.

An interesting development, if they can get them to market as advertised, eventually.
But the hype over such developments enabling big wind and big solar is a bit overdone. The problem is the huge expense of being forced to back up intermittent, unreliable power sources.
The expense is huge whether you are using natural gas turbine backup or you are using exorbitantly expensive battery backup such as this technology. And they never include that in “levelised cost comparisons.”
They artificially hold down the proposed costs of the big wind and big solar projects — on paper — until it is too late to do anything about it. Then power consumers are forced to accept huge cost increases as just something to be expected in the new order of things.
At the same time, crafty investors who know how to game the system — such as Warren Buffett — make out like bandits from government subsidies, guarantees, tax breaks, etc. Did you know that 12 of President Obama’s favourite green companies are in big financial trouble, after receiving over $5 billion in federal help? At least 5 are bankrupt, and the others are going down.


What’s a “zonc-air battery”? 😉
Pretty cool if it works well.


I want to believe this is going to happen, I would line up at midnight in a January blizzard outside Bestbuy, Toyota or Obama’s battery factory? But a little voice inside me is singing “Won’t be fooled again”
Dam my skeptical heart!


“In the next few years, an increasing amount of wind turbines and solar panels is expected to be built all around the world, reducing the stress that coal, fossil fuels and other polluting methods of harnessing energy does on our environment.”
Soooooo. Just how and with what are these bird killers and weed collectors being made? Pixie dust and unicorn farts? Ready by 2013?

a jones

I know something about accumulators of many different types. And I keep up with the developments.
I do not know what patents these people have, but I do know about the basic technology. And I have heard such claims time and again. It is a bit like fusion power or a cheaper better solar cell, it is always about thirty years in the future and has been all my life.
Zinc air cells work after a fashion with the particular advantage of offering very high discharge rates which is why they were the pet on one motor car company forty years ago: when electric cars were fashionable the last time around and going to free us from oil. Sound familiar?
Otherwise it is an utterly useless cell with drawbacks too many to mention.
It is just a salesman’s puff presumably to separate wealthy but otherwise innocent investors from their hard earned cash. Or possibly politicians who love to spend other peoples’ money on what they call investment. All of which is nothing new.
It’s balderdash in short.
Kindest Regards


Jake says:
January 16, 2012 at 9:09 pm
“Excellent, new patented battery technology. Now an oil company can buy it and sit on it for the next 20 years.”
You surely have some examples of oil companies doing that, and are happy to provide some links?


John F. Hultquist says:
January 16, 2012 at 9:19 pm
“Zinc is found underground, usually with other metals such as lead.
Wikipedia claims: “ At the current rate of consumption, these reserves are estimated to be depleted sometime between 2027 and 2055.”
So, along with all the other problems of solar and wind there will be additional mining and a price increase as use ramps up.”
When the price goes up, some of the known resources become known reserves, so the date of depletion is a moving target.

For stationary applications, zinc-air batteries may have a significant role. But for “rolling” energy, its problem is the air part. Their volume is far too great for anything on wheels to drag through air-resistance.
All of this will go “Poof” in a couple of years, though. The costs are going to crush renewables and their hangers-on. Britain, especially Scotland, will be at the bottom of the pile.

to explain the “volume” comment above, standard “energy density” stats are given on a per-kg basis. Zinc-air gets rid of lots of the Kgs, but at the expense of puffing up to huge size with air.

Cassandra King

Magic wands, if we invested enough in research and development then by 2100 ish all our problems would be solved. Its just a matter of investment. Pixie dust and wishing on a star could be the answer to our energy needs, and if ET comes calling then the skies the limit. So no need to modernise existing energy tech and utilise current energy stocks because with magic wands and pixie dust and wishing on a star we will all be in wonderland before we can click our heels three times.
Coming back to earth, the USA has enough shale gas reserves to last centuries and the UK has enough coal for gasification to last as long and making both nations future energy hubs, now that is what I call energy security. And in 100yrs who knows what power sources will be available, think back 100yrs and todays tech was not even a dream. What is missing from the energy planning equation is common sense, or for that matter any sense at all, our leaders are living in what can only be described as a mental fantasy island and advised by certified loonies and cretins.
There should be no problem, no worries, no fear, just hope and confidence. But then again the modern political class has found that by selling fear and guilt and uncertainty to the public they can exert a far greater control over us. What we need is a viable hard headed long term policy of real energy security, what we get is an incoherent mess of pseudo science and half baked politically inspired make believe doomed to fail.


In Alberta at 11:11 PM MST Jan 16, wind farms were operating at 1.85% of design capacity!
It will be -30°C across the south tonight and -35 across the north. There is/will be a slight breeze…not enough to make wind turbines spin well, but enough to drop the windchill to -40°C in many places tonight. We can expect the same for a few days.
Gonna take some incredible supply of batteries to keep us from dying. ☺


John F. Hultquist says:
January 16, 2012 at 9:19 pm

Zinc is found underground, usually with other metals such as lead.
Wikipedia claims: “ At the current rate of consumption, these reserves are estimated to be depleted sometime between 2027 and 2055.”

Neither zinc nor lead are at a price point that justifies investment in significant exploration, hence reserves are minimal. Were this technology to catch on and prices increase for either or both metals, there would be a significant increase in the reserve base. Neither of these metals are currently on any “endangered” list.

When we try and look into the future, we forget that history has shown us that most of what we know and enjoy today was not even remotely imagined a hundred years ago.
Our knowledge is growing exponentially. Computing speed is increasing exponentially. Computer size is decreasing exponentially.
To me, this means solutions to problems, such as energy, will be soon be solved, and, those solutions will be exponentially beyond where we are today.
I highly recommend to ayone interested in the future of energy, including energy storage, to take in this lecture:

The future’s so bright, we’re going to wear shades.


Both solar and wind should have been considered for practical application after related technologies such as this have been perfected.
We have still plenty of time, and all the troubles with solar and wind, IMHO, originate in the unnecessary hurry.


Electricity Declines 50% in U.S. as Shale Brings Natural Gas Glut: Energy
I think this battery is going to have a BIG problem. Thanks to fracking, we have NG at less than $2.60 per mm/Btus. which leaves coal, nuclear, wind and PV WAY behind.
“With abundant new supplies of gas making it the cheapest option for new power generation, the largest U.S. wind-energy producer, NextEra Energy Inc. (NEE), has shelved plans for new U.S. wind projects next year and Exelon Corp. (EXC) called off plans to expand two nuclear plants. Michigan utility CMS Energy Corp. (CMS) canceled a $2 billion coal plant after deciding it wasn’t financially viable in a time of “low natural-gas prices linked to expanded shale-gas supplies,” according to a company statement…….”. Wind is only competitive with NG when it is over $6.00 and that will be some time !

This is all pretty redundant now that NASA have finally perfected “cold fusion” http://technologygateway.nasa.gov/media/CC/lenr/lenr.html


Wikipedia claims: “At the current rate of consumption, these reserves are estimated to be depleted sometime between 2027 and 2055.”

According to another source, which appears to be a pamphlet produced by a Swedish mining company: “The best estimates say the world’s reserves of economically recoverable zinc ores are about 3,400 million tonnes, equal to about 400 years of use even if no recycling took place.”

George E. Smith;

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.
An example of the “scale” of some practical full scale renewable energy sources, would be the PV solar cell plant proposed for placement in the waste desert area in the so-Cal to 4-corners region of the USA, which was described in detail in the Jan 2008 issue of Scientific American Journal. Well they described two plants a PV solar cell one and a smaller, about 1/2 size one using a solar furnace of mirrors, and a high pressure steam turbine system, which is a very highly developed technology; aka US Navy nuclear carriers, and submarines. The numbers are classified, but it is believed that practical steam turbines with 40% solar to electrcity is about the limit.
The larger PV plant is 30,000 square miles, while the smaller solar furnace plant is only 16,000 square miles.
To get a grip of approximately what those sized mean; 30,000 square miles is 19.2 million acres. To picture that size, it is 12 times the area of the State of Delaware; well it’s exactly the size of the entire Arctic National Wildlife Reserve.
Actually the 40% efficiency for the mirror solar furnace system is grossly overstated. If you have ever seen a photo of such a plant, such as one in I believe Israel, what is immediately apparent, is that the mirrors will shadow each other, over the range of movement of the sun, so you have to space them very widely apart. There is more empty space, than there is mirror reflectors.
So the incoming solar to electric output is not even close to being 40%; well unless you imagine that there could be some other practical use for the interstitial land; like raising rabbits for food.
There is an inherent problem with solar furnaces, they are limited by the Carnot efficiency, and it is inherently impossible to convert 100% of the “heat” generated in the “working fluid” into electricity.
On the other hand PV solar cells are not so limited, and multijunction, multi bandgap solar cells recently achieved a new record of 43.5% solar EMR to electricity conversion. Offhand I don’t know the solar conditions assumed, but that is publicly available information. Also the crazy folks working on these PV structures, believe that they can reach 60% conversion efficiency; and frankly, I believe they will do exactly that in maybe the next five years. It would not surprise me, if one day they reach 75%. In theory, you can convert 100% of EM radiation to electricity; but in practice, the available material bandgaps and the difficulty of the structures, will keep them a good way below that. The short wavelength end of the stack should be doable with a GaN/InGaN junction, which is coming along nicely at UC Santa Barbara, under the guidance of Shuji Nakamura. I don’t think there is much advantage in going to Aluminum Nitride, because the UV end of the solar near black body spectrum is heavily attenuated in the earth atmosphere, so there can only be dregs to get at with AlN, and the Aluminum alloys are a bitch to work with.
So the bulk of the gain after they get the GaN/InGaN working will be in properly partitioning the longer wavelenght workload. There is a tendency to place too much of the spectrum in the hands of silicon, and some of the short end of that is better moved to the GaN.
At the long wavelength end, there is no need to go beyond about 4 microns.
The cost of these exotic technologies is somewhat irrelevent, since they can operate under many suns insolation. At UC Merced, they have multijunction cells running at hundreds of suns, with non-imaging optical concentrators. So you won’t need acres of the cell materials, which can thus be relatively expensive.
In solar PV, absolutely nothing matters except conversion efficiency (and safety/environment of course). So cheap PV materials that you can spray on a wooden fence from a garden hose for pennies, and get 5-10% efficiency, by plugging a couple of banana jacks into your coated paper tile roof, simply won’t fly. The Solyndra scam was an engineering and science scam, long before it became a finance and political scam. They could have offered those panels for peanuts, and nobody in their right mind would buy one.
If you have solar energy available on land that you own; why the hell would you waste that space on a Rube Goldberg solar system. It’s the land that costs the money.

Reblogged this on pindanpost.


Oh, noes! They’re gonna suck up all our oxygen to make power! (I can’t wait to hear someone say that).


Any idea of the amount of Zinc at $2,000/tonne is in one of these containers?


My opening guess: 75% turnaround efficiency.
Which means that the total energy going into the system and generating capacity would need to increase by up to 25% wherever batteries are involved in delivery. Expensive.


Saltspringson, you are a sod. I watched your link in fascination, He is an ignorant glib conman. Total waste of time.

Awesome article, actually. It is precisely stuff like this that will make solar in particular a viable supply. Right now I could break even on something like 15 year amortization of rooftop covering solar cells. The thing that makes it not really work is the combination of storage and the secondary problem of conversion (and hooking into the power grid to sell surplus back to the power company). The auxiliary hardware is a significant fraction of the cost of solar electrification on a household basis, and the ability to store for nightime use is crucial to people who live or work “off the grid” and want electricity — cabins in the woods, boats, farms, outbuildings. It also lets solar generation interface better with conventional power sources to e.g. pick up the air conditioning overload in summer without needing expensive natural gas generators that can quickly be brought online to buffer clouds and load fluctuations. A big set of batteries can even buffer conventional power generation, and let more power be generated at lower cost during off-peak times and then delivered during the demand peaks.
Hell, I’d invest. I wonder if they will work for laptops, too. I’d LOVE to be able to run a laptop for a day on a charge and not replace the battery for 30 years. Or a cell phone. Or a tablet computer. Or a flashlight. Current rechargable batteries such in so many ways — a whole new technology would be fabulous!


“Both solar and wind should have been considered for practical application after related technologies such as this have been perfected.”
It won’t make much difference over most of the country anyway. You still don’t get enough power from either to justify the expense and they are very fragile power generators. One good storm takes out your generation infrastructure. Compared to nuclear, it is a waste of money.
It makes sense on a small scale, like a house in the boonies or something but not at an industrial scale.


I’ve always pointed out to people that there are hidden costs of these alternative systems. Everyone touts the front end portion, the wind mill or the solar cell. But the back end of this is the energy storage in times when the energy production exceeds demand, how do you safely and cleanly store the excess energy for use later. No ‘greenie’ wants to think about chemical batteries.
The excess energy from these systems can be stored in other ways, not just chemically.
Per Wikipedia on Flywheel Energy Storage:
Flywheel Energy Systems “have long lifetimes (lasting decades with little or no maintenance; full-cycle lifetimes quoted for flywheels range from in excess of 10e5, up to 10e7, cycles of use), high energy densities (100-130 W·h/kg, or 360-500 kJ/kg), and large maximum power outputs. The energy efficiency (ratio of energy out per energy in) of flywheels can be as high as 90%. Typical capacities range from 3 kWh to 133 kWh. Rapid charging of a system occurs in less than 15 minutes.”
But I think one disadvantage is the cost listed in the same article:
Costs of a fully installed flywheel UPS are about $330 per 15 seconds at one kilowatt.
But would that come down with mass production?
So when I pose to ‘greenies’ how much do they want to $pend to save the environment, they always have the suggestions for other people, but never really follow their own advice.

Ehrenfried Loock

There is something interesting about that batterie in a Technology Review article but only poor details about the electrolyte they use, which is surely the main new component. I hope the patents will not be like the “All Vanadium Redox Batterie”-patent which claims nearly the whole organic and inorganic chemistry to be used in the electrolyte.
“Eos’s key advances involve changes in electrolyte chemistry and cell design. Zinc-air batteries typically use potassium hydroxide, a basic solution that absorbs carbon dioxide from the air. That causes potassium carbonate to build up, slowly clogging the cell’s air pores. Because Eos’s batteries use a novel pH-neutral electrolyte, Oster says, they do not absorb carbon dioxide. The company also uses a unique horizontal cell configuration that relies on gravity rather than a physical membrane to separate the liquid electrolyte from the air. The change, he says, prevents buildups on the zinc electrode from rupturing the membrane and causing cell failure.”

John Parsons

Interesting to see all the comments about how we couldn’t imagine the great advances in tech 100 years ago. What? 100 years ago we were burning stuff for energy. Today we are still burning stuff. 10,000 years ago we were burning stuff. If Tony gets his way we’ll be burning stuff til there’s nothing left to burn— or we are all toast. Jp


saltspringson says:
“The future’s so bright, we’re going to wear shades.”
Here at home we’ll play in the city, powered by the sun
Perfect weather for a streamlined world.
There’ll be spandex jackets one for everyone

A just machine to make big decisions,
programmed by fellows with compassion and vision
We’ll be clean when their work is done.
We’ll be eternally free and eternally young

What beautiful world this will be, what a glorious time to be free.

The future looks bright!


saltspringson says:
January 16, 2012 at 10:39 pm
“I highly recommend to ayone interested in the future of energy, including energy storage, to take in this lecture:

The future’s so bright, we’re going to wear shades.”
Using fly ash as part of cement is nothing new. Justin Hall seems to be a typical californian evangelist. Maybe his researchers discover something useful here and there, but the way he makes it sound is like they totally revolutionize everything they touch. I call BS.


Moderators, LamontT @9:17 pm
perhaps meant to correct it to “Zonk”?


Cold fusion gets 11,100,000 strikes on google and Andrea Rossi has got N.I. to herd his E-Cats .
He has delivered the first commercial version, with orders for thirteen more. The domestic version is due in the autumn . The Saudis will go from camels to camels in three generations.

Old Goat

Cassandra, agree 100% with your comments.


….that coal, fossil fuels and other polluting methods of harnessing energy does on our environment.
Intereseting as the post might be.IMO need to be careful doing one column accounting. The column in the ledger regarding the environmental impact of batteries is sorely missing.


Excellent, new patented battery technology. Now an oil company can buy it and sit on it for the next 20 years. By Jake on January 16, 2012 at 9:09 pm
Wow. Conspiracy theory much? I’ve seen ridiculous claims like that for as long as I can remember (and that’s getting to be a pretty long time these days). Like all through the Bush administration (the first one) and the end of the Reagan administration for the matter when we were told that the only reason we didn’t have clean renewables then was because the Reagan had gutted the research money that Carter had put in place to fund the research for our little utopian dream. Well, it’s 35 years since Carter. And back then and stretching into the early 70s and even 60s there were all of these ridiculous “the oil companies” or “the car companies” snatching up technologies and supressing them for profits. Where are these revolutionary technologies? Do you have a single example? All of the patents, if they ever existed and had their patents “snatched up” by Big Oil or the Big 3 (before Big Brother took over two of them – and Jimmy bailed one out in the 70s) those patents have long since expired. Why aren’t we living in the utopian world they promised now?
When I here that line all I can think of is Stephen Hyde sitting in a basement after “self medicating” and raging, “they have a car that runs on water, man!”
Now, if you were being srcastic and I missed, my apoligies.

It so blindingly obvious that it’s astounding no one picks up on this:
The more energy you store in solid state the more dangerous it becomes. No way i am going to live within 10 miles of a 1 terawatt electricity storage facility. A mere car 64 kw battery burns a house down…
The only safe way to store it is in inert fluids such as hydrocarbons that need an external ignition
So the best way to store electricity is to use to turn natural gas into diesel or petrol.
Saves ten problems at once. No need for silly electric cars with batterybombs and zillions of charge systems, but just everything stays the same. No infrastructure changes needed.
but why do it the easy way if you can do it the hard way. Indeed.

You don’t need fancy math to know that storage is not a solution.
If solar and wind were sort of “regularly intermittent”, it could work. If you could always count on wind to blow roughly every other week, or sun to shine roughly every other day, then you could downscale the constant sources and rely on storage for part of your load.
But wind and solar are not even semi-periodic. Nature is whimsical. You can’t count on having enough stored power somewhere in your grid. Even with perfect cheap storage, you still need to build enough constantly running generators to account for your typical full load.

—–Apparently, this company (EOS) has overcome the recharge limitation that exists in conventional zinc-air batteries, and supposedly has several patents on the technology.
—- Anyone have actual patent numbers? I didn’t see any on a casual look at the web site. Do they actually exist?


you had asked the key question right in the introduction – “What is the conversion efficiency?” – and strangely only a single person ventured to comment on that topic (Jordan. his guess: 75%).
Unfortunately, the efficiency for Zinc-Air has an upper theoretical limit of 60% determined by physico-chemical properties, but one might be happy to get out 50% in a final system. This is far below the current best standard of pumped storage hydroelectricity of 75-80%. Lead acid batteries are in the same ballpark, Li-Ion may get up into even the 90s%. NiCd and NiMH are in the 70s%.
But for large scale energy storage you also need cycling stability, i.e. how many times can you go through a charge-discharge cycle before the battery is deteriorated, because the cost of an installation is determined by the cost-per-kWh-storage-capcacity divided by the cyles-tolerated. In terms of cycles Lead Acid (LA) performs rather poorly compared to the other battery types, but then LA batteries are cheaper per kWh-storage capacity. Li-Ion are high in cost but promises to be more cycle tolerant, though that remains to be established on a large deployment. Presently Zinc-Air batteries exhibit VERY low cycle stability, well below that of LA, though this may improve in development.
However, you can’t overcome the efficiency limit, which limits the usefulness particularly to industrial storage deployments, since you always need to feed the batteries twice the kWh you want to extract! This immediately doubles the electricity cost and turns it into a big heat generator!
It may still be acceptable when high energy density (per volume and per weight) is required as in an electric car or other mobile operation. But large scale energy storage – I don’t see a chance.


Hey fellow WUWTs, is this thorium reactor for real or a scam? The guy behind it used to work at NASA. Thanks for feedback, just curious.
Kirk Sorensen: Thorium, an alternative nuclear fuel:


…built all around the world, reducing the stress that coal, fossil fuels and other polluting methods of harnessing energy does on our environment.

Wind turbines do cause pollution many thousands of miles from where you reside.
Toxic lake caused by mining for rare earth elements in China. They are used to make wind turbines.

John F. Hultquist
Re: “Wikipedia claims: “ At the current rate of consumption, these reserves are estimated to be depleted sometime between 2027 and 2055.””
Please quote reliable resources. See USGS documents on Zinc
USGS Mineral
Mineral Commodity Summaries: Zinc

World Resources: Identified zinc resources of the world are about 1.9 billion metric tons.

At the 2010 world production of 12 million metric tons, identified resources would last for 158 years. With an apparent abundant supply, that is just what has been discovered to date.
See also USGS 2009 Mineral Commodity Yearbook: Zinc
Since you brought it up, please take the time to correct Wikipedia citing USGS 2011, 2009.

Just imagine what size battery pack would be needed to back up New York City or Washington for 3-4 days 24 hours a day. After hurricanes there is often a very quiet aftermath of calm, windless, cloudy days. That would be no wind and no solar of any kind. The batteries required would be humungous. Also, such batteries need care and feeding as the work best in a certain temperature range. They are more complicated than first meets the eye.
How many more bandaids are they going to try to put on antiquated wind technology, whose lifetimes are much shorter than advertised, and solar which fails every day and only works well at certain latitudes.