Guest Post by Willis Eschenbach
Inspired by an interesting guest post entitled “An energy model for the future, from the 12th century” over at Judith Curry’s excellent blog, I want to talk a bit about energy storage.
The author of the guest post is partially right. His thesis is that solving the problem of how to store city-sized amounts of electricity would make a very big difference, particularly for intermittent sources like wind and solar. And he’s right, it would. But he’s wrong not to point out how devilishly difficult that goal has been to achieve in the real world.
Storage of electricity is a very strange corner of scientific endeavors. Almost everything in a 2013 car is very different from what was in a 1913 car … except for the battery. Automobile batteries are still lead-acid, and the designs only differ slightly from those of a hundred years ago.
Figure 1. Elements of a lead-acid car battery. SOURCE
Now, we do have nicads and such, but the automobile storage battery is the bellwether for the inexpensive storage of electricity. Cars need a surprisingly large amount of energy to start, particularly if they are balky. If there were a cheaper way to store that big charge, it would be on every car on the planet. Given that huge market, and the obvious profits therein, people have been busting their heads against the problem since before Thomas Edison made his famous statement about automobile batteries.
And despite that century-long huge application of human ingenuity, in 2013 the lead-acid battery still rules. It’s an anomaly, like fusion energy, a puzzle that has proven incredibly hard to solve. Potential solutions have all fallen by the wayside, due to cost, or capacity, or energy density, or dangerous components, or long-term stability, or clogging, or rarity of materials, or a habit of exploding or melting down, or manufacturing difficulties, the number of pitfalls is legion.
So I’ll get excited when we have something other than lead-acid batteries in our cars. Because that will be evidence that we’ve taken the first step … but even that won’t be enough. The other problem is the huge amount of energy we’re talking about. Here’s some back-of-the-envelope figures.
New York City’s electricity consumption averaged over a 24/7/365 basis is on the order of 5 gigawatts (5E+09 watts) continuous. Let’s take a city a tenth of that size, there’s plenty of them on the planet, China alone has dozens and dozens of cities that big, and lets consider how much storage we’d need to provide three days of stored electrical energy for that city. The numbers look like this
5.0E+08 watts continuous times 72 hours equals 3.6E+10 watt-hours of storage times 3.6E+03 seconds/hour gives 1.3E+14 joules of storage needed
So that means we’d need to store 130 terajoules (130E+12 joules) of energy … the only problem is, very few people have an intuitive grasp of how much energy 130 terajoules is, and I’m definitely not one of them.
So let me use a different unit of energy, one that conveys more to me. That unit is “Hiroshima-sized atom bombs”. The first atomic bomb ever used in a war, the Hiroshima bomb released the unheard of, awesome energy of 60 terajoules, enough to flatten a city.
And we’re looking to store about twice that much energy …
I’m sure that you can see the problems with scalability and safety and energy density and resource availability and security for that huge amount of energy.
So while I do like the guest author’s story, and he’s right about the city-sized storage being key … it’s a wicked problem.
Finally, as usual, Judith has put up an interesting post on her interesting blog. I don’t subscribe to a lot of blogs, but hers is near the top of the list. My thanks for her contribution to the ongoing discussion.
w.
PS—Edison’t famous statement about automobile batteries? He was offered big money in those days, something like ten grand from memory, to design and build a better battery for electric automobiles than the lead-acid battery. He took the money and went back to his laboratory. Month after month, there was no news from him. So the businessmen who’d put up the money went to see him. He said he didn’t have the battery, and in fact he didn’t even have the battery design.
Naturally, they accused him of having taken their money and done nothing. No, he assured them, that wasn’t right at all.
He said there had actually been significant progress, because he now knew of more than fifty ways NOT to make a battery for an electric automobile …
Curiously, Edison ended up inventing a nickel-iron-peroxide battery, which was a commercial failure … so even he couldn’t get past lead-acid.
Similarly, we now know hundreds and hundreds of ways not to make a battery for a city. So I suppose that’s progress in Edison’s terms, but after a century the wait’s getting long. I suspect we’ll solve the puzzle eventually, perhaps with something like a vanadium flow battery or whatever, but dang … it’s a slow one.
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Willis, I appreciate the thought butHhroshimas leave me and most people cold (dread). How about converting that into tonnes of gasoline? Then we can picture a storage tank, with that amount of fuel and how long it would keep New York going.
Fairbanks Alaska has a city sized UPS. But it wouldn’t last very long (17 minutes). I make it 11MWH or about 4E10 Joules.
http://www.wired.com/science/discoveries/news/2008/08/dayintech_0827
Lead-acid battery is not the most efficient way of storing energy. The reason why we still use it in our automobiles is that it suits the purpose perfectly but the purpose is not storing large amount of energy. There are numerous criteria to fit: small size and weight, sufficient capacity, resistance to the charge/discharge conditions in cars, and most importantly ability to provide high power output in short time. Efficiency in storing the energy is not among them. Other batteries can store energy much more efficiently but don’t fit the purpose for automobiles.
Wow, just did it, from http://www.evworld.com/library/energy_numbers.pdf, seems it is 200,000 barrels per day of gasoline. Thats the size of a big crude oil tank. 2,000,000 barrels being the capacity of one standard supertanker. So thats one of those every ten days. Thats some battery
From what I understand, the best and most cost effective way to store energy is hold water at a high elevation and discharge it to a lower elevation as is done with water behind damns. Which means that wind and hydroelectric could complement each other well. In fact, I believe Danish wind farms sell much of their excess power when conditions are favorable to other Scandinavian countries who have abundant hydro power, albeit at a loss in many cases. You might think that California might be able to take advantage of its topography, reliable sea breezes and sunshine but they are quite averse to dams.
It’s all about the electrons. They have to stored somewhere. Lots of stored electrons requires lots of heavy space. Simple really. It’s a matter of physics – always will be. That’s what Edison found out.
How about a few thousand 1,000 ton Tungsten fly wheels dotted about the city and rotating at speeds that keep the surfaces just subsonic. That should be about the right order of magnitude.
Obviously try and keep them pointed away from fragile objects in case they get loose…
😉
What would help me to visualise this is, how many car batteries would be needed to store the electricity to power an average home for 3 days in winter, including heating?
Willis Eschenbach,
Great post here and excellent comments on Judith Curry’s thread too. I’ve added several comments to the Judith Curry thread to explain some of the costs and other issues for readers.
WUWT readers might find two charts on the Electricity Storage Association web site interesting ‘per cycle costs’ and ‘capital costs’ ($ per kW and $ per kWh storage capacity).
http://www.electricitystorage.org/technology/storage_technologies/technology_comparison
The ‘per-cycle costs’ chart show that the cost of electricity from batteries is in the order of 10 to 100 times the cost of pumped hydro energy storage. Pumped hydro energy storage is already expensive and not economically viable for storing intermittent power sources, such as from wind and solar power sources.
The ‘Capital Cost’ chart shows that Na-S batteries (the most suitable for large scale at the moment) shows that
– capital cost per unit power ($/kW) = 1,000 – 3,000 (let’s say $2,000/kW)
– capital cost per unit energy storage ($/kWh) = 200 – 1,000 (let’s say $500/kWh)
Let’s do a rough estimate of the cost of energy storage for Willis figures for New York City;
Average power demand = 5 GW @ur momisugly $2,000/kW = $10 billion
Storage capacity required (for 72 hours) = 36 GWh @ur momisugly $500/kWh = $18 billion
Wholesale Cost of Electricity from storage (ref. ‘per-cycle’ cost chart) = 10 c/kWh PLUS the average buy price for renewable energy and transmission @ur momisugly 20 c/kWh = 30 c/kWh (wholesale).
Add distribution and retail costs.
My suspicion these costs are a gross underestimate.
A few things to point out:
1. You mean “Times by 3.6E+03 seconds per day,” not divided by.
2. This problem is already fairly well solved where there is sufficient hydroelectric storage capacity – but the required geography limits its application. Norway is doing quite a good trade in buying cheap excess renewables from the rest of Europe and selling it back later when demand is high. Using the lead-acid battery as a comparison is not terribly relevant – as others have pointed out, it has quite different performance requirements to large-scale storage.
3. Someone mentioned flywheel storage. I think someone was trying this in New York. The major problem seems to be that a mechanical failure in a 1MWHr flywheel at full charge is hard to distinguish from a small bomb.
The other scary aspect of a 1.3E+14 Joule battery is what happens when something (inevitably) goes wrong. A few hundred thousand barrels of gasoline would certainly make a fire to remember in case of an accident, but should your entire battery decide to short you’ll have those “Hiroshimas” of energy released all at once. Just like the real thing, but bigger.
On the plus side, of course, your energy consumption would drop to levels acceptable to any greenie after your demise.
Reckon we’ve got it already – coal, gas, nuclear, oil. More energy than you can shake a stick at with a well established delivery system. Just perfect really
Son of Mulder–
Willis chose a city 1/10 the size of New York or about a million people. So divide his 1.3 X 10^14 by 10^6 to get 1.3 X 10^8 joules. Oddly enough, using Grey Lensman’s link, we find that the very first item on the list of joule equivalents is 1 gallon of gasoline, which is said to contain….1.3 X 10^8 joules.
I haven’t the faintest idea of whether any of this makes any sense, however.
Willis, you have 5.0E+08 watt = 5 Gigawatts.
that should be 5.0E+09. watts. Therefore 1300 TeraJoules.
Coal energy = 6.70 KWH / kg coal
coal with 40% energy conversion = 2.68 KWH / kg coal to elec generation
coal rail car = 100000. kg
coal unit train 100 cars = 2.68E+07 KWH elec gen
coal unit train 100 cars = 1.12 GW-Day elec gen
1 GW-day = 86.40 TeraJoules
coal unit train 100 cars = 96.5 terajoules
So use a coal unit train (converted to electricity at 40%) as an everyday concept for a GW-day or 100 TeraJoule of electrical energy.
Tom, you shouldn’t type ‘small bomb’ into a forum. When you type ‘small bomb’ into the internet, the NSA (or GCHQ if you’re in Britain) will knock on your
Battery storage – like solar, the big breakthrough is just around the corner, and has been for many decades. They just keep butting up against the laws of chemistry and physics, which apparently can be overcome with further research grants
Also, I don’t want to be living anywhere near a large battery array based on current technologies. To describe such a site as hazardous is an understatement. Try, tick, tick, tick. It is much safer, cheaper and more practical to produce electricity as and when it is needed, such as – now here’s an idea – coal, gas or nuclear power on a well managed grid.
For a city, the answer is pretty simple. Electrolyze wastewater to make H2 and O2. Let the O2 go, since you can get it anywhere you have air. It would be better to liquefy the H2 since otherwise the pressure and/or volume get’s quite large. A gallon of gasoline contains 1.3×10^8 J, so we need 10^6 gallons equivalent. Turns out 1 kg of LH2 has almost the same energy as a gallon of gasoline, but takes up 4 gallons of volume. Many cities have million gallon water tanks and we don’t notice them. Storage of sufficient LH2 is on a scale that is practical. Then the question is what to do with the LH2. It’s a half-cell and we could use large scale fuel cells to generate power, or run a gas turbine. With nuclear power it would be worthwhile to work on a LH2 delivery system to run vehicles, and replace gasoline, at least when 1 kg of LH2 has about the same price as a gallon of gasoline.
Haha Jim, they haven’t got me yet.
Thinking about this some more, the Hiroshima bomb is not a very useful comparison, either. It might happen to have around the same energy content, but comparing grid-scale energy supply to something that’s designed to release all its stored energy as quickly as possible is not going to give you an intuitive feel for the problem. How often would I have to set one off to power a city of 1/10th the size of NY? AFAICT, about every 36 hours. To make the sort of hand-waving approximation that Wills seems to love, suppose the bomb released all its energy in 5ms and we need to stretch that to cover 36 hours, so we need to reduce the energy intensity by 36 * 3600 / 0.005 = 25,920,000 times. I had a fairly sketch idea what the energy intensity of an atom bomb looked like in the first place; now I’ve got to divide that by 25 million and I’ve completely lost it.
Could I suggest tons of oil equivalent as an alternative? It’s a kind of standard when talking about large-scale energy.
http://www.forbes.com/sites/markgibbs/2013/05/20/finally-independent-testing-of-rossis-e-cat-cold-fusion-device-maybe-the-world-will-change-after-all/
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.
We need 140,000,000 kg of 400Ah Lithium Batteries just to store 1 GW-day.
That would be the mass of about TEN coal unit trains.
1 coal unit train, filled from Black Thunder and delivered to St. Louis costs about $300,000.
A lithium-ion battery bank big enought to store a GW-day would cost $60,000,000,000.
It is a 200,000 times cheaper the store electrical energy in the form of coal to use on demand than in a lithium-ion battery bank. Finally, you cannot recharge a battery bank 10,000 times before needing to replace it.
Calculations…..
ClaytonPower 400Ah Lithium-ion battery = 5.83 kg/Kwh
1 GW-Day = 24,000,000.00 Kwh
ClaytonPower 400Ah Lithium-ion battery = 140,032,414. kg battery/GW-Day
cost of lithium-ion battery = 2.50 $/whr. (Wikipedia)
cost of lithium-ion battery = 2500.00 $/kwh
cost of lithium-ion battery $60 billion / GW-day
Gasoline pumping stations are dangerous- the design is inherently bad. They’ve had 150 Fires. Much better would be have an internal pipe to deliver the gasoline and external in which take out the air/ fuel fumes so it solidly seats with gas tank. Then anyone could pump almost anything- it would just need somewhere to the vent the gases and perhaps a quick clean of air to get the last of the liquid out the hose.
As others have suggested, the so-called AC Batteries or more properly called Pumped Storage Hydroelectric could provide city-sized energy storage. Some facilities, such as Cabin Creek in Colorado, have more than 300 meters of vertical capacity owing to the mountains in the area, but the Ludington Pumped Storage facility is just 34 m in height, 4 km long and 1.6 km wide. Neither of these facilities is large enough to solve the 500 MW problem for 72 hours (though Ludington is close at 500 MW for ~50 hrs and you need to keep 100 Mm^3 of water laying around).
That is probably safer than storing 600,000 barrels of gasoline as well–and less susceptible to spoilage.
In one of Willis’ prior stories, as we were discussing (read: butting heads) 😉 his (to me, worthwhile) challenges encouraged me to do some digging.
One of the things I found that seemed promising was a hybrid hydro process – “pumped storage”. Water is stored in a reservoir at a higher elevation and released to drive turbines at peak demand times during the day – when electricity is both scarce and at it most expensive. That water is captured and held in a lower elevation reservoir and then pumped back up to the top at night when energy is cheap and relatively plentiful.
Some (not all) of the main, regular generation facilities pretty much must run 24/7 as it would be far more expensive (and difficult in many cases) to stop and start them. The power at night from one of these would effectively be essentially free, as it has to run anyway.
A wiki article notes they recover appx 75-80% of pumping costs in generation from the pumped storage. But again, if the pumping energy is from a fixed traditional plant as I understand they need to run all the time anyway – they need constant load.
“Pumped storage” like this is essentially a big battery – a large reservoir of stored power. They are able to start up quickly and make rapid adjustments in output unlike traditional generation.
More info:
http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
Willis – maybe you could take a look at how much energy could be generated with a modest head difference – maybe say 50 feet – which could be more easily achieved in a “constructed” reservoir system (as opposed say to using natural terrain and damming). How bi and deep a resevoir you’d need. It seems these could also be recreational lakes as well?
Stephen Rasey says:
June 30, 2013 at 12:47 am
Thanks, Stephen. Evidently you weren’t paying attention when I said NYC uses 5 GW, and we were going to use a city a tenth of that size …
w.
Grey Lensman says:
June 29, 2013 at 11:59 pm
Thanks, Lensman, but I picked the unit specifically because a battery with two Hiroshima’s of energy contained in it should make you feel dread … as Steve C. said downthread from you post …
w.