I was just reading a story about a 300 MW lithium ion battery (the worlds largest) that is coming on line in California. Just how large, physically, is such a thing? Accompanying the story is a photo of what is called an electric storage container in France. It appears to be many individual units/batteries/whatever linked together, each with its own cooling fan. What are the limitations or disadvantages to having one large battery as opposed to hundreds or thousands of smaller ones? What hazards do such mega batteries present? Fire? Hazardous waste when used up?
“One large battery” is always made of “hundreds or thousands of smaller ones”. “Battery”, used correctly, is always multiple cells.
AFAIK, none of these super-sized grid storage batteries have any shocking advances in cell tech or battery design, just scaling.
There are some pics in the article below that show the size of a battery pack. At a guess maybe 20’x7’ per pack and they use multiple battery packs (20 in the pic for 100MW but not sure if it needs more and that is just a start).
Maybe this is it?
https://www.spglobal.com/marketintelligence/en/news-insights/latest-news-headlines/52610550
Yep, even in a car battery (something we think of as ‘a big battery’ in everyday terms), there are multiple cells - in part because the normal voltage of a lead acid cell is ~2 volts, so you have to put 6 of them in series to make ~12 volts for a standard car battery. If you want a battery with more current capacity and the same voltage, you put two of these sets of 6 in parallel.
Same with any other type of cell - it’s probably theoretically possible to make a very, very high capacity Lithium cell - like if you just took the design of an 18650 (18mm diameter, 65mm long) and made and an 18650000 instead (18mm diameter, 65 metres long) - it would have the same voltage as any other Lithium cell, except it would be very bad to use - even ignoring the difficulty of manufacture for something like that, it means a lot of the current that you want out of the thing has to flow the whole length of the cell just to get out, so internal resistances and heat dissipation become a serious problem.
Now, it’s absolutely true that “battery” gets used for things which are properly called “cells”. So talking about a pair of “AA batteries” in your TV remote is colloquially common but factually imprecise.
Still, mega-batteries are indeed batteries and made up of thousands of cells. Much of the basic technology in grid storage would be the same as in an electric vehicle pack, a Tesla Powerwall in a house, or even in the battery in your laptop. The needs are the same: managing charging and discharging, cooling, charge leveling, etc.
Sure, but that’s just like using ‘dice’ to refer to a single chance cube - it’s very forgivable, when ‘die’ means to become deceased, as ‘cell’ means a detention room.
It’s not imprecise at all. The definition of “battery” includes single cells, as shown by these definitions from Oxford:
and from Merriam Webster:
Right. Meaning does migrate, colloquially.
From an engineering perspective, the distinction remains valuable and useful. And this is an engineering discussion.
So, what is the limiting/optimum size of the individual cells? For Tesla, mega-battery or whatever?
That is a great question which clearly demonstrates that you’re understanding the engineering issues at play.
And which I’m not qualified to answer, because it’s a bit of a specialty. 
There are folks here who have some experience (or at least did some of the reading) who may address that. However, there’s a real possibility that these new megabattery plans are based on “commodity” (or at least pre-existing) cell technology and the engineering novelty of this is simply scaling up battery pack design, along with multi-battery coordination (since each of those big cabinets is probably one or a few large batteries with their own internal controls).
Yeah, I just did a quick bit of searching on what factors affect the performance of a Lithium cell and the answer is: Factors. Lots of them.
Electrode thickness, porosity, material; electrolyte viscosity, composition, particle size, etc. the list goes on and on.
As gnoitall says, a lot of the projects where you’re seeing the implementation of battery storage, they’re just using what’s commonly manufactured already, I think it’s actually true that the battery packs in Tesla vehicles, for example, are using stacks of 18650 cells - really just like a very big (and physically better engineered) version of the USB power bank you might buy for recharging your phone.
Back to basics. For modern lithium Ion cells, a good number to use for energy density is 260 Watt-hours/kg.
Watt-hours is important, because ‘Watts’ doesn’t tell you anything useful about how much storage there is. For example, you might think that a 100 MW battery system like South Australia’s was pretty big, and could back up a 50MW power plant successfully. But that battery system can only produce 100 MW for about an hour (it has a total energy of 100 MWh). That might be very useful for fast load following so long as the duty cycle is lower than the charge cyvle, but it won’t protect you from, say, a cloudy day if you are reliant on solar power.
Anyway, let’s say a battery has 500 MWh capacity. The cell weight before packaging and structural support etc would be 1,923,076 kg of active material (anode, cathode, binder, electrolyte). That’s an ideal number, and doesn’t includevthe weights of the intermediate chemicals used in production.
These batteries are currently only useful for smoothing energy as supply and demand changes during the day. They do not have anywhere near the capacity to provide true medium or long term storage.
For example, let’s say you wanted to replace the Diablo Canyon power station with solar and wind. Due to unreliability of both, you decide to supplement it with battery backup good for a week of energy if the sun doesn’t shine and the wind doesn’t blow.
Diablo Canyon produces about 18,000 GWh per year, or about 50 GWh per day. So a week’s storage would be 350 GWh.
That’s 1.35 X 10^9 kilograms of batteries for one week of storage for one large power station. That’s roughly the weight of 1.35 million Tesla batteries, but of course by the time you package all those cells the weight would be higher.
For comparison, that’s about the same as the entire production of batteries for Evs per year right now. And Diablo Canyon only provides about 9% of California’s electricity. And a 1 week backup is not nearly enough for a zero-carbon, fully renewable grid. Unless you are going to heavily over-build your grid, you need months worth of backup for winter. That’s simply beyond the scale of what we could feasibly do woth batteries using any current or upcoming battery tech.
So, the 18650 is the optimum size of a single cell? With millions in a mega battery the size Sam_Stone is talking about, some are bound to faulty. What percentage before its a real problem? Or would it just be a miniscule drop in storage capacity? Battery tech has come a long way but it seems it has an ever longer way to go before massive medium/long term storage makes a big impact. That said, who knows what’s just around the corner?
P.S. - Thanks gnoitall but I’m pretty clueless. Curious but lacking in a technical understanding.
I think a lot of that is just the same sort of phenomenon that made AA the most common size for disposable cells - small enough to fit in most things, but with enough capacity to be worthwhile, so they get widely adopted, which drives the market demand up, which drives the unit price down, which encourages further adoption, etc.
It’s also useful from the perspective of being a pedantic wanker who likes to annoy people with unnecessary conceptual precision. Note that this is not at all a judgmental statement. I myself enjoy being a pedantic wanker, and I shall proceed forthwith to annoy my family by asking them to bring a fresh “AAA cell” to feed the television remote.
No. For the Model 3, Tesla switched to the 2170 cell (21mm x 70mm). The total amount of power is a function of the cell volume, so making them bigger means more total power. But apparently they can also get power into and out of the larger ones a bit quicker. I’m not sure, but they may have changed the cell chemistry somewhat for the 2170 to get the better functionality.
They are now transitioning to a larger tabless cell, the 4680, which has 5 times the volume of the 2170.
Again, we trip over the exact meaning of a word. In this case, “battery.”
In any case, I seem to recall reading that when fancy car batteries lose the omph needed to power a car, they enter a secondary market. They are used in static installations as backup devices and so on.
I read about Flow Batteries a while back, but nothing lately. Are they now considered a dead end or still being improved?
I’m not a battery, or cell, engineer, but it sounded promising when I read about it.
Curiously, I can’t see anyone in this thread getting it wrong. A couple of people apparently worrying about that happening, but nothing, apparently, to worry about.