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MIT Develops Fast Charging Liquid Flow Batteries
An anonymous reader sends this from the MIT News office:
"A radically new approach to the design of batteries, developed by researchers at MIT, could provide a lightweight and inexpensive alternative to existing batteries for electric vehicles and the power grid. The technology could even make 'refueling' such batteries as quick and easy as pumping gas into a conventional car (abstract). The new battery relies on an innovative architecture called a semi-solid flow cell, in which solid particles are suspended in a carrier liquid and pumped through the system. In this design, the battery’s active components — the positive and negative electrodes, or cathodes and anodes — are composed of particles suspended in a liquid electrolyte. These two different suspensions are pumped through systems separated by a filter, such as a thin porous membrane."
You beat me to it.
The idea has been around a long time, but making it work is a wholly different kettle of electromotive potential.
Innocent people shouldn't be forced to pay for inferior software development.
--"Code Complete" Microsoft Press
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Don't spill that shit. Imagine the average "I always top off my tank" bone head at a "gas pump" spilling what is basically the first practical, room temprature binary explosive all over the outside of his Jetta. Granted it isn't a proper explosive, it would be more of a flash of heat and electrical potential as the two materials mixed without the interleaving membrane.
As a sealed cell this is a fine idea. As a dispensed material it has "technical issues".
Innocent people shouldn't be forced to pay for inferior software development.
--"Code Complete" Microsoft Press
Well, we are talking scales and scales here. The energy density of gasoline is still about a 100 times higher than that of the best batteries available. And it's not like there hasn't been any research on batteries.
Nitpic: the market for electric model airplanes took off before, with the NiMH cells. Of course, LiPo batteries are a lot nicer still.
It's got electrolytes!
I'm not sure comparing 30lbm propane gas cylinder swaps to swapping batteries is a fair comparison. (Assuming that's what you meant; I'm not aware of anywhere that swaps gasoline cans.)
That said, there are many groups working on swappable battery packs. Part of the problem, though, is that you have structural issues, alignment issues, storage issues (it's a lot easier to store and move liquids than it is 100+ lbm battery packs), matching the correct battery pack to the correct vehicle, and issues like making sure that the terminals don't short to anything during the swap. Liquids also lend themselves much easier to continuous processes where swappable batteries are inherently batch. Managing an inventory of batteries is a lot more difficult than managing a giant tank.
There are pros and cons to both approaches, but in general liquid-based approaches are much more flexible.
"There are a dozen opinions on a matter until you know the truth. Then there is only one." - CS Lewis (paraprhase)
I'm a big believer in the personal freedom offered by owner-driven vehicles, even if the driver is often the only person in the vehicle. Therefore, I am in favor of advanced battery technology that will allow a gradual transition of the world's fleet of personal vehicles to all electric drive rather than gasoline and diesel. Gasoline and diesel require a state of constant war in the Middle East to sustain.
I have a very big issue with what appears to be publicly-funded research being siphoned straight off into some corporate treasuries.
This BS needs to stop. Repeal the Bayh-Dole Act. It has done nothing but harm the public and our economy.
Hard to tell which is more important: groundwater or air. I was actually arguing for sealed batteries as opposed to liquid flow battery juice. Concentrating the job of filling batteries with highly reactive heavy metal containing liquid compounds seems like a job best done in a small number of well-regulated facilities with serious containment and trained, careful personnel rather than at tens of thousands of little stations maybe inspected once every few years with the filling done by commuters in a rush or other careless people. I don't see why you can't have strings of batteries on serpentine chain belts that you can feed into cars while replacing the old ones.
If someone could develop an actual 100% efficient quick-charging battery that could compete with a tank of gas, that would also be great, as well as a complete miracle. The problem without such a battery, and the reason something else is needed, is that the energy transfer rate from a typical gas pump is on the order of 10 MW, which is possible because it's a simple transfer of an inert substance. Charging a chemical battery requires energy conversion. If the conversion is 99% efficient, then that means that, to keep up with a gas pump, around 100 KW of heat is produced, which is a lot of heat to handle without the car melting and the person filling it bursting into flame, not to mention that the 99% efficiency is probably a pipe dream. Aside from that, it means that the electric equivalent of even a small four pump gas station has to be wired for 40 MW (buffering power somehow with ultracapacitors or a flywheel or something sounds doable until you look at what's actually available and do the math and realize they just wouldn't cut it for the usage patterns of a typical gas station) and so does the one right across the street.
There is a reason it's called "topping off" if my father's long-ago explanation is to be believed...
First: there is no "drain hole" in the fuel system (at least in the US etc) since the fuel system is supposed to be vapor tight. There _is_ a small drain hole behind the typical fuel filler door which mostly exists to prevent water from getting caught inside the compartment and rusting things out. That said...
We pump gas _far_ too fast to be environmentally sound. It _froths_ out of the hose in a turbulent flow and a lot of vapor escapes because of the frothing, which is why we now have those vapor recovery hoods etc on a lot of pumps.
When the tank is nearly full, e.g. "as full as it ought to be", the froth boils up the fill-pipe and triggers the back-pressure sensor causing the nozzle to click closed. I few seconds latter the frothing settles and there is now a space in the tank. "Topping off" is the attempt to fill that space.
Back in the before time, that is, before gas was expensive and mileage was important, getting that quarter of a gallon into the car meant getting another three or four miles before needing to fill up. Nobody cared that the net effect was 3 cents of gas gushing out of the pipe and onto the ground because everybody thought "what the heck" because nobody knew that dispersing hydrocarbons did anything but smell nice and industrial. Plus gas fill points were low and typically at the bumper so it didn't even ruin the paint job.
Now days, "topping off" is as bad as it ever was, and worse too boot. The attempt to fill that last little bit not only causes gas to gush out onto your paint job, and pollute the environment, not it also can put liquid gasoline into the vapor recovery system. This can cause the back-pressure valve in the pump to "miss" the fact that froth is rising in the fill tube. You can end up pumping gas right back out of your car and into the gas station tanks ( this costs you money) and then when you separate the nozzle from the car a _lot_ of gas can have collected in that rubber hood thing which then goes everywhere.
Better yet, then next guy will get the same treatment if there is still liquid gas in the vapor recovery system. I filled up my Prius in a bad part of town the other day, and when I pulled the nozzle out, a good 3 cups of gas went everywhere. Some person before me must have "topped off" and that turned the vapor recovery system into a siphon. Who knows how many people that effected before me, and after as now _my_ gas was in the hose for the next guy.
Your gas tank is never supposed to be _full_ by absolute measure. Just like every other container of liquid you have ever dealt with, there is a little space at the top.
Topping off _any_ container is the act of trying to fill that last little bit between "properly full" and "absolutely full" and it _always_ results in waste and spillage due to over-filling.
In my grandfather's age, the tank wasn't full until some spilled out. Topping off was the norm. People still do it because that's how they learned to do it "no matter what the sign says, my daddy showed me good"; this is the law of the dumb.
Innocent people shouldn't be forced to pay for inferior software development.
--"Code Complete" Microsoft Press
Various governments around the world can impose a tax on the liquid, effectively being able to keep that huge income stream intact. When the price at the pump is 75% tax (in my glorious socialist EU country), at 1,70€/liter...
Electric cars can use 20Amp 3-phase chargers to charge the batteries (albeit slowly) without requiring any changes in the electrical systems of a house. This makes government budget centers iffy, since they cannot easily tax you (despite the fact that in many EU countries you already pay for a yearly tax in excess of 150€).
Cars with liquid-rechargeable batteries would allow them to control distribution of the liquid and keep taxing it.
"The new semi-solid flow batteries pioneered by Chiang and colleagues overcome this limitation, providing a 10-fold improvement in energy density over present liquid flow-batteries, and lower-cost manufacturing than conventional lithium-ion batteries."
It's statements like this that make me cringe when I look at the puffery which comes out of academia. 10 * better than A, and cheaper than B. Is it 10 * better than B? Or as good as B? Or (more likely) 1/10th as good as B.
Trick is, a natural gas tank is just a can full of natural gas. and 30 pounds of natural gas is pretty much like any 30 pounds of natural gas.
Batteries, on the other hand, age. As they get older, they hold less energy. So, you take your brand new battery (which you paid a pretty penny for when you bought your new electric car, and which will take your car 200+ miles), and swap it for a five-year-old battery which only holds enough energy for 150 miles. Or 100 miles, if it's a cheap knockoff. Or less, perhaps.
As long as not all batteries are identical in performance, hot-swapping them will only be popular with people who currently have crappy batteries...
"I do not agree with what you say, but I will defend to the death your right to say it"
With a useful load is the real trick to electric anything.
Sure you can have an electric car today. Try loading up 2-3 of your friends, luggage for 4-5 days, to go anywhere?
The few cars that might get 200 mile range are suddenly cut down to 75.
Electric will come when two things happen. Better energy storage, and people get over nuclear power fears. With out nuclear power generation electric cars are worthless. Solar, wind hydro, geothermal, tidal, won't produce enough power to cover current needs, let alone tripling it by 30% of the population using electric cars.
i thought once I was found, but it was only a dream.
If my math is right, you're off by nearly a factor of 10.
To replace every ICE passenger vehicle in America with an EV with double the battery capacity of the Nissan Leaf would increase annual US electric consumption by 40% not a 300% increase by replacing only a third.
Passenger vehicles in US incl SUVs = approx 250,000,000 (2006)
Nissan Leaf battery capacity is 24 kWH so double = 48kWh
Assume full charge every 3 days so annual # of fillups = 120
(The vehicle number is somewhat low but the charging and capacity numbers are high) .384 or 38.4%
Total electricity usage for EVs = 250000000 x 48 kW-hrs x 120 / yr = 1 440 000 000 000 kWh/yr or 1,440,000,000 MWh/yr
Annual US electricity usage for 2009 = 3,750,000,000 MWh/yr
Divide total projected EV usage / Annual current usage =
Not that's current USAGE not current capacity; having only a fraction of those EVs enabled with Vehicle-to-Grid in large population centers would give the grid enormous benefits for distributed storage. Businesses and manufacturing may not be so happy as the cheap or free nighttime power they've enjoyed would become a thing of the past.
Pain is merely failure leaving the body
A fuel cell basically "burns" (uses up) its reagent to make electricity directly.
This (according to the article) is a reversible reaction between two liquids, one acting as an anode and one acting as a cathode, where the reaction is bounded by a membrane. It is really more of the "capacitance gel" idea, only with two carries (which makes sense).
Think of it as two halves of a standard battery that can only interact when brought into proximity. While electrons (or maybe ions or something beyond my simple ability translate, not having seen the research or studied in the field) pass through the membrane by definition, the idea is that the charged medium is not part of the fixed assembly, so the fixed assembly (the reactor and membrane) is permanent while the charged part moves.
In a standard battery the anode and cathode are permanent parts of the battery. When the battery is discharged the whole battery is trashed. For instance, and alkaline battery is assembled in a charged state, the dissolving of the metals in the alkaline solution is what makes the voltage. Lead-acid batteries wear out because the lead is changed by the charging process (applying voltage in the presence of acid solution) and changed back by the discharge. This cycling slowly causes the lead to flake and degrade until there is either so much lead flakes in the battery that a cell shorts out because of the lead connecting the two parts, or the odd chemical impurities and available oxygen slowly make the lead into a chemical that will not react with the acid correctly any more.
In this arrangement the parts that would degrade are in the fluids, draining and replacing the fluids "assembles a new, fully charged battery". In this model the ideal of pulling into a service station and replacing your discharged battery pack with a new, charged one, becomes practical.
In the alternate, as a rechargeable battery the non-solid nature of the battery itself lets the battery be charged and cooled all at once. The anode and cathode material won't "flake" because it isn't sold to begin with. Plus nearly all of the anode and cathode material is used by weight, there is no "inner core" area acting as a superstructure. This should improve the energy density (how many kilowatt hours you can store per pound etc).
In the rechargeable battery usage the battery would probably need to be changed regularly, like an oil change, but _then_ one could probably use charged plates to separate/filter the degraded particles from the good ones, so the "battery" could be recycled in place instead of having to take it back to a factory.
There is a lot potential wins here, but it is _very_ unlike a fuel cell.
Innocent people shouldn't be forced to pay for inferior software development.
--"Code Complete" Microsoft Press
I just read the Advanced Energy Materials article (which you can easily find by googling the title and filtering for pdf).
The idea itself is interesting, and could potentially remove some manufacturing problems (i.e. no need to dry, calender, cut electrodes and then assemble single cells and wire them in a pack) but I see a couple of big flaws in it:
1) Let's get off the table the idea of "refueling". Li-ion batteries are assembled in their discharged state. The slurries containing LiCoO2 and Li4Ti5O12 (as per the article), when put in contact, produce exactly 0 energy. You have to either charge them using electricity, or prepare slurries of Li0.5CoO2 and Li7Ti5O12. Neither of the two materials is stable in air, thus I don't think it's possible to prepare a "refueling" system with current Li-ion battery materials.
2) The beauty of Li-ion batteries is that they have 99.995% efficiency round-trip. This system seems to be based on very thick slurries which probably require strong pumps to circulate in a system, thus killing such efficiency.
3) What's more, the slurries are prepared with highly flammable solvents (dioxolane). Not sure I'd like to carry around two tanks of the stuff, considering that a breach in the separator or in the "fuel" lines could ignite the whole thing.
It is true that changing materials is a simpler problem than designing a completely new system, but as the authors themselves admit this is just a readaptation of an old system.
I think it would be much more practical to redesign redox flow batteries to use non-aqueous electrolytes, thus allowing to work in a larger potential window (water only allows about 1.5V).
I'm not sure things are looking up for A123, and I hope Prof. Chiang won't sink with this idea either. Good luck to all the researchers involved.
It's a bit like where we would be if we had at this moment just discovered petroleum as a viable engine fuel, but for some reason what we actually have in production is tar. Tar has terrible viscosity and it doesn't make a very good fuel, so now the options are to create a full infrastructure creating future fuel lock-in, or handle this a special case while volumes are low and standardize on something sensible later on.
Petrol (gasoline for the Americans), diesel and engine oil are all highly dangerous and extremely harmful to the environment if spilled. We still manage to use them in unimaginable quantities every day without unmanageable problems. I think the toxicity of liquid-based batteries would easily be mitigated by safe storage designs and fool-proof extraction and refilling procedures. Yeah, yeah, I know nothing is fool proof but you can imagine a pair of tubes you have to screw onto your car and an automated retrieval and refilling procedure at fuel stations.
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