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The article isn't very clear. The car still has a battery, this goes in the stationary charging system. It's used to increase the current when charging electri
by joshe 8y ago
The article isn't very clear.
The car still has a battery, this goes in the stationary charging system. It's used to increase the current when charging electric batteries. Most electric batteries can accept much more current than commercial electricity drops can provide. This system stores the current in stationary flywheels and then discharges it quickly when a car pulls up and plugs in.
So this provides something like a Tesla super charger, without having to call up the power company to rewire your gas station. They call it a "Kinetic Battery". In the video below, the CEO makes the claim that flywheels are much better for this because you can get many more discharge/charge cycles out of flywheels than with chemical batteries.
You can imagine that rewiring electric infrastructure all over the country would be quite a bit more expensive than just plugging in their system. You could also imagine a solar powered system (off the grid even) slowly being charged and then recharging a car in 10 minutes.
Cool idea!
Interview with CEO https://www.youtube.com/watch?v=YxRfPtYmTDE https://www.youtube.com/watch?v=YxRfPtYmTDE
- desireco42 8y agoThank you for explaining clearly what article failed to mention. I assumed some of this, but not the whole.
- kibwen 8y ago> Most electric batteries can accept much more current than commercial electricity drops can provide. Just how much headroom is there? I'm under the impression that avoiding excessive heat is the key to battery longevity, so the question is whether or not this extra current increases heat levels to degrees that will have a measurable negative impact on the long-term capacity of the battery.
- vvanders 8y agoDepends on C values, thermal limits, etc. The single data point I have of 75k miles, once a week charging at 120kW from ~20% -> 60% shows very little degradation to the pack on our Model S. Also, when it's warmer out I've seen warnings that in-cabin AC is lowered to divert to help cool the pack so I'm sure it's a question of thermals + number of parallel modules.
- tigershark 8y agoAccordingly to Musk the limit charge power for the Tesla in the future superchargers is around 200kw if I remember correctly.
- rory096 8y agoBut Tesla limits supercharging after too many cycles: https://electrek.co/2017/05/07/tesla-limits-supercharging-speed-number-charges/ https://electrek.co/2017/05/07/tesla-limits-supercharging-sp...
- vvanders 8y agoThat's still a lot of DCFC(~20k miles based on 0.33kwH/mi) and even then it's limited down to 90kW from 120kW. FWIW you only see 120kW on the first ~35% of the pack and quickly tapers down to sub 100kW after that approaching home charging speeds for the last 80-100%.
- mikeash 8y agoI believe that turned out to only be for one particular revision of the battery pack.
- joshe 8y agoTLDR; Faster chargers are useful now and more of them would be great! The cells charge in parallel (there are on the order of 15,000 cells in car batteries), so at least right now the charger power is the constraint and not the battery chemistry. The most power you'd ever really need to deliver is maybe 3-400 miles of range in 5 minutes. So at a point, that we are pretty close to, you don't really need to charge any faster. Using Tesla as an example of our current charging constraints: The Level 1 chargers that plugin into a normal outlet are at 2 kW. In-home charging (Level 2) maxes out at about 17 kW, (close to the most the average house circuit can handle). An average gas station or retail parking lot is probably close to this. More likely it is down at 11 kW. At Super chargers, the Model 3 can currently accept a max of 120 kW, and the chargers can put out a max of 200 kW. Tesla has teased doing more, including a Megacharger for their semi's, that seems like it would work at more than 1000 kW. See https://www.teslarati.com/tesla-semi-megacharger-charging-port-close-up-look/ https://www.teslarati.com/tesla-semi-megacharger-charging-po.... And also "Super charger V3" at something more than 350 kW. Very roughly, kW is proportional to how much range you get for the amount of charge time. So 120 kW charging is about 10 times faster than 11 kW Level 2 charging. Also very roughly, a Tesla Model 3 could charge it's 300 mile (75kWh) battery in about 5 minutes at a 1000 kW charging rate. It is worth noting is that this particular need, dumping 75kWh of power in 5 minutes, will exist even as battery technology improves. Fast charging is not gating on electric cars because home and work charging works quite well. But there will be demand for fast charging as a convenience to electric car owners. Good links and details here: https://en.wikipedia.org/wiki/Tesla_Supercharger https://en.wikipedia.org/wiki/Tesla_Supercharger
- _bxg1 8y agoIs it conceivable that the same type of battery could be used in cars as well, or would the capacity/falloff/external forces be too limiting?
- XorNot 8y agoGyroscopic forces are a big problem as is trying to get enough mass.
- marshray 8y agoAngular momentum increases linearly with mass but with the square of the radius. So another key solution to capacity is to increase the size of the flywheel. Obviously there are real limits to this in a car.
- _bxg1 8y agoI could see it being used as a "quick-charge" portion of the capacity. i.e. you have a full-sized battery, but also a small flywheel so that if you're really in a pinch you can rapidly charge enough to get somewhere without waiting for an hour. It'd be like having a small SSD paired with a large HDD.
- Filligree 8y agoYou'd get better results using the same weight for more batteries.
- deleted 8y ago[deleted]
- Johnny555 8y agohttps://en.wikipedia.org/wiki/Flywheel_energy_storage#Transportation https://en.wikipedia.org/wiki/Flywheel_energy_storage#Transp...
- beat 8y agoThere have been experimental race cars from Chrysler, Porsche, and others, using flywheels in hybrid systems.
- davefp 8y ago> This system stores the current in stationary flywheels Well, rotating flywheels. It amazes me just how much energy you can story in a flywheel. They're really neat devices.
- saynay 8y agoI believe Verizon has a datacenter that has a number of 15 ft concrete flywheels that provides emergency power.
- toast0 8y agoThis is a pretty common way to bridge the gap between when utility power drops and when emergency generators are started and ready to handle the load. I believe flywheel systems can be more compact and don't have the same maintenance demands, but may be more limited as to energy capacity and duration of service.
- reaperducer 8y agoDidn't Twitter have one of these on its roof in SoMa? I vaguely remember reading that somewhere.
- sandworm101 8y agoWhat is amazing is the rotational speeds involved. Say the flywheel weighed as much as a tesla. Think of the energy. Say you want to store enough energy so that a tesla can accelerate itself from zero to 100mph ten times. That amount of energy in a flywheel weighing the same as the tesla would mean the flywheel spinning at +/- 1000mph. Either this flywheel weighs hundreds of tons, or it is spinning at supersonic speeds. Either way, you better have some good bearings.
- endymi0n 8y agoThe magical word here is „angular momentum“. The energy that a chunk of mass can store in a flywheel is squared with the distance of that mass to the center of its rotation axis. If you distribute the Tesla sized mass around the edges of a 4m sized Flywheel now (spare a few % for the wheel and structural support), it can store quite a few dozen times the energy of the same sized Tesla going the same speed.
- dghughes 8y ago> Most electric batteries can accept much more current than commercial electricity drops can provide. Current or voltage? I thought Telsa Superchargers use higher voltage to charge quicker. More "pressure" (voltage) versus more flow (current).
- juliangoldsmith 8y agoIt would most likely be current in this case. 480V is available commercially, based on a quick search. Tesla batteries seem to provide around 400V. To fully charge an 85 kWh battery in one hour, using a 480V supply, you would need to draw over 177A, assuming perfect efficiency. That is an absolutely ridiculous amount of current, and that would only charge one vehicle.
- kpil 8y agoMy house can load 105A. I sometimes use 120 kWh on a really cold day, so it's not peaking anywhere near that current, at least not for long. I'm not driving 400km every day so the grid will definitely handle it. But there is a lot of potential to reduce network costs if the charger negotiated with the grid.
- juliangoldsmith 8y agoYour house can load 105A, but that's most likely at 120V/220V, and as you said, it doesn't maintain that for long. Based on 120 kWh over 24 hours, your house, on a cold day, draws around 500 W. To fully charge a single 100 kWh battery, like you'd find in a new Model S, in an hour, you would need to draw 100 kW. That would be 200 times the average load on your house, drawn continuously, and that's only to charge one vehicle. Something like a flywheel battery does have a lot of potential to save money, or even earn money, if it communicated with the grid. A large rotating mass could potentially store a lot of energy, and would be increasingly useful with the rise of renewable energy.
- kalenx 8y ago
- mikeash 8y agoTesla already does this in some locations, using stationary li-ion batteries to even out demand with their Superchargers.
- lb1lf 8y ago-We're about to try out the same idea locally, on a larger scale - ferries are about to go electric, the grid is not stiff enough to handle the peak load (4.7MW for 5 minutes every 30 minutes) and hence bunkers (for lack of a better term) containing tons and tons of li-ion batteries are needed to make for a sustainable draw from the grid. The battery storage facilities won't win any architectural awards as they are currently envisioned, but I can't wait to see whether this will actually work reliably; our first few attempts at electric ferries had some teething problems, mostly with the charge process taking too long to establish. The ferries run on a tight schedule; hence charge time dropped significantly as establishment was slow, and ferry batteries slowly depleted over the course of the day. Anyway - 4.7MW translates into some quite massive shore power connectors, and they need to mate quickly and reliably - and when the weather gets rough, everything in the surrounding environment will be soaked in salt water. Interesting times.
- ryanmarsh 8y agoSo now they have a cache invalidation problem, right? When do they move power to the flywheel (friction expires the electrons) and when do they allow for cache misses to hit their connection with the power company?