Super capacitors, (like lead-acid batteries) can store large amounts of energy and deliver huge currents. Unlike batteries though, they can be charged as fast as they can be discharged. And they don’t lag too much in terms of energy density.
They are still rather pricey, but not prohibitively so. And they can be charged/discharged more times over their lifetime compared to batteries.
Are there any applications that were previously impossible or impractical with conventional technology that will now benefit from supercaps?
I can think of a few niche uses where a handheld device needing a few minutes’ operating charge would use a supercap more effectively than a battery. Other than that, cost, energy density and likely storage time would be on the side of batteries.
Static RAM backup is the #1 use of super caps.
They don’t have the lifespan limitation of batteries, and they can be recharged almost instantly. They are no good for year-long memory retention, but for power-outage ride-through, they are perfect.
Most fictional notions of “super batteries” are based on a capacitor-like design. (The Riverworld saga’s “batacitors,” late Heinlein “Shipstones” etc.) I’d guess that any real breakthrough in electrical storage will take place along the lines of storing a charge directly, like capacitors, and not in any kind of state or chemical change like batteries. I don’t think extremely high capacity, low-leakage capacitors alone are any revolutionary step along that path, though. We’ve had them for decades and the only change is that they’ve gotten surprisingly compact for large, low-voltage values.
There are a lot of companies/people experimenting with supercaps for regenerative braking. Batteries cannot be charged very fast, and this limits how much energy you can recover from regen braking. Supercaps can be charged much faster, which means more energy recovered. They are more tricky to work with though, since their voltage varies much more than a battery. The i-ELOOP system available for the 2014 Mazda-6 is the first to be commercially available.
On a smaller scale, one application I appreciate personally is the “standlight” feature on dynamo-powered bicycle lights. It keeps the light on for a few minutes after the bike has stopped, so the light stays on while you are stopped at an intersection.
3-phase electric motors being run on single-phase current use bigazz capacitors.
I see it on balers in my industry (paper balers, not hay balers) where the building only has single phase but they need to run a 10hp motor to power a hydraulic pump for a baler.
By bigazz capacitors I mean coke can sized - I don’t know how large you were thinking.
Industrial automation benefits from it a fair bit. For example, preserving power long enough to write processor RAM contents to on-board storage (SD card, etc) so running can resume as soon as power is restored. Power inverters for motors also benefit from anything that stabilizes your output.
Well, there are superscaps, and then there are supercaps.
Some electronic devices employ electrolytic capacitors that have extremely high capacitance values (e.g. 3 farads) and operate at a DC logic level (e.g. 3.3 VDC). These are often called hold up caps, because they “hold up” the rail voltage when the DC power supply is not available for some reason. This is done to maintain the contents in memory, a clock, and/or to maintain some other functionality of the device. On some portable devices, for example, hold up caps will maintain the DC logic rails for a minute or two while the battery is being changed. If the load is extremely light, such as a micropower μP, a hold up cap can maintain power for many days.
And then there are capacitors that are trying to compete with batteries that are used in high power devices like power tools and electric cars. A number of companies are trying to come up with such capacitors, but I don’t believe they’ve even come close to achieving an energy density on par with electrochemical batteries.
Some remote solar powered things use capacitors. Think a train crossing light in the middle of nowhere. You just need a bit of juice once in a while or a tiny trickle amount continuously. Whenever there is a “breakthrough” in nano-graphene-unobtainium capacitors, PV storage is almost always mentioned.
Note that most types of rechargeable batteries don’t do well when temps vary between -40 and 120F.
What I’ve seen based on the energy density in using supercaps to replace batteries you’d want devices that can be recharged more frequently than a battery, however that recharge time is much shorter. So a drill/driver for use at home that can be plugged in somewhere periodically to recharge in a few minutes would work out, but at a remote worksite where you may not be able to readily recharge it would give you too short of a life to be practical.
Newer devices claim long term energy retention, and a lot of lightweight batteries don’t do well with that anyway, but it may not be the kind of thing you’d use in safety device that has to hold a charge over time. They might be better than batteries in safety devices that are usually plugged in but have to operate during intermittent outages because they’re total life is longer than conventional batteries.
These may work well for low power applications where a little extra weight in energy storage doesn’t matter allowing disposable batteries to be eliminated. Something like a wireless mouse might benefit.
The biggest advantage so far is the rapid recharge time. If you need a flashlight for 5 minutes to find something in the attic you could get it charged up in about 5 minutes even if it’s completely dead. But taking a flashlight on a camping trip you probably want something with conventional batteries and a longer active time.
An early application was to build the plot of a 1950’s science fiction movie around a supercapacitor. In This Island Earth, our hero, Dr. Cal Meacham, gets a supercap from an alien civilization, orders some additional parts from the alien’s catalog and proceeds to build an Interocitor to communicate with the alien named Exeter.
I was an instructor in the LORAN school when I was an Electronics Technician in the USCG. We used transmitters with a 3.5 MW output to send signals as an aid to navigation. The signal was bursts of 8 or 9 100 usec pulses. These groups would be transmitted up to 30 times a second. So some pretty herky capacitors were useful to keep the transmitted power up during the burst transmission. They recovered/recharged during the rest period.
Actually there’s nothing preventing you from recharging a cap faster than it is discharged.
Assuming that a flashlight draws 100mA and with the specific cap lasts for 5 minutes of runtime, you can fully recharge the cap with 1Amp for 30 seconds or 2 Amps for 15 seconds.
Many single-phase AC motors are “capacitor start,” which means a separate startup winding and series capacitor are used to initially get the motor spinning. (The capacitor creates a phase shift in the startup winding relative to the main winding. So when the torque created by the main winding is near zero during rotation, the torque created by the startup winding is at or near its peak.) Once the motor is up to speed, the starting winding and capacitor are taken out of the circuit, and the motor runs solely on the main winding. Note that three phase motors don’t require this.
