You may have heard the term supercapacitor before, or maybe you have an idea about how we use them in everyday life. Many people think they’re related lithium-ion batteries. We’ll outline the basics of supercapacitors vs batteries and break down their advantages and disadvantages as a storage medium.
What is a Supercapacitor?
In short, supercapacitors are high-capacity capacitors. They have higher capacitance and lower voltage limits than other types of capacitors, and functionally, they lie somewhere in between electrolytic capacitors and rechargeable batteries.
What this means in practice is that they:
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Charge much faster than batteries
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Can store much more energy than electrolytic capacitors
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Have a lifespan (measured in charge/discharge cycles) somewhere between the two (more than rechargeable batteries and less than electrolytic capacitors)
For a lifespan comparison, consider that while electrolytic capacitors have an unlimited number of charge cycles, lithium-ion batteries average between 500 and 10,000 cycles. Supercapacitors and ultracapacitors, however, have a lifespan ranging from 100,000 to a million cycles.
Advantages and Disadvantages of Supercapacitors
The benefits of supercapacitors include:
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Balancing energy storage with charge and discharge times. While they can’t store as much energy as a comparably sized lithium-ion battery (they store roughly ¼ the energy by weight), supercapacitors can compensate for that with the speed of charge. In some cases, they’re nearly 1,000x faster than the charge time for a similar-capacity battery.
Some electric toys that use supercapacitors can charge almost instantly. Companies like Nawa are looking to implement the same idea in real electric cars. Imagine electric cars powered by supercapacitors (rather than rechargeable batteries) that could charge to full in less time than it takes to fill a fossil fuel motor with gasoline, rather than the hours of charge time typically required by battery-operated cars.
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Wide-ranging Operating Temperatures. Supercapacitors have a much broader effective operating temperature (from roughly -40F to +150F).
On the other hand, the speed of energy exchange is, in some sense, a bug as well as a flaw. Here are some disadvantages of supercapacitors:
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Self-discharge rate. Supercapacitors aren’t well-suited for long-term energy storage. The discharge rate of supercapacitors is significantly higher than lithium-ion batteries; they can lose as much as 10-20 percent of their charge per day due to self-discharge.
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Gradual voltage loss. While batteries provide a near-constant voltage output until spent, the voltage output of capacitors declines linearly with their charge.
Where are Ultracapacitors Used For?
Ultracapacitors are extraordinarily well suited to any application that expects frequent charge and discharge cycles, extreme operating temperatures, or rapid discharge of high amounts of energy. Here are some exciting applications on the horizon:
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Public Transportation. Hybrid buses and other vehicles (such as small electric cars for ride-sharing) can benefit from supercapacitors’ wide operating temperature. Supercapacitors may help ensure that vehicles will work well even in the dead of winter or the dog days of summer. In China, some hybrid buses already use supercapacitors to boost acceleration, and supercapacitors help trams travel from one stop to the next, recharging at the stations.
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Hybrid supercapacitor-battery. This arrangement would combine the supercapacitor’s rapid energy intake with the battery’s long-term storage abilities, offering the best of both worlds. A successful merging of these technologies would enhance the balance between charge time and range. We would also see exciting possibilities to improve regenerative braking efficiency in everything from electric cars to hybrid trains and construction equipment.
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Extending run times. Run times may seem minor compared to the other applications. But consider the benefits of extending the life of consumer electronics (such as laptops and mobile devices) and stabilizing the power supply in devices that have fluctuating loads. Power tools like electric drills have considerably shorter run times when they employ supercapacitors rather than batteries, but you can recharge them rapidly (in about 90 seconds), making them efficient for on-site job use.
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Power stabilization. Supercapacitors are useful for a variety of power-stabilizing applications like backup systems and power buffers. They provide significant cost savings in uninterruptible power supplies when they replace electrolytic capacitors.
Supercapacitors fall somewhere between traditional electrolytic capacitors and rechargeable batteries in lifespan, energy storage, and efficient operating temperature. They effectively bridge the functional gap between these two technologies and are gaining traction as we develop new ways to use their unique combination of energy exchange and storage abilities. Pairing supercapacitors with batteries in hybrid arrays offers the possibility to get the best of both worlds. We should expect to see supercapacitors more often in the future.
