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What role will supercapacitors play in the design of future energy systems?
By Austin Mori, Senior Business Development Engineer, Business Development and Product Marketing Department, Murata Electronics North America
Within just a handful of years, devices that previously housed no electronics—let alone information processing capabilities—have become increasingly “smart.” To fully realize the benefits of IoT, their performance levels have also improved exponentially.
When a smart device becomes multi-functionalized, it consumes high power at peak operation. Since these devices typically have limited space for a battery, there is an inherent challenge in increasing power when needed. This imbalance between power supply and demand will certainly continue as IoT becomes more ubiquitous.
That said, we must leverage energy storage solutions that are mountable in a small space. Supercapacitors that are both high capacitance and high output can achieve this. When the supercapacitor is used as an auxiliary power supply during peak output, it can reduce the size of the supply units, add a higher output function, and improve overall performance. Sample applications include peak-output auxiliary power supplies for light-emitting diodes (LEDs), compact DC motor devices, smart meters, and Remote Keyless Entry (RKE) systems.
The low-ESR and high-capacitance features of supercapacitors can also stabilize operations by leveling large fluctuations of a power voltage line. Given that, they are ideally suited as a power supply for audio equipment, various communication, security, and healthcare devices. There is tremendous demand for supercapacitors that can deliver low ESR levels in a thin package and discharge electricity with a large output of watts.
Moving forward, portable devices will become more multi-functionalized, downsized, and lightweight. Supercapacitors will enable the performance improvement of such devices by reducing battery load.
By Atsushi Hitomi, Department Head, EDLC-BU, New Business Promotion Center, TDK Corporation
Today’s Wireless Sensor Networks (WSN) are at the core of the Internet of Things (IoT). They are useful in a variety of industrial and consumer applications, such as industrial process monitoring and control, machine health monitoring, and so on.
WSNs are composed of "nodes"—from a few to several hundreds to thousands, where each node is connected to one (or sometimes several) sensors. Currently, WSNs with a limited number of sensors/nodes are typically powered with a primary battery. This becomes problematic, however, when sensor terminal/nodes number in the thousands on the network.
Scientists seeking to solve this problem have powered sensors by combining a secondary battery and an energy harvester, such as a solar cell, piezoelectric generator, and/or thermoelectric (Seebeck) generator. Energy harvesters typically cannot generate a large amount of power, and the secondary battery often requires recharging after every radio wave transmission. In addition, secondary batteries have been found to offer internal resistance that may interrupt sufficient charging by the energy harvesters.
To solve these problems, scientists have developed Electric Double Layer Capacitors (EDLCs, also known as supercapacitors). EDLCs have proven to have longer cyclic lives and offer only minor internal resistance, in contrast to secondary batteries, such as lithium ion batteries. Further, the combination of an EDLC and an energy harvester (e.g., amorphous-silicon film solar-cell) can provide an effective replacement to battery-powered sensor devices.
For networked IoT devices used outdoors, EDLCs also feature excellent temperature characteristics, with the ability to operate under freezing conditions. As a result, EDLCs can support various applications, including acting as secondary batteries for IoT devices used in harsh conditions.
By Eric DeRose, Field Application Engineer, AVX Corporation
Supercapacitors exhibit a unique combination of characteristics, including extremely high pulse power, capacitance densities, rapid charge and discharge capabilities that allow design engineers to achieve significantly extended battery lifespans and back up times when used in conjunction with a secondary battery. As such, supercapacitors are being broadly employed in the energy harvesting, instantaneous power pulse, and power hold-up circuits of a wide variety of next-generation energy systems designed to satisfy increasingly challenging power, size, cost, and efficiency demands.
Supercapacitors are playing a huge role in the development of future renewable energy systems, including: solar, wind, hydropower systems, and even vibrational and RF energy systems. Alternative energy sources are now experiencing high demand due to the economical improvements they enable, but all of these technologies currently suffer from a great deal of wasted energy that supercapacitors can effectively harvest.
Supercapacitors also play an important role in start-stop applications within automotive engines. Typically designed into the power hold-up circuits of these applications, supercapacitors provide critical support for the vehicle restart process to prolong battery life.
Supercapacitors are also being employed in the energy systems of various wearable technologies. Wearables haven’t yet fully matured as a market, but have already gained notable traction in watches, fitness monitors, and offer outstanding potential utilization benefits for applications including: medical devices, military equipment, infotainment electronics, and IoT devices. In these applications, supercapacitors not only extend battery life, which simultaneously enables cost savings resulting from the ability to achieve similar lifetimes with smaller batteries, but also extend the range of transmitted data between devices due to the comparatively low equivalent series resistance (ESR) and correspondingly higher current pulse capabilities of supercapacitors compared to batteries.
In response to the significantly increased employment of supercapacitors across several market sectors, suppliers throughout the passive component industry are striving to further maximize the energy and power density these components offer while continuing to limit their ESR to help engineers achieve even more efficient and effective energy systems.
By Dick Stacey, Battery Gauging Products Systems Engineer, Texas Instruments
More applications will be able to harness the advantages of supercapacitors, which include virtually unlimited charge/recharge cycles and instantaneous discharge. Charging a supercapacitor is much more straightforward than charging a battery.
Consider a system with a large cache critical to its operation that must be stored in nonvolatile memory before it’s lost forever. Moving a large amount of information from a cache into nonvolatile memory creates a large surge in current which many batteries cannot handle due to their internal impedance. In the event of a main power failure, using a supercapacitor enables a large, almost instantaneous energy dump.
Backup power is not limited to cache-to-flash-type operations. Brownouts can cause all sorts of issues for microcontroller systems. Supercapacitors can provide a controlled power down even in during a catastrophic power loss.
Emergency lighting is an example of a system that would benefit from supercapacitor supplemental power. When the source power is out, the backup battery takes over with alerts like lights and sirens, which may be too taxing for the battery, so adding supercapacitors avoids long-term issues such as battery overheating due to large surge currents.
Energy-harvesting applications can benefit from the shrinking size and reduced leakages of supercapacitors as well. Remote sensors that gather data and report back to the main system, possibly through Bluetooth low energy, cellular networks or other wireless systems, can be designed with supercapacitors charged via solar, geothermal or vibration. Charging may take some time with limited energy-harvesting sources, but designers can work out the details during initial system design.
Lastly, supercapacitors enable quick-charge applications. Charging a flashlight can be a very quick process, especially when paired with efficient light-emitting diodes. Other applications benefiting from quick charging times include point-of-sale scanners, electric toothbrushes, electric shavers, laser pointers, power tools, gaming controllers, and IoT products.
By James “Jim” Montgomery, Senior Product Manager,
Embedded Solutions, GE Energy Connections
The historical role of supercapacitors or “supercaps” has been to fill the gap in time between an electrical power failure and the startup of backup generators. The goal is to provide just enough juice to get the backup generator started and stabilized before the generator begins handling the load.
We don’t see that role changing significantly in the future, however, there may be new applications. One such application is the use of supercaps to allow peak shaving, where computing needs occasionally require more power than is available to the computing rack. These typically short-in-duration events are well-suited for supercaps. In this application, supercaps are employed to provide the shortfall of energy during the peak energy demand, providing the extra boost needed during the peak, and then are recharged when the peak demand subsides.
https://www.ecnmag.com/article/2017/04/brainstorm-role-supercapacitors-future-energy-systems
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