From electric vehicles to harvested-energy IoT, supercapacitors are helping solve power challenges

By Spencer Chin, contributing editor

Supercapacitors
continue to gain usage as more applications require storing and releasing high
amounts of energy in short periods. The devices, which have two plates soaked
in an electrolyte and are separated by a very thin insulator, store
considerably more energy than conventional capacitors. Compared to batteries,
they have lower overall storage capacity but higher energy density.

The
performance characteristics of supercapacitors are suiting them for
applications requiring a high number of rapid charge and discharge cycles and
for systems implementing energy recovery. These include hybrid-electric vehicles,
wind turbines, rail transit, consumer electronics, and electric grid systems.

Market
research studies continue to project a bright future for the technology. One
recent study, by Zion Market Research of Sarasota, Florida, projects the
supercapacitor market to grow from $684.7 million in 2016 to over $2 billion by
2022, at a compound annual growth rate of 20.5%.

Another
recent study, by Research and Markets, projects the supercapacitor market to
grow at a compound annual growth rate of 18.6% from 2017 through 2022, reaching
$2.44 billion. The study adds that the limitations to more rapid growth include
high supercapacitor prices and the lack of industry-wide experience.

Dr.
Priva Bendale, Senior Director of Applications Engineering at supercapacitor
supplier Maxwell Supercapacitor (San Diego, California), said that
supercapacitor adoption will increase as users become more familiar with the
technology.

“The
industry’s limited understanding of supercapacitor technology, performance, and
perception of high-cost solutions creates barriers for supercapacitor
integration. Through continuing education about products and performance
benefits in a variety of applications, we are overcoming these hurdles and growing
new markets for products.”

Supercapacitor
manufacturers continue to improve the power handling and performance of their
parts. One recent supercapacitor introduction from AVX Corporation (Fountain
Inn, South Carolina), the SCC Series (see Fig.
1
), is rated 2.7 V and delivers capacitance values from 1 F to 3,000 µF and
low ESR from 0.16 to 200 mΩ. The SCC is designed to deliver good pulse-power-handling
characteristics. It can be used alone or in conjunction with primary or
secondary batteries to provide extended backup time, longer battery life, and
instantaneous pulse power as needed. The supercapacitor is available in various
case sizes with diameters from 6.3 to 60 mm, case lengths from 12 to 165 mm,
and a choice of radial, solder pin, or cylindrical leads.

Supercap-Fig-1-AVX-SCC-supercap

Fig. 1: AVX’s SCC Series is rated 2.7 V
and delivers capacitance values from 1 F to 3,000 µF and low ESR from 0.16 to
200 mΩ
.

Nesscap
Energy Inc. (Toronto) has introduced its N60 3-volt (3-V) 3,400-farad
ultracapacitor cell, which, according to the company, delivers 40% more energy
and 42% greater power density compared with the company’s older 2.7-volt 3,000-farad
cell.

According
to the company, the N60 offers a number of benefits to system integrators,
including the ability to scale up system voltages to attain more power and
energy within the size and weight specifications of their existing designs.
Systems can also be designed with fewer cells resulting in smaller size,
reduced weight, and lower cost. N60 may be used as a standalone solution or
integrated with battery technology to achieve optimal power, energy, and cost
parameters, depending on the needs of the application.

Maxwell
Technologies Inc. now offers a 51-V ultracapacitor module (see Fig. 2) that uses the company’s 2.85-V,
3,400-F ultracapacitor to optimize the performance of hybrid buses and other
high-duty-cycle applications. The module is pin-compatible with the company’s
existing 48-V supercapacitor module.

Supercap-Fig-2-Maxwell-supercap-module

Fig. 2: Maxwell’s 51-V ultracapacitor
module uses the company’s 2.85-V, 3,400-F ultracapacitor to optimize the
performance of hybrid buses and other high-duty cycle-applications.

The
ultracapacitor module incorporates an active cooling system that improves the
part’s continuous current rating by nearly 90% and ensures optimal performance
over temperatures from –40°C to 65°C.
It incorporates Maxwell’s proprietary DuraBlue™ Advanced Shock and Vibration
Technology into the design, which provides three times the vibrational
resistance and four times the shock immunity of previous ultracapacitor-based
competitive offerings.

Supercharging portable devices
Supercapacitors
are also targeting portable devices such as wearables and mobile phones to meet
peak power needs. Earlier this year, Murata Manufacturing Co. Ltd. introduced
the DMH Series supercapacitor (Fig. 3).
This part stands just 0.4 mm high to fit in thin devices, yet supplies 35 mF at
4.5 V, which provides an ample boost for lithium-ion batteries. The
supercapacitor achieves an equivalent series resistance of 300 mΩ at 1 kH and
operates over a –40°C to 85°C range.

Supercap-Fig-3-muratadmhsupercap

Fig. 3. Measuring only 0.4 mm high,
Murata’s DMH Series supplies 35 mF at 4.5 V to boost the peak capacity of
lithium-ion batteries.

Along
the same lines, Australia-based CAP-XX earlier this year launched
its first compact cylindrical supercapacitors to provide high performance at
low cost to power IoT industrial and consumer devices, from energy harvesting
for wireless sensors to peak power support for wireless transmissions.

CAP-XX offers single-cell (2.7 V) or
dual-cell (5.4 V) cylindrical supercapacitors in lengths as short as 12 mm long
and available in diameters of 6.3 mm (400 mΩ) and 8 mm (180 mΩ). The largest 400-F
supercapacitor is 68 mm long and 35 mm in diameter (3 mΩ).

Future applications
Scientists
continue to look at new applications and materials for supercapacitors.
Recently, researchers at UCLA and the University of Connecticut developed a biofriendly
energy storage system called a biological supercapacitor, which operates using
charged particles, or ions, from fluids in the human body. The biosupercapacitor
comprises a carbon nanomaterial called graphene layered with modified human
proteins as an electrode, a conductor through which electricity from the energy
harvester can enter or leave.

The
research team envisions the supercapacitor leading to longer-lasting cardiac
pacemakers and other implantable medical devices.

Scientists
are also looking at alternative materials to the conventional carbon, which
require high processing temperatures and the use of harsh chemicals to produce.
Researchers at the Massachusetts Institute of Technology developed a
supercapacitor that uses no conductive carbon, instead employing a series of
metal organic frameworks that provide a large surface area. According to the
researchers, the technology has the potential to produce high-power
supercapacitors with performance comparable to existing carbon-based ones.

For more insight into supercapacitors
and their uses, check out these articles and product briefs from the AspenCore
network:

Supercapacitor boasts large capacity,
low ESR
— Murata has launched what it calls the world’s
lowest-profile 0.4-mm supercapacitor. The DMH Series of supercapacitors is
designed to facilitate peak power assist with lithium-ion batteries in wearable
and other portable devices such as smartphones and smartcards.

Simple-to-use
auto-balancing for supercaps
— Advanced Linear Devices offers a universal PCB designed to automatically
balance leakage currents and manage overvoltage, enabling ultra-low-power usage
in supercapacitors used in a series stack.

High-energy-density
supercapacitors: alternative to battery power storage
— This technology could revolutionize devices that have
previously relied on battery power to operate.

Plug and play your way to
balancing supercapacitors
— Balancing
supercapacitors can be difficult, but a new solution combines all of the
circuitry needed to balance them quickly.

Using a supercapacitor for
power management and energy storage with a small solar cell, Part 1
— This
two-part series will examine solar cell performance, how to select and size the
supercapacitor, requirements of supercapacitor charging circuits, and charging
IC characteristics. Part Two (linked to at end of Part One) includes two case
studies illustrating how to use supercapacitors.