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Within just a few years, devices that
previously housed no electronics
– let alone information processing
capabilities – have become increasingly
‘smart’, joining the Internet of Things.
To fully realise the benefits of IoT,
intelligent device performance levels
and functionality have increased
exponentially.
Increased functionality, however,
means more complexity and the higher
power-draw that entails. Engineers
have gone to great lengths to minimize
watts dissipated with dynamic modes
of operation such as putting a device
to ‘sleep’ when processing demand
is low, but there are some functions
that need bursts of power, such as
wireless communications or a flash
from an LED. It’s not just micro-
power circuits that need this function;
devices that include small motors,
ranging from coin-cell to cylinder
and laminate types in order of peak
current rating – see Figure 2. The
laminate types in the DMT and DMF
series from Murata are typical for use
in load-levelling applications.
The particular performance of a
supercap comes from its construction.
It has no dielectric like other capacitor
types, but an Electrical Double
Layer (EDL). This is formed from an
interface of active carbon powder and
an electrolyte. The storage of charge
is not by a chemical process but by
the physical movement of ions to the
pores in the carbon layers. The pores
provide a huge surface area for charge
to accumulate, giving capacitance
values in excess of 1 Farad at 5 V
rating. Equivalent Series Resistance
(ESR) values are moderate, typically
50 to 500 milliohms, effectively
What role will supercapacitors play in the design
of future energy systems?
Kunio Nomura , Murata
smart meters and audio amplifiers for
example all need this feature of peak
power capability without a size or cost
overhead.
To size the device battery for these
peak loads is inefficient, bulky and
expensive, so some form of peak load-
levelling is desirable. This is where
supercapacitors come in.
A traditional lithium or alkaline
battery has been a solution, but the
technologies have their limitations.
Compared with batteries, a ‘supercap’
has much higher power density, up to
100,000 times more than a Li-MnO2
coin cell for example. The supercap
wins hands-down for relatively high
power for long periods, and is an order
of magnitude better than the closest
battery performance – see Figure 1.
There are different form-factors of
supercaps for different applications,
40 l New-Tech Magazine Europe