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It’s a different story when you look
at industrial applications and the
IoT. Firstly, device downtime may
have more serious consequences.
Operators of battery-powered
networks therefore need to monitor
charge levels and periodically
recharge or replace batteries to
ensure uptime.
Secondly, industrial and IoT
deployments typically include tens
or hundreds of devices. Maintaining
this number of batteries represents
a major overhead.
Energy-harvesting: Ideal for the IoT
Energy-harvesting is an ideal way for
IoT kit to reduce or even eliminate
its reliance on batteries. And by
blending this approach with a low-
power design, it’s possible to create
kit that can run almost perpetually.
To achieve this goal, the first step
is to select the most appropriate
means of harvesting energy for
the use case. Solar or thermal may
seem obvious choices, but can
be inconsistent in their delivery of
power. The source of energy needs
to be available when the device is
being used.
At the same time, the device needs
a low-power design – and this goes
beyond simply using low-power
components. Ultimately, it must
be able to operate within a limited
power budget.
An example of good batteryless
device design is the RF-based
contactless smartcard. Inside,
they contain a memory chip and
antenna, which performs the dual
purpose of communicating and
harvesting energy. Most of the time,
the card is ‘off’, and uses no power.
But when it comes within the RF
field of a reader or writer device,
the card is energized, enabling the
reader/writer to communicate with
it wirelessly.
Because the card only needs power
to perform read or write operations,
RF-based energy harvesting is ideal:
there will always be an RF reader/
writer as a source of power. And
if designers keep to standards,
including NFC or RFID, they know
what power budget their card must
work within, which simplifies the
design process.
Smartcards for authentication or
contactless payments represent one
of the biggest and most high-profile
uses of RF energy-harvesting, but
the technique could be used in
many other scenarios. Sensors,
thermometers or even displays can
be powered using RF-harvested
energy.
E-paper: the display
technology that doesn’t
require a battery
Made famous by the Kindle ebook
reader, e-paper is a particularly
interesting
technology
for
manufacturers
of
batteryless
industrial or IoT devices, because it
enables them to incorporate displays
into their designs.
E-paper uses very little power:
where traditional active-matrix LCDs
need a power-hungry backlight to
make the image visible, e-paper uses
electrophoretically charged physical
ink particles to create an image,
off which ambient light can reflect.
Consequently, the content of an
Embedded Solutions
Special Edition
Figure 1: This graph shows the current used during an update to an e-paper display
(Source: Pervasive Displays)
64 l New-Tech Magazine Europe