Page 272 - Shaping smarter and more sustainable cities - Striving for sustainable development goals

Requirements of the technology

(i) To be able to harvest energy efficiently
It is required to be able to get a sufficient amount of electricity to move sensing devices, to
process signals and to convey data through wireless networks. For instance, the amount of
electricity produced is relatively small when only one kind of environmental energy source
is used among light, vibrations, heat and radio waves. In contrast to this, when energy is
derived from multiple environmental energy sources, a larger amount of electricity can be
acquired.
(ii) To be small and thin

Sensing devices are to be attached to various mobile objects including the human body and
the number of them is to be enormous. It is required to be small and thin in order to be able
to adapt to wide range of objects and to lessen the environmental burden as much as
possible even if the number of them is huge. It is also required to be able to get enough
output power even though they are small and thin.
(iii) To be more durable

Since sensing devices are to be attached to various mobile objects including the human body,
they are likely to be exposed to various environmental conditions. It is required that they
do not malfunction easily even if they are moved or subject to a wide range of temperatures
or moisture ranges.
(iv) Not to use hazardous substances

The thermoelectric conversion is the direct conversion of temperature differences to
electric voltage. A thermoelectric material creates a voltage when there is a different
temperature on each side. The heavy metals such as bismuth telluride (Bi‐Te) that have
been used widely as the thermoelectric materials are toxic and not environmentally friendly.
Such materials with large negative environmental impacts are not suitable for use in
wireless ICT that is widely distributed to the environment. In contrast to this, for example,
some oxide materials can be used as thermoelectric material with a small negative
environmental impact.

Examples of application area:
(i) Environmental monitoring area
To detect environmental change and occurrence of disasters using environmental sensors.

(ii) Facility management area
To detect troubles in airplanes, automobiles or plants instantaneously.
(iii) Healthcare area
To monitor the user's physical condition constantly by attaching a device to the user's skin,
to provide health guidance from a Cloud application, and to automatically call for an
ambulance in an emergency.

262 ITU‐T's Technical Reports and Specifications