22 - Friday, February 3, 1989 ~ North Shore News

Coming soon: cars
with smart windews

THE AUTOMOBILE industry is
one of the biggest potential mar-
kets for a new ‘‘smart’’ window
being developed by University of
Guelph physics professor Jim
Stevens and Swedish colleagues.

Smart windows will regulate the
transmission of radiant energy,
darkening like tinted glasses when
the sun comes out and bleaching to
transparency when it is overcast.

The windows will be built like a
sandwich, says Stevens. Each win-
dow will consist of two pieces of
glass coated on the inside with a
transparent material that makes
the glass surface conductive. An
electrochromic layer will color and
bleach as charged atoms or ions
move through it.

And in the middle, Stevens’ in-
vention of a solid electrolyte will
cement the two pieces of glass
together and provide a source of
ions.

The system will use a small
power source and a sensing device
to tell the window whether it is
dark or light, says Stevens. In its
bleached state, a smart window
will allow about 80 per cent of the
sun’s radiant energy to pass
through the glass, but will cut the
transmission to about 20 per cent
when tinted.

Other coatings can be added to
make the glass selective as to the
amount of radiation passing
through it, whether ultraviolet,
visible or heat.

The potential savings in air con-
ditioning and heating costs make
the window a natural for use in
automobiles and duildings. Stevens
estimates that the auto industry
worldwide uses 200 million square
metres of glass per year, of which
100 to 130 million square metres
are already treated witn a coating
or laminant.

He says there is also interest in
developing the technology for eye-
glasses, where the power source
would be provided by a tiny built-
in battery much like those used to
operate hearing aids. .

This fall, Stevens received a
three-year, $150,000 strategic stant
from the Natural Sciences and
Engineering Research Council to

continue studies on the chemistry

of the electrolyte. This project ill
use the expertise of physics pro-
fessor Ken Jeffrey and the tech-
nique of nuclear magnetic reso-
hance to study the motion cf the
ions in the electrolyte.

Researchers at Hart Chemicais
Ltd. and Nacan Products Lid. will
collaborate in studying the feasibil-
ity of commercial production.

The polymeric electrolyte, which
makes the smart window work, is
the result of Stevens’ efforts to
find a solid material to replace liq-
uid electrolytes such as those used
in automobile batteries. There is a

worldwide effort to develop a
See Polymesic
Page 24

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