Civil Engineering Reference
In-Depth Information
(Granqvist
2006
,
2012a
). However, a number of recent market analyses indicate
that the time may now be ready for electrochromic glazings to fulfill their long-
term promises and take their proper place as a key technology for near-zero-
energy building refurbishment.
First of all, one should note that the market for flat glass is huge by any
standards: The annual production is about six billion square meters per year and is
predicted to have an annual growth rate of roughly 6 % (Freedoniagroup
2011
).
Most of this is high-quality glass produced by the float process and intended for
use in windows in buildings of different kinds. This glass is also suitable as a
substrate for surface coatings.
Electrochromics is one of the ''green nanotechnologies'' (Smith and Granqvist
2010
), which enjoy intense interest today.
Section 1
, discusses why this is so and
also looks at the electromagnetic radiation in our natural surroundings in order to
define a basis for treating energy-efficient fenestration.
Section 2
outlines a stan-
dard oxide-based ''battery-type'' electrochromic device and treats the materials of
its components; the discussion includes electrochromic oxides and their nanofe-
atures and optical absorption mechanisms, transparent and electrically conducting
contacts, and electrolytes and their functionalization. Some parts of this section go
rather deeply into material science and can be omitted by readers who want to get a
general view of electrochromic glazings.
Section 3
then covers electrochromic
devices with foci on important challenges and on constructions of particular
interest for practical implementation of electrochromic glazing. Some alternatives
to the ''battery-type'' device are touched upon. Concluding remarks are given in
Sect. 4
. Parts of the presentations below are adaptations and updates of earlier,
recent topic chapters by Granqvist (
2013a
,
b
).
1.1 ''Natural'' Radiation and Why Switchable Glazing
is Needed
Windows and glass facades are important for near-zero-energy building refur-
bishment. The fundamental reason why this is so is that they are weak links in the
buildings' energy system and frequently let in or let out too much energy, which
then must be balanced by energy-guzzling cooling or heating. And the solution to
this conundrum is not that the windows must be made small, because we need
windows for visual indoors-outdoors contact and for daylighting, which have been
identified as essential factors for human well-being and for good task performance
in work by Heshong et al. (
2002a
,
b
) and others.
Energy-efficient windows must function in harmony with nature and make good
use of the light and energy that nature offers; therefore, we now turn to the
electromagnetic radiation in our natural surroundings (Granqvist
1981
; Smith and
Granqvist
2010
). Thermal radiation is given by a blackbody spectrum multiplied
by a material-dependent emittance and serves as a suitable starting point. Figure
1
shows that blackbody radiation lies in the 3 \ k \ 50 lm wavelength range for
