Thermochromic Glazing for “Zero Net Energy”
House
R.E.Arutjunjan*, T.S.Markova**, I.Y.Halopenen***, I.K.Maksimov***, A.I.Tutunnikov**, O.V.Yanush**.
*
ZAO METROBOR, **Technological University of Plant Polymers, *** BorGlass, St.-Petersburg, Russia
Keywords
1 = Dynamic control of solar energy 2 = “Smart window” 3 = Thermochromic laminated glass
4 = Heat transfer modelling
Abstract in summer even in Northern European “Zero net energy” (ZNE) homes provide
climates. most of their own energy, so the
Thermochromic laminated glazing
It is well known that half of the economic benefit to owners is free
(TLG) enables to regulate daylight
energy consumed throughout the energy provided by the ZNE design
automatically adapting dynamically
developed world is used to heat, cool and thermochromic technologies.
to the continuously changing climatic
and light buildings. Power supply It is possible to design a ZNE home
Poster 14
conditions, aids in reducing the energy
sector is not only the primary source to support several types of cottage
needs of a building and providing
of electrical and thermal energy but industry, so the homes help the owners
thermal comfort. Neither electrical
the main source of greenhouse gases generate income.
power nor driving unit are required. The
– caused principally by the burning of So TLG can solve the problem
polymeric interlayer of TLG is doped
fossil fuels as well. In Russia fuel and concerned creation of energy conserving
with complexes of transition metals,
energy complex emits about 70 per glass whose properties and activity are
which change their coordination and
cent of the total volume of greenhouse affected by external stimuli.
transmission or colour of the film under
gases.
influence of light and heat fluxes. Now
Use of “smart windows” in building Dynamic solar control and
we have neutral colour conversions
constructions can significantly reduce effectiveness of TLG
from light to dark (grey or brown) and
energy consumption and carbon dioxide
coloured ones from rosy or yellow to Materials and technology
(the main contributor to the greenhouse
blue and green at our disposal.
effect) emissions, retain energy in New developed thermochromic
In combination with Low-E glass, TLG
building. The ecological goal of “smart laminated glass “glass-pane –
makes possible to create regulated cover
window” is to exploit solar energy thermochromic interlayer – glass-pane”
heating for “zero net energy” houses
resources to meet the energy needs of (TLG) with variable transmission includes
(“intelligent facades”). Energy modelling
a building. polymeric interlayer, which is doped
of the heat-transfer in ventilated
“Smart” glazing can be divided with complexes of transition metals (Fe,
facades has shown that TLG can provide
into some major categories: non- Cu, Cr, Co etc.).
decrease of 15-30% in the building
electrically activated (photochromic The change of the complexes
energy consumption during the winter
and thermochromic) and electrically coordination occurs under influence
heating time in climatic conditions of
activated types. The most popular and of light or heat fluxes, that results in
some regions in Russia. During summer
most complicated is electrochromic. reversible change of transmission and/
time the reduction of solar energy gain
The electrically activated devices have or colour of TLG. At present we have
reaches 30-40% and it is enough to get
the advantage of automatic control. conversions from light grey or brown to
rid of air-conditioning at all.
For the electronically switchable dark grey or brown and coloured ones
technologies, costs are probably in the from rosy or yellow to blue or green at
Introduction our disposal.
range of several hundreds US$/m2. As
Glazing with changing optical and to photochromic glass it is not presently Thermochromic interlayer is
thermal properties called as “Variable produced in sufficient sizes or at low synthesized on the water-soluble
Transmission Windows” has been enough cost (about 500 US$/m2) to polymer base at 900C. The hot
desired for many years. Such product allow its use in buildings or cars. polymeric melt is extruded through
offering the best balance between heat Thermochromic laminated glazing the draw plate onto unadhereable
loss and solar energy gain is the most (TLG) developed in TUPP is a “smart” underlying material or directly on the
appropriate. “Intelligent facades” with glazing that regulates the entry glass. The drying process is controlled
“smart glazing” should be dynamic and of light on a programmable and over with spectroscopy. Thickness of
flexible to exterior environment and automatic basis. No electrical power, the film is within 0.3-1 mm. The value
occupant needs and desires and also be or other power is needed to operate of adhesion can be varied within the
able to reduce energy requirements. the thermochromic system. Use of interval 1-20 kg/cm.
So far, glass technology aiming to thermochromic material allows the Water-soluble thermochromic
reduce the energy needs of a building creation of “intelligent” windows interlayer must be protected against
has largely used passive materials (tinted and facades. These techniques allow exposure to the atmosphere. For this
glass), whose properties do not change building, with extensive glazing, to purpose earlier we developed “glass-
with climatic conditions. Their chief adapt dynamically and continuously to pane – thermochromic interlayer
disadvantages are that they become ever changing climatic conditions - and – curable resin – glass-pane” type of
warm themselves and visibly coloured. thereby minimize energy requirements. TLG from resin laminating technology.
In regions such as Northern Europe Thermochromic materials are affordable However, flat TLG can be produced
where high visible light transmission is and have a service life of over dozen more cheaply using the autoclave
favoured it is undesirable because of years. Cost of TLG can be estimated at process than a resin laminating process
unattractiveness of tinted glass in winter 50 US$/m2. In combination with Low- requiring additional materials and
low light conditions. Besides, tinted E glass, TLG makes possible to create equipment (a filling table, a curing area,
glazed buildings have drawbacks of regulated cover heating for “zero net an uniform source of UV radiation). Now
heat losses in winter and overheating energy” houses (“intelligent facades”). we have worked out the technology of
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thermochromic films autoclaving under on photochromic and electrochromic of the heat-transfer throw this type of
heat and pressure, similar to known one base TLG is produced significantly more IG-unit was carried out under condition
for PVB foil. We have achieved higher cheaply. Contrary to photochromic air-mass 2. It was shown that the
level of interlayer thermoplasticity using glazing TLG is manufactured using lower temperature of external pane rises from
plasticizers that in turn lets us laminate temperatures and more cheaply raw 45 to 600C under increasing of outside
TLG at reduced and readily available materials. Compared to electrochromic air temperature in the interval 25-350C.
temperatures (<1000C). glazing, TLG is characterized by simple The calculation suggests 33-42% air
design, feasibility of large glass area conditioning power can be saved by the
Daylight Regulation and Advantages production and having no regulatory IG-unit supplied with TLG in the climatic
of TLG imperative. conditions of the middle latitudes (550)
Chief advantages of TLG are the in Russia in summer time.
TLG enables to regulate daylight
following: daylight regulation adapted As a contrast to tinted or coated
automatically, adapting dynamically
on a programmable and automatic basis glass products TLG has non linear
to the continuously changing climatic
without using of any electrical power or glazing square dependence of
conditions, aids in reducing the energy
driving unit, no blinding effect; simple thermochromic efficiency (fig.3.). The
needs of a building and providing
design, cheap laminating technology same value of illuminance inside of the
thermal comfort. Neither electrical
and raw materials, feasibility of large room realised with different squares
power nor driving units are required.
glazing area production, high material of glazing will be reduced (as solar
TLG can be also used in exterior and
UV-stability established by UV-testing, radiation increases) to a greater extent
interior design as a vitrage consisted of
cyclic recurrence unlimited in number, for greater square of glazing. So the
elements with changing colour.
storage in a wide range from –500C to more square the glazing the more
One of the major trends expected in
+800C. effective the TLG operating work.
Poster 14
the area of “Smart windows” was the
development of colour-neutral products.
Calculations of TLG effectiveness Another implications for window glass
At present we have conversions from
design
slightly grey or slightly green to dark From properties of thermochromic
grey, from lightly brown to dark brown, material described above it is clear Another area of application is a design
from pink to blue, and from yellow to that the energy efficiency of a glazing of stained glass panels. The picture of
green at our disposal. system can be improved by using of the stained glass panel assembled out
The energy-efficient glass market is TLG unit as an outdoor pane of IG- of coloured thermochromic laminated
currently driven by U-value decreasing. unit. Estimation for energy saving was glasses will change its image during a
As it is known it is necessary to decrease performed based on reduction of total day.
the solar gain in the South latitude to energy admittance from glazing system It is shown that complexes of
avoid overheating of the room. But before and after the TLG was installed. transition metals providing TLG
local building codes of some cities The parameters needed were shading properties can be used as dyes for
(San Francisco, Calgary, Singapore coefficient and U factors, daily average photo-curable resins, for example, for
etc.) limits the visible reflectivity to solar radiation data of the location, colouring resins such as “Naftolan
less than 20% or lower. This leads to room and outdoor temperatures, solar UV11” of Chemetall GmbH, “PK-P1”
inevitable warming up of the window exposure hours.
and that is the best condition for TLG The course of the temperature from
operating with high efficiency because the outside (tout) to the inside (tin) across
TLG absorbs visible and near infrared an IG-unit is shown in Fig.1. The basic
rays and then reradiates energy in far equation of the total heat admission
infrared region. through IG-unit for estimation of daily
In winter in regions such as Northern power consumption saving by TLG is:
Europe it is desirable to increase the
total solar heat transmittance of the Q = T(tTLG, s) · I + U · (tTLG −tin) (1)
window for the purpose of decreasing tout
“effective U-value”. In the same place in where T(tTLG,s) is total solar heat tTLG
summer more expensive air conditioning transmittance as a function of TLG
will induce to increase solar control. temperature tTLG (see Fig.2) and an angle
Considering that our TLG is responsive s of incidence of the sun rays. I is local TLG tin
to both the temperature and light flux solar radiation at specific orientation,
this contradiction can be resolved. In obtained from meteorological service.
winter because of the low temperature U is a total heat transfer coefficient
(T<200C) outside TLG will constantly depending on the temperature Figure 1.
have the maximum light transmittance, of different parts of IG-unit in a Illustration of heat transmittance calculation.
and in summer (T>200C) TLG will complicated way. tTLG, tin are TLG and tout, tin, tTLG are outdoor, indoor, and TLG tem-
normally regulate transmittance, indoor temperatures. Energy modelling perature.
protecting from overheating.
In combination with Low-e coating
Fig.2.
TLG can serve for “zero net energy”
houses (“Intelligent facades”). In winter Temperature depend-
ent visible spectra of
solar energy through clear TLG will heat TLG interlayer of neu-
a wall and the energy accumulated by tral type in the wave-
the wall remains inside owing to Low- length range 400-700
nm. The temperature
e. In summer time TLG transforms the (t, 0C) is given on
solar energy into heat, which will be each curve.
reflected by Low-e in far infrared region
without blinding effect.
This product is toxic-free. Service
life of TLG is several dozen of years.
Thermochromic dyes consumption
ranges from 2 to 20 g/m2. Cost of TLG
can be evaluated at 50 US$/m2. As a
contrast to available “smart glazing”
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of AOZT Bikos and some others in pink, Fig.3.
rosy, brown, yellow-green, blue, and Reduction of integral
their combinations. Dye consumption transmittance (T20 C /
T60 C) under influence
ranges from 2 to 20 g/m2 depending of light or heat radia-
on intensity of the colour. Cost of these tion as a function of
tinted laminated glass is estimated at 30 initial light transmit-
tance. (1) - TLG of
US$/m2. brown type, (2) - TLG
of grey type, (3) - TLG
Conclusions of rosy-blue type.
A new type of variable transmittance
window for automatic regulation of
lighting is proposed. TLG is a laminated
glass or glasspackage in which the
inner polymer layer has the property of
reversibly change light transmittance
under influence of light or heat
radiation. The colour of TLG may vary
from slightly grey or slightly green to
dark grey, from lightly brown to dark
brown, from pink to blue, and from
yellow to green and some others.
Poster 14
The picture of the stained glass panel
assembled out of TLG will change its cover heating for “zero net energy” summer time the reduction of solar
image during the day. houses (“intelligent facades”). Energy energy gain reaches 30-40% and it is
In combination with Low-E glass, modelling of the heat-transfer in IG- enough to get rid of air-conditioning at
TLG makes possible to create regulated units with TLG has shown that during all.
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