Researchers at the University of
California’s Berkeley Lab have developed a new type of material which
can selectively control the flow of light and/or heat passing through a
window, thus potentially enabling major energy savings in large office
buildings.
At a time when total spending on heating,
lighting and air conditioning in buildings accounts for close to 40% of
the United States’ annual energy bill, researchers at the
Lawrence Berkeley National Laboratory have
developed a new process for automatically filtering sunlight and
controlling heat influx through windows. A glass compound which can be
triggered to become more opaque – or more impervious to heat-producing
near-infrared light – according to the intensity of the sunlight
striking the window has the potential to generate huge energy cost
savings. In fact a general trend towards ‘smart’ windows has definitely
taken off, and, according to a report from market research and analysis
firm
NanoMarkets,the overall smart windows market will double from a current value of $2.3 billion to $4.7 billion by 2018.
Composite material that controls both light and heat
Glass which is able to change tint and so adapt to variations in the
intensity of natural light has already been on the market for a number
of years. However the new process developed by the Berkeley Lab
researchers makes use of two electrochromic (i.e. which change color
under electrical stimulus) compounds whose combined properties can not
only automatically trigger the window glass to turn more opaque but also
provide a mechanism for blocking the heat from sunlight while still
allowing light to pass through.The glass is made using niobium oxide and
then coated or sprayed with nanocrystals of indium tin oxide, which is
not only highly conductive of electricity but also exhibits the property
of remaining transparent and is already being used in the manufacture
of LCDs and touchscreens. A small burst of electricity will induce the
glass to allow light to pass through but block the heat, while an
increase in the electrical charge will turn the glass completely opaque.
This smart economical system can therefore enable more efficient
regulation of light and heat levels in the building.
Towards smarter buildings
Against the background of widespread attempts to reduce the world’s
energy bill, smart windows appear to offer an efficient alternative for
controlling the energy consumed in heating and air conditioning systems.
The new process claims to be able to filter up to 35% of UV rays
without reducing the light level in a room. However, the materials
needed to make such ‘smart windows’ are still very costly and the
manufacturing process will need to be simplified if the costs involved
are to be justified by the energy savings achieved. Nevertheless the
market for smart windows for both commercial/industrial buildings and
private homes is rising steadily, and recently the French glassmaking
giant Saint-Gobain acquired the Minnesota, US-based start-up
Sage Electrochromicsfor
€80 million, in a move to diversify into smart glass. Given the
considerable cost of the materials involved, Berkeley Lab’s new
electrochromic technology will probably currently appeal mainly to
corporate customers, who could make estimated savings of over 25% on
their firm’s heating and cooling bill.
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