New solar thermal technology can transform ordinary windows into solar-powered heaters that can increase window
temperatures by nearly 15 degrees F. in
cold weather, according to a new study
published in the journal Nano Letters.
The new surfaces utilize tiny plasmonic
nanoantennas made of nickel-aluminum
oxide that are patterned onto glass as an
array. The antennas absorb light, which then
heats the entire surface, potentially offsetting how much additional heating is needed.
The antennas absorb sunlight much more
efficiently than the bare substrate and are
transparent, colorless to the naked eye and
capable of preserving nearly the entire color
spectrum of sunlight.
Cold windows significantly impact building heating requirements because anyone
sitting near them radiates their body heat
toward the cold window, which then necessitates a higher indoor temperature to maintain comfort, explains the research team, led
by Alexandre Dmitriev of the University of
Gothenburg. A warmer window won’t act
That Deliver Heat
HOW REGULAR GLASS WINDOWS CAN
TRANSFORM INTO SUN-POWERED HEATERS
IN COLD WEATHER
as a heat sink, so FMs may be able to turn
down the artificial heating by a few degrees,
potentially saving money.
The research team now aims to achieve
even larger temperature increases by
enabling the nanoantennas to absorb UV
and near-infrared radiation, which make up
a large portion of solar radiation.
RESEARCHER BO SHEN of Oak Ridge National Labo-
ratory works with a prototype window air conditioning
unit that uses propane as its refrigerant.
Refrigerant of Choice
for Small Spaces?
PROTOTYPE WINDOW AC UNIT BEATS
ENERGY STAR EFFICIENCY HIGH MARK
A window air conditioning unit that uses
propane as its refrigerant cooled air
with 17% higher efficiency than the best
comparable ENERGY STAR commercial
unit, according to the Oak Ridge National
Laboratory researchers that designed the
early stage technology.
“Propane offers superior thermodynamic
SOLAR THERMAL WINDOWS powered by nanoantennas heat up when the light hits
them, helping avoid the "heat sink" effect of cold windows. The tiny plasmonic
antennas (a and b) are crafted from nickel-aluminum oxide and patterned onto glass
as an array (c). The end result: a transparent surface that efficiently absorbs sunlight.
properties and creates 700%
less pollution than standard
refrigerants,” says researcher
Brian Fricke. “We developed a
system that takes advantage
of these qualities and reduces
global warming potential.”
Ideal for small office spaces,
the unit includes a novel heat
exchanger, compressor and
controls that require less pro-
pane than similar units that
are already in use overseas.
The Oak Ridge prototype is
the first propane-powered
window air conditioner that
can meet U.S. building safety