vehicles, space-launch vehicles, and portable
electronic devices. By being able to store
and conduct energy on the same wire, heavy,
space-consuming batteries could become a
thing of the past. It is possible to further miniaturize the electronic devices or the space that
has been previously used for batteries could be
used for other purposes. In the case of launch
vehicles, that could potentially lighten the load,
making launches less costly, Thomas says.
Thomas and his team began with a single
copper wire. Then he placed a sheath over the
wire made up of nanowhiskers the team grew on
the outer surface of the copper wire. These whiskers were then treated with a special alloy, which
created an electrode. Two electrodes are needed
for the powerful energy storage. So they had to
figure out a way to create a second electrode.
They did it by adding a thin plastic sheet
around the whiskers and wrapping it around
using a metal sheath after generating nanowhiskers on the second electrode and outer
covering. The layers were then glued together
with a special gel. Because of the insulation,
the inner copper wire retains its ability to
channel energy, but the layers around the wire
independently store powerful energy.
In other words, Thomas and his team created
a supercapacitor on the outside of the copper
wire. Supercapacitors store powerful energy, like
that needed to start a vehicle or heavy-construc-tion equipment.
Although more work needs to be done, Thomas
says the technique should be transferable to other
types of materials. That could lead to specially
treated clothing fibers being able to hold enough
power for big tasks.
Bringing Cheaper, Lighter
Solar Cells Outdoors
Think those flat, glassy solar panels on your
neighbor’s roof are the pinnacle of solar technology? Think again.
Researchers in the University of Toronto’s
Edward S. Rogers Sr. Department of Electrical
& Computer Engineering have designed and
tested a new class of solar-sensitive nanopar-ticle that outshines the current state of the art
employing this new class of technology.
This new form of solid, stable light-sensitive
nanoparticles, called colloidal quantum dots,
could lead to cheaper and more flexible solar
cells, as well as better gas sensors, infrared
lasers, infrared light emitting diodes and more.
The work, led by post-doctoral researcher
Zhijun Ning and Professor Ted Sargent, was
published in Nature Materials.
Collecting sunlight using these tiny colloidal
quantum dots depends on two types of semiconductors: n-type, which are rich in electrons;
and p-type, which are poor in electrons. The
problem? When exposed to the air, n-type
materials bind to oxygen atoms, give up their
electrons, and turn into p-type.
Ning and colleagues modeled and demonstrated a new colloidal quantum dot n-type
material that does not bind to oxygen when
exposed to air.
Maintaining stable n- and p-type layers
simultaneously not only boosts the efficiency of
light absorption, but also opens up a world of
new optoelectronic devices that capitalize on
the best properties of both light and electricity.
For you and me, this means more sophisticated
weather satellites, remote controllers, satellite
communication, or pollution detectors.
“This is a material innovation, that’s the first
part, and with this new material we can build
new device structures,” says Ning. “Iodide is
almost a perfect ligand for these quantum solar
cells with both high efficiency and air stability—
no one has shown that before.”
Ning’s new hybrid n- and p-type material
achieved solar power conversion efficiency
up to eight percent—among the best results
reported to date.
But improved performance is just a start
for this new quantum-dot-based solar cell
architecture. The powerful little dots could be
mixed into inks and painted or printed onto
thin, flexible surfaces, such as roofing shingles,
dramatically lowering the cost and accessibility
of solar power for millions of people.
“The field of colloidal quantum dot photovoltaics requires continued improvement in
absolute performance, or power conversion
efficiency,” says Sargent. This research was
conducted in collaboration with Dalhousie University, King Abdullah University of Science and
Technology, and Huazhong University of Science
Co-authors Zhijun Ning (left) and Oleksandr Voznyy
(right) examine a film coated with colloidal quantum
dots (Photo by Roberta Baker)
and the second position is set to exhaust
at a minimum flow rate when the sash is
closed. To control vapor concentrations
inside fume hoods ANSI/AIHA Z9.5 notes
150 to 375 hood ACH have been used
when attempting to save energy. 6
Auto sash operators close the fume
hood sash with occupancy sensors that
detect when the user is not at the hood
after a set period of time. Combined with
a VAV or a two-position mechanical system that reduces airflow, significant energy
savings can be had. Mott Manufacturing
states a 6-ft hood with a face velocity of
100 fpm could save $1,294 annually with
a closer and VAV system. Sash closers are
not inexpensive and add to the overall cost
of the hood. Some facilities will establish
fume hood sash management plans with
signage and staff training that instruct on
proper sash management in lieu of closers
or in facilities with existing hoods that do
not have closers.
Maintaining a holistic view of fume
hoods and the part they play in the air
management system of a building is the
key to reducing their energy impact. The
fume hood selection, its options and
arrangement within the lab can be optimized; and when working together will
result in significant energy savings for the
1. Energy Use and Savings Potential for
Laboratory Fume Hoods, by Evan Mills
and Dale Sartor, Lawrence Berkeley
National Laboratory, 2006
2. Prudent Practices in the Laboratory:
Handling and Management of Chemical
Hazards, ©2011 National Academy of
3. ANSI/AIHA Z9.5-2012 Laboratory
4. Calculations made using Laurence
Berkeley National Lab Fume Hood Energy
Model Calculator with Boston as the location: http://fumehoodcalculator.lbl.gov/
5. “VAV and Low Flow: Which Strategies Save
More?” 2007 Labs21 presentation by Victor
6. ANSI/AIHA Z9.5-2012 Laboratory
Ronald Blanchard, AIA, LEED, AP
BD+C, is an associate and Andrea Love,
AIA, LEED, AP BD+C, is a building scientist, both with Payette, Boston, Mass.