Tech Briefs Magazine - April 2021 - 42

Power & Energy

Sorghum, shown here, is a common bioenergy crop and was used in this study. (Credit: Marilyn
Sargent/Berkeley Lab)

how much of a particular bioproduct
would plants need to make in order to
make the process economically feasible?
Researchers gathered information on
a group of well-studied bioproducts that
plants can already effectively produce,

ranging from flavors and fragrances to biodegradable plastic. They then designed
and simulated what it would take to
extract these bioproducts from plant
material in the context of an ethanol
biorefinery. In this setting, valuable bio-

products would be extracted from the
plant, while the remaining plant material would be converted into ethanol.
This helped them answer two important questions: what amount of bioproduct the plant needs to produce in order
to make the process of extracting it
worthwhile and what amount needs to
be made in order to reach the target
ethanol selling price of $2.50 per gallon.
Results showed that the amount plants
need to make is actually quite feasible.
When accumulated at 0.6% of the biomass dry weight, a compound such as
limonene - used in flavor and fragrance
- would offer net economic benefits to
biorefineries. If they can harvest 10 dry
metric tons of sorghum biomass from an
acre of land, they need to recover only
around 130 pounds of limonene from
that biomass. The analysis suggests that
just five commercial-scale biorefineries
could support the entire projected 2025
market demand for limonene.
For more information, contact Laurel
Kellner at lkellner@lbl.gov; 510-590-8034.

Supercapacitors for Wearable Devices
These robust supercapacitors still work when stretched to eight times their original size.
Duke University, Durham, North Carolina and Michigan State University, East Lansing

esearchers have engineered a novel
type of supercapacitor that remains
fully functional even when stretched to
eight times its original size. It does not
exhibit any wear and tear from being
stretched repeatedly and loses only a
few percentage points of energy performance after 10,000 cycles of charg-

ing and discharging. The supercapacitor could be part of a power-independent, stretchable, flexible electronic system for applications such as wearable
electronics or biomedical devices.
A supercapacitor (also sometimes referred to as an ultracapacitor) stores
energy like a battery but with some impor-

When carbon nanotube forests are placed on an elastomer substrate pre-stretched in two directions, it creates a maze of spaghetti instead of rows, improving the stretchable supercapacitor's
performance. (Credit: Duke University)

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tant differences. Unlike batteries, which
store energy chemically and generate
charges through chemical reactions, an
electrostatic double-layer supercapacitor
(EDLSC) stores energy through charge
separation and cannot create its own electricity. It must be charged from an outside
source. During charging, electrons are
built up on one part of the device and
removed from the other, so that when the
two sides are connected, electricity quickly flows between them.
Also unlike batteries, supercapacitors
are able to discharge their energy in
short but massive bursts, rather than
through a long, slow trickle. They can
also charge and discharge much faster
than a battery and tolerate many more
charge-discharge cycles than a rechargeable battery. This makes them perfect
for short, high-power applications such
as setting off the flash in a camera or the
amplifiers in a stereo. But most supercapacitors are just as hard and brittle as
any other component on a circuit board.
The new stamp-sized supercapacitor
can carry more than two volts. When connecting four together, as many devices
Tech Briefs, April 2021

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Tech Briefs Magazine - April 2021

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