Miraculous
Transformation
Techno Talk
Mark Nelson
A famous Biblical story described the transformation of water into wine. Today the closest we can
get to this is turning beer into electricity, which is somewhat less impressive but more consistently
repeatable. That’s not the only weirdness here: we present a new design of battery that is powered
by human bodily fluids. All in the best of taste of course.
Y
ou are probably wondering
why anybody would wish to
turn ale into electricity. That
would surely be a wicked waste of
good beer. It would indeed, but only
if it had been fresh. Unfortunately,
during the lockdown a lot of good
beer passed beyond its drink-by date.
Most of this went down the drain but
an enterprising brewery in Dorset had
the notion of turning this surplus into
green energy, generating enough electricity to power close to 17,000 average
homes for one day.
The futurenetzero.com website relates how the family-owned Hall &
Woodhouse brewery found a sustainable solution for all this expired beer
by using it to generate electricity. It
installed a wastewater treatment plant
that creates biogas, which in turn is
used to generate electricity for powering its packaging lines and utilities.
What’s more, the Blandford Forum
brewery has set monthly targets for its
use of self-generated electricity, in its
aim to become fully carbon neutral.
Declared head brewer, Toby Heasman:
‘Although lockdown meant that many
of our pubs had to return unsold beer
back to the brewery, the silver lining
has been that none of this has gone to
waste. Thanks to our wastewater treatment plant, all of the returned beer has
been used to generate green electricity.’
Health sensors powered by your
own body
In case you were unaware, your fingertips are one of the sweatiest parts
of the body, which is doubtless the
reason why jewellers and conservers
of ancient manuscripts all wear white
gloves. However, if you wear medical
body sensors for tracking your health
and nutrition, you might be pleased
to learn that small biofuel cells can
harvest enough energy from fingertip
sweat to power the sensors all day.
PhD student Lu Yin is one of the engineers at the University of California,
San Diego who have developed a thin,
flexible strip like an Elastoplast that
can be worn on a fingertip to generate
10
small amounts of electricity when a
person’s finger sweats or presses on it.
It’s by no means the first wearable
power source powered by bodily fluids,
but what’s special about this sweat-fuelled device is that it generates power
even while the wearer is asleep or sitting still. In the world of wearables
this is potentially a big deal, because
researchers have now figured out how
to harness the energy that can be extracted from human sweat produced
even when a person is not moving.
Says Yin, ‘Unlike other sweat-powered wearables, this one requires no
exercise, no physical input from the
wearer in order to be useful. This work
is a step forward to making wearables
more practical, convenient and accessible for the everyday person. It also
generates extra power from light finger presses – activities such as typing,
texting, playing the piano or tapping
in Morse code can also become sources of energy.’
A key differentiator of this latest
energy harvesting technology is that
it could serve as a power source anytime, anywhere. It does not have the
same limitations as, for example, solar
cells, which only work under sunlight, or thermoelectric generators,
which work only when there’s a large
temperature difference between the
device and the surroundings.
Power-packed plaster
Visually, the device looks just like a
sticky plaster; in other words, a thin,
flexible strip that can be wrapped
around the fi ngertip. A padding of
carbon foam electrodes absorbs sweat
and converts it into electrical energy. The electrodes are equipped with
enzymes that trigger chemical reactions between lactate and oxygen
molecules in sweat to generate electricity. Underneath the electrodes is a
chip of piezoelectric material, which
scavenges mechanical movement to
generate additional electrical energy
when pressed. As the wearer sweats
or presses on the strip, the electrical
energy gets stored in a small capacitor
and is discharged to other devices
when needed. These devices can be
integrated with the energy harvesters
to power an integrated sensing system
with dedicated electrochromic displays (see: https://bit.ly/pe-dec21-ecd).
Each finger pad can generate between 20 and 40µW of power. This
may sound like small beer, but during 10 hours of a researcher’s sleep,
the device collects almost 400mJ of
energy – crucially, enough to power
an electronic wristwatch for 24 hours.
From one hour of casual typing and
clicking on a mouse, the device collected almost 30mJ. And this is just
from one fingertip. Strapping devices on the user’s remaining fingertips
would generate 10-times more energy,
the researchers say.
Where next?
The researchers have already hooked
up their device to a vitamin C sensor
that they developed in the lab. They
had a subject take a vitamin C pill and
then use the finger-powered system to
read their vitamin C level. They also
connected their energy harvester to
an electronic system consisting of a
chemical sensor connected to a small
low-power display, which shows a numerical reading of the sensor’s data. In
yet another experiment, the researchers showed that their system could
also be used with a lab-built sodium
sensor to read the sodium ion level of
a saltwater solution. Other potential
measurement targets are heart rate, vitamin deficiencies and glucose levels.
‘Our goal is to make this a practical
device,’ states Yin. ‘We want to show
that this is not just another cool thing
that can generate a small amount of energy and then that’s it – we can actually
use the energy to power useful electronics such as sensors and displays.’
To that end, the team is making further improvements to the device so that
it is more efficient and durable. Future
studies will include combining it with
other types of energy harvesters to create a new generation of self-powered
wearable systems.
Practical Electronics | December | 2021
