During his
doctoral studies, David Carlstedt was part of the research team that in 2021
was able to demonstrate a carbon fiber-based structural battery with unprecedented
multifunctional properties. A lot of research has been done that lead to the
breakthrough, and the work has taken place across several scientific
disciplines and academic institutions. In the project one also wanted to develop
a working prototype. David was part of a large interdisciplinary team that was
commissioned to build and test such a prototype.
"I have
probably built and tested close to 100 batteries over time. When one of them
finally worked and showed values that had never been measured before, at first,
I had a hard time believing that it was correct. It was a really cool feeling
when I understood that we had managed to produce such a good and unique
structural battery,” says David.
A carbon fiber-based structural battery cell, with
unprecedented multifunctional properties, is here seen lighting up a
diode lamp. Image: David Carlstedt
Structural batteries have also been described as "mass-less energy storage".
This can be explained by the fact that when the energy storage becomes part of
the load-bearing structure, the weight and space previously taken up by the
battery also "disappears". This in turn means less material
consumption for the same type of construction, which leads to additional weight
savings. Another advantage is that the structural battery is ductile and could
be used to build, for example, car bodies, bicycle frames or aircraft.
"If you look at how a modern smartphone is constructed, it is, in addition to various electronics, basically one or more batteries with a protective and load-bearing
material all around. If energy storage is instead integrated into the casing
itself, it could be thinner and lighter, as well as enable new innovative
design solutions. If you then apply this technology to vehicles and aircraft,
you can make significant improvements in terms of efficiency, because weight plays
such a crucial role in energy consumption during transport,” David explains.
Interfering physical processes - a challenge in structural batteries
The
structural battery technology has many advantages, but it also has challenges.
Crucial to understanding how a material or battery behaves is to be able to compute
the physical equilibrium processes for electric charge, mechanical load, heat
and mass transport. For example, to avoid overheating in a battery, you must be
able to make exact calculations of the heating effects that occur.
To make
calculations for physical balance in both batteries and construction materials
separately, is well understood and has established calculation models. But if
the battery and construction material become one and the same, the complexity
increases when the different physical processes affect each other. This is called
"coupling effects". In a structural battery, this means, among other
things, that the electrochemical processes, which is the battery function
itself, affect the load-bearing capacity, and that the mechanical loads in turn
affect the electrochemical processes.
"In my
research, I have studied different coupling effects between the physical
processes and developed new calculation models that can be used to understand
the behavior of the structural battery. We have applied and combined
interdisciplinary methods. For example, we have used existing methods to solve
complex mathematical problems as well as strategies for describing the physical
processes and essential couplings. To some extent, there are such coupling
effects in different structures in nature, but the material we use for the
structural battery is unique in its kind. Therefore, there has been no need to
address this particular problem before," David explains.
About the future
Leif Asp
leads the research on structural batteries at Chalmers, and he has high hopes about
further progress in the near future.
“A lot has
happened in recent times, both in terms of scientific progress and interest. Now we
have also trained our first doctoral student with a focus on structural
batteries. Companies from all over the world have contacted us so there is a
huge interest in this technology. We are already in a new project where we hope
to be able to produce a structural battery that is about as strong as aluminum,
and with a much higher energy density than with the current structural battery.
We hope to be able to present the results within the next year,” says Leif Asp.
David Carlstedt
has had Leif Asp as a supervisor during his doctoral studies, and he predicts a
very bright future for David.
“We are
very happy to be able to educate across disciplines in a project like this.
David has gained an incredible experience of working in interdisciplinary
contexts, and his knowledge will be highly sought after in both academia and
industry,” says Leif.
After his
doctoral studies, David will start working with structural simulations of
batteries at Volvo Cars. David is very much looking forward to this exciting
new assignment and believes he will make great use of his knowledge acquired
during his doctoral studies. In the automotive industry, there is currently an
extensive shift towards electric powered vehicles and batteries play a key role
in this. David therefore sees this as a very exciting area to continue his
journey in. He also speculates on future uses for structural batteries.
“The
electric power technology of the future may consist of several different types
of solutions depending on the area of application. In satellites and small
aircraft, where low weight is highly sought after, one could imagine that our
type of ductile carbon fiber-based structural battery would be a suitable
solution. In an electric car, it is conceivable that certain parts of the body
or interior are built with structural batteries to, for example, operate window
lifts, sound systems or similar. What happens depends very much on how the
industry decides to invest and develop this type of technology. Whatever
happens, it will be very exciting to follow the development, and hopefully be a
part of it,” says David.
David Carlstedt will
doctorate on March 17, 2022 with the thesis
Computational modelling of structural battery composites.
Text & photo: Marcus Folino
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