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(From left) Venkat Srinivasan, Adam Weber and Vince Battaglia will develop a flow battery for the electric grid. (Photo by Roy Kaltschmidt/Berkeley Lab Public Affairs)
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Lawrence Berkeley National Laboratory, known for having one of the top
research programs in the country for batteries and fuel cells for vehicle
applications, has decided to enter another area in the battery world. It has
been granted $1.6 million in American Recovery and Reinvestment Act funds to
develop a novel storage device for the electric grid.
The funding comes from the Department of Energy’s Advanced Research Projects
Agency-Energy (ARPA-E), whose mission is to invest in projects that will
develop transformational energy technologies. The award is part of the $92
million announced by ARPA-E this month for “43 cutting-edge research projects
that aim to dramatically improve how the U.S. uses and produces energy.”
Grid-scale storage would allow grid operators to use more renewable energy,
such as wind and solar, which are known as “variable loads” because they are
inconstant. A grid-scale battery could collect all the energy generated when,
say, the wind blows during sunrise and sunset and then discharge during the
rest of the day, allowing the grid to distribute the energy when demand is
higher. Without such storage capabilities, operators struggle to balance supply
with demand on the instantaneous basis people expect.
To meet the grid’s storage needs, the Berkeley Lab team has proposed a flow battery
using hydrogen-bromine chemistry. “At the end of the project, we expect to have
a high power, high efficiency, long life, low cost, safe storage device,” says
Berkeley Lab scientist Venkat Srinivasan, the lead investigator on the project.
Flow batteries are different from conventional batteries in that the energy
and power are separated. In this way, flow batteries are similar to fuel cells
and are also analogous to a car, where the internal combustion engine provides
the power and the fuel tank provides the energy. To get faster acceleration, or
more power, one can simply increase the size of the engine, and to increase the
range, one can increase the size of the tank.
Similarly, a flow battery has a reactor that provides the power and external
tanks that store the chemical reactants which provide the energy. “This is one
advantage over traditional batteries: you have some degree of scalability,”
says Srinivasan. “To get more energy, you can increase the tank size. If you
use very cheap chemicals, even if the reactor is expensive, the overall cost
per unit of energy comes down because the energy scales with the volume of
chemicals.”
The Berkeley Lab team, which also includes scientists Vince Battaglia and
Adam Weber, is supported by a team of major private-sector partners to help
develop other components of the flow battery. One critical task is to
synthesize a novel, low-cost membrane. The membrane essentially separates the
cathode from the anode and prevents reactants from mixing while still providing
good conductivity. The team decided to look to chemical giant DuPont.
“We needed somebody very good in membranes to work with us because we’re not
experts in that area,” says Srinivasan. “DuPont is the world leader in
ion-exchange membranes.”
For the catalyst, Berkeley Lab is teaming with the Bosch Group to come up
with a new, cheaper material to catalyze the electrochemical reactions. Because
platinum, the metal commonly used as a catalyst in fuel cells, is expensive and
may be prone to deactivation by bromine, the scientists will be looking for
alternative cheaper metals. 3M, which makes an advanced nanostructured thin
film electrocatalyst, is also a partner in the project.
For the electrochemical reactions, hydrogen and bromine are both inexpensive
chemicals and, together, a hydrogen-bromine system has been shown to provide
good efficiency, high power and reversible reactions. Reversibility is
essential because a flow battery must charge as well as discharge. However,
because bromine gas is toxic, another task in this project is to find ways to
minimize or eliminate the production of bromine gas by modifying the
electrolyte.
While the technical challenges present some risk, Srinivasan, Battaglia and
Weber intend to take advantage of everything scientists have learned from fuel
cell advances in the last 20 years and apply them to flow batteries, which
generally have not been able to achieve high efficiencies. At the end of this
ARPA-E funded two-year project, Berkeley Lab hopes to have a proof-of-concept for
a flow battery that will have a high round-trip efficiency of 80 percent and
cost less than $100 per kilowatt-hour of energy.
Even if hydrogen-bromine turns out not to be the “winning” combination for a
flow battery, Srinivasan says: “That is not so important. What we bring to the
table is not the chemistry, but a group of people that have expertise to solve
all these problems, irrespective of the chemistry. We’ll be developing the
skill sets in the next couple of years to understand the fundamentals of flow
battery operation. We’ll have the ability to go forward and work with any
chemistry.”
Lawrence Berkeley National Laboratory provides solutions to the world’s most
urgent scientific challenges including clean energy, climate change, human
health, and a better understanding of matter and force in the universe.
Berkeley Lab is a world leader in improving our lives and knowledge of the
world around us through innovative science, advanced computing and
technology that makes a difference. Berkeley Lab is a U.S. Department of Energy
(DOE) national laboratory. It conducts unclassified scientific research and is
managed by the University
of California for the DOE
Office of Science.
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