IEEE Spectrum November, 2017 - 39
THE POSITIVE and negative sides
of a vanadium redox-flow battery
are separated by a membrane
that selectively allows protons to
go through. During charging, an
applied voltage causes vanadium
ions to each lose an electron on the
THIS
BATTERY
FLOWS
positive side. The freed electrons
flow through the outside circuit to
the negative side, where they are
stored. During discharging, the
stored electrons are released,
flowing back through the outside
circuit to the positive side.
H+
O
2-
V5+
H
O2H+
H+
O2-
Cl-
Cl-
H+
Cl-
+
H+
H+
e
V4+
O2-
O2-
H
O2-
O2-
Cl-
H+
O
H+
H+
2- V4+
H+
V2+
H+
+
POSITIVE CELL
V 4 +/V 5 +
H+
H+
V3+
O2H+
Cl-
H
H+
H+
Cl-
NEGATIVE CELL
V 2 +/V 3 +
V3+
H+
+
e
O2-
H+
H+
ELECTROLYTE
TANK
e
ELECTRODE
ION-SELECTIVE
MEMBRANE
e
PUMP
POWER SOURCE/LOAD
TODAY'S STATE-OF-THE-ART vanadium redoxflow batteries started out as a modest research
project at the Pacific Northwest National Laboratory (PNNL), a U.S. Department of Energy lab in
Washington state. The PNNL team, which I led,
came together in 2007, at a time when world oil
prices were steadily climbing. The economies of China and India
were experiencing double-digit growth, and environmentalists were
concerned about the accelerating rate at which they (and other countries) were consuming fossil fuels. In the United States, awareness
was starting to build about the potential of renewable but intermittent energy sources like wind and solar.
Against that backdrop, we decided to search for a better way to store
renewable energy as a means of promoting its adoption while also
improving grid reliability. Our group included the lab's top experts on
power, materials, and chemistry, as well as an intellectual-property
lawyer, Peter Christiansen, who has a background in power engi-
T
ILLUSTRATION BY
James Provost
neering. Peter helped focus our efforts on technologies that would have the greatest societal
impact. In 2009, our group began receiving significant support from the DOE's Energy Storage
Program, which boosted our annual R&D budget
to US $10 million.
At the outset, it wasn't at all obvious that flow batteries were the way to go. Indeed, we started off by
reviewing all of the various battery technologies,
including lithium ion, sodium sulfur, advanced lead
acid, redox flow, and a few other novel concepts.
Then as now, attention was being lavished
mainly on high-power lithium-ion batteries.
According to Greentech Media, over 90 percent
of energy storage systems deployed in the United
States in 2015 and 2016 were Li-ion batteries, and
that's likely to be true this year as well. The techSPECTRUM.IEEE.ORG
|
NORTH AMERICAN
|
NOV 2017
|
39
https://www.pnnl.gov/
https://www.pnnl.gov/
https://www.energy.gov/oe/activities/technology-development/energy-storage
https://www.energy.gov/oe/activities/technology-development/energy-storage
http://www.cesa.org/assets/2016-Files/ESTAP-Webinar-Slides-4.19.16.pdf
http://www.cesa.org/assets/2017-Files/ESTAP-webinar-slides-1.27.2017.pdf
http://SPECTRUM.IEEE.ORG
Table of Contents for the Digital Edition of IEEE Spectrum November, 2017
IEEE Spectrum November, 2017 - Cover1
IEEE Spectrum November, 2017 - Cover2
IEEE Spectrum November, 2017 - 1
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IEEE Spectrum November, 2017 - Cover3
IEEE Spectrum November, 2017 - Cover4
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