PNNL researcher
Xiaoliang Wei prepares a small demonstration organic flow battery.
(December 21, 2015) PNNL
organic battery will be cheaper than standard vanadium flow battery
Energy storage system owners could see significant savings
from a new flow battery technology that is projected to cost 60 percent less
than today's standard flow batteries.
The organic aqueous flow battery, described in a paper
published in the journal Advanced Energy Materials, is expected to cost $180
per kilowatt-hour once the technology is fully developed. The lower cost is due
to the battery's active materials being inexpensive organic molecules, compared
to the commodity metals used in today's flow batteries.
"Moving from transition metal elements to synthesized
molecules is a significant advancement because it links battery costs to
manufacturing rather than commodity metals pricing" said Imre Gyuk, energy
storage program manager for the Department of Energy's Office of Electricity
Delivery and Energy Reliability (OE), which funded this research.
"The battery's water-based liquid electrolytes are also
designed to be a drop-in replacement for current flow battery systems,"
said PNNL materials scientist Wei Wang, one of the paper's corresponding
authors. "Current flow battery owners can keep their existing
infrastructure, drain their more expensive electrolytes and replace them with
PNNL's electrolytes."
Changing currents
Flow batteries generate power by pumping liquids from
external tanks into a central stack. The tanks contain liquid electrolytes that
store energy. When energy is needed, pumps move the electrolytes from both
tanks into the stack where electricity is produced by an electrochemical
reaction.
Both flow and solid batteries, such as the lithium-ion
batteries that power most electric vehicles and smartphones today, were
invented in the 1970s. Lithium-ion batteries can carry much more energy in a
smaller space, making them ideal for mobile uses. The technology gained market
acceptance quickly, for both mobile uses like cell phones and larger,
stationary uses like supporting the power grid.
Lithium-ion batteries now make up about 70 percent of the
world's working, grid-connected batteries, according to data from DOE-OE's
Global Energy Storage Database. However issues with performance, safety and
lifespan can limit the technology's use for stationary energy storage.
Flow batteries, on the other hand, store their active
chemicals separately until power is needed, greatly reducing safety concerns.
Vanadium-based flow batteries have become more popular in recent years,
especially after PNNL developed a new vanadium battery design in 2011 that
increased storage capacity by 70 percent. Three different companies have
licensed the technology behind PNNL's vanadium design.
Nearly 79 percent of the world's working flow batteries are
vanadium-based, according to data from the Global Energy Storage Database.
While vanadium chemistries are expected to be the standard for some time,
future flow battery cost reductions will require less expensive alternatives
such as organics.