This is
promising although we have one side of the battery so far. Also little is said yet about energy density.
A flow
battery using organic reagents with low cost and excellent physical
characteristics is a great idea. Now we
have to really get there. We really do
not want the tank farm to be too big.
I also
think that we are going to get there. I
am more optimistic about the Vanadium oxide solution because it already works
well, but because I also have reason to suspect that the energy density can be
at least tripled which resolves the cost problem.
New Battery Material Could Help Wind and Solar Power Go Big
Low-cost
materials could make storing hours of power from a wind farm economically
feasible.
Liquid
energy: Novel energy storage materials flow from the white
containers shown here into a fuel-cell like device in the foreground, where
they generate electricity.
Utilities
would love to be able to store the power that wind farms generate at night—when
no one wants it—and use it when demand is high during the day. But conventional
battery technology is so expensive that it only makes economic sense to store a
few minutes of electricity, enough to smooth out a few fluctuations from gusts
of wind.
Harvard
University researchers say they’ve developed a new type of battery that could
make it economical to store a couple of days of electricity from wind farms and
other sources of power. The new battery, which is described in the
journal Nature, is
based on an organic molecule—called a quinone—that’s found in plants such as
rhubarb and can be cheaply synthesized from crude oil. The molecules could
reduce, by two-thirds, the cost of energy storage materials in a type of
battery called a flow battery, which is particularly well suited to storing
large amounts of energy.
If it
solves the problem of the intermittency of power sources like wind and solar,
the technology will make it possible to rely far more heavily on renewable
energy. Such batteries could also reduce the number of power plants needed on
the grid by allowing them to operate more efficiently, much the way a battery
in a hybrid vehicle improves fuel economy.
In a flow
battery, energy is stored in liquid form in large tanks. Such batteries have
been around for decades, and are used in places like Japan to help manage the
power grid, but they’re expensive—about $700 per kilowatt-hour of storage
capacity, according to one estimate. To make storing hours of energy from wind
farms economical, batteries need to cost just $100 per kilowatt-hour, according
to the U.S. Department of Energy.
The energy
storage materials account for only a fraction of a flow battery’s total cost. Vanadium,
the material typically used now, costs about $80 per kilowatt-hour. But that’s
high enough to make hitting the $100 target for the whole system impossible. Michael
Aziz, a professor of materials and energy technologies at
Harvard University who led the work, says the quinones will cut the energy storage material costs down to just $27
per kilowatt-hour. Together with other recent advances in bringing down the
cost of the rest of the system, he says, this could put the DOE target in
reach.
The
Harvard work is the first time that researchers have demonstrated
high-performance flow batteries that use organic molecules instead of the metal
ions usually used. The quinones can be easily modified, which might make it
possible to improve their performance and reduce costs more. “The options
for metal ions were pretty well worked through,” Aziz says. “We’ve now
introduced a vast new set of materials.”
After
identifying quinones as potential energy storage molecules, the Harvard
researchers used high-throughput screening techniques to sort through 10,000
variants, searching for ones that had all the right properties for a battery,
such as the right voltage levels, the ability to withstand charging and
discharging, and the ability to be dissolved in water so they could be stored
in liquid tanks.
So far the
researchers are using quinones only for the negative side of the battery. The
positive side uses bromine, a corrosive and toxic material. The researchers
are developing new versions of the quinones that could replace the bromine.
The
Harvard researchers are working with the startup Sustainable Innovations to develop
a horse-trailer sized battery that can be used to store power from solar panels
on commercial buildings.
The
Harvard researchers still need to demonstrate that the new materials are
durable enough to last the 10 to 20 years that electric utilities would like
batteries to last, says Robert Savinell, a professor of engineering and
chemical engineering at Case Western Reserve University. Savinell wasn’t
involved with the Harvard work. He says initial durability results for the
quinones are promising, and says the new materials “without a doubt” can be
cheap enough for batteries that store days of electricity from wind farms. And
he says the materials “can probably be commercialized in a relatively short
time”—within a few years.
The
researchers face competition from other startups developing cheaper flow
batteries, such as EnerVault and Sun Catalytix (see “Startup
EnerVault Rethinks Flow Battery Chemistry” and “Sun
Catalytix Seeks Second Act with Flow Battery”). Sun Catalytix is developing
inorganic molecules to improve performance and lower cost, although it isn’t
saying much about them. EnerVault uses iron and chromium as storage materials
and is developing ways to reduce the cost of the overall system.
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