Solar already provides peak power at peak load, and through distribution
is resilient, and that plus ever-decreasing prices will drive solar
deployments up exponentially for a decade or so yet.
If we add an inexpensive metal-free battery,
solar will take over even faster.
And that’s what Harvard’s School of Engineering and Applied Sciences has just
published as a discovery.
Harvard SEAS PR of 8 January 2014,
Organic mega flow battery promises breakthrough for renewable
energy:
Harvard technology could economically store energy for use when the wind doesn’t blow and the sun doesn’t shine,
The paper reports a metal-free flow battery that relies on the
electrochemistry of naturally abundant, inexpensive, small organic
(carbon-based) molecules called quinones, which are similar to
molecules that store energy in plants and animals.
And much less expensive, reported CBC News 9 January 2014,
Organic battery hailed as cheap renewable energy solution:
Harvard team uses material similar to molecules in rhubarb to store energy,
According to MIT Technology review, a conventional metal-reliant
flow battery costs an estimated $700 per kilowatt-hour of storage
capacity, whereas the Harvard team’s metal-free technology would
bring those costs down to $27 per kilowatt-hour.
Since this is basic research, there’s no telling when, if ever,
such batteries will be commercially available.
If they ever are, they will boost the already rocketing solar deployment curve.
Back to the SEAS PR:
To back up a commercial wind turbine, a large storage tank would be
needed, possibly located in a below-grade basement, said co-lead
author Michael Marshak, a postdoctoral fellow at SEAS and in the
Department of Chemistry and Chemical Biology. Or if you had a whole
field of turbines or large solar farm, you could imagine a few very
large storage tanks.The same technology could also have applications at the consumer
level, Marshak said. “Imagine a device the size of a home
heating oil tank sitting in your basement. It would store a day’s
worth of sunshine from the solar panels on the roof of your house,
potentially providing enough to power your household from late
afternoon, through the night, into the next morning, without burning
any fossil fuels.”
The organic chemicals used in these batteries are not only much less
expensive than metals in conventional batteries, also according to
the funding agency, ARPA-E:
If successful, Harvard’s organic flow battery design could hold up
to 10 times more energy by volume compared to other flow batteries.
Indeed, small enough to fit in your basement.
The paper is
A metal-free organic–inorganic aqueous flow battery
by
Brian Huskinson,
Michael P. Marshak,
Changwon Suh,
Süleyman Er,
Michael R. Gerhardt,
Cooper J. Galvin,
Xudong Chen,
Alán Aspuru-Guzik,
Roy G. Gordon,
and
Michael J. Aziz,
Nature
505,
195–198
(09 January 2014)
doi:10.1038/nature12909.
As the fraction of electricity generation from intermittent
renewable sources—such as solar or wind—grows, the
ability to store large amounts of electrical energy is of increasing
importance. Solid-electrode batteries maintain discharge at peak power for
far too short a time to fully regulate wind or solar power output1, 2. In contrast, flow
batteries can independently scale the power (electrode area) and
energy (arbitrarily large storage volume) components of the system by
maintaining all of the electro-active species in fluid form3,
4, 5. Wide-scale utilization of
flow batteries is, however, limited by the abundance
and cost of these materials, particularly those using
redox-active metals and precious-metal electrocatalysts6, 7. Here we describe
a class of energy storage materials that exploits the favourable
chemical and electrochemical properties of a family of molecules known
as quinones. The example we demonstrate is a metal-free flow battery
based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid
(AQDS). AQDS undergoes extremely rapid and reversible two-electron
two-proton reduction on a glassy carbon electrode in sulphuric acid. An
aqueous flow battery with inexpensive carbon electrodes, combining the
quinone/hydroquinone couple with the Br2/Br−
redox couple, yields a peak galvanic power density exceeding 0.6 W cm−2 at 1.3 A cm−2. Cycling
of this quinone–bromide flow battery showed >99 per
cent storage capacity retention per cycle. The organic anthraquinone
species can be synthesized from inexpensive commodity chemicals8. This organic approach permits tuning
of important properties such as the reduction potential and solubility by
adding functional groups: for example, we demonstrate that the addition
of two hydroxy groups to AQDS increases the open circuit potential of
the cell by 11% and we describe a pathway for further increases in
cell voltage. The use of π-aromatic
redox-active organic molecules instead of redox-active metals represents
a new and promising direction for realizing massive electrical energy
storage at greatly reduced cost.
-jsq