We do not get a lot here, including the all-important
energy density. Otherwise it appears
promising and deliverable so we will likely see more of this company. I do like the lack of an acid solution for the
system itself as that ends no end of operational difficulties.
Vanadium Redox has not gone away either, so the age
of utility grade energy storage is fast approaching. Flow batteries are the natural fix there.
This particular aspect of grid architecture is the
low lying fruit of our grid system. A storage
option hugely increases grid capacity.
Startup Shows Off Its
Cheaper Grid Battery
Sun
Catalytix is making a new type of flow battery that could store hours’ worth of
energy on the grid.
Startup Sun
Catalytix is designing a flow battery for grid energy storage that uses custom
materials derived from inexpensive commodity chemicals. It joins dozens of
other companies seeking to make a device that can cheaply and reliably provide
multiple hours of power to back up intermittent wind and solar power.
The MIT spinoff,
which hopes to differentiate itself with a novel chemistry and inexpensive
mechanical systems, is testing a small-scale five-kilowatt prototype. It
projects that a full-scale system, which it expects to make in 2015 or 2016,
will cost under $300 per kilowatt-hour, or less than half as much as the
sodium-sulfur batteries now used for multihour grid storage.
Sun Catalytix CEO
Mike Decelle says one advantage of the company’s technology is that it uses
cheap ingredients. “We’re sourcing some this stuff really, really cheaply in
ton quantities [from China] right now,” he says, standing in a doorway so the
names of the chemicals are not readable to a visitor. “That’s where you’ve got
to source and the kind of quantities you need.”
The active
material in a typical flow battery is a metal, such as vanadium or zinc,
dissolved in a liquid electrolyte. To create a current, the liquids are pumped
from large tanks into a device where an electrochemical reaction occurs across
a membrane. The electrolytes are pumped in the reverse direction to charge the
battery. One big advantage of flow batteries is that the amount of energy they
store can be increased by simply making the tanks larger.
Sun Catalytix’s
electrolytes are made from metals combined with ligands, or molecules that bind
to metal atoms. Using synthetic metal-ligand compounds as the active battery
materials gave engineers more design flexibility in pursuing an inexpensive,
safe battery that can last 15 years with daily charging, according to the
company.
In one version of
the battery being developed at its lab, two square plates made of
carbon-plastic composite, each about as thick as a piece of paper, are stacked
with a thin plastic membrane between them to form a cell. During charging and
discharging, the two liquid electrolytes travel through grooves carved within
each plate to trigger the chemical reaction across the membrane.
The prototype
system, held in a glass enclosure, is made up of 50 cells in two horizontal
rows, or “stacks.” The cells are not wired individually; instead, the current
travels through the plates from one end of the stack to the other, which saves
costs on wiring. Below the stacks are tanks of liquid electrolytes, pumps,
valves, and tubes made of PVC plastic—all of which is off-the-shelf equipment.
A full-scale system would use hundreds of cells, each roughly the size of a
pizza box.
One way Sun
Catalytix’s batteries are different from more conventional flow batteries,
according to the company, is that the active materials are dissolved in a
near-neutral aqueous solution that is safe in the case of a spill and not
corrosive to pumps and valves. Most flow-battery electrolytes are strong
acids, which could cause safety concerns if the technology is used in buildings
and can require containment vessels that introduce more cost, says Venkat
Srinivasan, head of the Energy Storage and Distributed Resources Lab at
Lawrence Berkeley National Laboratory.
Sun Catalytix is
also competing with companies making compressed-air storage machines and
batteries with their own novel chemistries, such as a zinc-air battery from Eos
Energy Storage and a liquid-metal battery from Ambri. (See “Cheap Batteries for Backup Renewable Energy” and “Ambri’s Better Battery.”) Decelle thinks Sun
Catalytix’s battery will have an advantage over Ambri’s in terms of safety. A
liquid-metal battery operates at several hundred degrees Celsius, which “might
give some customers pause,” he says.
Sun Catalytix
intends to pilot-test a full-scale battery in 2015. A one-megawatt system would
fit into two 20-foot shipping containers, and the tanks of electrolytes would
require more shipping containers, depending on how many hours of power are
needed. The company, which has raised $16.5 million in investments, is now
seeking more money from corporations and venture capitalists to build
larger-scale prototypes. It intends to manufacture the cell stacks itself and
rely on contract manufacturers or systems integrators to assemble the final
product, Decelle says.
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