Well, if their technology gets past "vapor", it's a milestone for
distributed solar and wind generation. Put me down !
Peri
------ Original Message ------
From: "len moskowitz via EV" <[email protected]>
To: "EVDL" <[email protected]>
Sent: 24-Sep-15 2:47:23 PM
Subject: [EVDL] Safer Flow Batteries for Grid Storage
http://www.ecnmag.com/news/2015/09/rechargeable-battery-power-home-rooftop-solar-panels
A Rechargeable Battery To Power A Home From Rooftop Solar Panels
Thu, 09/24/2015 - 2:19pm
A team of Harvard scientists and engineers has demonstrated a
rechargeable battery that could make storage of electricity from
intermittent energy sources like solar and wind safe and cost-effective
for both residential and commercial use. The new research builds on
earlier work by members of the same team that could enable cheaper and
more reliable electricity storage at the grid level.
The mismatch between the availability of intermittent wind or sunshine
and the variability of demand is a great obstacle to getting a large
fraction of our electricity from renewable sources. This problem could
be solved by a cost-effective means of storing large amounts of
electrical energy for delivery over the long periods when the wind
isn't blowing and the sun isn't shining.
In the operation of the battery, electrons are picked up and released
by compounds composed of inexpensive, earth-abundant elements (carbon,
oxygen, nitrogen, hydrogen, iron and potassium) dissolved in water. The
compounds are non-toxic, non-flammable, and widely available, making
them safer and cheaper than other battery systems.
"This is chemistry I'd be happy to put in my basement," says Michael J.
Aziz, Gene and Tracy Sykes Professor of Materials and Energy
Technologies at Harvard Paulson School of Engineering and Applied
Sciences (SEAS), and project Principal Investigator. "The non-toxicity
and cheap, abundant materials placed in water solution mean that it's
safe—it can't catch on fire—and that's huge when you're storing large
amounts of electrical energy anywhere near people."
The research appears in a paper published today in the journal Science.
This new battery chemistry was discovered by post-doctoral fellow
Michael Marshak and graduate student Kaixiang Lin working together with
co-lead author Roy Gordon, Thomas Dudley Cabot Professor of Chemistry
and Professor of Materials Science at Harvard.
"We combined a common organic dye with an inexpensive food additive to
increase our battery voltage by about 50 percent over our previous
materials," says Gordon. The findings "deliver the first
high-performance, non-flammable, non-toxic, non-corrosive, and low-cost
chemicals for flow batteries."
Unlike solid-electrode batteries, flow batteries store energy in
liquids contained in external tanks, similar to fuel cells. The tanks
(which set the energy capacity), as well as the electrochemical
conversion hardware through which the fluids are pumped (which sets
peak power capacity), can be sized independently. Since the amount of
energy that can be stored can be arbitrarily increased by scaling up
only the size of the tanks, larger amounts of energy can be stored at
lower cost than traditional battery systems.
The active components of electrolytes in most flow battery designs have
been metal ions such as vanadium dissolved in acid. The metals can be
expensive, corrosive, tricky to handle, and kinetically sluggish,
leading to inefficiencies. Last year, Aziz and his Harvard colleagues
demonstrated a flow battery that replaced metals with organic
(carbon-based) molecules called quinones, which are abundant, naturally
occurring chemicals that are integral to biological processes like
photosynthesis and cellular respiration. While quinones in aqueous
solution formed the negative electrolyte side of the battery, the
positive side relied on a conventional bromine-bearing electrolyte that
is used in several other batteries. The high performance and low cost
of the technology, which Harvard has licensed to a company in Europe,
hold the potential to provide scalable grid-level storage solutions to
utilities.
But bromine's toxicity and volatility make it most suitable for
settings where trained professionals can deal with it safely behind
secure fences.
So the team began searching for a new recipe that would provide
comparable storage advantages—inexpensive, long lasting,
efficient—using chemicals that could be safely deployed in homes and
businesses. Their new battery, described in a paper published today in
the journal Science, replaces bromine with a non-toxic and
non-corrosive ion called ferrocyanide.
"It sounds bad because it has the word 'cyanide' in it," explains
co-lead author Marshak, who is now assistant professor of chemistry at
the University of Colorado Boulder. "Cyanide kills you because it binds
very tightly to iron in your body. In ferrocyanide, it's already bound
to iron, so it's safe. In fact, ferrocyanide is commonly used as a food
additive, and also as a fertilizer."
Because ferrocyanide is highly soluble and stable in alkaline rather
than acidic solutions, the Harvard team paired it with a quinone
compound that is soluble and stable under alkaline conditions, in
contrast to the acidic environment of their original battery developed
last year.
Marshak compares exposure to the concentrated alkaline solution to
coming into contact with a damaged disposable AA battery. "It's not
something you want to eat or splash around in, but outside of that it's
really not a problem."
There are other advantages to using alkaline solution. Because it is
non-corrosive, the flow battery system components can be constructed of
simpler and much less expensive materials such as plastics.
"First generation flow batteries were single-element couples -
transition metals like vanadium or iron or chrome," says Michael Perry,
Project Leader for Electrochemical Systems at United Technologies
Research Center, who was not involved in the work. "Now we're seeing
the possibility of engineered molecules giving us the properties and
attributes that we want in one complete system. More work is required
and justified but the Harvard team is really demonstrating the promise
of next-generation chemistries."
Robert F. Savinell, Distinguished University Professor and George S.
Dively Professor of Engineering at Case Western Reserve University,
another battery expert who was not part of the Harvard research, agrees
that the new technology offers significant advantages over other flow
batteries concepts, including "potential very low costs with
sustainable materials, high efficiencies at practical power densities,
and safe and simple operation." He adds: "It should be expected that
this flow battery approach will have a short development and scale-up
path for fast commercial introduction."
Harvard's Office of Technology Development has been working closely
with the research team to navigate the shifting complexities of the
energy storage market and build relationships with companies well
positioned to commercialize the new chemistries.
The demand for battery storage is driven by regulatory factors as much
as economic ones. In some states, as well as many parts of the world,
if it can't be instantaneously used by meeting electricity demand,
solar energy incident on solar panels goes to waste unless the
electricity is stored. However, in many states, customers have the
right to sell electricity produced by rooftop solar panels at high
consumer rates under a regulatory scheme called net metering. Under
those circumstances, consumers have little incentive to install
batteries. But market experts like William W. Hogan, Raymond Plank
Professor of Global Energy Policy at Harvard Kennedy School, believe
that such policies are ultimately "uneconomic and unsustainable." And
as more and more homeowners install solar panels, utilities are
opposing requirements to buy electricity from their customers.
Hogan says net metering is one of a series of "regulatory gimmicks
designed to make solar more attractive" and predicts that eventually
consumers with rooftop photovoltaic panels will lose the option of
exchanging electricity for discounts on their utility bills. When that
happens, these homeowners have an incentive to invest in battery
storage.
That's the emerging market opportunity that Tesla Motors entrepreneur
Elon Musk hopes to leverage with his company's recently-announced
Powerwall system. But the flow battery design engineered by Aziz and
his Harvard colleagues offers potential advantages in cost and the
length of time it can maintain peak discharge power compared to lithium
batteries.
"This has potential because photovoltaics are growing so fast," Aziz
says. "A cloud comes over your solar installation and BAM - the
production goes crashing down. Then the cloud goes away and the
production goes shooting up. The best way of dealing with that is with
batteries."
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