Vanadium will lead to high capacity storage of surplus solar and wind energy

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http://m.bbc.co.uk/news/magazine-27829874

Vanadium: The metal that may soon be powering your neighbourhood
By Laurence Knight BBC World Service

14 June 2014 Last updated at 00:24

Hawaii has a problem, one that the whole world is likely to face in
the next 10 years. And the solution could be a metal that you've
probably never heard of - vanadium.

Hawaii's problem is too much sunshine - or rather, too much solar
power feeding into its electricity grid.

Generating electricity in the remote US state has always been painful.
With no fossil fuel deposits of its own, it has to get oil and coal
shipped half-way across the Pacific.

That makes electricity in Hawaii very, very expensive - more than
three times the US average - and it is the reason why 10% and counting
of the islands' residents have decided to stick solar panels on their
roof.

The problem is that all this new sun-powered electricity is coming at
the wrong place and at the wrong time of day.

Hawaii's electricity monopoly, Heco, fears parts of the grid could
become dangerously swamped by a glut of mid-day power, and so last
year it began refusing to hook up the newly-purchased panels of
residents in some areas.

And it isn't just Hawaii.

"California's got a major problem," says Bill Radvak, the Canadian
head of American Vanadium, America's only vanadium mining company.

"The amount of solar that's coming on-stream is just truly remarkable,
but it all hits the system between noon and 4pm."

That does not marry well with peak demand for electricity, which
generally comes in the late afternoon and evening, when everyone
travels home, turns on the lights, heating or air conditioning, boils
the kettle, bungs dinner in the microwave, and so on.

What the Golden State needs is some way of storing the energy for a
few hours every afternoon until it is needed.

And Radvak thinks he holds the solution - an electrochemical solution
that exploits the special properties of vanadium.


Back in 2006, when Radvak's company decided to reopen an old vanadium
mine in Nevada, electricity grids were the last thing on their minds.

Back then, vanadium was all about steel. That's because adding in as
little as 0.15% vanadium creates an exceptionally strong steel alloy.

"Steel mills love it," says Radvak. "They take a bar of vanadium,
throw it in the mix. At the end of the day they can keep the same
strength of the metal, but use 30% less."

It also makes steel tools more resilient. If the name vanadium is
vaguely familiar to you, it is probably because you have seen it
embossed on the side of a spanner.

And because vanadium steel retains its hardness at high temperatures,
it is used in drill bits, circular saws, engine turbines and other
moving parts that generate a lot of heat.

So steel accounts for perhaps 90% of demand for the metal.


Vanadium's alloying properties have been known about for well over a
century. Henry Ford used it in 1908 to make the body of his Model T
stronger and lighter.

For the same reasons - and also for its heat resistance - it was used
to make portable artillery pieces and body armour in the First World
War.

But vanadium's history seemingly goes back even further. Indeed,
mankind may have been unwittingly exploiting the metal as far back as
the 3rd Century BC.


That is when "Damascus steel" first began to be manufactured.

Swords made of the steel were said to be so sharp that a hair would
split if it were dropped on to the blade.

Damascus steel scimitars were credited with enabling Muslim warriors
to fight off the Crusades.


Samples taken from a handful of antiques were found to contain tiny
amounts of impurities, including - crucially - vanadium.

Bizarrely, this two-millennium-old steel-making tradition vanished in
the mid-18th Century. The vanadium-rich iron deposits in southern
India from which the steel was fashioned must finally have become
exhausted, or so the theory goes.

Today, vanadium mainly goes into structural steel, such as in bridges
and the "rebar" used to reinforce concrete.

It is a small and sometimes volatile market. Supply is dominated by
China, Russia and South Africa, where the metal is extracted mostly as
a useful by-product from iron ore slag and other mining processes.

China - which is midway through the longest and biggest construction
boom in history - also dominates demand.

A recent decision by Beijing to stop using low-quality steel rebar has
bumped up forecast demand for vanadium by 40%.

Yet the biggest source of future demand may have nothing to do with
steel at all, and may instead exploit vanadium's unusual
electro-chemical nature.


"Vanadium was actually discovered twice, and one of the discoverers
was the Swedish chemist Nils Sefstrom, who named it after the Norse
goddess of beauty, Vanadis," says the Italian chemist, Prof Andrea
Sella of University College London.

To explain why, Sella produces a flask of an easily misidentified
yellow-coloured liquid.

It is, he says, a solution of "oxidised" vanadium in sulphuric acid -
that is, vanadium that has been stripped of all five of its outermost
electrons (it inhabits column five of the periodic table).

He then adds a shiny lump of a zinc-mercury amalgam and begins to
shake the concoction violently.

"The zinc is going to allow us to put electrons back onto the vanadium
- the chemical process we call 'reduction'," he explains.

The solution quickly turns green, and then gradually becomes blue.
"And if we keep shaking for another few minutes, we will eventually
end up with a violet colour."

Each change of colour represents one further electron being passed on
to the vanadium.

"The ease with which you can hand electrons to the vanadium and take
them away - this is the basis of a very, very stable battery."

Vanadium "redox flow" batteries are indeed stable. They can be
discharged and recharged 20,000 times without much loss of
performance, and are thought to last decades (they have not been
around long enough for this to have been demonstrated in practice).

They can also be enormous, and - in large part thanks to their
vanadium content - expensive. The smallest of the "Cellcube" batteries
that American Vanadium is producing in partnership with German
engineering firm Gildemeister has a footprint the size of a parking
bay and costs $100,000.


How does a Vanadium Redox Flow Battery work?


Consists of two giant tanks of different solutions of vanadium
dissolved in sulphuric acid, separated by a membrane

The battery produces an electrical current as the fluids are pumped
past electrodes on either side of the battery In one tank, the
vanadium releases electrons, turning from yellow to blue In the other
tank, the vanadium receives electrons, turning from green to violet
The electrons pass around a circuit, generating a current, while at
the same time a matching number of protons (hydrogen ions) pass across
the membrane between the two solutions
The BBC's headquarters in London - home to 7,000 employees - would
need one the size of two 12-metre trailers, Radvak says, perched up on
the roof or perhaps buried underground.

His firm is providing the batteries' key ingredient, the electrolyte
(the fluid in the battery).

It is the same chemical solution as in Sella's demonstration, and -
conveniently enough - is also the end-product of the standard process
of using sulphuric acid to leach the vanadium out of its ore.

Radvak says that among his target customers are large corporate
electricity consumers such as the Metropolitan Transport Authority,
which runs New York's subway, and with whom his firm has just signed a
pilot deal to supply Cellcube batteries.


Such companies are facing ever higher charges for the electricity they
use during the peak hours of the day, and the Canadian claims they can
cut their bills by a quarter if they use a battery to draw down the
daytime electricity they need during the night, when it is cheapest.

By flattening out demand between the daily peaks and troughs, the
batteries also help out the electricity companies.

One of their biggest expenses is investing in the extra power station
capacity that is only ever called upon for a few hours each year when
the weather, holidays and the time of day all conspire to produce the
biggest peak in electricity demand.

That challenge of balancing electricity supply and demand is set to
get a whole lot more difficult as ever more solar and wind energy is
added to the grid.


Which brings us back to Hawaii.

Rooftop solar panels don't just produce electricity at the "wrong"
time of day, they also produce it at a low voltage, which, according
to the German renewable energy entrepreneur Alexander Voigt, means it
is effectively trapped at the level of the local community.

"Our traditional electricity grid is built in a way that the energy
flows from the high voltage to the low voltage, and not the other way
round," he says.

That means the solar energy can only be shared among the few
households - typically just a village or a town neighbourhood - that
happen to share the same transformer station that plugs them into the
high-voltage national grid.

Voigt helped set up the vanadium battery company that was later bought
up by Gildemeister. He foresees the batteries being built next to
transformers, where they can store up each community's daily solar
surplus, before releasing it back again in the evening.

It is a rosy image, but it does prompt two obvious questions.

First, why should vanadium batteries be the technology of choice?

For example, there is a glut of cheap lithium batteries these days,
after manufacturers built out their capacity heavily in anticipation
of a hybrid and electric cars boom that has yet to arrive.

Lithium batteries can deliver a lot of power very quickly, which is
great if you need to balance sudden unexpected fluctuations - as may
be caused by passing clouds for solar, or a passing gale for wind.

But a lithium battery cannot be recharged even a tenth as many times
as a vanadium battery - it's likely to die after 1,000 or 2,000
recharges.

Nor can lithium batteries scale up to the size needed to store an
entire community's energy for several hours. By contrast, vanadium
batteries can be made to store more energy simply by adding bigger
tanks of electrolyte. They can then release it at a sedate pace,
unlike conventional batteries, where greater storage generally means
greater power.

At the other end of the scale, there are also plenty of large-scale
energy storage systems under development, such as those exploiting
liquefied air, and the 1,000-fold shrinkage in the volume of the air
when it is cooled to -200C.

But these systems take up a lot of space, Mr Voigt says, and are
better suited to the very largest-scale facilities that will be needed
to serve for instance a large offshore wind farm plugging into the
high-voltage national grid.

The second really big question for vanadium is whether the world
contains enough of the stuff.

The immediate challenge is that the birth of the vanadium battery
business is coming just as China is ramping up its demand for vanadium
steel.

But there is also a longer-term problem - the quantities of vanadium
added to steel alloys are so tiny that it is not economic to recover
it from the steel at the end of its life. So for the battery market,
that vanadium is effectively lost forever.

But Mr Voigt remains optimistic.

"Like with all raw materials, it's always a question of how stable is
the need of the market, and how big are the incentives for the
industry to set up new mines."

With demand on an upward trend, American Vanadium is not the only one
trying to fill the gap. For example, rival battery-maker Imergy has
developed a cheap ways of producing vanadium electrolyte from iron ore
slag and the fine ash produced by coal-burning.

Over the longer term, demand for vanadium steel could be met by
melting down and recasting old vanadium steel rather than making it
afresh, so that freshly mined vanadium could be channelled into the
energy market instead.

And in the very long run, perhaps we will harvest vanadium from sea
squirts - there are plenty of them in the Pacific.


Sea squirts


Vanadium is an essential micronutrient for animals, but toxic in large
dosages Some sea squirts accumulate vanadium in their bodies, turning
their blood green, possibly in order to protect them from predators
Closely related to vertebrates, in their larval stage sea squirts look
like tadpoles and swim around But once they find an appropriate rock
to attach to, they metamorphose into something resembling a
brightly-coloured vegetable They never leave their spot, and feed by
filtering tasty morsels from the sea water they pump through their
bodies Having committed themselves to this life of tedium, they also
digest their redundant brains Some fungi also accumulate vanadium,
including the bright red and white poisonous, hallucinogenic mushroom
known as the fly agaric

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