Liquid Metal batteries for Stationary applications ?

[Mike O'Dell]

liquid sodium-chloride batteries have been around for some time.

the current state-of-the-art in grid-scale power storage is NKK's NaS
battery - liquid sodium and liquid sulfur. the "membrane" separating the
two is a ceramic formulated to allow the electron and ion exchanges
without allowing them to combine willy-nilly. the battery operates
at 300C.  the system consists of the battery plant plus 
charger/inverters.  a "module" is rated to supply 1-Megawatt
for 6 hours. they can supply it with a 2-Megawatt inverter which
reduces the life to only about 2 hours. the battery can do essentially
100% depth of discharge with no ill effects. it can go from charge to
discharge in 100s of milliseconds so it can be used for multiple
purposes in the grid.  all this go-fast is neither small nor cheap.
the module is 40 feet long, about 8 feet wide, and about 12 feet tall.
it weights about 40 tons (memory on the weight is hazy).

the development program has been running for almost 10 years and
has absorbed between 1 and 2 billion USD. it was funded by
Tokyo Electric because all of their base-load generation is nuclear
and since they have to import natural gas, the usual turbine
peakers are not a viable alternative. Nuke plants throttle up
or down very slowly - the thermal mass is *immense* - plus you
want to run them flat-out as much as possible because there is
a *lot* of money sitting there depreciating, and watts per dollar
is the coin of the realm. while pumped-hydro is still the most
popular grid-scale storage technology (and we have the biggest
one in the world here in Virginia), it requires geography,
geology, and they need to be where you need them lest the
transmission losses make the economics problematic.

there is an amazing horse-race going on to develop viable grid-scale
storage technology that's cheaper than NaS and one much less likely
to enrage the locals when they find out you are putting a few tons
of liquid sodium and liquid sulfur just down the street from them
at the local substation.

some schemes are indeed batteries of various chemistries,
others compress air into large caverns (pumped-hydro with
really, REALLY thin water), and there's a thermal storage
design which i saw the other day which seems truly wacko,
but if liquid sodium/liquid sulfur doesn't *peg* the wackometer,
nothing does, so that hardly disqualifies anything.

there was recently a Dept of Energy meeting down at National Harbor
where the various contestants for the DoE awards and loads were
pitching woo and i attended.

the reality, though, is that in the US, the competition for
any storage technology is the natural-gas-fired gas-turbine peaker.
you can install as many of those as you want for about $2/watt
and the carbon/hydrogen bonds in methane are a splendidly-efficient
way to store energy. True, it ain't great compared to gasoline or
diesel fuel, but it's lightyears better than any known electrochemistry.

so while it's true that all the big power player are installing
battery systems (all of them are NKK's NaS i believe), they are
doing it go get experience with how they can be used in the US
grid environment. we're a long way from them becoming a genuine
architectural component which is routinely used for designing
power grid infrastructure (which it is in Japan).

i can go on about this for quite some time, but i'll spare you.
there are, though, 3 very different ways batteries can be used
in networks, but that's another lengthy treatise.

	-mo


On 4/28/10 11:01 PM, Andre Kesteloot wrote:
> http://www.popularmechanics.com/science/energy/next-generation/liquid-metal-batteries-storage-breakthrough?src=rss
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