POWER February 2012 - 10

discharge a battery-to easily go in and out without damaging
the electrode.
To maximize the benefit of the open structure, the researchers
needed to use the right size ions. Too big, and the ions would
tend to get stuck and could damage the crystal structure when
they moved in and out of the electrode. Too small, and they might
end up sticking to one side of the open spaces between atoms,
instead of easily passing through. The right-sized ion turned out
to be hydrated potassium, a much better fit than other hydrated
ions such as sodium and lithium. The speed of the electrode
is further enhanced because the particles of electrode material
that the researchers synthesized are tiny even by nanoparticle
standards-a mere 100 atoms across.
" At a rate of several cycles per day, this electrode would have
a good 30 years of useful life on the electrical grid, " said Colin
Wessells, a graduate student in materials science and engineering,
who is the lead author of a paper describing the research,
published in November in Nature Communications.
The research seeks to overcome cost concerns associated with
grid energy storage as opposed to energy density. " We decided
we needed to develop a 'new chemistry' if we were going to make
low-cost batteries and battery electrodes for the power grid, "
Wessells said. The researchers chose to use a water-based electrolyte,
which Wessells described as " basically free compared to
the cost of an organic electrolyte " such as is used in lithium-ion
batteries. They made the battery electric materials from readily
available precursors such as iron, copper, carbon, and nitrogen-
all of which are extremely inexpensive compared with lithium.
The only major obstacle to finessing the new electrode is that
its chemical properties cause it to be usable only as a highvoltage
electrode, the researchers say. Every battery needs two
electrodes-a high-voltage cathode and a low-voltage anode-in
order to create the voltage difference that produces electricity.
Efforts to find another material to use for the anode, which will
be necessary before researchers can build an actual battery, are
2. Cost breakthrough. Stanford researchers have used nanoparticles
of a copper compound to develop a high-power battery electrode
that is reportedly so inexpensive to make that it could be used to build
batteries big enough for economical large-scale energy storage on the
grid. The development could result in a breakthrough for large-scale
battery storage projects like AES Energy Storage's newly built AES
Laurel Mountain, a wind generation plant in West Virginia composed
of 98 MW of wind generation and 32 MW of integrated battery-based
energy storage. Courtesy: AES Energy Storage
under way, and they have already uncovered " some promising
candidates. "
Novel Floating Wind Turbine Deployed in
the Atlantic
A semi-submersible structure supporting a 2-MW wind turbine
was towed nearly 350 kilometers (217.5 miles) to water depths
of about 35 meters (114.8 feet) into open Atlantic waters and
deployed off the coast of Aguçadoura, Portugal, last November
(Figure 3). Though the WindFloat project joins a handful of similar
projects under development, because it offers novel possibilities
for offshore wind projects in regions with large and deep
coastlines, it has been shoring up interest in the budding floating
offshore wind sector.
The WindFloat was developed by partners of the WindPlus Joint
Venture, consisting of Seattle-based Principle Power, Energias de
Portugal (EDP), A. Silva Matos, Vestas Wind Systems, InovCapital,
and Fundo de Apoio à Inovação. More than 60 European vendors
reportedly helped assemble, install, and precommission the system
integrating a Vestas V80-2.0 MW wind turbine on land at the
Lisnave facility, near Setubal, Portugal.
The system was then towed-without " the use of any heavy
lift equipment offshore, " as Principle Power noted-217.5 miles
in Atlantic waters. As of January, developers were commissioning,
testing, and starting up the WindFloat, activities that include conducting
trial operations and a phased ramp-up to full capacity.
The project isn't the first floating wind turbine, nor the largest:
In June 2009, Siemens Energy and Norway's Statoil towed a
2.3-MW wind turbine 12 km (7.4 miles) to a water depth of about
722 feet at a North Sea location (for more information on this
POWER Top Plant, see our December 2009 issue). That project
continues to operate, and Statoil recently applied for a lease
with the U.S. Bureau of Ocean Energy Management to test a pilot
Hywind floating project in the Gulf of Maine.
What sets the WindFloat apart from Hywind and other floating
wind projects is that, unlike the Hywind, which is essentially like
a buoy (a spar moored on three lines) on which a turbine has
been built, the WindFloat is a semi-submersible structure moored
by four to six lines that almost acts like a tripod. The WindFloat
is also distinct in that it can be towed out to sea fully commis3.
Floating an idea. Partners of the WindPlus Joint Venture-
including Seattle-based Principle Power, Portuguese utility Energias de
Portugal, and Danish wind firm Vestas-have towed and deployed a
2-MW floating wind turbine roughly 217 miles into open Atlantic waters.
Courtesy: Energias de Portugal
10
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POWER February 2012

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