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Chemical Technology • February 2015
RENEWABLES
advances are in the field of clean energy. His response:
perovskites.
The problem with existing photovoltaics is that they rely
on slabs of crystalline silicon which are expensive and
difficult to grow. Perovskites can be produced from simple
bulk chemicals. Methylammonium lead halide is the cur-
rent leading perovskite material having gone from a 3,8 %
conversion of sunlight to electricity to 19,3 % over the five
years to 2015. Researchers believe they can get it to 50 %.
Henry Snaith, a physicist at the University of Oxford, has
already spunout his research intoanewcompany calledOxford
PhotoVoltaics. They are working with glass manufacturers to
create perovskite glazing materials. This will add 10 % to the
price of existing glass, give it a slight grey tinge, and permit
electricity generation at 6-8 % efficiency. They want to follow
that up with perovskite-embedded roofing tiles.
There are some concerns about the use of lead in the
current formulation, even though Snaith points out that
existing coal produces 10 times the lead for the amount
needed in a 1 terrawatt perovskite array. Researchers are
already looking for alternatives, with tin perovskites being
a recent prospect.
The next problem is energy storage, but even here there
are numerous options, ranging from fast-charging capaci-
tors for regenerative braking, and metal-air batteries.
Metal-air, and aluminium-air batteries in particular, are
amongst themost interesting for future energy storage. They
offer the most energy dense power storage currently known
but are difficult to recharge. Aluminium, which is cheap and
abundant, offers promise but the current approach converts
the anode to hydrated aluminium. Technically, this can be
recovered and converted back into aluminium, but you’re
still going to be physically replacing the anode when you
need a recharge.
A recent announcement by Fuji Pigment is that they have
solved the lifespan problem by incorporating a secondary
battery into the design. They hope to commercialise this
by 2016 which means we should see some prototypes
demonstrated later this year.
Flow batteries are another alternative, and work by
pumping liquid electrolytes of iron, zinc or potassium
through a cell. Increasing the scale of the battery is a matter
of increasing the electrolyte volume. The costs come from
the electrolyte solution and the ion-exchange membranes.
The heavy subsidies aimed at residents have obscured
a mature market message. It is not economic or efficient
to distribute generation to individual home-owners. Imag-
ine maintaining your own flow battery, or monitoring and
replacing aluminium anodes in your metal-air battery in a
dedicated battery-room at the bottom of the garden.
The likelihood is that local utilities will act as energy
stores for residents and businesses, and they will buy energy
from the most effective suppliers. Solar during peak sun-
shine, wind during appropriate weather, and from nuclear
(if we’re ever allowed, or Zuma has his way) or gas when
nothing else is available.
Electric cars will still be able to act as peak energy stores
in such a design but such a grid will need to be extremely
flexible to handle multiple energy sources, load balancing,
as well as mobile battery stores in motor-vehicles.
That also requires flexible regulators. And, as with so
many things, the technology will become available long
before the politics is ready to absorb it.