This a neat idea.
If it can be properly miniaturized to allow the design of an efficient insulation
and heat transfer system it may well be useful.
What is useful is the production of carbon monoxide and hydrogen in exchange
for the solar input.
Even splitting out the two components may be the answer
in terms of economics. At least it gives
us an independent source of hydrogen that is not costing us good fuel. So this protocol may really have a future in
some application or the other.
Ultimately this is a heat engine system doing the same
thing as the mirror systems, but possibly a lot cleverer.
New solar fuel machine 'mimics plant life'
By Neil BowdlerScience
reporter, BBC News
In the prototype, sunlight heats a ceria
cylinder which breaks down water or carbon dioxide
A prototype solar device has been unveiled which mimics
plant life, turning the Sun's energy into fuel.
The machine uses the Sun's
rays and a metal oxide called ceria to break down carbon dioxide or water into
fuels which can be stored and transported.
Conventional photovoltaic
panels must use the electricity they generate in situ, and cannot deliver power at night.
Details are published in the
journal Science.
The prototype, which was
devised by researchers in the US
and Switzerland
Ceria has a natural
propensity to exhale oxygen as it heats up and inhale it as it cools down.
If as in the prototype,
carbon dioxide and/or water are pumped into the vessel, the ceria will rapidly
strip the oxygen from them as it cools, creating hydrogen and/or carbon
monoxide.
Hydrogen produced could be
used to fuel hydrogen fuel cells in cars, for example, while a combination of
hydrogen and carbon monoxide can be used to create "syngas" for fuel.
It is this harnessing of
ceria's properties in the solar reactor which represents the major
breakthrough, say the inventors of the device. They also say the metal is
readily available, being the most abundant of the "rare-earth"
metals.
Methane can be produced using
the same machine, they say.
Refinements needed
The prototype is grossly
inefficient, the fuel created harnessing only between 0.7% and 0.8% of the
solar energy taken into the vessel.
Most of the energy is lost
through heat loss through the reactor's wall or through the re-radiation of
sunlight back through the device's aperture.
But the researchers are
confident that efficiency rates of up to 19% can be achieved through better
insulation and smaller apertures. Such efficiency rates, they say, could make
for a viable commercial device.
"The chemistry of the
material is really well suited to this process," says Professor Sossina
Haile of the California Institute of Technology (Caltech). "This is the
first demonstration of doing the full shebang, running it under (light) photons
in a reactor."
She says the reactor could be
used to create transportation fuels or be adopted in large-scale energy plants,
where solar-sourced power could be available throughout the day and night.
However, she admits the fate
of this and other devices in development is tied to whether states adopt a
low-carbon policy.
"It's very much tied to
policy. If we had a carbon policy, something like this would move forward a lot
more quickly," she told the BBC.
It has been suggested that
the device mimics plants, which also use carbon dioxide, water and sunlight to
create energy as part of the process of photosynthesis. But Professor Haile
thinks the analogy is over-simplistic.
"Yes, the reactor takes
in sunlight, we take in carbon dioxide and water and we produce a chemical
compound, so in the most generic sense there are these similarities, but I
think that's pretty much where the analogy ends."
Daniel Davies, chief
technology officer at the British photovoltaic company Solar Century, said the
research was "very exciting".
"I guess the question is
where you locate it - would you put your solar collector on a roof or would it
be better off as a big industrial concern in the Sahara and then shipping the
liquid fuel?" he said.
Solar technology is moving
forward apace but the overriding challenges remain ones of efficiency, economy
and storage.
New-generation "solar tower"
plants have been built in Spain
and the United States
A new Spanish project will use molten
salts to store heat from the Sun for up to 15 hours, so that the plant could
potentially operate through the night.
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