The sun's core is so hot, and there is so much
pressure, nuclear fusion takes place: hydrogen is changed to helium. Nuclear fusion
creates heat and photons (light). The amount of solar heat and light is enough
to light up Earth’s day and keep our planet warm enough to support life. But we
still cannot capture enough energy from it.
According to Professor Erwin Reisner from Cambridge University, it’s possible to create fuel from thin air with artificial leaves.
Erwin and his team to capture more
of that free energy.
Although solar panels are used to convert light from the sun, they have made significant advances in the last several years, becoming cheaper and more efficient, they just provide electricity, not storable liquid fuels, which are still in great demand.
Professor Reisner raised a question – he said
when we have covered that 25%, what do we do next?
Plants are a beautiful and massive inspiration because they
have learned over millions of years how to take up sunlight and store the energy
in energy carriers.
Reisner believes that artificial photosynthesis will be
one part of that energy portfolio over the next two decades.
As we all know, when plants photosynthesis, they take up
water and carbon dioxide and use light from the sun to convert these raw
materials into the carbohydrates they need for growth.
Reisner and his team want to replicate this, however
they don’t really want to make carbohydrates because they make a lousy, so
instead of making carbohydrates, they will try to make something that can be
more readily used.
An additional problem is that plants aren’t actually
terribly good at photosynthesis, converting only around one or two percent of
solar energy into fuel.
Therefore the US Department of Energy has concluded that
for artificial photosynthesis to be viable economically, efficiency needs to
rise to between five and 10%.
How promising
this research would be?
Professor Reisner and his team have worked on several
approaches, including a system that mimics natural photosynthesis, using
enzymes to split water and create hydrogen for fuel.
But the efficiency is still low, and as a gas, hydrogen is
difficult to store.
It might be more promising in the long term – the team
recently developed a small device that converts sunlight, carbon dioxide and
water into oxygen and formic acid, a liquid fuel that has a high energy
density.
The device contains a panel that sits in a bath of water
and carbon dioxide. Under sunlight, the panel releases electrons, which combine
with the carbon dioxide and the protons in the water to make formic acid.
According to Reisner, these systems are like panels or
sheets; it’s a fragile device – you can almost think of it as a sheet of
paper.
The incredible thing about the device is the fact that
it is standalone. It doesn’t require an external power source, nor any top-ups
of additional catalysts.
Similar
projects – the center for hybrid approaches in Solar Energy to Liquid Fuels
(Chase) and the Liquid Sunlight Alliance (Lisa)
Chase the project led by the University of North Carolina at Chapel Hill
is working on practical applications similar to the Cambridge device by
developing systems that, like solar panels, use semiconductors to absorb light,
and then use various different catalysts to convert carbon dioxide to fuel.
A particular focus of this research is the concept of
cascade catalysts. Turning carbon dioxide into a usable fuel involves making
more than one chemical transformation, and catalysts can handle only one at a
time.
The first one does the first step and then passes its products
off to the next catalyst. Each one would be operating a very highly selective
process and handing off after that individual step to the partner down the
road.
Lisa
project is taking a more theoretical approach, focused on improving
every stage and component of artificial photosynthesis. Potential catalysts and
processes are modeled by computers before they’re tried out.
They have a vigorous theory effort, and the theory and
the experiment go hand in hand researchers now have the world’s
largest database.
According to Prof Dempsey,
the bad news is that they are not likely to see fields full of photosynthesis
panels anytime soon, there are still major stumbling blocks.
Bringing together all the technology into one bundle is a
problem.
"There's
been some incredible science in terms of light-harvesting, in terms of the
catalysis that makes the fuel and in terms of managing systems.
"But the integration of these individual components into a system
capable of artificial photosynthesis is a huge challenge."
It's
also difficult to ensure that the reactions produce a commercially-viable fuel,
with many of the catalysts that can achieve this being too expensive or too
inefficient for large-scale use.
"When you're dealing with constant radiation [sunlight] that can
cause a reaction that can be highly detrimental and corrosive."
As a result, artificial photosynthesis still can't produce liquid fuel
cheaply to compete with fossil fuels. "But the dynamic
can change very quickly,
Conclusion
The oil price can change, taxation can change. And when
things start shifting, at some point in the future, the price of artificial
photosynthesis will go down, and the price of fossil fuels will go up.
"If you go back 10 years, even the most optimistic
predictions for the cost of photovoltaic-derived electricity did not match what
happened.
The cost came down
by 85%, which is incredible. Once the economy of scale comes in, a lot is possible.
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