| Scientists mimic essence of plants' energy storage system
CAMBRIDGE,
Mass. -- In a revolutionary leap that could transform solar power from
a marginal, boutique alternative into a mainstream energy source, MIT
researchers have overcome a major barrier to large-scale solar power:
storing energy for use when the sun doesn't shine.
Until
now, solar power has been a daytime-only energy source, because storing
extra solar energy for later use is prohibitively expensive and grossly
inefficient. With today's announcement, MIT researchers have hit upon a
simple, inexpensive, highly efficient process for storing solar energy.
Requiring nothing but abundant, non-toxic natural materials,
this discovery could unlock the most potent, carbon-free energy source
of all: the sun. "This is the nirvana of what we've been talking about
for years," said MIT's Daniel Nocera, the Henry Dreyfus Professor of
Energy at MIT and senior author of a paper describing the work in the
July 31 issue of Science. "Solar power has always been a
limited, far-off solution. Now we can seriously think about solar power
as unlimited and soon."
Inspired by the photosynthesis
performed by plants, Nocera and Matthew Kanan, a postdoctoral fellow in
Nocera's lab, have developed an unprecedented process that will allow
the sun's energy to be used to split water into hydrogen and oxygen
gases. Later, the oxygen and hydrogen may be recombined inside a fuel
cell, creating carbon-free electricity to power your house or your
electric car, day or night.
The key component in Nocera and
Kanan's new process is a new catalyst that produces oxygen gas from
water; another catalyst produces valuable hydrogen gas. The new
catalyst consists of cobalt metal, phosphate and an electrode, placed
in water. When electricity — whether from a photovoltaic cell, a wind
turbine or any other source — runs through the electrode, the cobalt
and phosphate form a thin film on the electrode, and oxygen gas is
produced.
Combined with another catalyst, such as platinum,
that can produce hydrogen gas from water, the system can duplicate the
water splitting reaction that occurs during photosynthesis.
The
new catalyst works at room temperature, in neutral pH water, and it's
easy to set up, Nocera said. "That's why I know this is going to work.
It's so easy to implement," he said.
'GIANT LEAP' FOR CLEAN ENERGY
Sunlight
has the greatest potential of any power source to solve the world's
energy problems, said Nocera. In one hour, enough sunlight strikes the
Earth to provide the entire planet's energy needs for one year.
James
Barber, a leader in the study of photosynthesis who was not involved in
this research, called the discovery by Nocera and Kanan a "giant leap"
toward generating clean, carbon-free energy on a massive scale.
"This
is a major discovery with enormous implications for the future
prosperity of humankind," said Barber, the Ernst Chain Professor of
Biochemistry at Imperial College London. "The importance of their
discovery cannot be overstated since it opens up the door for
developing new technologies for energy production thus reducing our
dependence for fossil fuels and addressing the global climate change
problem."
'JUST THE BEGINNING'
Currently
available electrolyzers, which split water with electricity and are
often used industrially, are not suited for artificial photosynthesis
because they are very expensive and require a highly basic (non-benign)
environment that has little to do with the conditions under which
photosynthesis operates.
More engineering work needs to be
done to integrate the new scientific discovery into existing
photovoltaic systems, but Nocera said he is confident that such systems
will become a reality.
"This is just the beginning," said
Nocera, principal investigator for the Solar Revolution Project funded
by the Chesonis Family Foundation and co-Director of the Eni-MIT Solar
Frontiers Center. "The scientific community is really going to run with
this."
Nocera hopes that within 10 years, homeowners will be
able to power their homes in daylight through photovoltaic cells, while
using excess solar energy to produce hydrogen and oxygen to power their
own household fuel cell. Electricity-by-wire from a central source
could be a thing of the past.
###
The project is part of the MIT Energy Initiative, a program designed
to help transform the global energy system to meet the needs of the
future and to help build a bridge to that future by improving today's
energy systems. MITEI Director Ernest Moniz, Cecil and Ida Green
Professor of Physics and Engineering Systems, noted that "this
discovery in the Nocera lab demonstrates that moving up the
transformation of our energy supply system to one based on renewables
will depend heavily on frontier basic science."
The success of
the Nocera lab shows the impact of a mixture of funding sources –
governments, philanthropy, and industry. This project was funded by the
National Science Foundation and by the Chesonis Family Foundation,
which gave MIT $10 million this spring to launch the Solar Revolution
Project, with a goal to make the large scale deployment of solar energy
within 10 years.
sOURCE: http://www.eurekalert.org/pub_releases/2008-07/miot-df073008.php [www.eurekalert.org]
| 
Capturing light: Ordinarily, the flat wires on the surface of solar cells that are used to collect electrical current prevent light from reaching the active material in a cell, reducing efficiency. A new design traps much of the light that would have been reflected. In the picture, some of the red light from a laser is redirected from the wire to areas on the cell where the light can be absorbed. The new approach dramatically helps improve the performance of solar cells without increasing costs. /Credit: 1366 Technologies
Solar cells provide great
opportunities for future large-scale electricity generation. However,
there are currently significant limitations, such as the relatively low
output of most solar cells (typically fifteen percent) and high
manufacturing costs.
