Beyond Fossil Fuels
Finding New Ways to Fill the Tank
Riccardo Signorelli, chief executive of FastCap Systems, which is
developing capacitors using nanotube technology.
Published: August 18, 2010
CAMBRIDGE, Mass. — Most research on renewable energy has focused on
replacing the electricity that now comes from burning coal and natural
gas. But the spill in the Gulf of Mexico, the reliance on Middle East
imports and the threat of
global warming are reminders that
oil is also a pressing worry. A lot of problems could be solved with
a renewable replacement for oil-based gasoline and diesel in the fuel
tank — either a new liquid fuel or a much better battery.
Yet, success in this field is so hard to reliably predict that
research has been limited, and even venture capitalists tread lightly.
Now the federal government is plunging in, in what the energy secretary,
Steven Chu, calls the hunt for miracles.
The work is part of the mission of the new Advanced Research Projects
Agency - Energy, which is intended to finance high-risk, high-reward
projects. It can be compared to the
Defense Advanced Research Projects Agency, part of the Pentagon,
which spread seed money for projects and incubated a variety of useful
technologies, including the Internet.
The goal of this agency, whose budget is $400 million for two years,
is to realize profound results — such as tens of millions of motor
vehicles that would run 300 miles a day on electricity from clean
sources or on liquid fuels from trees and garbage.
One miracle would be a better battery. A pound of gasoline holds
about 35 times more energy than a pound of lead-acid batteries and about
six times more than
lithium-ion batteries. Cars must carry their energy and expend
energy to carry it, so the less weight per unit of energy, the better.
David Danielson, an Energy Department official, oversees a program to
invest in start-up companies with new approaches to batteries, which is
a new strategy; in the early 1990s, the department decided to
concentrate all its efforts in lithium-ion research and gave up on other
chemistries.
One new technology would allow every car, at modest extra cost, to
shut down automatically at each stop sign or red light; when the driver
tapped the accelerator, the battery would instantly get it going again.
(Hybrids like the Prius do that, but at a substantial cost premium.)
A team at an infant company is using tiny carbon structures called
nanotubes to store electricity. The goal is to create something the size
of a flashlight battery, holding only about 30 percent as much energy,
but able to charge or discharge in two seconds, almost forever.
The technology could form part of the battery pack for a car, cheaply
delivering the energy for a jackrabbit start, without damaging
conventional chemical batteries, which can store vastly more energy but
can only accept or deliver it slowly.
It could also provide a cellphone battery that would charge in five
minutes. That kind of battery is called a capacitor.
Joel E. Schindall, a professor at the
Massachusetts Institute of Technology and a scientist on the
project, pointed out that a capacitor was the original battery.
Benjamin Franklin built a set of glass bottles that stored
electricity and released it all at once; he called it a battery because,
like guns, the bottles fired simultaneously.
But the nanotubes are modern. The walls of the tubes are about 12
atoms thick, and they grow, like leaves of grass, with just enough space
between them to provide docking stations for charged particles. So a lot
of charged particles can fit into a small space, with very light
structures. He compares the device to a book shelf with very thin
shelves placed exactly far enough apart to accommodate the books.
Because the connection is physical, not chemical, the charged particles
can attach and detach almost instantly. The result is a small, light,
powerful package.
The project started out with a Ph.D candidate, Riccardo Signorelli,
using tweezers to put tiny squares of aluminum into a vacuum chamber and
then pumping in a hydrocarbon gas. When heated, the hydrogen burns away
and the carbon atoms arrange themselves into tubes. The breakthrough was
doing that on a surface that would conduct electricity.
Dr. Signorelli, now with his Ph.D, is chief executive of FastCap
Systems, which, with government help, is converting an industrial loft
into a factory.
In another M.I.T. lab, Gerbrand Ceder is developing a “materials
genome,” using computers to predict the qualities of materials that
could be used in batteries, and then fabricating the ones that the
computer finds promising. A materials genome would speed the
distribution of knowledge about materials and make development of new
materials faster, he said, an idea that impresses officials at the
Energy Department.
ARPA-E invested $3.2 million in a battery developed with a materials
genome in a start-up company, run by Professor Ceder, that is exploring
magnesium. In batteries today, whether they are lithium-ion or
old-fashioned lead-acid, an atom shuttles between the positive and
negative terminal, carrying a single electron, as the battery charges
and discharges. But a magnesium atom would carry two electrons, so a
battery storing a given amount of energy could be nearly halved in size
and weight.
Another approach being financed by ARPA-E is to convert the
tremendous amount of energy stored by plants and trees to a car fuel.
Scientists are tantalized by plants and trees because they store far
more energy than is consumed by cars, trucks, trains and planes, and
they do it by taking carbon out of the atmosphere. But they do not give
that energy back in an easy-to-use form, at least not without taking
millions of years to turn into oil. Instead, they make energy-bearing
sugars in a form called cellulose, which forms the sinew or skeleton of
the plant.
Cellulose is hard to break down. “Cotton is pure cellulose,” said
Eric Toone, who is Mr. Danielson’s counterpart for
biofuels at the Energy Department. “When you take your cotton shirt
and put it in a washing machine, it still comes out as a cotton shirt.”
Engineers have tried using steam, acids and enzymes to break
cellulose into useful sugars. The enzymes are usually made by
gene-modified bacteria or fungi and resemble the saliva of termites,
which is notoriously good at dissolving cellulose. So far, none are
commercial, but with Energy Department help, some researchers are trying
new methods.
Take Michael Raab, whose start-up, Agrivida, in Medford, Mass., is
tinkering with the genes of grass and sorghum to develop plants that
make the enzymes internally and digest their own cellulose on cue,
leaving behind a murky brown concoction of sugars that can be converted
into gasoline, diesel or jet fuel.
Deep inside their cells, his plants produce a smooth, nonreactive
molecule, but when the plant is exposed to heat and a change in acidity,
the molecule breaks open, like a beer bottle smashed against the bar.
The jagged edges are enzymes. They rip apart cell walls and leave
fragments that are useful sugars.
Sugars — both the common kind that comes in paper packets for coffee
and some more exotic types — can be converted by yeast into ethanol, a
technology known since ancient times. Or they can be fed to gene-altered
bacteria that will excrete diesel or gasoline components. Or they can be
converted chemically, with catalysts.
All these steps, including the tricky one of recovering sugar from
cellulose, can be done already, but not cheaply enough to produce tens
of billions of gallons a year.
The Energy Department is putting $4.6 million into Agrivida, and
similar sums into other start-up firms, many of them intent on finding
gasoline substitutes. It is, said one department official, “real science
fiction stuff,” ideas promising enough to attract a few million dollars
for research but not quite promising enough to draw the private capital
required for small-scale production.
Copyright 2010 The New York Times
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