IEEE Spectrum July, 2011 - 18

$338 billion to $476 billion

in Hazel Township, Pa.,
to take advantage of it.
One challenge will be
competition from batterybased frequency regulators, which are cheaper
per megawatt to install.
Several battery systems
are testing the market,
including a 20-MW frequency regulating facility that Arlington, Va.-
based power firm AES is
building in Johnson City,
N.Y. The $22 million plant
uses lithium batteries
from A123 Systems.
If facilities such as

drumroll, pleaSe:
A carbon-fiber flywheel is
removed from a coating
chamber. photo: BEacon powEr corp.

AES's succeed, frequency
regulation could soon
be lithium batteries'
biggest market. Sanyo
Electric, the market leader
in lithium-ion battery
production, bets that
frequency regulation and
other grid applications
will account for twofifths of lithium battery
sales in 2020. Electric
vehicles and consumer
electronics will split the
rest of the $60 billion
market, Sanyo predicts.
Beacon, for its part,
bets that the apparent cost
18

advantage of batteries
will literally erode with
time, as constant cycling
degrades their capacity.
The company says its
flywheels in Massachusetts
experience the equivalent
of 6000 cycles of full
charge and discharge or
more per year and are
designed to withstand that
abuse for 20 years, with
minimal maintenance or
performance degradation.
Kema's Hawkins
agrees that batteries
will lose their edge over
flywheels under that level
of use. "A battery really
doesn't like to be totally
charged and discharged,"
says Hawkins, "whereas
flywheels can handle a
pretty severe duty cycle."
But he says that
another threat looms, one
that could eviscerate the
market for frequency
regulation: millions of
electric vehicles. Plugged
in to the grid, they could
respond to frequency
deviations at the local level.
Pacific Northwest
National Laboratory, a unit
of the U.S. Department of
Energy, proved a similar
concept a few years ago,
showing that electric water
heaters and dryers could
correct frequency dips by
temporarily turning off
their heating elements. In
March, PNNL licensed the
concept to Texas-based
semiconductor start-up
Encryptor, which hopes to
make chips for appliances.
So in the future, the
frequency regulator could
be you.
-Peter Fairley

NA * IEEE SpEctrum * july 2011

cost of building a u.S. smart grid, according to a report
by the Electric power research Institute.

Superconductor
Logic Goes
Low-Power
energy-efficient superconducting circuits
could be key to future supercomputers

T

ransistor-based
semiconductors
have dominated the
computing industry since its
start. But a much more exotic,
transistor-less option has long
been lurking in the wings.
Superconducting circuits,
which boast resistance-less
wires and ultrafast switches,
can perform the tasks that
silicon-based systems do in
a fraction of the time.
Now new logic designs
are emerging that suggest
superconducting processors
could be not only faster but
also tens or even hundreds
of times as energy efficient
as their CMOS cousins. And
these processors could provide a much-needed path to
the next generation of supercomputers, proponents say.
This next generation,
called exaflop computers,
would be capable of
executing a quintillion
(1018) operations per second,
about 1000 times as many
as existing computers can.
Once thought to be just 5 or
10 years away, they now seem
nearly impossible. A recent
estimate suggests that an
exascale supercomputer built
using CMOS technology
would consume some 500
megawatts-the output of
a modest nuclear power

plant. "What everybody's
shooting for is to be able to
overturn [that] result," says
Erik DeBenedictis of Sandia
National Laboratories,
in Albuquerque. "Now
there's a glimmer of light
that it might happen."
Superconducting
circuits have long been an
attractive option for ultrafast
processors. Chilled down to
a few degrees above absolute
zero, superconducting logic
gates can perform operations
in picoseconds with less than
a microwatt of power. Simple
superconducting logic circuits
have been shown to operate at
speeds of up to 770 gigahertz.
But the technology
has been slow to make its
way into complex circuits.
Since the early 1990s, most
superconducting circuits
have been built using a design
called rapid single-flux
quantum (RSFQ) logic, which
relays bits of information
in the form of short voltage
pulses carried by tiny,
speeding vortices of current.
RSFQ has been used to
build a number of specialized
devices needed for highthroughput and numerically
intensive applications, such
as communications receivers
and signal processing. But
the design consumes too
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Table of Contents for the Digital Edition of IEEE Spectrum July, 2011
