 |
| The NaS battery system could
help utilities avoid construction of new transmission
lines, substations and power plants. Plus, they
make wind power more reliable and provide backup
power in case of outages, such as the one that
hit New York City last week during a heat wave. |
Batteries have long been vital to
laptops and cellphones. They are increasingly supplying
electricity to an unlikely recipient: the power
grid itself.
Until recently, large amounts of electricity
could not be efficiently stored. Thus, when you
turn on the living-room light, power is instantly
drawn from a generator.
A new type of a room-size
battery, however, may be poised to store energy
for the nation's vast electric grid almost as easily
as a reservoir stockpiles water, transforming the
way power is delivered to homes and businesses.
Compared with other utility-scale batteries plagued
by limited life spans or unwieldy bulk, the sodium-sulfur
battery is compact, long-lasting and efficient.
Using so-called NaS batteries, utilities could defer
for years, and possibly even avoid, construction
of new transmission lines, substations and power
plants, says analyst Stow Walker of Cambridge Energy
Research Associates. They make wind power — wildly
popular but frustratingly intermittent — a more
reliable resource. And they provide backup power
in case of outages, such as the one that hit New
York City last week.
Such benefits are critical,
because power demand is projected to soar 50% by
2030 and other methods of expanding the power supply
are facing growing obstacles. Congress is likely
to cap carbon dioxide emissions by traditional power
plants to curtail global warming. Meanwhile, communities
are fighting plans for thousands of miles of high-voltage
transmission lines needed to zap electricity across
regions.
A test case in West
Virginia
American Electric Power (AEP), one of the
largest U.S. utilities, has been using a 1.2 megawatt
NaS battery in Charleston, W.Va., the past year
and plans to install one twice the size elsewhere
in the state next year. Dozens of utilities are
considering the battery, says Dan Mears, a consultant
for NGK Insulators, the Japanese company that makes
the devices.
"If you've got these batteries distributed
in the neighborhood, you have, in a sense, lots
of little power plants," Walker says. "The difference
between these and diesel generators is these batteries
don't need fuel" and don't pollute.
The NaS battery
is the most advanced of several energy-storage technologies
that utilities are testing. The oldest and most
widespread form of energy storage in the USA, pumped
hydroelectricity, collects water after it spins
a turbine and uses a small amount of electricity
to send it back and repeat the process.
Lead-acid
batteries — the same kind used in cars — were installed
by Southern California Edison in 1988. But the batteries,
though inexpensive, typically fill warehouse-size
buildings and last about five years. That's because
the acid that connects positive and negative electrodes
corrodes components.
An NaS battery, by contrast,
uses a far more durable porcelain-like material
to bridge the electrodes, giving it a life span
of about 15 years, Mears says. It also takes up
about a fifth of the space. Ford Motor pioneered
the battery in the 1960s to power early-model electric
cars; NGK and Tokyo Electric refined it for the
power grid.
Since the 1990s, Japanese businesses
have installed enough NaS batteries to light the
equivalent of about 155,000 homes, says Brad Roberts,
head of the Electricity Storage Association. In
the USA, AEP is using the 30-foot-wide by 15-foot-igh
battery to supply 10% of the electricity needs of
2,600 customers in north Charleston, says Ali Nourai,
AEP manager of distributed energy. The battery,
which cost about $2.5 million, is charged by generators
from the grid at night, when demand and prices are
low, and discharged during the day when power usage
peaks.
By easing strains on the grid, especially
on the hottest summer days, the battery lets AEP
postpone by about seven years the roughly $10 million
upgrade of a substation and reduce the chances of
a blackout, Nourai says. After it upgrades the substation,
AEP can move the battery to another location.
"Our
vision is to have (batteries) throughout our system,"
he says.
Storing wealth from wind farms
A more intriguing
goal is to wring more energy out of the wind farms
that are cropping up across the country. Wind typically
blows hard at night when power demand is low, producing
energy that cannot be used. When demand peaks midday,
especially in the summer, wind is often sporadic
or absent. NaS batteries could let AEP store wind-generated
power at night for daytime use.
Next year, AEP plans
to install another NaS battery in West Virginia
to provide backup power in case of an outage — the
first such application of the technology, Nourai
says. The battery would kick in automatically, so
customers would see no disruption.
Other utilities
are planning or considering the technology. In Long
Island, N.Y., a group of utilities plans this summer
to install an NaS battery at a bus depot. The battery
is charged at night, when power prices are low,
and discharged during the day to pump natural gas
into tanks to provide fuel for the buses, says Mike
Saltzman of the New York Power Authority. That cuts
electric costs for the bus company and eases stresses
on the grid. Pacific Gas & Electric is leaning toward
installing a much larger, 5-megawatt battery by
2009, enough to power about 4,000 homes, says PG&E's
Jon Tremayne.
The biggest drawback is price. The
battery costs about $2,500 per kilowatt, about 10%
more than a new coal-fired plant. That discourages
independent wind farm developers from embracing
the battery on fears it will drive the wholesale
electricity prices they charge utilities above competing
rates, says Christine Real de Azua, spokeswoman
for the American Wind Energy Association.
Mass production,
however, is expected to drive prices down, Mears
says. He predicts NaS batteries will start to become
widespread within a decade.
Meanwhile, other storage
devices are gaining traction, too. A group of Iowa
municipal utilities plans to use wind turbines to
compress air during off-peak hours that will be
stored in an underground cavern. The air would be
released at peak periods to run turbines and generate
power for about 200,000 homes. Another technology,
the flywheel, has a massive cylinder that can spin
for days after being started by a generator. The
cylinder can then activate a turbine to supply electricity
for a few seconds or minutes when it's needed, for
instance, to head off an interruption to a computer
center from a lightning strike.
"We'd like to see
storage ubiquitous," says Imre Gyuk, head of energy
storage for the Department of Energy, which helped
fund the AEP project. "Stick it any place you can
stick it."
