33 / 132
EuroWire – January 2012
31
Transatlantic cable
“That’s the challenge you have in running the power system,”
Mr Wald was told by Mark T Osborn, a General Electric executive
who is working on a similar installation in Oregon. “Storage
has been thought about for years, but the costs have always
been too high. Now when you’re trying to integrate more
renewable resources, storage becomes more necessary.” Even
in the millions, though, batteries are not up to storing a night’s
wind production and giving it back during the day. Nor can they
supply power when the wind turbines are idle for more than a
few minutes. The batteries are so small – between C and D cell
in size – that the wind farm could fully charge them in as little
as 15 minutes. Even at a time of peak demand the energy stored
would be worth only a few hundred dollars. Wrote Mr Wald:
“The economics can be likened to storing tap water in a solid
gold vessel.”
Eventual pro ts, bigger projects
But the batteries perform two other tasks that hold promise for
the energy industry. According to AES, rather than storing power
on a daily basis the installation will justify itself by storing energy
for minutes at a time, repeatedly. In the space of an hour, the
output from the wind farm could go from 98mW to zero.
“In any short couple-minute interval, it could vary 20 or 30 or
40 per cent,” said John M Zahurancik, vice president for operations
and deployment at AES Energy Storage. By smoothing out the
changes the batteries would enable the rest of the grid to catch
up. The battery installation at Laurel Mountain is also expected to
prove useful with a di erent kind of grid stabilisation: keeping the
alternating current system correctly synchronised.
To hold the system as close to 60 cycles as possible the regional
grid operator, PJM Interconnection, sends a signal every four
seconds, instructing that power to be added or withdrawn as
needed.
“Experts foresee other roles as the grid evolves,” Mr Wald
wrote. “For example, PJM operates a real-time market in
which electricity is priced in ve-minute blocks. At a given
location, the price from one block to the next can vary
signi cantly.” A big battery array could make money in that
market, according to David L Hawkins, a senior consultant
at KEMA, the energy consultancy based in Arnhem, the
Netherlands. “It’s kind of like being a day trader on Wall
Street,” Mr Hawkins told the
Herald Tribune
. “If you see a
$30 price spread, you can make some interesting trades
doing it over and over in the course of a day.”
Postscript . . .
On 9
th
November, in the same publication, Mr Wald reported
that between 3
rd
October and 18
th
October the battery
installation at the Laurel Mountain wind farm was the site
of a big bird kill. Some 500 nocturnal migrants of 30-plus
species were found to have “either collided with structures
at the [electrical] substation or circled to the point of
exhaustion,” according to a report by a wildlife biologist with
the Canadian consulting service Stantec. The report, for the
US Fish and Wildlife Service, a bureau of the Dept of Interior,
said that the birds had not been killed by the blades of the
wind machines; rather, they seemed to have been drawn
to lights around the storage batteries and the associated
substation.