EoW January 2012

Transatlantic cable

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regional grid operator, PJM Interconnection, sends a signal every four seconds, instructing that power to be added or withdrawn as needed.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.

“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.

31

EuroWire – January 2012