A wind farm I visited last week has 98 megawatts of power, meaning it could run 30-odd Super Wal-Marts. But the maximum power of a battery installation is just 32 megawatts, or just one-third of that wind power, and it fills up in 15 minutes.As I wrote in Saturday’s paper, energy storage will be critical to making wind power more useful. Some wind farms are forced to dump a substantial portion of their production because they churn out megawatts in the middle of the night, when there is very little demand for it. At such times, some grid operators even charge generators for making power rather than paying them for it.
Still, the technology of batteries is changing. The ones in use at the Laurel Mountain wind farm in West Virginia are cylindrical, in a standard industry size that is between the C and D cells that are familiar to consumers. According to Bud Collins, vice president of A123 Systems, which supplied the batteries, the next iteration will be completely different, shaped like fat magazines.
Originally developed for the electric car industry, they will have more capacity.
The batteries at Laurel Mountain are stored in racks like those in a computer data center with air-conditioning units in between to keep them from overheating. As they charge and discharge, some of the energy is lost as heat. (In fact, the round-trip efficiency is about 90 percent; the other 10 percent either becomes heat or is used to power the air-conditioners.)
But if the number of batteries is increased, the amount of current running through each one will be smaller and heat buildup will be lower. That will allow the batteries to be more tightly packed without overheating, engineers say.
Costs are falling, as they are for various electronic components, but the economics of batteries remain dicey. One factor working in favor of more battery storage, though, is changes in the way grid operates.
PJM, the 13-state grid operator, functions both as a market for electricity and a market for various other services that batteries can help supply. One is regulation, which means injecting or subtracting power rapidly to keep the grid at a strict 60 cycles per second, the alternation in alternating current. The batteries do that now.
But another service for which batteries could be paid is “fast response.” Since a wind farm or a solar farm can change power levels very quickly, faster than most fuel-burning generators can adjust to, the grid operator needs other resources that can jump in and increase output or cut it almost instantly.
Scott Baker, a solutions analyst for PJM who specializes in the integration of energy technology with the grid, says the company is rewriting its rules in a way that will mean more revenue for batteries and other sources that can expand output quickly.
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