Tuesday, November 19, 2013

No. 807: Controlling power transmission and distribution on the second time scale (November 19, 2013)

Increased power supply increases frequency, while decreased power supply decreases frequency. Hence, electric power companies control output to keep frequency of their power transmission networks stable because failure to stabilize the frequency leads to power outage. NEC developed a technology to control power transmission and distribution by seconds. The new technology measures frequency and monitors overs and shorts of power using equipment installed in a lithium-ion battery. At the request of electric power companies managing power transmission networks, it controls storage and discharge of electricity automatically. It can control more than one million storage batteries. Repetition of discharge and charge is supposed to shorten the life of a lithium-ion battery, but the fluctuation of life can be ignored as long as remaining amount is kept around 50%.   

A company that manages power supply of multiple buildings is called aggregator. Electric power companies can reduce investment on equipment for the adjustment of power supply and demand using the service offered by aggregator. Aggregators have great presence in the U.S., but they are not widespread in Japan. NEC wishes to open up the road of the aggregation business with this new technology. In addition, the technology to manage a large number of batteries by remote control can be applied to the smart city concept. In Japan, electricity retailing will be liberalized in 2016. Because the output by photovoltaic and wind generation largely depends on weather, NEC’s new technology to control and adjust power supply on the second time scale will be of great help to the spread of renewable energy.  

Various efforts are being made to establish
stable power supply (Tokyo Station at night)

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