'Hybrid Power Storage System' Stabilizes Solar, Wind Electricity

2014/04/08 18:22
Kenji Kaneko, Nikkei BP CleanTech Institute

The Chugoku Electric Power Co Inc announced that it will use a "hybrid power storage system" to compensate the unstable outputs of solar and wind power generation facilities in a field test.

The test will be carried out in Oki Islands, Shimane Prefecture, Japan. It was selected as "the Storage Battery Verification Project for the Introduction of Renewable Energy to Isolated Islands in Fiscal 2014."

The hybrid power storage system is Japan's first storage battery system that was developed for controlling power grid facilities and consists of sodium-sulfer (NAS) and lithium-ion (Li-ion) rechargeable batteries.

Because the outputs of solar and wind power generation facilities sharply fluctuate depending on weather, it is necessary to adjust the fluctuation to keep the quality of electricity. Especially in isolated islands whose power grid is not connected to the main land, the scale of power grid is smaller than that in the main land, increasing the impact of the fluctuation in the amount of electricity generated. Therefore, to introduce large-scale solar and wind power generation facilities, the output fluctuation needs to be adjusted.

The field test will be performed in the aim of maximizing the amount of renewable energy-derived electricity generated in Oki Islands. To achieve that goal, The Chugoku Electric Power will establish the hybrid power storage system by combining two types of rechargeable batteries that have different properties and taking advantage of each of the two types. In the test, the company will verify technologies related to the efficient charge/discharge and control of the rechargeable batteries in cooperation with a local government, etc.

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Specifically, 4.2MW of NAS batteries and 2MW of Li-ion batteries will be set up in Nishinoshima-chou, Oki-gun, Oki Islands.

There are two kinds of output fluctuations related to solar and wind power generation facilities. They are "fast, small fluctuation (short-period fluctuation)," which is caused by clouds changing solar irradiation or changes in wind speed, and "slow, large fluctuation (long-period fluctuation, surplus electricity), which is caused by changes in the position of the sun.

In isolated islands, such output fluctuations are adjusted with diesel generators. However, when the amount of renewable energy-derived electricity drastically increases, it causes a shortage of adjusting power, making it necessary to use rechargeable batteries for the adjustment.

The Chugoku Electric Power will establish a system that uses high-output Li-ion batteries and large-capacity NAS batteries to compensate the fast, small fluctuation and slow, large fluctuation, respectively. And the company will test technologies for the coordination of the two kinds of batteries.