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Japan's Northernmost Mega Solar Plant Fighting Against Snow (page 3)

5-year struggle over tilt angle, height of mounting system

2013/12/22 19:34
Kenji Kaneko, Nikkei BP CleanTech Institute
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Utilization rate even on par with national average of 11.8%

When studying grid stabilization technologies using large secondary cells, NEDO installed NGK Insulators Ltd's sodium-sulfur (NAS) cells with 1.5MW output in conjunction with the 5MW solar power plant (Fig. 6). The system was operated primarily focusing on two technologies: "output fluctuation control" and "programmed operation."

In solar power generation, the output drastically fluctuates in a short time should clouds block the sun on a sunny day. If such fluctuation could be controlled, the load on the power grid can be alleviated. Setting a target of controlling the range of fluctuation by about 80%, a control effect almost equivalent to this target was confirmed in the verification test.

"Programmed operation" is a method of controlling the operation to achieve the programmed load (trend in the amount of power generation) by predicting the hourly output of solar power generation based on the weather forecast and formulating a power generation program in advance in accordance with the discharge and charge of the secondary cells. Although the reproducibility is significantly affected by the accuracy of the weather forecast-based prediction of the power generation volume, improvement in the prediction accuracy was confirmed through the verification test.

After the verification test, Wakkanai Megasolar Power Plant became a facility for the power selling business run by Wakkanai City. Following the implementation of the feed-in tariff scheme, the plant now brings about power sales of ¥140 to 150 million to the city every year. The plant is also the focus of studies where the aging impact can be assessed since it is one of the first large-scale solar power plants in Japan.

In fiscal 2010, its yearly utilization rate was 11.8%; in fiscal 2011 the rate was 10.1%; and in fiscal 2012 the rate was 10.1%. Despite the slight fluctuations caused by the weather, the rate has been stable since operations started in 2006.

Cold regions do not seem to be suited for solar power generation, but this plant can achieve a facility utilization rate equivalent to the national average (12%), as seen in fiscal 2010. In the amount of power generation by month, its facility utilization rate was relatively higher in Japan during the cold period without snow from April to June (Fig. 7).

From this verification test, key factors and challenges to large-scale solar power plants in snowy regions surfaced; that is, (1) how to boost the amount of power generation through measures against snow cover during the period between November and February where the amount of power generation decreases greatly and (2) how to generate as much power as possible in spring and summer, when it can generate more power than in other months.