Hybrid power plant combining 50MW solar, 6MW wind power

The wind is always strong throughout the year in the Atsumi Peninsula of Aichi Prefecture, Japan, where local people get excited for "Hatsudako (first kite)" to wish for the growth of children and "Kenkadako (fighting kite)" to make kites fight in the "Tahara Kite Festival" in May. Tahara City takes up almost the entire peninsula, forming Japan's largest-class wind farm in its coastal area thanks to the favorable wind conditions. The "Tahara Solar Wind Power Plant" is also located in this wind farm.

Fig. 1: The Tahara Solar Wind Power Plant (three wind turbines from the left belong to this plant) (source: Mitsui Chemicals)

The mega-solar plant consists of solar panels with an output of 50MW, PV inverters with a rated capacity of 35MW and three large wind turbines with a total output of 6MW (2MW each). Its annual power generation is expected to total approximately 67,500MWh combining solar and wind power. This amount is equivalent to the consumption of 19,000 households, which correspond to roughly 90% of all households in Tahara City. The plant has been generating power favorably with the amount outperforming the estimate four years after the plant started operation.

Mitsui Chemicals, which led the plant development, boasts Japan's top-level achievements in diagnosis/assessment services for solar panels and overall solar power plants. The company has been asked to diagnose about 500 mega-solar plants thus far, with their total capacity reaching about 2.5GW. Mitsui Chemicals is now embarking on business development overseas, making a strategic move into the Indian market by leveraging its experience in Japan.

Mitsui Chemicals embarked on the solar panel diagnosis business because it had accumulated expertise in a resin material used for panels. The company has marketed a sealing material for panels for roughly 30 years. It is a film called ethylene vinyl acetate copolymer resin (EVA), which plays an important role in maintaining solar panel quality by keeping the airtight property between the cover glass and the cells (power generation elements).

Based on such panel expertise, Mitsui Chemicals began to assess power plants and has accumulated methods of predicting the power generation amount by monitoring more than 10 sites from Hokkaido to Kyushu.

"Now the accuracy has improved to within 1% on an annual basis between our estimate in advance and the actual value," said Tsuyoshi Shioda, senior manager of energy solutions, Next Generation Business Development Division, Mitsui Chemicals.

Panels of 4 different manufacturers installed

In fact, the Tahara Solar Wind Power Plant also plays the role of a verification site to accumulate expertise on assessing and analyzing such solar power generation systems of Mitsui Chemicals.

What indicates this are the four different types of solar panels adopted at this plant. The breakdowns are 26MW single crystal silicon type manufactured by LG Electronics Inc, a total of 20MW polycrystalline silicon type manufactured by Kyocera Corp and Sharp Corp, and 4MW CIS chemical compound type manufactured by Solar Frontier KK.

As you walk on the maintenance road in the middle from the entrance toward the seaside, you can see the four different types of solar panels one after another and easily understand the differences in cell colors and stripes. Products of Toshiba Mitsubishi-Electric Industrial Systems Corp (TMEIC) were adopted in all areas for the PV inverters (Fig. 2).

Fig. 2: TMEIC PV inverters and panels of LG Electronics, Kyocera, Sharp and Solar Frontier were adopted for solar power generation. (source: Nikkei BP)

"Adopting panels of four different types on this scale is like running four mega-solar power plants on one site," Shioda said. "On the other hand, we can observe a variety of aging changes through operation and maintenance, which can be leveraged for our solar panel and power plant assessment business."