Japan's Northernmost Mega Solar Plant Fighting Against Snow
5-year struggle over tilt angle, height of mounting system
"Milk Road" is one of the main roads from Wakkanai Airport to the city of Wakkanai. Every morning, trucks loaded with fresh milk use the road, driving from local farms to milk processing factories. As the road supports the regional economy, in winter, snow is removed preferentially from this road. As you drive along Milk Road, you will see a group of solar panels neatly standing close together in the midst of the wetland and green hills. This is the 5MW "Wakkanai Megasolar Power Plant" (Fig. 1).
Polycrystalline silicon panel chosen from 5 types
The construction of this power plant commenced in 2006 as a verification facility of New Energy and Industrial Technology Development Organization (NEDO). The construction cost totaled approximately ¥5 billion (approx US$48 million). The project was aimed at operating a large-scale solar power generation system under severe weather conditions such as snow cover and frigidity, and studying grid stabilization technologies that leverage large-sized secondary cells.
The facility was transferred for free to Wakkanai City in March 2011 following the five-year verification test. Along with the 74 wind power facilities with approximately 76MW output in the city, the solar power plant is now a showpiece attraction for visitors as a renewable energy facility that represents the "environmental city Wakkanai," which is aiming for energy self-sufficiency.
Starting as a verification facility, the power plant gradually expanded as different kinds of solar panels were installed in four phases. In phase 1, in 2006, five types of solar panels from nine manufacturers were set up to verify the amount of power generation during the cold season.
Introduced then were the single- and poly-crystalline silicon panels manufactured by Sharp Corp, Kyocera Corp, Mitsubishi Electric Corp and SunPower Corp of the US; the multi-junction silicon (HIT solar) panels manufactured by Sanyo Electric Corp (now Panasonic Corp); the amorphous silicon (non-crystalline silicon) panels manufactured by Kaneka Corp and Mitsubishi Heavy Industries (MHI) Ltd; and the CIS panels manufactured by Solar Frontier KK and Honda Soltec Co Ltd.
After monitoring the amount of power generation for a year and calculating the "performance ratio (PR) rating," which indicates to what extent the expected power generation yield has been achieved, the crystalline silicon type showed relatively better results.
In solar cells, power generation loss increases in accordance with a rise in temperature. The loss at high temperature is large in the crystalline silicon cells though their conversion efficiencies are higher than the other types of solar cells. Their PR ratings were higher probably because such flaws of crystalline silicon cells did not show much thanks to the low temperature in the verification project in Wakkanai.
Based on the assessment, crystalline silicon panels and polycrystalline ones, in particular, whose cost efficiency is higher among those tested, were installed in and after phase 2. As a result, the polycrystalline silicon panels account for roughly 90% of the solar panels with 5MW output.
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