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79MW Solar Plant Achieves Utilization Rate of 17.6% in Tohoku (page 4)

2x areal efficiency, 1.6x overloading by setting up more than 1MW per 1ha

2019/06/24 17:59
Kenji Kaneko, Nikkei BP Intelligence Group, CleanTech Labo
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Space to stop arrays shading behind on spring and autumnal equinox

If panels are set up in such a conventional style, arrays will not shade other panels between 9am and 3pm, when the most power is generated, even on the winter solstice (when the sun's culmination altitude is the lowest during the year). In other words, arrays are spaced so they will not shade the panels between 9am and 3pm on the winter solstice at most solar power plants. This is because, in this way, no panels are shaded from 9am to 3pm, when the most power is generated, throughout the year.

If the conditions to "keep arrays from shading panels between 9am and 3pm on the winter solstice" is applied to the Watari Solar Power Plant, where each array consists of panels in eight rows, the space between the arrays will reportedly be as long as "about 3.8m." This is because the height of an eight-row array, whose width (depth) is about 8m, reaches 2.7m on the highest rear side even if it is only tilted by 10°.

However, the space between the arrays is "1.4m," less than half of the Watari Solar Power Plant. In fact, the space between the arrays at this power plant corresponds to "keeping the arrays from shading panels from 9am to 3pm on the spring and autumnal equinox." As the sun's culmination altitude on the spring and autumnal equinox is in the middle of that on the midsummer and winter solstices, some panels are shaded half a year from the autumnal equinox day to the winter solstice through the spring equinox (Fig. 6).

Fig. 6: Array designs at Watari Solar Power Plant. Distance to "keep arrays from shading panels from 9am to 3pm on spring and autumnal equinox" adopted. KC arrays manufactured by Kyocera, SF arrays made by Solar Frontier (source: Yamasa)

Yet Yamasa adopted such a design because it analyzed, as a result of computer simulations, the amount of annual power generation rises by boosting the areal efficiency to increase the number of solar panels despite the loss from the panels shaded for half a year.

The company estimates the annual power generation will total 75,880,000kWh and the utilization factor of the PV inverters and the grid facilities will reach 17.57%. Compared with the utilization factor of 15 to 16% estimated for other new mega-solar plants in Japan, this plant outperforms the national average by several points despite being located in the Tohoku region.

Compared with the adjacent mega-solar plant with a conventional design, it is so evident how narrow the space is between the arrays is and how high the areal efficiency is at the Watari Solar Power Plant. In the drone photo shot from above, no ground can be seen as the panels appear to be connected with each other at the Watari Solar Power Plant, whereas the ground between the arrays can be seen at the conventionally designed mega-solar plant (Fig.7).

Fig. 7: Conventionally designed mega-solar plant left bottom, Watari Solar Power plant top (source: Yamasa)