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Japan's Largest Solar Plant Withstands Ash, Salt, Strong Wind (page 3)

Widespread effort to realize 70MW output, finish construction in 14 months

2013/12/01 19:56
Shinichi Kato, Nikkei BP CleanTech Institute
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PV inverter selected focusing on protection against salt

Kagoshima Mega Solar Power explained that the major factor behind choosing SMA Solar Technology's PV inverter was its salt-resistance. To prevent salt damage, Japanese manufacturers' PV inverters for large-scale solar power plants had to be housed in a chassis that is covered by another salt-resistant chassis. This requires not only extra expense for the additional chassis but also running costs for the air-conditioning system necessary to keep the temperature inside the chassis from rising.

On the other hand, SMA Solar Technology's PV inverter has the benefit that it can be installed without such additional chassis and air-conditioning system because it features salt-resistance as a standard specification. It requires no additional chassis and air-conditioning system thanks to its simple structure based on natural cooling by fans and thermal exchange with the enclosed space.

"Although there were still some uncertain aspects including the support system, we took our chances based on SMA Solar Technology's global share of 30% and abundant experience in hostile regions such as salt damaged areas and deserts," said Michihiro Kita, Engineering Division, Kyocera Solar.

As it requires neither additional chassis nor air-conditioning system, SMA Solar Technology's PV inverter has the additional benefit of only taking up a smaller space. Just like the tilted angle of the solar panels, this compactness counted a lot in setting up the solar panels to realize 70MW output.

Also, SMA Solar Technology's string monitoring system was adopted for this plant. It measures the amount of power generation by each string consisting of multiple panels and detects malfunctions through embedding sensors with the connecting box (Fig. 4).

Japan's 1st lightning rods for solar panels

At Kagoshima Nanatsujima Mega-Solar Power Plant, 2MW of power generation facilities are allocated to each block of about 210 x 110m. There are 36 blocks. Each block is filled with solar panels arranged like a grid. And four 500kW PV inverters and transforming substations are positioned on the path located in the middle of each block (Fig. 5). These paths allow a 4t truck with a crane to pass and workers to promptly replace defective components, for example, if a PV inverter becomes out of order.

Placing PV inverters in the middle of each block helped to reduce the time and cost required to construct the plant, enabling the collection of electricity at the shortest distance from the connecting box that connects the solar panels in series and to linearly lay the grid underground between the PV inverters and the transformer substation to the northwest of the power plant. Kyushu Electric Power's Goino transforming station is located about 350m from the solar power plant and connected with the grid via the underground transmission wire.

Furthermore, 1,380 4.5m-high lightning rods were erected around the solar panels, PV inverters and transformer substations. This is said to be the only case in Japan in which solar panels are protected by lightning rods (Fig. 6). There was lots of lightning from Sept 1 to 3, 2013, when the plant was under construction, and the plant was reportedly struck. Along with the lightning rods, the power plant is also equipped with infrared sensors and security cameras.

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