Sheep, Silo Give Bucolic Atmosphere to Solar Plant

16MW power plant built on undulating golf course

2014/01/26 03:41
Shinichi Kato, Nikkei BP CleanTech Institute

A silo rises and sheep idyllically browse on grass around it. That is where "Nikke Machinaka Power Plant Akashi Tsuchiyama" started operation in Inamicho, Kako-gun, Hyogo Prefecture. The pastoral atmosphere is completely different from the generally cold image of mega (large-scale) solar power plants (Fig. 1 & 2).

This is a mega solar power plant with 16.817MW output constructed by the Japan Wool Textile Co Ltd (Nikke) on the former "Nikke Golf Club Tsuchiyama Course," a miniature golf course that closed in September 2012.

To keep project costs low, Nikke built the plant by making the smallest changes possible to the former golf course site. As a result, the ponds and undulations that characterized the golf course were left unchanged while as many trees as possible were left. The former clubhouse is now being used as a station where electrical chief engineers are on standby and the sheep rest at night. The sheep are kept in the former bathroom.

To offer comfort, friendliness

Sheep and goats have recently been adopted for weeding at many mega solar power plants, but, in the case of Nikke, their adoption was, in fact, not primarily aimed at weeding.

The glass-covered solar panels cannot help but give a hard impression. When as many as 50,000 such panels are spread across the site, what measures can be applied so as not to give a cold, suffocating impression to the neighboring residents? Nikke tackled this challenge.

The company left a large portion of the green from the golf course (Fig. 3) and pastured the sheep with the aim of offering comfort and friendliness instead. A sheep is also used as a mascot character of Nikke, whose original business is wool spinning and weaving, and, therefore, plays a part in the company's public relations.

There are three sheep that are put out to graze in an area of about 15,000m2 in the plant site, which has a total area of approximately 220,000m2. This 15,000m2 is the area where most of the golf course's greens have been kept. The other area is covered by weed control sheets.

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Before the use of the sheep, Nikke verified in May and June 2013 whether or not the sheep would climb onto the panels or chew the wires. The company concluded that the sheep would do no harm to the facilities. And it released the three sheep adopted from Rokkosan Pasture (Kobe City, Hyogo Prefecture) into the site in October 2013 when the plant started selling electricity. The sheep management is entrusted to the subsidiary Nikke Fudosan. The sheep attendants are local residents.

As for the weeding effect in question, "The sheep have grown fat, eating more grass than expected," an attendant of Nikke Fudosan said (Fig. 4). However, it also slowly became apparent that the sheep have strong preferences, being reluctant to eat certain kinds of grass and eating tree leaves at heights above themselves.

Silo from time of sheep farm

The land where the mega solar power plant was constructed had been once used as a pasture for cows and sheep for wool spinning and weaving, Nikke's original business, before being used as a golf course. A reminder of that time is the silo used to store feedstuff. Situated on the east, south and west sides of the solar panels today are plants, a school and a hospital, respectively (Fig. 5).

While considering changing the land's usage resulting from factors including a decreased golfing population, Nikke discussed a plan to flatten the land and sell it to Hyogo Prefecture for an industrial park development. Hit by the Lehman Shock in 2008, however, it became uncertain whether Nikke could find a buyer who would use the land in an optimal way. The company then decided to enter the market for selling electricity based on mega solar power plants and closed the golf course in September 2012 as the feed-in-tariff (FIT) program for reusable energy was implemented in July the same year.

When the mega solar power plant project is completed, the total output will reach 16.817MW. Phase 1 area's output totals 11.035MW, and power generation started in October 2013. Phase 2 is slated for an output of 5.782MW, and power generation will start in February 2014. The number of solar panels installed in Phase 1 and 2 is 36,784 and 18,068, respectively. The amount of power generation in the Phase 1 area, which has started power sales, has reportedly met the estimates.

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Efforts to keep development, construction costs low

Although many trees were cut down to convert the golf course into a mega solar power plant, the land's properties such as typical golf course undulations and ponds were almost unchanged. This was because the redevelopment costs were taken into consideration. Trees were only cut down because the amount of power generation would lower should the trees shade the panels in accordance with their position to the panels.

Because the lack of foundation work left the undulations, some solar panels are tilted at different angles depending on the slopes. But most of the panels of the plant are directly facing south and tilted at 10° when installed (Fig. 6).

Because of the undulating land, construction efficiency would decline with mounting systems that use concrete foundations. To lower the cost, the plant deployed a "stake-driving-type" mounting system, which allows constructors to dig a hole in the ground and directly drive a stake into it when installing the system.

Takenaka Corp designed and constructed the plant. The suppliers of the solar panels, PV inverters, mounting system and other facilities have not been revealed. Operation and management is being entrusted to Nikke's subsidiary Nikke Machine Manufacturing Corp.

PV inverters in solid airtight concrete shed

What is eye-catching in terms of the facilities is the housing of PV inverters in a solid concrete shed (Fig. 7). PV inverters contained in metal housings are often seen at many mega solar power plants, but Nikke contained them in a concrete shed.

"Some questioned whether such a fort-like shed was really needed, but we were prudent in preparing a concrete shed in view of heat and dust impacts," said Manager Masakazu Kimura of the Real Estate Section, Area Development Department, Human and Future Development Division, Nikke. "We were proved right after all, I believe."

In the 11.035MW capacity Phase 1, the solar panels were installed in five blocks with PV inverters into which the generated electricity is input.

Also, to proactively accept visitors including local residents, a 6m-wide lane and an observation deck were set up along the perimeter on the east and south sides. The lane was made wide enough for a bus to run along.