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Maximising the power of the sun

The 235MW Setouchi Kirei solar plant in Okayama prefecture is the largest in Japan.

Project Setouchi Kirei mega-solar power plant, Japan

ClientSetouchi Future Creations LLC

ExpertiseOwner’s engineer, including energy yield and performance assessment, design review, construction supervision, project management

Some 900,000 solar panels have been installed on a former salt field site in Setouchi City. The power plant is a clean source of energy for about 80,000 homes. A new seawall was built as part of the project and provides additional flood protection for the local community, while the existing habitats for rare birds, including the Eastern marsh harrier and the Black-faced spoonbill, were carefully preserved. We were owner’s engineer for Setouchi Future Creations LLC, assessing energy yield, drafting plant test procedures, supporting contract negotiations and advising on procurement.

We introduced a new way of improving the accuracy of weather forecasts and got the backing from investors for our approach. This involved using data from the local weather station to correct satellite information to estimate long-term irradiance. After financial close, we provided site construction management services. Commercial operation started in October 2018 and the city is receiving income through land-lease arrangement with the solar plant’s owner.

Almost 40,000 people live in Setouchi City and neighbourhoods on its southern edge bordering Kinkai Bay are at risk of flooding from tsunami and tidal surges. A 1.6km-long embankment along the bay to the east of the solar plant was built as part of the scheme, providing protection for residents and valuable agricultural land as well as the array.


solar panels

The 900,000 solar panels cover about 260ha and can generate 235MW during peak sunlight hours, saving about 192,000 tonnes of carbon each year compared with a fossil-fuel plant with a similar capacity. It halves average annual CO2 emissions from Setouchi City.

Reed beds, water ways, creeks and willow forests had formed on the site since salt production ended in 1971. The solar scheme set aside a 16ha area of the site for animals and plants. The area is known as Kinkai habitat and it is home to birds, such as the Japanese Nightingale, the Great Reed Warbler and Zitting Cisticola, as well as small mammals like the Japanese marten.

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