The fourth stage would see turbines of up to 3MW capacity and 135-metre tip height installed at the site 40km east of Edinburgh.

The development already consists of the operating 62.5MW Crystal Rig and 138MW Crystal Rig 2, using turbines from Nordex and Siemens respectively.

A seven-turbine third phase is currently seeking consent.

Norway-based Fred Olsen Renewables said of the planned fourth batch of turbines: “There is sufficient capacity at the existing Crystal Rig substation to accommodate a grid connection for the proposed development and together with the level of wind resource in the area, the proposed development is in an ideal location to help contribute to the UK and Scottish Government’s 2020 renewable energy targets.”

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