The tests are being carried out by Mitsubishi Power’s parent company, Mitsubishi Heavy Industries, as part of a 4-year JPY 8 billion (€65 million) deal.
Mitsubishi's financial commitment to the project casts another shadow over Vestas' hopes that it can bring in the Japanese company as a partner on its own V164 8MW turbine.
In August, Vestas said it was in talks with Mitsubishi about a possible partnership. However, neither company has commented since then.
The drivetrain technology for the SeaAngel was developed by Scottish company Artemis Intelligent Power, which was acquired by Mitsubishi Power Systems Europe in 2010.
New Energy and Industrial Technology Development Organisation (Nedo), an independent administrative agency with ties to Japan's economic, trade and industry ministry, is providing 50% of the funds, Masaharu Ito, director of the new energy technology department at Nedo, said.
Tests using 2.4MW technology commenced last year at Mitsubishi's Yokohama Dockyard and Machinery Works, and the company plans to conduct proving tests in the UK using 7MW turbines in 2013.