Roscommon-born O'Connor made 48m when selling renewable energy firm Airtricity for 1.2bn in 2007. He invested most of it into setting up Mainstream Renewables, which recently signed a deal worth $1.5bn (1.3bn) that will see it develop Vietnam's wind energy offerings.
Japanese trading house Marubeni spent 100m for a 25pc stake three years ago, valuing the business at 400m. The former Bord na Móna boss has a 35pc stake but is likely to be diluted further as he seeks to raise another 75m in funding. He backed a consortium that unsuccessfully tried to rescue Plymouth football club. It was later bought out of administration.