The first stage of fundraising has now been completed, while GIB seeks additional funds to achieve its goal to raise a total of £1bn, dedicated only for offshore wind development.
UK pension funds and a sovereign wealth manager are the initial investors and GIB invested £200m in the initial financing.
UK GIB chief executive Shaun Kingsbury said: "By 2020 we expect it to be providing enough clean, green energy to power the electricity needs of 8.2m homes across the UK."
"The fund will create significant benefits for the UK by mobilising capital into the UK offshore wind sector from new, long-term investors seeking good, risk adjusted returns.
"New investors will allow the original developers to sell down their stakes and use the proceeds to finance new renewable energy projects."
GIB has already transferred its 20% and 24.95% stakes in the 317MW Sheringham Shoal and 90MW Rhyl Flats offshore wind farms respective, into the fund.
The two offshore wind farms can generate 1,290GWh of renewable energy annually which is enough to power 305,000 UK homes.
UK GIB fund managing director Karl Smith said: "The fund gives GIB a new opportunity to create value for its investors through active asset management, leveraging its deep industry insight, relationships and significant capital base."
