Norwegian low-carbon investment company Aker Horizons has taken a 75% ownership stake in Irish developer Mainstream Renewable Power for €750m ($910m) as part of a plan to “rapidly accelerate” a global expansion strategy that aims to move 5.5GW of new wind and solar assets to financial close by 2023.

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Under the terms of the agreement, which is based on a corporate valuation of up to €1bn ($1.2bn) including a €100m earn out in 2023, Mainstream will continue to operate under its current banner led by CEO Mary Quaney, with company founder Eddie O’Connor remaining as chairman, retaining a minority interest ahead of a planned initial public offering “within the next two to three years”.

“We are thrilled to partner with Mainstream as we accelerate our journey of what we call planet-positive investing,” said Kristian Monsen Røkke, CEO of Aker Horizons. “Mainstream’s role as a pioneer in renewables and its strong entrepreneurial culture is a good fit as we carve out our path forward in the energy transition.

“Through the acquisition of Mainstream, Aker Horizons will gain a platform to drive forward its plans in renewable energy and position itself in a growing market for hybrid projects.”

Quaney said: “Hav[ing] a highly respected business [such] as Aker Horizons on board, [will] enable Mainstream to materially accelerate its growth plans to deliver a global portfolio of wind and solar assets”, adding that the growth strategy would set the company “firmly on track to becoming one of the world’s first pure-play renewable energy majors”.

O’Connor said the investment was “the crucial next step in the vision we set out for Mainstream in 2008 to lead the global transition to renewable energy and rid the world of CO2 emissions.

“It means we can widen our scope for entry into new markets and further deepen and expand our leadership position in existing ones, such as in Chile where we will soon be supplying the equivalent of one in seven Chilean homes with power from our wind and solar facilities.”

Aker Horizons was formed as part of a restructuring at oil & gas contractor Aker Solutions that involved the spin-out clean-energy units Aker Offshore Wind and Aker Carbon Capture.

Mainstream has “significant interests” in wind and solar developments across Latin America, Asia-Pacific and Africa, as well as in the global offshore wind sector, with over 1.2GW of major capital projects currently under construction.

Rothschild & Co acted as financial advisor to Mainstream on the transaction, and Linklaters, Byrne Wallace and Philip Lee advised on legal elements of the buy-in.

· The story headline was amended to reflect the fact that Aker Horizons’ 75% stake in Mainstream would amount to an investment of around €750,000, rather than the full valuation of the company, €1bn.