The Abu Dhabi National Energy Company (Taqa) will invest £25 million (€28 million) and UK utility Octopus Energy will invest £5 million in the Xlinks hybrid energy project.
Xlinks plans to build 10.5GW of wind and solar capacity in Morocco with 5GW/20GWh of battery storage. It will use this to supply the UK with 3.6GW of firm clean power, around 8% of the country's estimated electricity needs, via four 3,800km subsea HVDC cables.
The project is due to be completed in 2030. Octopus had already joined as a partner last year.
Xlinks said the investments were "a critical early milestone" that validates its ambitious plans. The project will ultimately require much higher investment, for an estimated total cost of £16 billion.