LIVERPOOL, England — When engineers faced resistance from residents in Denmark over plans to build wind turbines on the Nordic country’s flat farmland, they found a better locale: the sea. The offshore wind farm, the world’s first, had just 11 turbines and could power about 3,000 homes.

That project now looks like a minnow compared with the whales that sprawl for miles across the seas of Northern Europe.

Off this venerable British port city, a Danish company, Dong Energy, is installing 32 turbines that stretch 600 feet high. Each turbine produces more power than that first facility.

It is precisely the size, both of the projects and the profits they can bring, that has grabbed the attention of financial institutions, money managers and private equity funds, like the investment bank Goldman Sachs, as well as wealthy individuals like the owner of the Danish toymaker Lego. As the technology has improved and demand for renewable energy has risen, costs have fallen.